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rulimine/stage2/lib/elf.c

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C
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#include <stdint.h>
#include <stddef.h>
#include <lib/blib.h>
#include <lib/libc.h>
#include <lib/elf.h>
#include <lib/print.h>
#include <mm/pmm.h>
#include <fs/file.h>
#define PT_LOAD 0x00000001
#define PT_INTERP 0x00000003
#define PT_PHDR 0x00000006
#define ABI_SYSV 0x00
#define ARCH_X86_64 0x3e
#define ARCH_X86_32 0x03
#define BITS_LE 0x01
#define ET_DYN 0x0003
#define SHT_RELA 0x00000004
#define R_X86_64_RELATIVE 0x00000008
/* Indices into identification array */
#define EI_CLASS 4
#define EI_DATA 5
#define EI_VERSION 6
#define EI_OSABI 7
struct elf64_hdr {
uint8_t ident[16];
uint16_t type;
uint16_t machine;
uint32_t version;
uint64_t entry;
uint64_t phoff;
uint64_t shoff;
uint32_t flags;
uint16_t hdr_size;
uint16_t phdr_size;
uint16_t ph_num;
uint16_t shdr_size;
uint16_t sh_num;
uint16_t shstrndx;
};
struct elf32_hdr {
uint8_t ident[16];
uint16_t type;
uint16_t machine;
uint32_t version;
uint32_t entry;
uint32_t phoff;
uint32_t shoff;
uint32_t flags;
uint16_t hdr_size;
uint16_t phdr_size;
uint16_t ph_num;
uint16_t shdr_size;
uint16_t sh_num;
uint16_t shstrndx;
};
struct elf64_phdr {
uint32_t p_type;
uint32_t p_flags;
uint64_t p_offset;
uint64_t p_vaddr;
uint64_t p_paddr;
uint64_t p_filesz;
uint64_t p_memsz;
uint64_t p_align;
};
struct elf32_phdr {
uint32_t p_type;
uint32_t p_offset;
uint32_t p_vaddr;
uint32_t p_paddr;
uint32_t p_filesz;
uint32_t p_memsz;
uint32_t p_flags;
uint32_t p_align;
};
struct elf64_shdr {
uint32_t sh_name;
uint32_t sh_type;
uint64_t sh_flags;
uint64_t sh_addr;
uint64_t sh_offset;
uint64_t sh_size;
uint32_t sh_link;
uint32_t sh_info;
uint64_t sh_addralign;
uint64_t sh_entsize;
};
struct elf32_shdr {
uint32_t sh_name;
uint32_t sh_type;
uint32_t sh_flags;
uint32_t sh_addr;
uint32_t sh_offset;
uint32_t sh_size;
uint32_t sh_link;
uint32_t sh_info;
uint32_t sh_addralign;
uint32_t sh_entsize;
};
struct elf64_rela {
uint64_t r_addr;
uint32_t r_info;
uint32_t r_symbol;
uint64_t r_addend;
};
int elf_bits(struct file_handle *fd) {
struct elf64_hdr hdr;
fread(fd, &hdr, 0, 20);
if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
print("elf: Not a valid ELF file.\n");
return -1;
}
switch (hdr.machine) {
case ARCH_X86_64:
return 64;
case ARCH_X86_32:
return 32;
default:
return -1;
}
}
static int elf64_apply_relocations(struct file_handle *fd, struct elf64_hdr *hdr, void *buffer, uint64_t vaddr, size_t size, uint64_t slide) {
// Find RELA sections
for (uint16_t i = 0; i < hdr->sh_num; i++) {
struct elf64_shdr section;
fread(fd, &section, hdr->shoff + i * sizeof(struct elf64_shdr),
sizeof(struct elf64_shdr));
if (section.sh_type != SHT_RELA)
continue;
if (section.sh_entsize != sizeof(struct elf64_rela)) {
print("elf: Unknown sh_entsize for RELA section!\n");
return 1;
}
// This is a RELA header, get and apply all relocations
for (uint64_t offset = 0; offset < section.sh_size; offset += section.sh_entsize) {
struct elf64_rela relocation;
fread(fd, &relocation, section.sh_offset + offset, sizeof(relocation));
switch (relocation.r_info) {
case R_X86_64_RELATIVE:
// Relocation is before buffer
if (relocation.r_addr < vaddr)
continue;
// Relocation is after buffer
if (vaddr + size < relocation.r_addr + 8)
continue;
// It's inside it, calculate where it is
uint64_t *ptr = (uint64_t *)((uint8_t *)buffer - vaddr + relocation.r_addr);
// Write the relocated value
*ptr = slide + relocation.r_addend;
break;
default:
print("elf: Unknown RELA type: %X\n", relocation.r_info);
return 1;
}
}
}
return 0;
}
int elf64_load_section(struct file_handle *fd, void *buffer, const char *name, size_t limit, uint64_t slide) {
struct elf64_hdr hdr;
fread(fd, &hdr, 0, sizeof(struct elf64_hdr));
if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
print("elf: Not a valid ELF file.\n");
return 1;
}
if (hdr.ident[EI_DATA] != BITS_LE) {
print("elf: Not a Little-endian ELF file.\n");
return 1;
}
if (hdr.machine != ARCH_X86_64) {
print("elf: Not an x86_64 ELF file.\n");
return 1;
}
struct elf64_shdr shstrtab;
fread(fd, &shstrtab, hdr.shoff + hdr.shstrndx * sizeof(struct elf64_shdr),
sizeof(struct elf64_shdr));
char *names = ext_mem_alloc(shstrtab.sh_size);
fread(fd, names, shstrtab.sh_offset, shstrtab.sh_size);
for (uint16_t i = 0; i < hdr.sh_num; i++) {
struct elf64_shdr section;
fread(fd, &section, hdr.shoff + i * sizeof(struct elf64_shdr),
sizeof(struct elf64_shdr));
if (!strcmp(&names[section.sh_name], name)) {
if (section.sh_size > limit)
return 3;
if (section.sh_size < limit)
return 4;
fread(fd, buffer, section.sh_offset, section.sh_size);
return elf64_apply_relocations(fd, &hdr, buffer, section.sh_addr, section.sh_size, slide);
}
}
return 2;
}
int elf32_load_section(struct file_handle *fd, void *buffer, const char *name, size_t limit) {
struct elf32_hdr hdr;
fread(fd, &hdr, 0, sizeof(struct elf32_hdr));
if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
print("elf: Not a valid ELF file.\n");
return 1;
}
if (hdr.ident[EI_DATA] != BITS_LE) {
print("elf: Not a Little-endian ELF file.\n");
return 1;
}
if (hdr.machine != ARCH_X86_32) {
print("elf: Not an x86_32 ELF file.\n");
return 1;
}
struct elf32_shdr shstrtab;
fread(fd, &shstrtab, hdr.shoff + hdr.shstrndx * sizeof(struct elf32_shdr),
sizeof(struct elf32_shdr));
char *names = ext_mem_alloc(shstrtab.sh_size);
fread(fd, names, shstrtab.sh_offset, shstrtab.sh_size);
for (uint16_t i = 0; i < hdr.sh_num; i++) {
struct elf32_shdr section;
fread(fd, &section, hdr.shoff + i * sizeof(struct elf32_shdr),
sizeof(struct elf32_shdr));
if (!strcmp(&names[section.sh_name], name)) {
if (section.sh_size > limit)
return 3;
if (section.sh_size < limit)
return 4;
fread(fd, buffer, section.sh_offset, section.sh_size);
return 0;
}
}
return 2;
}
int elf64_load(struct file_handle *fd, uint64_t *entry_point, uint64_t *top, uint64_t slide, uint32_t alloc_type) {
struct elf64_hdr hdr;
fread(fd, &hdr, 0, sizeof(struct elf64_hdr));
if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
print("Not a valid ELF file.\n");
return -1;
}
if (hdr.ident[EI_DATA] != BITS_LE) {
print("Not a Little-endian ELF file.\n");
return -1;
}
if (hdr.machine != ARCH_X86_64) {
print("Not an x86_64 ELF file.\n");
return -1;
}
*top = 0;
for (uint16_t i = 0; i < hdr.ph_num; i++) {
struct elf64_phdr phdr;
fread(fd, &phdr, hdr.phoff + i * sizeof(struct elf64_phdr),
sizeof(struct elf64_phdr));
if (phdr.p_type != PT_LOAD)
continue;
uint64_t load_vaddr = phdr.p_vaddr;
if (load_vaddr & ((uint64_t)1 << 63))
load_vaddr -= FIXED_HIGHER_HALF_OFFSET_64;
load_vaddr += slide;
uint64_t this_top = load_vaddr + phdr.p_memsz;
if (this_top > *top)
*top = this_top;
memmap_alloc_range((size_t)load_vaddr, (size_t)phdr.p_memsz, alloc_type, true);
fread(fd, (void *)(uint32_t)load_vaddr, phdr.p_offset, phdr.p_filesz);
size_t to_zero = (size_t)(phdr.p_memsz - phdr.p_filesz);
if (to_zero) {
void *ptr = (void *)(uint32_t)(load_vaddr + phdr.p_filesz);
memset(ptr, 0, to_zero);
}
if (elf64_apply_relocations(fd, &hdr, (void *)(uint32_t)load_vaddr, phdr.p_vaddr, phdr.p_memsz, slide))
return -1;
}
*entry_point = hdr.entry + slide;
return 0;
}
int elf32_load(struct file_handle *fd, uint32_t *entry_point, uint32_t *top, uint32_t alloc_type) {
struct elf32_hdr hdr;
fread(fd, &hdr, 0, sizeof(struct elf32_hdr));
if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
print("Not a valid ELF file.\n");
return -1;
}
if (hdr.ident[EI_DATA] != BITS_LE) {
print("Not a Little-endian ELF file.\n");
return -1;
}
if (hdr.machine != ARCH_X86_32) {
print("Not an x86_32 ELF file.\n");
return -1;
}
*top = 0;
for (uint16_t i = 0; i < hdr.ph_num; i++) {
struct elf32_phdr phdr;
fread(fd, &phdr, hdr.phoff + i * sizeof(struct elf32_phdr),
sizeof(struct elf32_phdr));
if (phdr.p_type != PT_LOAD)
continue;
uint32_t this_top = phdr.p_vaddr + phdr.p_memsz;
if (this_top > *top)
*top = this_top;
memmap_alloc_range((size_t)phdr.p_paddr, (size_t)phdr.p_memsz, alloc_type, true);
fread(fd, (void *)phdr.p_paddr, phdr.p_offset, phdr.p_filesz);
size_t to_zero = (size_t)(phdr.p_memsz - phdr.p_filesz);
if (to_zero) {
void *ptr = (void *)(phdr.p_paddr + phdr.p_filesz);
memset(ptr, 0, to_zero);
}
}
*entry_point = hdr.entry;
return 0;
}
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