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ClickHouse/src/Common/Dwarf.cpp
Azat Khuzhin 7e130aeb69 Add support for DWARF-5 (without emitting them in binaries) 
ClickHouse changes to the folly parser:
- use camel_case
- add NOLINT
- avoid using folly:: (use std:: instead)
- avoid using boost:: (use std:: instead)

But note, now it has not been enabled by default (like it was
initially), because you may need recent debugger to support DWARF-5
correctly, and to make debugging easier, let's do this later.

A good example is gdb 10, even though it looks like it should support
it, it still produce some errors, like here [1]:

    Dwarf Error: DW_FORM_strx1 found in non-DWO CU [in module /usr/bin/clickhouse]

  [1]: https://github.com/ClickHouse/ClickHouse/pull/40772#issuecomment-1236331323

And not only it complains, apparently it can "activate" SDT probes
(replace "nop" with "int3"), and I believe this is what happens here
[2].

  [2]: https://github.com/ClickHouse/ClickHouse/pull/41063#issuecomment-1242992314

There you got int3 in the case when ClickHouse got SIGTRAP:

<details>

```
    0x7f494705e093 <+1139>: jne    0x7f494705e450            ; <+2096> [inlined] update_tls_slotinfo at dl-open.c:732
    0x7f494705e099 <+1145>: testl  %r13d, %r13d
    0x7f494705e09c <+1148>: je     0x7f494705e09f            ; <+1151> at dl-open.c:744:6
    0x7f494705e09e <+1150>: int3
->  0x7f494705e09f <+1151>: movl   -0x54(%rbp), %eax
    0x7f494705e0a2 <+1154>: testl  %eax, %eax
    0x7f494705e0a4 <+1156>: jne    0x7f494705e410            ; <+2032> at dl-open.c:745:5

But if I repeat the query it does not:

    0x7ffff7fe5093 <+1139>: jne    0x7ffff7fe5450            ; <+2096> [inlined] update_tls_slotinfo at dl-open.c:732
    0x7ffff7fe5099 <+1145>: testl  %r13d, %r13d
    0x7ffff7fe509c <+1148>: je     0x7ffff7fe509f            ; <+1151> at dl-open.c:744:6
    0x7ffff7fe509e <+1150>: nop
->  0x7ffff7fe509f <+1151>: movl   -0x54(%rbp), %eax
    0x7ffff7fe50a2 <+1154>: testl  %eax, %eax
    0x7ffff7fe50a4 <+1156>: jne    0x7ffff7fe5410            ; <+2032> at dl-open.c:745:5
```

</details>

Test command was:

    clickhouse local --stacktrace -q "select * from file('data.capnp', 'CapnProto', 'val1 char') settings format_schema='nonexist:Message'

*P.S. I did this, because I have libraries compiled with DWARF5 (i.e. glibc), and dwarf parser simply fails on my dev env.*

Refs: 490b287ca3
(cherry picked from commit ee5696bb32)
(cherry picked from commit e03870bc8b)
Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com>
2022-09-11 21:06:14 +02:00

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#if defined(__ELF__) && !defined(OS_FREEBSD)
/*
* Copyright 2012-present Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/** This file was edited for ClickHouse.
*/
#include <cstring>
#include <Common/Elf.h>
#include <Common/Dwarf.h>
#include <Common/Exception.h>
#define DW_CHILDREN_no 0
#define DW_FORM_addr 1
#define DW_FORM_block1 0x0a
#define DW_FORM_block2 3
#define DW_FORM_block4 4
#define DW_FORM_block 9
#define DW_FORM_exprloc 0x18
#define DW_FORM_data1 0x0b
#define DW_FORM_ref1 0x11
#define DW_FORM_data2 0x05
#define DW_FORM_ref2 0x12
#define DW_FORM_data4 0x06
#define DW_FORM_ref4 0x13
#define DW_FORM_data8 0x07
#define DW_FORM_ref8 0x14
#define DW_FORM_ref_sig8 0x20
#define DW_FORM_sdata 0x0d
#define DW_FORM_udata 0x0f
#define DW_FORM_ref_udata 0x15
#define DW_FORM_flag 0x0c
#define DW_FORM_flag_present 0x19
#define DW_FORM_sec_offset 0x17
#define DW_FORM_ref_addr 0x10
#define DW_FORM_string 0x08
#define DW_FORM_strp 0x0e
#define DW_FORM_indirect 0x16
#define DW_FORM_strx 0x1a
#define DW_FORM_addrx 0x1b
#define DW_FORM_ref_sup4 0x1c
#define DW_FORM_strp_sup 0x1d
#define DW_FORM_data16 0x1e
#define DW_FORM_line_strp 0x1f
#define DW_FORM_implicit_const 0x21
#define DW_FORM_rnglistx 0x23
#define DW_FORM_loclistx 0x22
#define DW_FORM_ref_sup8 0x24
#define DW_FORM_strx1 0x25
#define DW_FORM_strx2 0x26
#define DW_FORM_strx3 0x27
#define DW_FORM_strx4 0x28
#define DW_FORM_addrx1 0x29
#define DW_FORM_addrx2 0x2a
#define DW_FORM_addrx3 0x2b
#define DW_FORM_addrx4 0x2c
#define DW_TAG_compile_unit 0x11
#define DW_TAG_subprogram 0x2e
#define DW_TAG_try_block 0x32
#define DW_TAG_catch_block 0x25
#define DW_TAG_entry_point 0x03
#define DW_TAG_common_block 0x1a
#define DW_TAG_lexical_block 0x0b
#define DW_AT_stmt_list 0x10
#define DW_AT_comp_dir 0x1b
#define DW_AT_name 0x03
#define DW_AT_high_pc 0x12
#define DW_AT_low_pc 0x11
#define DW_AT_entry_pc 0x52
#define DW_AT_ranges 0x55
#define DW_AT_abstract_origin 0x31
#define DW_AT_call_line 0x59
#define DW_AT_call_file 0x58
#define DW_AT_linkage_name 0x6e
#define DW_AT_specification 0x47
#define DW_AT_str_offsets_base 0x72
#define DW_AT_addr_base 0x73
#define DW_AT_rnglists_base 0x74
#define DW_AT_loclists_base 0x8c
#define DW_AT_GNU_ranges_base 0x2132
#define DW_AT_GNU_addr_base 0x2133
#define DW_LNE_define_file 0x03
#define DW_LNS_copy 0x01
#define DW_LNS_advance_pc 0x02
#define DW_LNS_advance_line 0x03
#define DW_LNS_set_file 0x04
#define DW_LNS_set_column 0x05
#define DW_LNS_negate_stmt 0x06
#define DW_LNS_set_basic_block 0x07
#define DW_LNS_const_add_pc 0x08
#define DW_LNS_fixed_advance_pc 0x09
#define DW_LNS_set_prologue_end 0x0a
#define DW_LNS_set_epilogue_begin 0x0b
#define DW_LNS_set_isa 0x0c
#define DW_LNE_end_sequence 0x01
#define DW_LNE_set_address 0x02
#define DW_LNE_set_discriminator 0x04
#define DW_LNCT_path 0x1
#define DW_LNCT_directory_index 0x2
#define DW_LNCT_timestamp 0x3
#define DW_LNCT_size 0x4
#define DW_LNCT_MD5 0x5
#define DW_RLE_end_of_list 0x0
#define DW_RLE_base_addressx 0x1
#define DW_RLE_startx_endx 0x2
#define DW_RLE_startx_length 0x3
#define DW_RLE_offset_pair 0x4
#define DW_RLE_base_address 0x5
#define DW_RLE_start_end 0x6
#define DW_RLE_start_length 0x7
namespace DB
{
namespace ErrorCodes
{
extern const int CANNOT_PARSE_DWARF;
}
Dwarf::Dwarf(const std::shared_ptr<Elf> & elf)
: elf_(elf)
, abbrev_(getSection(".debug_abbrev"))
, addr_(getSection(".debug_addr"))
, aranges_(getSection(".debug_aranges"))
, info_(getSection(".debug_info"))
, line_(getSection(".debug_line"))
, line_str_(getSection(".debug_line_str"))
, loclists_(getSection(".debug_loclists"))
, ranges_(getSection(".debug_ranges"))
, rnglists_(getSection(".debug_rnglists"))
, str_(getSection(".debug_str"))
, str_offsets_(getSection(".debug_str_offsets"))
{
// Optional sections:
// - debugAranges_: for fast address range lookup.
// If missing .debug_info can be used - but it's much slower (linear
// scan).
// - debugRanges_ (DWARF 4) / debugRnglists_ (DWARF 5): non-contiguous
// address ranges of debugging information entries.
// Used for inline function address lookup.
if (info_.empty() || abbrev_.empty() || line_.empty() || str_.empty())
{
elf_ = nullptr;
}
}
Dwarf::Section::Section(std::string_view d) : is64_bit(false), data(d)
{
}
#define SAFE_CHECK(cond, ...) do { if (!(cond)) throw Exception(ErrorCodes::CANNOT_PARSE_DWARF, __VA_ARGS__); } while (false)
namespace
{
// Maximum number of DIEAbbreviation to cache in a compilation unit. Used to
// speed up inline function lookup.
const uint32_t kMaxAbbreviationEntries = 1000;
// All following read* functions read from a std::string_view, advancing the
// std::string_view, and aborting if there's not enough room.
// Read (bitwise) one object of type T
template <typename T>
requires std::is_trivial_v<T> && std::is_standard_layout_v<T>
T read(std::string_view & sp)
{
SAFE_CHECK(sp.size() >= sizeof(T), "underflow: expected bytes {}, got bytes {}", sizeof(T), sp.size());
T x;
memcpy(&x, sp.data(), sizeof(T));
sp.remove_prefix(sizeof(T));
return x;
}
// Read (bitwise) an unsigned number of N bytes (N in 1, 2, 3, 4).
template <size_t N>
uint64_t readU64(std::string_view & sp)
{
SAFE_CHECK(sp.size() >= N, "underflow");
uint64_t x = 0;
memcpy(&x, sp.data(), N);
sp.remove_prefix(N);
return x;
}
// Read ULEB (unsigned) varint value; algorithm from the DWARF spec
uint64_t readULEB(std::string_view & sp, uint8_t & shift, uint8_t & val)
{
uint64_t r = 0;
shift = 0;
do
{
val = read<uint8_t>(sp);
r |= (uint64_t(val & 0x7f) << shift);
shift += 7;
} while (val & 0x80);
return r;
}
uint64_t readULEB(std::string_view & sp)
{
uint8_t shift;
uint8_t val;
return readULEB(sp, shift, val);
}
// Read SLEB (signed) varint value; algorithm from the DWARF spec
int64_t readSLEB(std::string_view & sp)
{
uint8_t shift;
uint8_t val;
uint64_t r = readULEB(sp, shift, val);
if (shift < 64 && (val & 0x40))
{
r |= -(1ULL << shift); // sign extend
}
return r;
}
// Read a value of "section offset" type, which may be 4 or 8 bytes
uint64_t readOffset(std::string_view & sp, bool is64_bit)
{
return is64_bit ? read<uint64_t>(sp) : read<uint32_t>(sp);
}
// Read "len" bytes
std::string_view readBytes(std::string_view & sp, uint64_t len)
{
SAFE_CHECK(len <= sp.size(), "invalid string length: " + std::to_string(len) + " vs. " + std::to_string(sp.size()));
std::string_view ret(sp.data(), len);
sp.remove_prefix(len);
return ret;
}
// Read a null-terminated string
std::string_view readNullTerminated(std::string_view & sp)
{
const char * p = static_cast<const char *>(memchr(sp.data(), 0, sp.size()));
SAFE_CHECK(p, "invalid null-terminated string");
std::string_view ret(sp.data(), p - sp.data());
sp = std::string_view(p + 1, sp.size());
return ret;
}
// Get a string from the section
std::string_view getStringFromStringSection(std::string_view section, uint64_t offset)
{
SAFE_CHECK(offset < section.size(), "invalid section offset");
std::string_view sp(section);
sp.remove_prefix(offset);
return readNullTerminated(sp);
}
// Skip over padding until sp.data() - start is a multiple of alignment
void skipPadding(std::string_view & sp, const char * start, size_t alignment)
{
size_t remainder = (sp.data() - start) % alignment;
if (remainder)
{
SAFE_CHECK(alignment - remainder <= sp.size(), "invalid padding");
sp.remove_prefix(alignment - remainder);
}
}
}
Dwarf::Path::Path(std::string_view baseDir, std::string_view subDir, std::string_view file)
: baseDir_(baseDir), subDir_(subDir), file_(file)
{
using std::swap;
// Normalize
if (file_.empty())
{
baseDir_ = {};
subDir_ = {};
return;
}
if (file_[0] == '/')
{
// file_ is absolute
baseDir_ = {};
subDir_ = {};
}
if (!subDir_.empty() && subDir_[0] == '/')
{
baseDir_ = {}; // subDir_ is absolute
}
// Make sure it's never the case that baseDir_ is empty, but subDir_ isn't.
if (baseDir_.empty())
{
swap(baseDir_, subDir_);
}
}
size_t Dwarf::Path::size() const
{
size_t size = 0;
bool needs_slash = false;
if (!baseDir_.empty())
{
size += baseDir_.size();
needs_slash = baseDir_.back() != '/';
}
if (!subDir_.empty())
{
size += needs_slash;
size += subDir_.size();
needs_slash = subDir_.back() != '/';
}
if (!file_.empty())
{
size += needs_slash;
size += file_.size();
}
return size;
}
size_t Dwarf::Path::toBuffer(char * buf, size_t bufSize) const
{
size_t total_size = 0;
bool needs_slash = false;
auto append = [&](std::string_view sp)
{
if (bufSize >= 2)
{
size_t to_copy = std::min(sp.size(), bufSize - 1);
memcpy(buf, sp.data(), to_copy);
buf += to_copy;
bufSize -= to_copy;
}
total_size += sp.size();
};
if (!baseDir_.empty())
{
append(baseDir_);
needs_slash = baseDir_.back() != '/';
}
if (!subDir_.empty())
{
if (needs_slash)
{
append("/");
}
append(subDir_);
needs_slash = subDir_.back() != '/';
}
if (!file_.empty())
{
if (needs_slash)
{
append("/");
}
append(file_);
}
if (bufSize)
{
*buf = '\0';
}
SAFE_CHECK(total_size == size(), "Size mismatch");
return total_size;
}
void Dwarf::Path::toString(std::string & dest) const
{
size_t initial_size = dest.size();
dest.reserve(initial_size + size());
if (!baseDir_.empty())
{
dest.append(baseDir_.begin(), baseDir_.end());
}
if (!subDir_.empty())
{
if (!dest.empty() && dest.back() != '/')
{
dest.push_back('/');
}
dest.append(subDir_.begin(), subDir_.end());
}
if (!file_.empty())
{
if (!dest.empty() && dest.back() != '/')
{
dest.push_back('/');
}
dest.append(file_.begin(), file_.end());
}
SAFE_CHECK(dest.size() == initial_size + size(), "Size mismatch");
}
// Next chunk in section
bool Dwarf::Section::next(std::string_view & chunk)
{
chunk = data;
if (chunk.empty())
return false;
// Initial length is a uint32_t value for a 32-bit section, and
// a 96-bit value (0xffffffff followed by the 64-bit length) for a 64-bit
// section.
auto initial_length = read<uint32_t>(chunk);
is64_bit = (initial_length == uint32_t(-1));
auto length = is64_bit ? read<uint64_t>(chunk) : initial_length;
SAFE_CHECK(length <= chunk.size(), "invalid DWARF section");
chunk = std::string_view(chunk.data(), length);
data = std::string_view(chunk.end(), data.end() - chunk.end());
return true;
}
std::string_view Dwarf::getSection(const char * name) const
{
std::optional<Elf::Section> elf_section = elf_->findSectionByName(name);
if (!elf_section)
return {};
#ifdef SHF_COMPRESSED
if (elf_section->header.sh_flags & SHF_COMPRESSED)
return {};
#endif
return { elf_section->begin(), elf_section->size()};
}
// static
bool Dwarf::readAbbreviation(std::string_view & section, DIEAbbreviation & abbr)
{
// abbreviation code
abbr.code = readULEB(section);
if (abbr.code == 0)
return false;
// abbreviation tag
abbr.tag = readULEB(section);
// does this entry have children?
abbr.has_children = (read<uint8_t>(section) != DW_CHILDREN_no);
// attributes
const char * attribute_begin = section.data();
for (;;)
{
SAFE_CHECK(!section.empty(), "invalid attribute section");
auto attr = readAttributeSpec(section);
if (attr.name == 0 && attr.form == 0)
break;
}
abbr.attributes = std::string_view(attribute_begin, section.data() - attribute_begin);
return true;
}
// static
void Dwarf::readCompilationUnitAbbrs(std::string_view abbrev, CompilationUnit & cu)
{
abbrev.remove_prefix(cu.abbrev_offset);
DIEAbbreviation abbr;
while (readAbbreviation(abbrev, abbr))
{
// Abbreviation code 0 is reserved for null debugging information entries.
if (abbr.code != 0 && abbr.code <= kMaxAbbreviationEntries)
{
cu.abbr_cache[abbr.code - 1] = abbr;
}
}
}
size_t Dwarf::forEachChild(const CompilationUnit & cu, const Die & die, std::function<bool(const Die & die)> f) const
{
size_t next_die_offset = forEachAttribute(cu, die, [&](const Attribute &) { return true; });
if (!die.abbr.has_children)
{
return next_die_offset;
}
auto child_die = getDieAtOffset(cu, next_die_offset);
while (child_die.code != 0)
{
if (!f(child_die))
{
return child_die.offset;
}
// NOTE: Don't run `f` over grandchildren, just skip over them.
size_t sibling_offset = forEachChild(cu, child_die, [](const Die &) { return true; });
child_die = getDieAtOffset(cu, sibling_offset);
}
// childDie is now a dummy die whose offset is to the code 0 marking the
// end of the children. Need to add one to get the offset of the next die.
return child_die.offset + 1;
}
/*
* Iterate over all attributes of the given DIE, calling the given callable
* for each. Iteration is stopped early if any of the calls return false.
*/
size_t Dwarf::forEachAttribute(const CompilationUnit & cu, const Die & die, std::function<bool(const Attribute & die)> f) const
{
auto attrs = die.abbr.attributes;
auto values = std::string_view{info_.data() + die.offset + die.attr_offset, cu.offset + cu.size - die.offset - die.attr_offset};
while (auto spec = readAttributeSpec(attrs))
{
auto attr = readAttribute(cu, die, spec, values);
if (!f(attr))
{
return static_cast<size_t>(-1);
}
}
return values.data() - info_.data();
}
Dwarf::Attribute Dwarf::readAttribute(const CompilationUnit & cu,
const Die & die,
AttributeSpec spec,
std::string_view & info) const
{
// DWARF 5 introduces new FORMs whose values are relative to some base attrs:
// DW_AT_str_offsets_base, DW_AT_rnglists_base, DW_AT_addr_base.
// Debug Fission DWARF 4 uses GNU DW_AT_GNU_ranges_base & DW_AT_GNU_addr_base.
//
// The order in which attributes appear in a CU is not defined.
// The DW_AT_*_base attrs may appear after attributes that need them.
// The DW_AT_*_base attrs are CU specific; so we read them just after
// reading the CU header. During this first pass return empty values
// when encountering a FORM that depends on DW_AT_*_base.
auto get_string_using_offset_table = [&](uint64_t index)
{
if (!cu.str_offsets_base.has_value())
{
return std::string_view();
}
// DWARF 5: 7.26 String Offsets Table
// The DW_AT_str_offsets_base attribute points to the first entry following
// the header. The entries are indexed sequentially from this base entry,
// starting from 0.
auto sp = str_offsets_.substr(*cu.str_offsets_base + index * (cu.is64Bit ? sizeof(uint64_t) : sizeof(uint32_t)));
uint64_t str_offset = readOffset(sp, cu.is64Bit);
return getStringFromStringSection(str_, str_offset);
};
auto read_debug_addr = [&](uint64_t index)
{
if (!cu.addr_base.has_value())
{
return uint64_t(0);
}
// DWARF 5: 7.27 Address Table
// The DW_AT_addr_base attribute points to the first entry following the
// header. The entries are indexed sequentially from this base entry,
// starting from 0.
auto sp = addr_.substr(*cu.addr_base + index * sizeof(uint64_t));
return read<uint64_t>(sp);
};
switch (spec.form)
{
case DW_FORM_addr:
return {spec, die, read<uintptr_t>(info)};
case DW_FORM_block1:
return {spec, die, readBytes(info, read<uint8_t>(info))};
case DW_FORM_block2:
return {spec, die, readBytes(info, read<uint16_t>(info))};
case DW_FORM_block4:
return {spec, die, readBytes(info, read<uint32_t>(info))};
case DW_FORM_block:
[[fallthrough]];
case DW_FORM_exprloc:
return {spec, die, readBytes(info, readULEB(info))};
case DW_FORM_data1:
[[fallthrough]];
case DW_FORM_ref1:
return {spec, die, read<uint8_t>(info)};
case DW_FORM_data2:
[[fallthrough]];
case DW_FORM_ref2:
return {spec, die, read<uint16_t>(info)};
case DW_FORM_data4:
[[fallthrough]];
case DW_FORM_ref4:
return {spec, die, read<uint32_t>(info)};
case DW_FORM_data8:
[[fallthrough]];
case DW_FORM_ref8:
[[fallthrough]];
case DW_FORM_ref_sig8:
return {spec, die, read<uint64_t>(info)};
case DW_FORM_sdata:
return {spec, die, static_cast<uint64_t>(readSLEB(info))};
case DW_FORM_udata:
[[fallthrough]];
case DW_FORM_ref_udata:
return {spec, die, readULEB(info)};
case DW_FORM_flag:
return {spec, die, read<uint8_t>(info)};
case DW_FORM_flag_present:
return {spec, die, 1ULL};
case DW_FORM_sec_offset:
[[fallthrough]];
case DW_FORM_ref_addr:
return {spec, die, readOffset(info, die.is64Bit)};
case DW_FORM_string:
return {spec, die, readNullTerminated(info)};
case DW_FORM_strp:
return {spec, die, getStringFromStringSection(str_, readOffset(info, die.is64Bit))};
case DW_FORM_indirect: // form is explicitly specified
// Update spec with the actual FORM.
spec.form = readULEB(info);
return readAttribute(cu, die, spec, info);
// DWARF 5:
case DW_FORM_implicit_const: // form is explicitly specified
// For attributes with this form, the attribute specification contains a
// third part, which is a signed LEB128 number. The value of this number
// is used as the value of the attribute, and no value is stored in the
// .debug_info section.
return {spec, die, static_cast<uint64_t>(spec.implicitConst)};
case DW_FORM_addrx:
return {spec, die, read_debug_addr(readULEB(info))};
case DW_FORM_addrx1:
return {spec, die, read_debug_addr(readU64<1>(info))};
case DW_FORM_addrx2:
return {spec, die, read_debug_addr(readU64<2>(info))};
case DW_FORM_addrx3:
return {spec, die, read_debug_addr(readU64<3>(info))};
case DW_FORM_addrx4:
return {spec, die, read_debug_addr(readU64<4>(info))};
case DW_FORM_line_strp:
return {spec, die, getStringFromStringSection(line_str_, readOffset(info, die.is64Bit))};
case DW_FORM_strx:
return {spec, die, get_string_using_offset_table(readULEB(info))};
case DW_FORM_strx1:
return {spec, die, get_string_using_offset_table(readU64<1>(info))};
case DW_FORM_strx2:
return {spec, die, get_string_using_offset_table(readU64<2>(info))};
case DW_FORM_strx3:
return {spec, die, get_string_using_offset_table(readU64<3>(info))};
case DW_FORM_strx4:
return {spec, die, get_string_using_offset_table(readU64<4>(info))};
case DW_FORM_rnglistx: {
auto index = readULEB(info);
if (!cu.rnglists_base.has_value())
{
return {spec, die, 0ULL};
}
const uint64_t offset_size = cu.is64Bit ? sizeof(uint64_t) : sizeof(uint32_t);
auto sp = rnglists_.substr(*cu.rnglists_base + index * offset_size);
auto offset = readOffset(sp, cu.is64Bit);
return {spec, die, *cu.rnglists_base + offset};
}
case DW_FORM_loclistx: {
auto index = readULEB(info);
if (!cu.loclists_base.has_value())
{
return {spec, die, 0ULL};
}
const uint64_t offset_size = cu.is64Bit ? sizeof(uint64_t) : sizeof(uint32_t);
auto sp = loclists_.substr(*cu.loclists_base + index * offset_size);
auto offset = readOffset(sp, cu.is64Bit);
return {spec, die, *cu.loclists_base + offset};
}
case DW_FORM_data16:
return {spec, die, readBytes(info, 16)};
case DW_FORM_ref_sup4:
case DW_FORM_ref_sup8:
case DW_FORM_strp_sup:
SAFE_CHECK(false, "Unexpected DWARF5 supplimentary object files");
default:
SAFE_CHECK(false, "invalid attribute form");
}
return {spec, die, 0ULL};
}
// static
Dwarf::AttributeSpec Dwarf::readAttributeSpec(std::string_view & sp)
{
Dwarf::AttributeSpec spec;
spec.name = readULEB(sp);
spec.form = readULEB(sp);
if (spec.form == DW_FORM_implicit_const)
{
spec.implicitConst = readSLEB(sp);
}
return spec;
}
Dwarf::CompilationUnit Dwarf::getCompilationUnit(uint64_t offset) const
{
// SAFE_CHECK(offset < info_.size(), "unexpected offset");
CompilationUnit cu;
std::string_view chunk(info_);
cu.offset = offset;
chunk.remove_prefix(offset);
// 1) unit_length
auto initial_length = read<uint32_t>(chunk);
cu.is64Bit = (initial_length == uint32_t(-1));
cu.size = cu.is64Bit ? read<uint64_t>(chunk) : initial_length;
SAFE_CHECK(cu.size <= chunk.size(), "invalid chunk size");
cu.size += cu.is64Bit ? 12 : 4;
// 2) version
cu.version = read<uint16_t>(chunk);
SAFE_CHECK(cu.version >= 2 && cu.version <= 5, "invalid info version");
if (cu.version == 5)
{
// DWARF5: 7.5.1.1 Full and Partial Compilation Unit Headers
// 3) unit_type (new DWARF 5)
cu.unit_type = read<uint8_t>(chunk);
if (cu.unit_type != DW_UT_compile && cu.unit_type != DW_UT_skeleton)
{
return cu;
}
// 4) address_size
cu.addr_size = read<uint8_t>(chunk);
SAFE_CHECK(cu.addr_size == sizeof(uintptr_t), "invalid address size");
// 5) debug_abbrev_offset
cu.abbrev_offset = readOffset(chunk, cu.is64Bit);
if (cu.unit_type == DW_UT_skeleton)
{
// 6) dwo_id
read<uint64_t>(chunk);
}
}
else
{
// DWARF4 has a single type of unit in .debug_info
cu.unit_type = DW_UT_compile;
// 3) debug_abbrev_offset
cu.abbrev_offset = readOffset(chunk, cu.is64Bit);
// 4) address_size
cu.addr_size = read<uint8_t>(chunk);
SAFE_CHECK(cu.addr_size == sizeof(uintptr_t), "invalid address size");
}
cu.first_die = chunk.data() - info_.data();
if (cu.version < 5)
{
return cu;
}
Die die = getDieAtOffset(cu, cu.first_die);
if (die.abbr.tag != DW_TAG_compile_unit)
{
return cu;
}
// Read the DW_AT_*_base attributes.
// Attributes which use FORMs relative to these base attrs
// will not have valid values during this first pass!
forEachAttribute(
cu,
die,
[&](const Attribute & attr)
{
switch (attr.spec.name)
{
case DW_AT_addr_base:
case DW_AT_GNU_addr_base:
cu.addr_base = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_loclists_base:
cu.loclists_base = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_rnglists_base:
case DW_AT_GNU_ranges_base:
cu.rnglists_base = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_str_offsets_base:
cu.str_offsets_base = std::get<uint64_t>(attr.attr_value);
break;
}
return true; // continue forEachAttribute
});
return cu;
}
// Finds the Compilation Unit starting at offset.
Dwarf::CompilationUnit Dwarf::findCompilationUnit(uint64_t targetOffset) const
{
// SAFE_CHECK(targetOffset < info_.size(), "unexpected target address");
uint64_t offset = 0;
while (offset < info_.size())
{
std::string_view chunk(info_);
chunk.remove_prefix(offset);
auto initial_length = read<uint32_t>(chunk);
auto is64_bit = (initial_length == static_cast<uint32_t>(-1));
auto size = is64_bit ? read<uint64_t>(chunk) : initial_length;
SAFE_CHECK(size <= chunk.size(), "invalid chunk size");
size += is64_bit ? 12 : 4;
if (offset + size > targetOffset)
{
break;
}
offset += size;
}
return getCompilationUnit(offset);
}
Dwarf::DIEAbbreviation Dwarf::getAbbreviation(uint64_t code, uint64_t offset) const
{
// Linear search in the .debug_abbrev section, starting at offset
std::string_view section = abbrev_;
section.remove_prefix(offset);
Dwarf::DIEAbbreviation abbr;
while (readAbbreviation(section, abbr))
if (abbr.code == code)
return abbr;
SAFE_CHECK(false, "could not find abbreviation code");
}
Dwarf::AttributeValue Dwarf::readAttributeValue(std::string_view & sp, uint64_t form, bool is64_bit) const
{
switch (form)
{
case DW_FORM_addr:
return uint64_t(read<uintptr_t>(sp));
case DW_FORM_block1:
return readBytes(sp, read<uint8_t>(sp));
case DW_FORM_block2:
return readBytes(sp, read<uint16_t>(sp));
case DW_FORM_block4:
return readBytes(sp, read<uint32_t>(sp));
case DW_FORM_block: [[fallthrough]];
case DW_FORM_exprloc:
return readBytes(sp, readULEB(sp));
case DW_FORM_data1: [[fallthrough]];
case DW_FORM_ref1:
return uint64_t(read<uint8_t>(sp));
case DW_FORM_data2: [[fallthrough]];
case DW_FORM_ref2:
return uint64_t(read<uint16_t>(sp));
case DW_FORM_data4: [[fallthrough]];
case DW_FORM_ref4:
return uint64_t(read<uint32_t>(sp));
case DW_FORM_data8: [[fallthrough]];
case DW_FORM_ref8:
return read<uint64_t>(sp);
case DW_FORM_sdata:
return uint64_t(readSLEB(sp));
case DW_FORM_udata: [[fallthrough]];
case DW_FORM_ref_udata:
return readULEB(sp);
case DW_FORM_flag:
return uint64_t(read<uint8_t>(sp));
case DW_FORM_flag_present:
return uint64_t(1);
case DW_FORM_sec_offset: [[fallthrough]];
case DW_FORM_ref_addr:
return readOffset(sp, is64_bit);
case DW_FORM_string:
return readNullTerminated(sp);
case DW_FORM_strp:
return getStringFromStringSection(str_, readOffset(sp, is64_bit));
case DW_FORM_indirect: // form is explicitly specified
return readAttributeValue(sp, readULEB(sp), is64_bit);
default:
SAFE_CHECK(false, "invalid attribute form");
}
}
/**
* Find @address in .debug_aranges and return the offset in
* .debug_info for compilation unit to which this address belongs.
*/
bool Dwarf::findDebugInfoOffset(uintptr_t address, std::string_view aranges, uint64_t & offset)
{
Section aranges_section(aranges);
std::string_view chunk;
while (aranges_section.next(chunk))
{
auto version = read<uint16_t>(chunk);
SAFE_CHECK(version == 2, "invalid aranges version");
offset = readOffset(chunk, aranges_section.is64Bit());
auto address_size = read<uint8_t>(chunk);
SAFE_CHECK(address_size == sizeof(uintptr_t), "invalid address size");
auto segment_size = read<uint8_t>(chunk);
SAFE_CHECK(segment_size == 0, "segmented architecture not supported");
// Padded to a multiple of 2 addresses.
// Strangely enough, this is the only place in the DWARF spec that requires
// padding.
skipPadding(chunk, aranges.data(), 2 * sizeof(uintptr_t));
for (;;)
{
auto start = read<uintptr_t>(chunk);
auto length = read<uintptr_t>(chunk);
if (start == 0 && length == 0)
break;
// Is our address in this range?
if (address >= start && address < start + length)
return true;
}
}
return false;
}
Dwarf::Die Dwarf::getDieAtOffset(const CompilationUnit & cu, uint64_t offset) const
{
SAFE_CHECK(offset < info_.size(), fmt::format("unexpected offset {}, info size {}", offset, info_.size()));
Die die;
std::string_view sp{info_.data() + offset, cu.offset + cu.size - offset};
die.offset = offset;
die.is64Bit = cu.is64Bit;
auto code = readULEB(sp);
die.code = code;
if (code == 0)
{
return die;
}
die.attr_offset = sp.data() - info_.data() - offset;
die.abbr = !cu.abbr_cache.empty() && die.code < kMaxAbbreviationEntries ? cu.abbr_cache[die.code - 1]
: getAbbreviation(die.code, cu.abbrev_offset);
return die;
}
/**
* Find the @locationInfo for @address in the compilation unit represented
* by the @sp .debug_info entry.
* Returns whether the address was found.
* Advances @sp to the next entry in .debug_info.
*/
bool Dwarf::findLocation(
uintptr_t address,
const LocationInfoMode mode,
CompilationUnit & cu,
LocationInfo & info,
std::vector<SymbolizedFrame> & inline_frames) const
{
Die die = getDieAtOffset(cu, cu.first_die);
// Partial compilation unit (DW_TAG_partial_unit) is not supported.
SAFE_CHECK(die.abbr.tag == DW_TAG_compile_unit, "expecting compile unit entry");
// Offset in .debug_line for the line number VM program for this CU
std::optional<uint64_t> line_offset = 0;
std::string_view compilation_directory;
std::optional<std::string_view> main_file_name;
std::optional<uint64_t> base_addr_cu;
forEachAttribute(cu, die, [&](const Attribute & attr)
{
switch (attr.spec.name)
{
case DW_AT_stmt_list:
// Offset in .debug_line for the line number VM program for this
// compilation unit
line_offset = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_comp_dir:
// Compilation directory
compilation_directory = std::get<std::string_view>(attr.attr_value);
break;
case DW_AT_name:
// File name of main file being compiled
main_file_name = std::get<std::string_view>(attr.attr_value);
break;
case DW_AT_low_pc:
case DW_AT_entry_pc:
// 2.17.1: historically DW_AT_low_pc was used. DW_AT_entry_pc was
// introduced in DWARF3. Support either to determine the base address of
// the CU.
base_addr_cu = std::get<uint64_t>(attr.attr_value);
break;
}
// Iterate through all attributes until find all above.
return true;
});
if (main_file_name)
{
info.has_main_file = true;
info.main_file = Path(compilation_directory, "", *main_file_name);
}
if (!line_offset)
{
return false;
}
std::string_view line_section(line_);
line_section.remove_prefix(*line_offset);
LineNumberVM line_vm(line_section, compilation_directory, str_, line_str_);
// Execute line number VM program to find file and line
info.has_file_and_line = line_vm.findAddress(address, info.file, info.line);
bool check_inline = (mode == LocationInfoMode::FULL_WITH_INLINE);
if (info.has_file_and_line && check_inline)
{
// Re-get the compilation unit with abbreviation cached.
cu.abbr_cache.clear();
cu.abbr_cache.resize(kMaxAbbreviationEntries);
readCompilationUnitAbbrs(abbrev_, cu);
// Find the subprogram that matches the given address.
Die subprogram;
findSubProgramDieForAddress(cu, die, address, base_addr_cu, subprogram);
// Subprogram is the DIE of caller function.
if (/*check_inline &&*/ subprogram.abbr.has_children)
{
// Use an extra location and get its call file and call line, so that
// they can be used for the second last location when we don't have
// enough inline frames for all inline functions call stack.
const size_t max_size = Dwarf::kMaxInlineLocationInfoPerFrame + 1;
std::vector<CallLocation> call_locations;
call_locations.reserve(Dwarf::kMaxInlineLocationInfoPerFrame + 1);
findInlinedSubroutineDieForAddress(cu, subprogram, line_vm, address, base_addr_cu, call_locations, max_size);
size_t num_found = call_locations.size();
if (num_found > 0)
{
const auto inner_most_file = info.file;
const auto inner_most_line = info.line;
// Earlier we filled in locationInfo:
// - mainFile: the path to the CU -- the file where the non-inlined
// call is made from.
// - file + line: the location of the inner-most inlined call.
// Here we already find inlined info so mainFile would be redundant.
info.has_main_file = false;
info.main_file = Path{};
// @findInlinedSubroutineDieForAddress fills inlineLocations[0] with the
// file+line of the non-inlined outer function making the call.
// locationInfo.name is already set by the caller by looking up the
// non-inlined function @address belongs to.
info.has_file_and_line = true; //-V1048
info.file = call_locations[0].file;
info.line = call_locations[0].line;
// The next inlined subroutine's call file and call line is the current
// caller's location.
for (size_t i = 0; i < num_found - 1; ++i)
{
call_locations[i].file = call_locations[i + 1].file;
call_locations[i].line = call_locations[i + 1].line;
}
// CallLocation for the inner-most inlined function:
// - will be computed if enough space was available in the passed
// buffer.
// - will have a .name, but no !.file && !.line
// - its corresponding file+line is the one returned by LineVM based
// on @address.
// Use the inner-most inlined file+line info we got from the LineVM.
call_locations[num_found - 1].file = inner_most_file;
call_locations[num_found - 1].line = inner_most_line;
// Fill in inline frames in reverse order (as expected by the caller).
std::reverse(call_locations.begin(), call_locations.end());
for (const auto & call_location : call_locations)
{
SymbolizedFrame inline_frame;
inline_frame.found = true;
inline_frame.addr = address;
if (!call_location.name.empty())
inline_frame.name = call_location.name.data();
else
inline_frame.name = nullptr;
inline_frame.location.has_file_and_line = true;
inline_frame.location.file = call_location.file;
inline_frame.location.line = call_location.line;
inline_frames.push_back(inline_frame);
}
}
}
}
return info.has_file_and_line;
}
void Dwarf::findSubProgramDieForAddress(const CompilationUnit & cu,
const Die & die,
uint64_t address,
std::optional<uint64_t> base_addr_cu,
Die & subprogram) const
{
forEachChild(cu, die, [&](const Die & child_die)
{
if (child_die.abbr.tag == DW_TAG_subprogram)
{
std::optional<uint64_t> low_pc;
std::optional<uint64_t> high_pc;
std::optional<bool> is_high_pc_addr;
std::optional<uint64_t> range_offset;
forEachAttribute(cu, child_die, [&](const Attribute & attr)
{
switch (attr.spec.name)
{
case DW_AT_ranges:
range_offset = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_low_pc:
low_pc = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_high_pc:
// The value of the DW_AT_high_pc attribute can be
// an address (DW_FORM_addr*) or an offset (DW_FORM_data*).
is_high_pc_addr = attr.spec.form == DW_FORM_addr || //
attr.spec.form == DW_FORM_addrx || //
attr.spec.form == DW_FORM_addrx1 || //
attr.spec.form == DW_FORM_addrx2 || //
attr.spec.form == DW_FORM_addrx3 || //
attr.spec.form == DW_FORM_addrx4;
high_pc = std::get<uint64_t>(attr.attr_value);
break;
}
// Iterate through all attributes until find all above.
return true;
});
bool pc_match = low_pc && high_pc && is_high_pc_addr && address >= *low_pc
&& (address < (*is_high_pc_addr ? *high_pc : *low_pc + *high_pc));
bool range_match = range_offset && isAddrInRangeList(cu, address, base_addr_cu, range_offset.value(), cu.addr_size);
if (pc_match || range_match)
{
subprogram = child_die;
return false;
}
}
findSubProgramDieForAddress(cu, child_die, address, base_addr_cu, subprogram);
// Iterates through children until find the inline subprogram.
return true;
});
}
/**
* Find DW_TAG_inlined_subroutine child DIEs that contain @address and
* then extract:
* - Where was it called from (DW_AT_call_file & DW_AT_call_line):
* the statement or expression that caused the inline expansion.
* - The inlined function's name. As a function may be inlined multiple
* times, common attributes like DW_AT_linkage_name or DW_AT_name
* are only stored in its "concrete out-of-line instance" (a
* DW_TAG_subprogram) which we find using DW_AT_abstract_origin.
*/
void Dwarf::findInlinedSubroutineDieForAddress(
const CompilationUnit & cu,
const Die & die,
const LineNumberVM & line_vm,
uint64_t address,
std::optional<uint64_t> base_addr_cu,
std::vector<CallLocation> & locations,
const size_t max_size) const
{
if (locations.size() >= max_size)
{
return;
}
forEachChild(cu, die, [&](const Die & child_die)
{
// Between a DW_TAG_subprogram and and DW_TAG_inlined_subroutine we might
// have arbitrary intermediary "nodes", including DW_TAG_common_block,
// DW_TAG_lexical_block, DW_TAG_try_block, DW_TAG_catch_block and
// DW_TAG_with_stmt, etc.
// We can't filter with locationhere since its range may be not specified.
// See section 2.6.2: A location list containing only an end of list entry
// describes an object that exists in the source code but not in the
// executable program.
if (child_die.abbr.tag == DW_TAG_try_block || child_die.abbr.tag == DW_TAG_catch_block || child_die.abbr.tag == DW_TAG_entry_point
|| child_die.abbr.tag == DW_TAG_common_block || child_die.abbr.tag == DW_TAG_lexical_block)
{
findInlinedSubroutineDieForAddress(cu, child_die, line_vm, address, base_addr_cu, locations, max_size);
return true;
}
std::optional<uint64_t> low_pc;
std::optional<uint64_t> high_pc;
std::optional<bool> is_high_pc_addr;
std::optional<uint64_t> abstract_origin;
std::optional<uint64_t> abstract_origin_ref_type;
std::optional<uint64_t> call_file;
std::optional<uint64_t> call_line;
std::optional<uint64_t> range_offset;
forEachAttribute(cu, child_die, [&](const Attribute & attr)
{
switch (attr.spec.name)
{
case DW_AT_ranges:
range_offset = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_low_pc:
low_pc = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_high_pc:
// The value of the DW_AT_high_pc attribute can be
// an address (DW_FORM_addr*) or an offset (DW_FORM_data*).
is_high_pc_addr = attr.spec.form == DW_FORM_addr || //
attr.spec.form == DW_FORM_addrx || //
attr.spec.form == DW_FORM_addrx1 || //
attr.spec.form == DW_FORM_addrx2 || //
attr.spec.form == DW_FORM_addrx3 || //
attr.spec.form == DW_FORM_addrx4;
high_pc = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_abstract_origin:
abstract_origin_ref_type = attr.spec.form;
abstract_origin = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_call_line:
call_line = std::get<uint64_t>(attr.attr_value);
break;
case DW_AT_call_file:
call_file = std::get<uint64_t>(attr.attr_value);
break;
}
// Iterate through all until find all above attributes.
return true;
});
// 2.17 Code Addresses and Ranges
// Any debugging information entry describing an entity that has a
// machine code address or range of machine code addresses,
// which includes compilation units, module initialization, subroutines,
// ordinary blocks, try/catch blocks, labels and the like, may have
// - A DW_AT_low_pc attribute for a single address,
// - A DW_AT_low_pc and DW_AT_high_pc pair of attributes for a
// single contiguous range of addresses, or
// - A DW_AT_ranges attribute for a non-contiguous range of addresses.
// TODO: Support DW_TAG_entry_point and DW_TAG_common_block that don't
// have DW_AT_low_pc/DW_AT_high_pc pairs and DW_AT_ranges.
// TODO: Support relocated address which requires lookup in relocation map.
bool pc_match
= low_pc && high_pc && is_high_pc_addr && address >= *low_pc && (address < (*is_high_pc_addr ? *high_pc : *low_pc + *high_pc));
bool range_match = range_offset && isAddrInRangeList(cu, address, base_addr_cu, range_offset.value(), cu.addr_size);
if (!pc_match && !range_match)
{
// Address doesn't match. Keep searching other children.
return true;
}
if (!abstract_origin || !abstract_origin_ref_type || !call_line || !call_file)
{
// We expect a single sibling DIE to match on addr, but it's missing
// required fields. Stop searching for other DIEs.
return false;
}
CallLocation location;
location.file = line_vm.getFullFileName(*call_file);
location.line = *call_line;
/// Something wrong with receiving debug info about inline.
/// If set to true we stop parsing DWARF.
bool die_for_inline_broken = false;
auto get_function_name = [&](const CompilationUnit & srcu, uint64_t die_offset)
{
Die decl_die = getDieAtOffset(srcu, die_offset);
auto & die_to_look_for_name = decl_die;
Die def_die;
// Jump to the actual function definition instead of declaration for name
// and line info.
// DW_AT_specification: Incomplete, non-defining, or separate declaration
// corresponding to a declaration
auto offset = getAttribute<uint64_t>(srcu, decl_die, DW_AT_specification);
if (offset)
{
/// FIXME: actually it's a bug in our DWARF parser.
///
/// Most of the times compilation unit offset (srcu.offset) is some big number inside .debug_info (like 434782255).
/// Offset of DIE definition is some small relative number to srcu.offset (like 3518).
/// However in some unknown cases offset looks like global, non relative number (like 434672579) and in this
/// case we obviously doing something wrong parsing DWARF.
///
/// What is important -- this bug? reproduces only with -flto=thin in release mode.
/// Also llvm-dwarfdump --verify ./clickhouse says that our DWARF is ok, so it's another prove
/// that we just doing something wrong.
///
/// FIXME: Currently we just give up parsing DWARF for inlines when we got into this situation.
if (srcu.offset + offset.value() >= info_.size())
{
die_for_inline_broken = true;
}
else
{
def_die = getDieAtOffset(srcu, srcu.offset + offset.value());
die_to_look_for_name = def_die;
}
}
std::string_view name;
if (die_for_inline_broken)
return name;
// The file and line will be set in the next inline subroutine based on
// its DW_AT_call_file and DW_AT_call_line.
forEachAttribute(srcu, die_to_look_for_name, [&](const Attribute & attr)
{
switch (attr.spec.name)
{
case DW_AT_linkage_name:
name = std::get<std::string_view>(attr.attr_value);
break;
case DW_AT_name:
// NOTE: when DW_AT_linkage_name and DW_AT_name match, dwarf
// emitters omit DW_AT_linkage_name (to save space). If present
// DW_AT_linkage_name should always be preferred (mangled C++ name
// vs just the function name).
if (name.empty())
{
name = std::get<std::string_view>(attr.attr_value);
}
break;
}
return true;
});
return name;
};
// DW_AT_abstract_origin is a reference. There a 3 types of references:
// - the reference can identify any debugging information entry within the
// compilation unit (DW_FORM_ref1, DW_FORM_ref2, DW_FORM_ref4,
// DW_FORM_ref8, DW_FORM_ref_udata). This type of reference is an offset
// from the first byte of the compilation header for the compilation unit
// containing the reference.
// - the reference can identify any debugging information entry within a
// .debug_info section; in particular, it may refer to an entry in a
// different compilation unit (DW_FORM_ref_addr)
// - the reference can identify any debugging information type entry that
// has been placed in its own type unit.
// Not applicable for DW_AT_abstract_origin.
location.name = (*abstract_origin_ref_type != DW_FORM_ref_addr)
? get_function_name(cu, cu.offset + *abstract_origin)
: get_function_name(findCompilationUnit(*abstract_origin), *abstract_origin);
/// FIXME: see comment above
if (die_for_inline_broken)
return false;
locations.push_back(location);
findInlinedSubroutineDieForAddress(cu, child_die, line_vm, address, base_addr_cu, locations, max_size);
return false;
});
}
bool Dwarf::findAddress(
uintptr_t address, LocationInfo & locationInfo, LocationInfoMode mode, std::vector<SymbolizedFrame> & inline_frames) const
{
locationInfo = LocationInfo();
if (mode == LocationInfoMode::DISABLED)
{
return false;
}
if (!elf_)
{ // No file.
return false;
}
if (!aranges_.empty())
{
// Fast path: find the right .debug_info entry by looking up the
// address in .debug_aranges.
uint64_t offset = 0;
if (findDebugInfoOffset(address, aranges_, offset))
{
// Read compilation unit header from .debug_info
auto unit = getCompilationUnit(offset);
if (unit.unit_type != DW_UT_compile && unit.unit_type != DW_UT_skeleton)
{
return false;
}
findLocation(address, mode, unit, locationInfo, inline_frames);
return locationInfo.has_file_and_line;
}
else if (mode == LocationInfoMode::FAST)
{
// NOTE: Clang (when using -gdwarf-aranges) doesn't generate entries
// in .debug_aranges for some functions, but always generates
// .debug_info entries. Scanning .debug_info is slow, so fall back to
// it only if such behavior is requested via LocationInfoMode.
return false;
}
else
{
SAFE_CHECK(mode == LocationInfoMode::FULL || mode == LocationInfoMode::FULL_WITH_INLINE, "unexpected mode");
// Fall back to the linear scan.
}
}
// Slow path (linear scan): Iterate over all .debug_info entries
// and look for the address in each compilation unit.
uint64_t offset = 0;
while (offset < info_.size() && !locationInfo.has_file_and_line)
{
auto unit = getCompilationUnit(offset);
offset += unit.size;
if (unit.unit_type != DW_UT_compile && unit.unit_type != DW_UT_skeleton)
{
continue;
}
findLocation(address, mode, unit, locationInfo, inline_frames);
}
return locationInfo.has_file_and_line;
}
bool Dwarf::isAddrInRangeList(const CompilationUnit & cu,
uint64_t address,
std::optional<uint64_t> base_addr,
size_t offset,
uint8_t addr_size) const
{
SAFE_CHECK(addr_size == 4 || addr_size == 8, "wrong address size");
if (cu.version <= 4 && !ranges_.empty())
{
const bool is64_bit_addr = addr_size == 8;
std::string_view sp = ranges_;
sp.remove_prefix(offset);
const uint64_t max_addr = is64_bit_addr ? std::numeric_limits<uint64_t>::max() : std::numeric_limits<uint32_t>::max();
while (!sp.empty())
{
uint64_t begin = readOffset(sp, is64_bit_addr);
uint64_t end = readOffset(sp, is64_bit_addr);
// The range list entry is a base address selection entry.
if (begin == max_addr)
{
base_addr = end;
continue;
}
// The range list entry is an end of list entry.
if (begin == 0 && end == 0)
{
break;
}
// Check if the given address falls in the range list entry.
// 2.17.3 Non-Contiguous Address Ranges
// The applicable base address of a range list entry is determined by the
// closest preceding base address selection entry (see below) in the same
// range list. If there is no such selection entry, then the applicable
// base address defaults to the base address of the compilation unit.
if (base_addr && address >= begin + *base_addr && address < end + *base_addr)
{
return true;
}
}
}
if (cu.version == 5 && !rnglists_.empty() && cu.addr_base.has_value())
{
auto rnglists = rnglists_;
rnglists.remove_prefix(offset);
while (!rnglists.empty())
{
auto kind = read<uint8_t>(rnglists);
switch (kind)
{
case DW_RLE_end_of_list:
return false;
case DW_RLE_base_addressx: {
auto index = readULEB(rnglists);
auto sp = addr_.substr(*cu.addr_base + index * sizeof(uint64_t));
base_addr = read<uint64_t>(sp);
}
break;
case DW_RLE_startx_endx: {
auto index_start = readULEB(rnglists);
auto index_end = readULEB(rnglists);
auto sp_start = addr_.substr(*cu.addr_base + index_start * sizeof(uint64_t));
auto start = read<uint64_t>(sp_start);
auto sp_end = addr_.substr(*cu.addr_base + index_end * sizeof(uint64_t));
auto end = read<uint64_t>(sp_end);
if (address >= start && address < end)
{
return true;
}
}
break;
case DW_RLE_startx_length: {
auto index_start = readULEB(rnglists);
auto length = readULEB(rnglists);
auto sp_start = addr_.substr(*cu.addr_base + index_start * sizeof(uint64_t));
auto start = read<uint64_t>(sp_start);
auto sp_end = addr_.substr(*cu.addr_base + index_start * sizeof(uint64_t) + length);
auto end = read<uint64_t>(sp_end);
if (start != end && address >= start && address < end)
{
return true;
}
}
break;
case DW_RLE_offset_pair: {
auto offset_start = readULEB(rnglists);
auto offset_end = readULEB(rnglists);
if (base_addr && address >= (*base_addr + offset_start) && address < (*base_addr + offset_end))
{
return true;
}
}
break;
case DW_RLE_base_address:
base_addr = read<uint64_t>(rnglists);
break;
case DW_RLE_start_end: {
uint64_t start = read<uint64_t>(rnglists);
uint64_t end = read<uint64_t>(rnglists);
if (address >= start && address < end)
{
return true;
}
}
break;
case DW_RLE_start_length: {
uint64_t start = read<uint64_t>(rnglists);
uint64_t end = start + readULEB(rnglists);
if (address >= start && address < end)
{
return true;
}
}
break;
default:
SAFE_CHECK(false, "Unexpected debug_rnglists entry kind");
}
}
}
return false;
}
Dwarf::LineNumberVM::LineNumberVM(
std::string_view data,
std::string_view compilationDirectory,
std::string_view debugStr,
std::string_view debugLineStr)
: compilationDirectory_(compilationDirectory)
, debugStr_(debugStr)
, debugLineStr_(debugLineStr)
{
Section section(data);
SAFE_CHECK(section.next(data_), "invalid line number VM");
is64Bit_ = section.is64Bit();
init();
reset();
}
void Dwarf::LineNumberVM::reset()
{
address_ = 0;
file_ = 1;
line_ = 1;
column_ = 0;
isStmt_ = defaultIsStmt_;
basicBlock_ = false;
endSequence_ = false;
prologueEnd_ = false;
epilogueBegin_ = false;
isa_ = 0;
discriminator_ = 0;
}
struct LineNumberAttribute
{
uint64_t content_type_code;
uint64_t form_code;
std::variant<uint64_t, std::string_view> attr_value;
};
LineNumberAttribute readLineNumberAttribute(
bool is64_bit, std::string_view & format, std::string_view & entries, std::string_view debugStr, std::string_view debugLineStr)
{
uint64_t content_type_code = readULEB(format);
uint64_t form_code = readULEB(format);
std::variant<uint64_t, std::string_view> attr_value;
switch (content_type_code)
{
case DW_LNCT_path: {
switch (form_code)
{
case DW_FORM_string:
attr_value = readNullTerminated(entries);
break;
case DW_FORM_line_strp: {
auto off = readOffset(entries, is64_bit);
attr_value = getStringFromStringSection(debugLineStr, off);
}
break;
case DW_FORM_strp:
attr_value = getStringFromStringSection(debugStr, readOffset(entries, is64_bit));
break;
case DW_FORM_strp_sup:
SAFE_CHECK(false, "Unexpected DW_FORM_strp_sup");
break;
default:
SAFE_CHECK(false, "Unexpected form for DW_LNCT_path");
break;
}
}
break;
case DW_LNCT_directory_index: {
switch (form_code)
{
case DW_FORM_data1:
attr_value = read<uint8_t>(entries);
break;
case DW_FORM_data2:
attr_value = read<uint16_t>(entries);
break;
case DW_FORM_udata:
attr_value = readULEB(entries);
break;
default:
SAFE_CHECK(false, "Unexpected form for DW_LNCT_directory_index");
break;
}
}
break;
case DW_LNCT_timestamp: {
switch (form_code)
{
case DW_FORM_udata:
attr_value = readULEB(entries);
break;
case DW_FORM_data4:
attr_value = read<uint32_t>(entries);
break;
case DW_FORM_data8:
attr_value = read<uint64_t>(entries);
break;
case DW_FORM_block:
attr_value = readBytes(entries, readULEB(entries));
break;
default:
SAFE_CHECK(false, "Unexpected form for DW_LNCT_timestamp");
}
}
break;
case DW_LNCT_size: {
switch (form_code)
{
case DW_FORM_udata:
attr_value = readULEB(entries);
break;
case DW_FORM_data1:
attr_value = read<uint8_t>(entries);
break;
case DW_FORM_data2:
attr_value = read<uint16_t>(entries);
break;
case DW_FORM_data4:
attr_value = read<uint32_t>(entries);
break;
case DW_FORM_data8:
attr_value = read<uint64_t>(entries);
break;
default:
SAFE_CHECK(false, "Unexpected form for DW_LNCT_size");
break;
}
}
break;
case DW_LNCT_MD5: {
switch (form_code)
{
case DW_FORM_data16:
attr_value = readBytes(entries, 16);
break;
default:
SAFE_CHECK(false, "Unexpected form for DW_LNCT_MD5");
break;
}
}
break;
default:
// TODO: skip over vendor data as specified by the form instead.
SAFE_CHECK(false, "Unexpected vendor content type code");
break;
}
return {
.content_type_code = content_type_code,
.form_code = form_code,
.attr_value = attr_value,
};
}
void Dwarf::LineNumberVM::init()
{
version_ = read<uint16_t>(data_);
SAFE_CHECK(version_ >= 2 && version_ <= 5, "invalid version in line number VM: {}", version_);
if (version_ == 5)
{
auto address_size = read<uint8_t>(data_);
SAFE_CHECK(address_size == sizeof(uintptr_t), "Unexpected Line Number Table address_size");
auto segment_selector_size = read<uint8_t>(data_);
SAFE_CHECK(segment_selector_size == 0, "Segments not supported");
}
uint64_t header_length = readOffset(data_, is64Bit_);
SAFE_CHECK(header_length <= data_.size(), "invalid line number VM header length");
std::string_view header(data_.data(), header_length);
data_ = std::string_view(header.end(), data_.end() - header.end());
minLength_ = read<uint8_t>(header);
if (version_ >= 4)
{ // Version 2 and 3 records don't have this
uint8_t max_ops_per_instruction = read<uint8_t>(header);
SAFE_CHECK(max_ops_per_instruction == 1, "VLIW not supported");
}
defaultIsStmt_ = read<uint8_t>(header);
lineBase_ = read<int8_t>(header); // yes, signed
lineRange_ = read<uint8_t>(header);
opcodeBase_ = read<uint8_t>(header);
SAFE_CHECK(opcodeBase_ != 0, "invalid opcode base");
standardOpcodeLengths_ = reinterpret_cast<const uint8_t *>(header.data()); //-V506
header.remove_prefix(opcodeBase_ - 1);
if (version_ <= 4)
{
// We don't want to use heap, so we don't keep an unbounded amount of state.
// We'll just skip over include directories and file names here, and
// we'll loop again when we actually need to retrieve one.
std::string_view sp;
const char * tmp = header.data();
v4_.includeDirectoryCount = 0;
while (!(sp = readNullTerminated(header)).empty())
{
++v4_.includeDirectoryCount;
}
v4_.includeDirectories = {tmp, header.data()};
tmp = header.data();
FileName fn;
v4_.fileNameCount = 0;
while (readFileName(header, fn))
{
++v4_.fileNameCount;
}
v4_.fileNames = {tmp, header.data()};
}
else if (version_ == 5)
{
v5_.directoryEntryFormatCount = read<uint8_t>(header);
const char * tmp = header.data();
for (uint8_t i = 0; i < v5_.directoryEntryFormatCount; i++)
{
// A sequence of directory entry format descriptions. Each description
// consists of a pair of ULEB128 values:
readULEB(header); // A content type code
readULEB(header); // A form code using the attribute form codes
}
v5_.directoryEntryFormat = {tmp, header.data()};
v5_.directoriesCount = readULEB(header);
tmp = header.data();
for (uint64_t i = 0; i < v5_.directoriesCount; i++)
{
std::string_view format = v5_.directoryEntryFormat;
for (uint8_t f = 0; f < v5_.directoryEntryFormatCount; f++)
{
readLineNumberAttribute(is64Bit_, format, header, debugStr_, debugLineStr_);
}
}
v5_.directories = {tmp, header.data()};
v5_.fileNameEntryFormatCount = read<uint8_t>(header);
tmp = header.data();
for (uint8_t i = 0; i < v5_.fileNameEntryFormatCount; i++)
{
// A sequence of file entry format descriptions. Each description
// consists of a pair of ULEB128 values:
readULEB(header); // A content type code
readULEB(header); // A form code using the attribute form codes
}
v5_.fileNameEntryFormat = {tmp, header.data()};
v5_.fileNamesCount = readULEB(header);
tmp = header.data();
for (uint64_t i = 0; i < v5_.fileNamesCount; i++)
{
std::string_view format = v5_.fileNameEntryFormat;
for (uint8_t f = 0; f < v5_.fileNameEntryFormatCount; f++)
{
readLineNumberAttribute(is64Bit_, format, header, debugStr_, debugLineStr_);
}
}
v5_.fileNames = {tmp, header.data()};
}
}
bool Dwarf::LineNumberVM::next(std::string_view & program)
{
Dwarf::LineNumberVM::StepResult ret;
do
{
ret = step(program);
} while (ret == CONTINUE);
return (ret == COMMIT);
}
Dwarf::LineNumberVM::FileName Dwarf::LineNumberVM::getFileName(uint64_t index) const
{
if (version_ <= 4)
{
SAFE_CHECK(index != 0, "invalid file index 0");
FileName fn;
if (index <= v4_.fileNameCount)
{
std::string_view file_names = v4_.fileNames;
for (; index; --index)
{
if (!readFileName(file_names, fn))
{
abort();
}
}
return fn;
}
index -= v4_.fileNameCount;
std::string_view program = data_;
for (; index; --index)
{
SAFE_CHECK(nextDefineFile(program, fn), "invalid file index");
}
return fn;
}
else
{
FileName fn;
SAFE_CHECK(index < v5_.fileNamesCount, "invalid file index");
std::string_view file_names = v5_.fileNames;
for (uint64_t i = 0; i < v5_.fileNamesCount; i++)
{
std::string_view format = v5_.fileNameEntryFormat;
for (uint8_t f = 0; f < v5_.fileNameEntryFormatCount; f++)
{
auto attr = readLineNumberAttribute(is64Bit_, format, file_names, debugStr_, debugLineStr_);
if (i == index)
{
switch (attr.content_type_code)
{
case DW_LNCT_path:
fn.relativeName = std::get<std::string_view>(attr.attr_value);
break;
case DW_LNCT_directory_index:
fn.directoryIndex = std::get<uint64_t>(attr.attr_value);
break;
}
}
}
}
return fn;
}
}
std::string_view Dwarf::LineNumberVM::getIncludeDirectory(uint64_t index) const
{
if (version_ <= 4)
{
if (index == 0)
{
// In DWARF <= 4 the current directory is not represented in the
// directories field and a directory index of 0 implicitly referred to
// that directory as found in the DW_AT_comp_dir attribute of the
// compilation unit debugging information entry.
return {};
}
SAFE_CHECK(index <= v4_.includeDirectoryCount, "invalid include directory");
std::string_view include_directories = v4_.includeDirectories;
std::string_view dir;
for (; index; --index)
{
dir = readNullTerminated(include_directories);
if (dir.empty())
{
abort(); // BUG
}
}
return dir;
}
else
{
SAFE_CHECK(index < v5_.directoriesCount, "invalid file index");
std::string_view directories = v5_.directories;
for (uint64_t i = 0; i < v5_.directoriesCount; i++)
{
std::string_view format = v5_.directoryEntryFormat;
for (uint8_t f = 0; f < v5_.directoryEntryFormatCount; f++)
{
auto attr = readLineNumberAttribute(is64Bit_, format, directories, debugStr_, debugLineStr_);
if (i == index && attr.content_type_code == DW_LNCT_path)
{
return std::get<std::string_view>(attr.attr_value);
}
}
}
// This could only happen if DWARF5's directory_entry_format doesn't contain
// a DW_LNCT_path. Highly unlikely, but we shouldn't crash.
return std::string_view("<directory not found>");
}
}
bool Dwarf::LineNumberVM::readFileName(std::string_view & program, FileName & fn)
{
fn.relativeName = readNullTerminated(program);
if (fn.relativeName.empty())
{
return false;
}
fn.directoryIndex = readULEB(program);
// Skip over file size and last modified time
readULEB(program);
readULEB(program);
return true;
}
bool Dwarf::LineNumberVM::nextDefineFile(std::string_view & program, FileName & fn) const
{
while (!program.empty())
{
auto opcode = read<uint8_t>(program);
if (opcode >= opcodeBase_)
{ // special opcode
continue;
}
if (opcode != 0)
{ // standard opcode
// Skip, slurp the appropriate number of LEB arguments
uint8_t arg_count = standardOpcodeLengths_[opcode - 1];
while (arg_count--)
{
readULEB(program);
}
continue;
}
// Extended opcode
auto length = readULEB(program);
// the opcode itself should be included in the length, so length >= 1
SAFE_CHECK(length != 0, "invalid extended opcode length");
read<uint8_t>(program); // extended opcode
--length;
if (opcode == DW_LNE_define_file)
{
SAFE_CHECK(version_ < 5, "DW_LNE_define_file deprecated in DWARF5");
SAFE_CHECK(readFileName(program, fn), "invalid empty file in DW_LNE_define_file");
return true;
}
program.remove_prefix(length);
}
return false;
}
Dwarf::LineNumberVM::StepResult Dwarf::LineNumberVM::step(std::string_view & program)
{
auto opcode = read<uint8_t>(program);
if (opcode >= opcodeBase_)
{ // special opcode
uint8_t adjusted_opcode = opcode - opcodeBase_;
uint8_t op_advance = adjusted_opcode / lineRange_;
address_ += minLength_ * op_advance;
line_ += lineBase_ + adjusted_opcode % lineRange_;
basicBlock_ = false;
prologueEnd_ = false;
epilogueBegin_ = false;
discriminator_ = 0;
return COMMIT;
}
if (opcode != 0)
{ // standard opcode
// Only interpret opcodes that are recognized by the version we're parsing;
// the others are vendor extensions and we should ignore them.
switch (opcode)
{
case DW_LNS_copy:
basicBlock_ = false;
prologueEnd_ = false;
epilogueBegin_ = false;
discriminator_ = 0;
return COMMIT;
case DW_LNS_advance_pc:
address_ += minLength_ * readULEB(program);
return CONTINUE;
case DW_LNS_advance_line:
line_ += readSLEB(program);
return CONTINUE;
case DW_LNS_set_file:
file_ = readULEB(program);
return CONTINUE;
case DW_LNS_set_column:
column_ = readULEB(program);
return CONTINUE;
case DW_LNS_negate_stmt:
isStmt_ = !isStmt_;
return CONTINUE;
case DW_LNS_set_basic_block:
basicBlock_ = true;
return CONTINUE;
case DW_LNS_const_add_pc:
address_ += minLength_ * ((255 - opcodeBase_) / lineRange_);
return CONTINUE;
case DW_LNS_fixed_advance_pc:
address_ += read<uint16_t>(program);
return CONTINUE;
case DW_LNS_set_prologue_end:
if (version_ == 2)
{
break; // not supported in version 2
}
prologueEnd_ = true;
return CONTINUE;
case DW_LNS_set_epilogue_begin:
if (version_ == 2)
{
break; // not supported in version 2
}
epilogueBegin_ = true;
return CONTINUE;
case DW_LNS_set_isa:
if (version_ == 2)
{
break; // not supported in version 2
}
isa_ = readULEB(program);
return CONTINUE;
}
// Unrecognized standard opcode, slurp the appropriate number of LEB
// arguments.
uint8_t arg_count = standardOpcodeLengths_[opcode - 1];
while (arg_count--)
{
readULEB(program);
}
return CONTINUE;
}
// Extended opcode
auto length = readULEB(program);
// the opcode itself should be included in the length, so length >= 1
SAFE_CHECK(length != 0, "invalid extended opcode length");
auto extended_opcode = read<uint8_t>(program);
--length;
switch (extended_opcode)
{
case DW_LNE_end_sequence:
return END;
case DW_LNE_set_address:
address_ = read<uintptr_t>(program);
return CONTINUE;
case DW_LNE_define_file:
SAFE_CHECK(version_ < 5, "DW_LNE_define_file deprecated in DWARF5");
// We can't process DW_LNE_define_file here, as it would require us to
// use unbounded amounts of state (ie. use the heap). We'll do a second
// pass (using nextDefineFile()) if necessary.
break;
case DW_LNE_set_discriminator:
discriminator_ = readULEB(program);
return CONTINUE;
}
// Unrecognized extended opcode
program.remove_prefix(length);
return CONTINUE;
}
Dwarf::Path Dwarf::LineNumberVM::getFullFileName(uint64_t index) const
{
auto fn = getFileName(index);
// DWARF <= 4: the current dir is not represented in the CU's Line Number
// Program Header and relies on the CU's DW_AT_comp_dir.
// DWARF 5: the current directory is explicitly present.
const std::string_view base_dir = version_ == 5 ? "" : compilationDirectory_;
return Path(base_dir, getIncludeDirectory(fn.directoryIndex), fn.relativeName);
}
bool Dwarf::LineNumberVM::findAddress(uintptr_t target, Path & file, uint64_t & line)
{
std::string_view program = data_;
// Within each sequence of instructions, the address may only increase.
// Unfortunately, within the same compilation unit, sequences may appear
// in any order. So any sequence is a candidate if it starts at an address
// <= the target address, and we know we've found the target address if
// a candidate crosses the target address.
enum State
{
START,
LOW_SEQ, // candidate
HIGH_SEQ
};
State state = START;
reset();
uint64_t prev_file = 0;
uint64_t prev_line = 0;
while (!program.empty())
{
bool seq_end = !next(program);
if (state == START)
{
if (!seq_end)
{
state = address_ <= target ? LOW_SEQ : HIGH_SEQ;
}
}
if (state == LOW_SEQ)
{
if (address_ > target)
{
// Found it! Note that ">" is indeed correct (not ">="), as each
// sequence is guaranteed to have one entry past-the-end (emitted by
// DW_LNE_end_sequence)
//
// NOTE: In DWARF <= 4 the file register is non-zero.
// See DWARF 4: 6.2.4 The Line Number Program Header
// "The line number program assigns numbers to each of the file
// entries in order, beginning with 1, and uses those numbers instead
// of file names in the file register."
// DWARF 5 has a different include directory/file header and 0 is valid.
if (version_ <= 4 && prev_file == 0)
{
return false;
}
file = getFullFileName(prev_file);
line = prev_line;
return true;
}
prev_file = file_;
prev_line = line_;
}
if (seq_end)
{
state = START;
reset();
}
}
return false;
}
}
#endif
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