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#include "elf.h"
bool elf64_validate(Elf64_Ehdr *ehdr, unsigned type, unsigned machine)
{
if (ehdr->e_ident[EI_MAG0] != ELFMAG0 ||
ehdr->e_ident[EI_MAG1] != ELFMAG1 ||
ehdr->e_ident[EI_MAG2] != ELFMAG2 ||
ehdr->e_ident[EI_MAG3] != ELFMAG3 ||
ehdr->e_ident[EI_CLASS] != ELFCLASS64 ||
ehdr->e_ident[EI_DATA] != ELFDATA2LSB ||
ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
ehdr->e_machine != machine ||
ehdr->e_type != type)
{
return false;
}
return true;
}
size_t elf64_size(Elf64_Ehdr *ehdr, Elf64_Phdr *phdrs)
{
size_t size = 0;
for (int i = 0; i < ehdr->e_phnum; i++)
{
if (phdrs[i].p_type != PT_LOAD)
{
continue;
}
if (phdrs[i].p_paddr + phdrs[i].p_memsz > size)
{
size = phdrs[i].p_paddr + phdrs[i].p_memsz;
if (phdrs[i].p_align > 1)
{
size = (size + phdrs[i].p_align - 1) &
~(phdrs[i].p_align - 1);
}
}
}
return size;
}
void elf64_reloc(Elf64_Ehdr *ehdr)
{
// locate the dynamic segment
Elf64_Phdr *phdrs = (Elf64_Phdr *)(ehdr->e_phoff + (uintptr_t)ehdr);
Elf64_Dyn *dyn = NULL;
Elf64_Rela *rela = NULL;
size_t rela_size;
int rela_count;
for (int i = 0; i < ehdr->e_phnum; i++)
{
if (phdrs[i].p_type != PT_DYNAMIC) continue;
dyn = (Elf64_Dyn *)(phdrs[i].p_offset + (uintptr_t)ehdr);
}
// parse the dynamic segment
while (dyn->d_tag != DT_NULL)
{
switch (dyn->d_tag)
{
case DT_RELA:
rela = (Elf64_Rela *)(dyn->d_ptr + (uintptr_t)ehdr);
break;
case DT_RELASZ:
rela_size = dyn->d_val;
break;
case DT_RELAENT:
rela_count = rela_size / dyn->d_val;
break;
default:
break;
}
dyn++;
}
// perform the actual relocations
for (int i; i < rela_count; i++)
{
union
{
Elf_Byte word8;
Elf64_Half word16;
Elf64_Word word32;
Elf64_Xword word64;
}
*reloc_ptr = NULL;
switch (ELF64_R_TYPE(rela[i].r_info))
{
case R_AMD64_RELATIVE:
reloc_ptr = (void *)(rela[i].r_offset + (uintptr_t)ehdr);
reloc_ptr->word64 = (rela[i].r_addend + (uintptr_t)ehdr);
break;
default:
break;
}
}
}
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