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chore: shorten change
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Signed-off-by: Darshan Sen <raisinten@gmail.com>
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RaisinTen committed Mar 2, 2023
1 parent 35a279f commit 2b7cbdd
Showing 1 changed file with 46 additions and 55 deletions.
101 changes: 46 additions & 55 deletions postject-api.h
Original file line number Diff line number Diff line change
Expand Up @@ -44,55 +44,11 @@ static inline bool postject_has_resource() {
}

#if defined(__linux__)
struct postject__dl_iterate_phdr_data {
void* data;
size_t size;
const char* elf_section_name;
size_t elf_section_name_size;
};

static int postject__dl_iterate_phdr_callback(struct dl_phdr_info* info,
size_t size,
void* opaque) {
struct postject__dl_iterate_phdr_data* data =
(struct postject__dl_iterate_phdr_data*)opaque;

// iterate program headers
for (unsigned i = 0; i < info->dlpi_phnum; i++) {
// skip everything but notes
if (info->dlpi_phdr[i].p_type != PT_NOTE)
continue;

// note segment starts at base address + segment virtual address
uintptr_t pos = (info->dlpi_addr + info->dlpi_phdr[i].p_vaddr);
uintptr_t end = (pos + info->dlpi_phdr[i].p_memsz);

// iterate through segment until we reach the end
while (pos < end) {
if (pos + sizeof(ElfW(Nhdr)) > end) {
break; // invalid
}

ElfW(Nhdr)* note = (ElfW(Nhdr)*)(uintptr_t)pos;
if (note->n_namesz != 0 && note->n_descsz != 0 &&
strncmp((char*)(pos + sizeof(ElfW(Nhdr))), data->elf_section_name,
data->elf_section_name_size) == 0) {
data->size = note->n_descsz;
// advance past note header and aligned name
// to get to description data
data->data = (void*)((uintptr_t)note + sizeof(ElfW(Nhdr)) +
roundup(note->n_namesz, 4));
// found the note, so terminate the search by returning 1
return 1;
}

pos += (sizeof(ElfW(Nhdr)) + roundup(note->n_namesz, 4) +
roundup(note->n_descsz, 4));
}
}

// wasn't able to find the note in the main executable program headers, so
// terminate the search
void* data) {
// Snag the dl_phdr_info struct for the main program, then stop iterating
*((struct dl_phdr_info*)data) = *info;
return 1;
}
#endif
Expand Down Expand Up @@ -167,14 +123,49 @@ static const void* postject_find_resource(
name = options->elf_section_name;
}

struct postject__dl_iterate_phdr_data data;
data.data = NULL;
data.size = 0;
data.elf_section_name = name;
data.elf_section_name_size = sizeof(name);
dl_iterate_phdr(postject__dl_iterate_phdr_callback, &data);
*size = data.size;
return data.data;
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))) {
ElfW(Phdr)* phdr = (ElfW(Phdr)*)p;

// skip everything but notes
if (phdr->p_type != PT_NOTE) {
continue;
}

// note segment starts at base address + segment virtual address
uintptr_t pos = (base_addr + phdr->p_vaddr);
uintptr_t end = (pos + phdr->p_memsz);

// iterate through segment until we reach the end
while (pos < end) {
if (pos + sizeof(ElfW(Nhdr)) > end) {
break; // invalid
}

ElfW(Nhdr)* note = (ElfW(Nhdr)*)(uintptr_t)pos;
if (note->n_namesz != 0 && note->n_descsz != 0 &&
strncmp((char*)(pos + sizeof(ElfW(Nhdr))), (char*)name,
sizeof(name)) == 0) {
*size = note->n_descsz;
// advance past note header and aligned name
// to get to description data
return (void*)((uintptr_t)note + sizeof(ElfW(Nhdr)) +
roundup(note->n_namesz, 4));
}

pos += (sizeof(ElfW(Nhdr)) + roundup(note->n_namesz, 4) +
roundup(note->n_descsz, 4));
}
}
return NULL;

#elif defined(_WIN32)
void* ptr = NULL;
char* resource_name = NULL;
Expand Down

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