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Better PHDR cache

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This commit is contained in:
Alexey Milovidov 2019-07-24 18:35:19 +03:00
parent cc7fe5fb8d
commit 796dfeb44e
1 changed files with 14 additions and 10 deletions
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24
libs/libcommon/src/phdr_cache.cpp
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@ -2,11 +2,11 @@
#include <link.h>
#include <dlfcn.h>
#include <assert.h>
#include <vector>
#include <array>
#include <cstddef>
#include <stdexcept>
namespace
{
@ -24,9 +24,11 @@ DLIterateFunction getOriginalDLIteratePHDR()
return reinterpret_cast<DLIterateFunction>(func);
}
// Never destroyed to avoid races with static destructors.
using PHDRCache = std::vector<dl_phdr_info>;
PHDRCache * phdr_cache;
constexpr size_t phdr_cache_max_size = 128;
size_t phdr_cache_size = 0;
using PHDRCache = std::array<dl_phdr_info, phdr_cache_max_size>;
PHDRCache phdr_cache;
}
@ -38,16 +40,16 @@ extern "C"
#endif
int dl_iterate_phdr(int (*callback) (dl_phdr_info * info, size_t size, void * data), void * data)
{
if (!phdr_cache)
if (0 == phdr_cache_size)
{
// Cache is not yet populated, pass through to the original function.
return getOriginalDLIteratePHDR()(callback, data);
}
int result = 0;
for (auto & info : *phdr_cache)
for (size_t i = 0; i < phdr_cache_size; ++i)
{
result = callback(&info, offsetof(dl_phdr_info, dlpi_adds), data);
result = callback(&phdr_cache[i], offsetof(dl_phdr_info, dlpi_adds), data);
if (result != 0)
break;
}
@ -60,10 +62,12 @@ void enablePHDRCache()
#if defined(__linux__)
// Fill out ELF header cache for access without locking.
// This assumes no dynamic object loading/unloading after this point
phdr_cache = new PHDRCache;
getOriginalDLIteratePHDR()([] (dl_phdr_info * info, size_t /*size*/, void * /*data*/)
{
phdr_cache->push_back(*info);
if (phdr_cache_size >= phdr_cache_max_size)
throw std::runtime_error("phdr_cache_max_size is not enough to accomodate the result of dl_iterate_phdr. You must recompile the code.");
phdr_cache[phdr_cache_size] = *info;
++phdr_cache_size;
return 0;
}, nullptr);
#endif