You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
78 lines
2.6 KiB
C++
78 lines
2.6 KiB
C++
4 years ago
|
#include "elf_load.hpp"
|
||
|
|
#include "elf_format.hpp"
|
||
|
|
|
||
|
|
#include <algorithm>
|
||
|
|
#include <cstring>
|
||
|
|
|
||
|
|
extern void *elf_load_offset;
|
||
|
|
static const unsigned char elf_header[] = { '\177', 'E', 'L', 'F' };
|
||
|
|
|
||
|
|
template<typename T>
|
||
|
|
constexpr static auto ptr_from_offset(void *base, uint32_t offset)
|
||
|
|
{
|
||
|
|
return reinterpret_cast<T>(reinterpret_cast<uint8_t *>(base) + offset);
|
||
|
|
}
|
||
|
|
|
||
|
|
static Elf32_Shdr *find_section(Elf32_Ehdr *ehdr, const char *name);
|
||
|
|
|
||
|
|
namespace elf {
|
||
|
|
|
||
|
|
entry_t elf_load(void *elf_data)
|
||
|
|
{
|
||
|
|
auto ehdr = reinterpret_cast<Elf32_Ehdr *>(elf_data);
|
||
|
|
if (std::equal(ehdr->e_ident, ehdr->e_ident + 4, elf_header))
|
||
|
|
return nullptr;
|
||
|
|
|
||
|
|
auto phdr = ptr_from_offset<Elf32_Phdr *>(elf_data, ehdr->e_phoff);
|
||
|
|
for (Elf32_Half i = 0; i < ehdr->e_phnum; i++) {
|
||
|
|
if (phdr->p_type == PT_LOAD) {
|
||
|
|
std::memcpy(ptr_from_offset<void *>(elf_load_offset, phdr->p_vaddr),
|
||
|
|
ptr_from_offset<void *>(elf_data, phdr->p_offset),
|
||
|
|
phdr->p_filesz);
|
||
|
|
//break;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Zero .bss section
|
||
|
|
if (auto bss_section = find_section(ehdr, ".bss"); bss_section) {
|
||
|
|
auto bss = ptr_from_offset<uint32_t *>(elf_load_offset, bss_section->sh_addr);
|
||
|
|
std::fill(bss, bss + bss_section->sh_size / sizeof(uint32_t), 0);
|
||
|
|
}
|
||
|
|
|
||
|
|
// Fix global offset table (GOT) entries
|
||
|
|
if (auto got_section = find_section(ehdr, ".got"); got_section) {
|
||
|
|
auto got = ptr_from_offset<void **>(elf_load_offset, got_section->sh_addr);
|
||
|
|
for (size_t i = 0; i < got_section->sh_size / sizeof(void *); i++)
|
||
|
|
got[i] = ptr_from_offset<void *>(got[i], reinterpret_cast<uint32_t>(elf_load_offset));
|
||
|
|
}
|
||
|
|
|
||
|
|
//// Run any initial constructors
|
||
|
|
//if (auto init_section = find_section(ehdr, ".init_array"); init_section) {
|
||
|
|
// auto init_array = reinterpret_cast<void (**)()>(elf_load_offset + init_section->sh_addr);
|
||
|
|
// std::for_each(init_array, init_array + init_section->sh_size / sizeof(void (*)()),
|
||
|
|
// [elf_load_offset](auto func) { (func + elf_load_offset)(); });
|
||
|
|
//}
|
||
|
|
|
||
|
|
return ptr_from_offset<entry_t>(elf_load_offset, ehdr->e_entry);
|
||
|
|
}
|
||
|
|
|
||
|
|
} // namespace elf
|
||
|
|
|
||
|
|
Elf32_Shdr *find_section(Elf32_Ehdr *ehdr, const char *name)
|
||
|
|
{
|
||
|
|
auto shdr = ptr_from_offset<Elf32_Shdr *>(ehdr, ehdr->e_shoff);
|
||
|
|
auto shdr_str = ptr_from_offset<Elf32_Shdr *>(ehdr,
|
||
|
|
ehdr->e_shoff + ehdr->e_shstrndx * ehdr->e_shentsize);
|
||
|
|
|
||
|
|
for (Elf32_Half i = 0; i < ehdr->e_shnum; i++) {
|
||
|
|
char *section = ptr_from_offset<char *>(ehdr, shdr_str->sh_offset) + shdr->sh_name;
|
||
|
|
if (!strcmp(section, name))
|
||
|
|
return shdr;
|
||
|
|
|
||
|
|
shdr = ptr_from_offset<Elf32_Shdr *>(shdr, ehdr->e_shentsize);
|
||
|
|
}
|
||
|
|
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|