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fix: crash in postject_find_resource() on Linux #77

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merged 5 commits into from
Mar 3, 2023
Merged

fix: crash in postject_find_resource() on Linux #77

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e08d9e4
fix: crash in `postject_find_resource()` on Linux
RaisinTen Feb 27, 2023
19ab453
chore: remove unnecessary if block
RaisinTen Feb 28, 2023
35a279f
fix: only iterate the main executable program headers
RaisinTen Mar 2, 2023
2b7cbdd
chore: shorten change
RaisinTen Mar 2, 2023
e656bc6
test: add comment about _GNU_SOURCE
RaisinTen Mar 2, 2023
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20 changes: 16 additions & 4 deletions postject-api.h
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,6 @@
#elif defined(__linux__)
#include <elf.h>
#include <link.h>
#include <sys/auxv.h>
#include <sys/param.h>
#elif defined(_WIN32)
#include <windows.h>
Expand Down Expand Up @@ -44,6 +43,16 @@ static inline bool postject_has_resource() {
return sentinel[sizeof(POSTJECT_SENTINEL_FUSE)] == '1';
}

#if defined(__linux__)
static int postject__dl_iterate_phdr_callback(struct dl_phdr_info* info,
size_t size,
void* data) {
// Snag the dl_phdr_info struct for the main program, then stop iterating
*((struct dl_phdr_info*)data) = *info;
return 1;
}
#endif

static const void* postject_find_resource(
const char* name,
size_t* size,
Expand Down Expand Up @@ -114,9 +123,12 @@ static const void* postject_find_resource(
name = options->elf_section_name;
}

uintptr_t p = getauxval(AT_PHDR);
size_t n = getauxval(AT_PHNUM);
uintptr_t base_addr = p - sizeof(ElfW(Ehdr));
struct dl_phdr_info main_program_info;
dl_iterate_phdr(postject__dl_iterate_phdr_callback, &main_program_info);

uintptr_t p = (uintptr_t)main_program_info.dlpi_phdr;
size_t n = main_program_info.dlpi_phnum;
uintptr_t base_addr = main_program_info.dlpi_addr;

// iterate program header
for (; n > 0; n--, p += sizeof(ElfW(Phdr))) {
Expand Down
4 changes: 4 additions & 0 deletions test/test.c
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Original file line number Diff line number Diff line change
@@ -1,3 +1,7 @@
#define _GNU_SOURCE // This is needed because postject-api.h uses
// dl_iterate_phdr and dl_phdr_info which are non-standard
// GNU extensions.

#include <stdio.h>
#include <string.h>

Expand Down