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postject-api.h
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postject-api.h
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#ifndef POSTJECT_API_H_
#define POSTJECT_API_H_
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#if defined(__APPLE__) && defined(__MACH__)
#include <mach-o/dyld.h>
#include <mach-o/getsect.h>
#elif defined(__linux__)
#include <elf.h>
#include <link.h>
#include <sys/auxv.h>
#include <sys/param.h>
#elif defined(_WIN32)
#include <windows.h>
#endif
struct postject_options {
const char* elf_section_name;
const char* macho_framework_name;
const char* macho_section_name;
const char* macho_segment_name;
const char* pe_resource_name;
};
inline void postject_options_init(struct postject_options* options) {
options->elf_section_name = NULL;
options->macho_framework_name = NULL;
options->macho_section_name = NULL;
options->macho_segment_name = NULL;
options->pe_resource_name = NULL;
}
static const void* postject_find_resource(
const char* name,
size_t* size,
const struct postject_options* options) {
// Always zero out the size pointer to start
if (size != NULL) {
*size = 0;
}
#if defined(__APPLE__) && defined(__MACH__)
char* section_name = NULL;
const char* segment_name = "__POSTJECT";
if (options != NULL && options->macho_segment_name != NULL) {
segment_name = options->macho_segment_name;
}
if (options != NULL && options->macho_section_name != NULL) {
name = options->macho_section_name;
} else if (strncmp(name, "__", 2) != 0) {
// Automatically prepend __ to match naming convention
section_name = (char*)malloc(strlen(name) + 3);
if (section_name == NULL) {
return NULL;
}
strcpy(section_name, "__");
strcat(section_name, name);
}
unsigned long section_size;
char* ptr = NULL;
if (options != NULL && options->macho_framework_name != NULL) {
ptr = getsectdatafromFramework(options->macho_framework_name, segment_name,
section_name != NULL ? section_name : name,
§ion_size);
} else {
ptr = getsectdata(segment_name, section_name != NULL ? section_name : name,
§ion_size);
if (ptr != NULL) {
// Add the "virtual memory address slide" amount to ensure a valid pointer
// in cases where the virtual memory address have been adjusted by the OS.
//
// NOTE - `getsectdataFromFramework` already handles this adjustment for
// us, which is why we only do it for `getsectdata`, see:
// https://web.archive.org/web/20220613234007/https://opensource.apple.com/source/cctools/cctools-590/libmacho/getsecbyname.c.auto.html
ptr += _dyld_get_image_vmaddr_slide(0);
}
}
free(section_name);
if (size != NULL) {
*size = (size_t)section_size;
}
return ptr;
#elif defined(__linux__)
if (options != NULL && options->elf_section_name != NULL) {
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));
// 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;
if (options != NULL && options->pe_resource_name != NULL) {
name = options->pe_resource_name;
} else {
// Automatically uppercase the resource name or it won't be found
resource_name = (char*)malloc(strlen(name) + 1);
if (resource_name == NULL) {
return NULL;
}
strcpy_s(resource_name, strlen(name) + 1, name);
CharUpperA(resource_name); // Uppercases inplace
}
HRSRC resource_handle =
FindResourceA(NULL, resource_name != NULL ? resource_name : name,
MAKEINTRESOURCEA(10) /* RT_RCDATA */);
if (resource_handle) {
HGLOBAL global_resource_handle = LoadResource(NULL, resource_handle);
if (global_resource_handle) {
if (size != NULL) {
*size = SizeofResource(NULL, resource_handle);
}
ptr = LockResource(global_resource_handle);
}
}
free(resource_name);
return ptr;
#else
return NULL;
#endif
}
#endif // POSTJECT_API_H_