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Avoid possibly concurrent reassignment of dl_iterate_phdr.

This commit is contained in:
A.J. Beamon 2019-01-24 13:28:45 -08:00
parent efe06d71ce
commit 7fde75c439
1 changed files with 8 additions and 3 deletions
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11
flow/SignalSafeUnwind.cpp
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@ -25,13 +25,14 @@ int64_t dl_iterate_phdr_calls = 0;
#ifdef __linux__
#include <link.h>
#include <mutex>
static bool phdr_cache_initialized = false;
static std::vector< std::vector<uint8_t> > phdr_cache;
static int (*chain_dl_iterate_phdr)(
int (*callback) (struct dl_phdr_info *info, size_t size, void *data),
void *data) = 0;
void *data) = nullptr;
static int phdr_cache_add( struct dl_phdr_info *info, size_t size, void *data ) {
phdr_cache.push_back( std::vector<uint8_t>((uint8_t*)info, (uint8_t*)info + size) );
@ -39,11 +40,15 @@ static int phdr_cache_add( struct dl_phdr_info *info, size_t size, void *data )
}
static void initChain() {
static std::once_flag flag;
// Ensure that chain_dl_iterate_phdr points to the "real" function that we are overriding
*(void**)&chain_dl_iterate_phdr = dlsym(RTLD_NEXT, "dl_iterate_phdr");
if (!chain_dl_iterate_phdr)
std::call_once(flag, [](){ *(void**)&chain_dl_iterate_phdr = dlsym(RTLD_NEXT, "dl_iterate_phdr"); });
if (!chain_dl_iterate_phdr) {
criticalError(FDB_EXIT_ERROR, "SignalSafeUnwindError", "Unable to find dl_iterate_phdr symbol");
}
}
void initSignalSafeUnwind() {
initChain();