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rulimine/common/lib/elf.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 <lib/rand.h>
#include <mm/pmm.h>
#include <fs/file.h>
#define PT_LOAD 0x00000001
#define PT_DYNAMIC 0x00000002
#define PT_INTERP 0x00000003
#define PT_PHDR 0x00000006
#define DT_NULL 0x00000000
#define DT_NEEDED 0x00000001
#define DT_RELA 0x00000007
#define DT_RELASZ 0x00000008
#define DT_RELAENT 0x00000009
#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 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 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;
};
struct elf64_dyn {
uint64_t d_tag;
uint64_t d_un;
};
int elf_bits(uint8_t *elf) {
struct elf64_hdr hdr;
memcpy(&hdr, elf + (0), 20);
if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
printv("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 bool elf64_is_relocatable(uint8_t *elf, struct elf64_hdr *hdr) {
if (hdr->phdr_size < sizeof(struct elf64_phdr)) {
panic(true, "elf: phdr_size < sizeof(struct elf64_phdr)");
}
// Find DYN segment
for (uint16_t i = 0; i < hdr->ph_num; i++) {
struct elf64_phdr phdr;
memcpy(&phdr, elf + (hdr->phoff + i * hdr->phdr_size),
sizeof(struct elf64_phdr));
if (phdr.p_type != PT_DYNAMIC) {
continue;
}
for (uint16_t j = 0; j < phdr.p_filesz / sizeof(struct elf64_dyn); j++) {
struct elf64_dyn dyn;
memcpy(&dyn, elf + (phdr.p_offset + j * sizeof(struct elf64_dyn)),
sizeof(struct elf64_dyn));
switch (dyn.d_tag) {
case DT_RELA:
return true;
}
}
}
return false;
}
static int elf64_apply_relocations(uint8_t *elf, struct elf64_hdr *hdr, void *buffer, uint64_t vaddr, size_t size, uint64_t slide) {
if (hdr->phdr_size < sizeof(struct elf64_phdr)) {
panic(true, "elf: phdr_size < sizeof(struct elf64_phdr)");
}
// Find DYN segment
for (uint16_t i = 0; i < hdr->ph_num; i++) {
struct elf64_phdr phdr;
memcpy(&phdr, elf + (hdr->phoff + i * hdr->phdr_size),
sizeof(struct elf64_phdr));
if (phdr.p_type != PT_DYNAMIC)
continue;
uint64_t rela_offset = 0;
uint64_t rela_size = 0;
uint64_t rela_ent = 0;
for (uint16_t j = 0; j < phdr.p_filesz / sizeof(struct elf64_dyn); j++) {
struct elf64_dyn dyn;
memcpy(&dyn, elf + (phdr.p_offset + j * sizeof(struct elf64_dyn)),
sizeof(struct elf64_dyn));
switch (dyn.d_tag) {
case DT_RELA:
rela_offset = dyn.d_un;
break;
case DT_RELAENT:
rela_ent = dyn.d_un;
break;
case DT_RELASZ:
rela_size = dyn.d_un;
break;
}
}
if (rela_offset == 0) {
break;
}
if (rela_ent != sizeof(struct elf64_rela)) {
print("elf: Unknown sh_entsize for RELA section!\n");
return 1;
}
for (uint16_t j = 0; j < hdr->ph_num; j++) {
struct elf64_phdr _phdr;
memcpy(&_phdr, elf + (hdr->phoff + j * hdr->phdr_size),
sizeof(struct elf64_phdr));
if (_phdr.p_vaddr <= rela_offset && _phdr.p_vaddr + _phdr.p_filesz > rela_offset) {
rela_offset -= _phdr.p_vaddr;
rela_offset += _phdr.p_offset;
break;
}
}
// This is a RELA header, get and apply all relocations
for (uint64_t offset = 0; offset < rela_size; offset += rela_ent) {
struct elf64_rela relocation;
memcpy(&relocation, elf + (rela_offset + offset), sizeof(struct elf64_rela));
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;
}
}
break;
}
return 0;
}
int elf64_load_section(uint8_t *elf, void *buffer, const char *name, size_t limit, uint64_t slide) {
struct elf64_hdr hdr;
memcpy(&hdr, elf + (0), sizeof(struct elf64_hdr));
if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
printv("elf: Not a valid ELF file.\n");
return 1;
}
if (hdr.ident[EI_DATA] != BITS_LE) {
printv("elf: Not a Little-endian ELF file.\n");
return 1;
}
if (hdr.machine != ARCH_X86_64) {
printv("elf: Not an x86_64 ELF file.\n");
return 1;
}
if (hdr.shdr_size < sizeof(struct elf64_shdr)) {
panic(true, "elf: shdr_size < sizeof(struct elf64_shdr)");
}
struct elf64_shdr shstrtab;
memcpy(&shstrtab, elf + (hdr.shoff + hdr.shstrndx * hdr.shdr_size),
sizeof(struct elf64_shdr));
char *names = ext_mem_alloc(shstrtab.sh_size);
memcpy(names, elf + (shstrtab.sh_offset), shstrtab.sh_size);
int ret;
for (uint16_t i = 0; i < hdr.sh_num; i++) {
struct elf64_shdr section;
memcpy(&section, elf + (hdr.shoff + i * hdr.shdr_size),
sizeof(struct elf64_shdr));
if (!strcmp(&names[section.sh_name], name)) {
if (limit == 0) {
*(void **)buffer = ext_mem_alloc(section.sh_size);
buffer = *(void **)buffer;
limit = section.sh_size;
}
if (section.sh_size > limit) {
ret = 3;
goto out;
}
if (section.sh_size < limit) {
ret = 4;
goto out;
}
memcpy(buffer, elf + (section.sh_offset), section.sh_size);
ret = elf64_apply_relocations(elf, &hdr, buffer, section.sh_addr, section.sh_size, slide);
goto out;
}
}
ret = 2;
out:
pmm_free(names, shstrtab.sh_size);
return ret;
}
/// SAFETY: The caller must ensure that the provided `elf` is a valid 64-bit
/// ELF file.
struct elf_section_hdr_info* elf64_section_hdr_info(uint8_t *elf) {
struct elf_section_hdr_info* info = ext_mem_alloc(sizeof(struct elf_section_hdr_info));
struct elf64_hdr hdr;
memcpy(&hdr, elf + (0), sizeof(struct elf64_hdr));
info->num = hdr.sh_num;
info->section_entry_size = hdr.shdr_size;
info->str_section_idx = hdr.shstrndx;
info->section_offset = hdr.shoff;
return info;
}
/// SAFETY: The caller must ensure that the provided `elf` is a valid 32-bit
/// ELF file.
struct elf_section_hdr_info* elf32_section_hdr_info(uint8_t *elf) {
struct elf_section_hdr_info* info = ext_mem_alloc(sizeof(struct elf_section_hdr_info));
struct elf32_hdr hdr;
memcpy(&hdr, elf + (0), sizeof(struct elf32_hdr));
info->num = hdr.sh_num;
info->section_entry_size = hdr.shdr_size;
info->str_section_idx = hdr.shstrndx;
info->section_offset = hdr.shoff;
return info;
}
int elf32_load_section(uint8_t *elf, void *buffer, const char *name, size_t limit) {
struct elf32_hdr hdr;
memcpy(&hdr, elf + (0), sizeof(struct elf32_hdr));
if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
printv("elf: Not a valid ELF file.\n");
return 1;
}
if (hdr.ident[EI_DATA] != BITS_LE) {
printv("elf: Not a Little-endian ELF file.\n");
return 1;
}
if (hdr.machine != ARCH_X86_32) {
printv("elf: Not an x86_32 ELF file.\n");
return 1;
}
if (hdr.shdr_size < sizeof(struct elf32_shdr)) {
panic(true, "elf: shdr_size < sizeof(struct elf32_shdr)");
}
struct elf32_shdr shstrtab;
memcpy(&shstrtab, elf + (hdr.shoff + hdr.shstrndx * hdr.shdr_size),
sizeof(struct elf32_shdr));
char *names = ext_mem_alloc(shstrtab.sh_size);
memcpy(names, elf + (shstrtab.sh_offset), shstrtab.sh_size);
int ret;
for (uint16_t i = 0; i < hdr.sh_num; i++) {
struct elf32_shdr section;
memcpy(&section, elf + (hdr.shoff + i * hdr.shdr_size),
sizeof(struct elf32_shdr));
if (!strcmp(&names[section.sh_name], name)) {
if (section.sh_size > limit) {
ret = 3;
goto out;
}
if (section.sh_size < limit) {
ret = 4;
goto out;
}
memcpy(buffer, elf + (section.sh_offset), section.sh_size);
ret = 0;
goto out;
}
}
ret = 2;
out:
pmm_free(names, shstrtab.sh_size);
return ret;
}
static uint64_t elf64_max_align(uint8_t *elf) {
uint64_t ret = 0;
struct elf64_hdr hdr;
memcpy(&hdr, elf + (0), sizeof(struct elf64_hdr));
if (hdr.phdr_size < sizeof(struct elf64_phdr)) {
panic(true, "elf: phdr_size < sizeof(struct elf64_phdr)");
}
for (uint16_t i = 0; i < hdr.ph_num; i++) {
struct elf64_phdr phdr;
memcpy(&phdr, elf + (hdr.phoff + i * hdr.phdr_size),
sizeof(struct elf64_phdr));
if (phdr.p_type != PT_LOAD)
continue;
if (phdr.p_align > ret) {
ret = phdr.p_align;
}
}
if (ret == 0) {
panic(true, "elf: Executable has no loadable segments");
}
return ret;
}
static void elf64_get_ranges(uint8_t *elf, uint64_t slide, struct elf_range **_ranges, uint64_t *_ranges_count) {
struct elf64_hdr hdr;
memcpy(&hdr, elf + (0), sizeof(struct elf64_hdr));
uint64_t ranges_count = 0;
if (hdr.phdr_size < sizeof(struct elf64_phdr)) {
panic(true, "elf: phdr_size < sizeof(struct elf64_phdr)");
}
for (uint16_t i = 0; i < hdr.ph_num; i++) {
struct elf64_phdr phdr;
memcpy(&phdr, elf + (hdr.phoff + i * hdr.phdr_size),
sizeof(struct elf64_phdr));
if (phdr.p_type != PT_LOAD)
continue;
if (phdr.p_vaddr < FIXED_HIGHER_HALF_OFFSET_64) {
continue;
}
ranges_count++;
}
if (ranges_count == 0) {
panic(true, "elf: Attempted to use PMRs but no higher half PHDRs exist");
}
struct elf_range *ranges = ext_mem_alloc(ranges_count * sizeof(struct elf_range));
size_t r = 0;
for (uint16_t i = 0; i < hdr.ph_num; i++) {
struct elf64_phdr phdr;
memcpy(&phdr, elf + (hdr.phoff + i * hdr.phdr_size),
sizeof(struct elf64_phdr));
if (phdr.p_type != PT_LOAD)
continue;
uint64_t load_addr = 0;
load_addr = phdr.p_vaddr;
if (phdr.p_vaddr < FIXED_HIGHER_HALF_OFFSET_64) {
continue;
}
load_addr += slide;
uint64_t this_top = load_addr + phdr.p_memsz;
ranges[r].base = load_addr & ~(phdr.p_align - 1);
ranges[r].length = ALIGN_UP(this_top - ranges[r].base, phdr.p_align);
ranges[r].permissions = phdr.p_flags & 0b111;
r++;
}
*_ranges_count = ranges_count;
*_ranges = ranges;
}
int elf64_load(uint8_t *elf, uint64_t *entry_point, uint64_t *top, uint64_t *_slide, uint32_t alloc_type, bool kaslr, struct elf_range **ranges, uint64_t *ranges_count, bool fully_virtual, uint64_t *physical_base, uint64_t *virtual_base, uint64_t *_image_size, bool *is_reloc) {
struct elf64_hdr hdr;
memcpy(&hdr, elf + (0), sizeof(struct elf64_hdr));
if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
printv("elf: Not a valid ELF file.\n");
return -1;
}
if (hdr.ident[EI_DATA] != BITS_LE) {
panic(true, "elf: Not a Little-endian ELF file.\n");
}
if (hdr.machine != ARCH_X86_64) {
panic(true, "elf: Not an x86_64 ELF file.\n");
}
if (is_reloc) {
*is_reloc = false;
}
uint64_t slide = 0;
bool simulation = true;
size_t try_count = 0;
size_t max_simulated_tries = 0x100000;
uint64_t entry = hdr.entry;
bool entry_adjusted = false;
uint64_t max_align = elf64_max_align(elf);
uint64_t image_size = 0;
if (hdr.phdr_size < sizeof(struct elf64_phdr)) {
panic(true, "elf: phdr_size < sizeof(struct elf64_phdr)");
}
if (fully_virtual) {
simulation = false;
uint64_t min_vaddr = (uint64_t)-1;
uint64_t max_vaddr = 0;
for (uint16_t i = 0; i < hdr.ph_num; i++) {
struct elf64_phdr phdr;
memcpy(&phdr, elf + (hdr.phoff + i * hdr.phdr_size),
sizeof(struct elf64_phdr));
if (phdr.p_type != PT_LOAD) {
continue;
}
// Drop entries not in the higher half
if (phdr.p_vaddr < FIXED_HIGHER_HALF_OFFSET_64) {
continue;
}
if (phdr.p_vaddr < min_vaddr) {
min_vaddr = phdr.p_vaddr;
}
if (phdr.p_vaddr + phdr.p_memsz > max_vaddr) {
max_vaddr = phdr.p_vaddr + phdr.p_memsz;
}
}
if (max_vaddr == 0 || min_vaddr == (uint64_t)-1) {
panic(true, "elf: Attempted to use fully virtual mappings but no higher half PHDRs exist");
}
image_size = max_vaddr - min_vaddr;
*physical_base = (uintptr_t)ext_mem_alloc_type_aligned(image_size, alloc_type, max_align);
*virtual_base = min_vaddr;
if (_image_size) {
*_image_size = image_size;
}
}
if (!elf64_is_relocatable(elf, &hdr)) {
simulation = false;
goto final;
} else {
if (is_reloc) {
*is_reloc = true;
}
}
again:
if (kaslr) {
slide = rand32() & ~(max_align - 1);
if (fully_virtual) {
if ((*virtual_base - FIXED_HIGHER_HALF_OFFSET_64) + slide + image_size >= 0x80000000) {
if (++try_count == max_simulated_tries) {
panic(true, "elf: Image wants to load too high");
}
goto again;
}
}
}
final:
if (top)
*top = 0;
bool higher_half = false;
for (uint16_t i = 0; i < hdr.ph_num; i++) {
struct elf64_phdr phdr;
memcpy(&phdr, elf + (hdr.phoff + i * hdr.phdr_size),
sizeof(struct elf64_phdr));
if (phdr.p_type != PT_LOAD)
continue;
// Sanity checks
if (phdr.p_filesz > phdr.p_memsz) {
panic(true, "elf: p_filesz > p_memsz");
}
uint64_t load_addr = phdr.p_vaddr;
if (phdr.p_vaddr >= FIXED_HIGHER_HALF_OFFSET_64) {
higher_half = true;
if (fully_virtual) {
load_addr = *physical_base + (phdr.p_vaddr - *virtual_base);
} else {
load_addr = phdr.p_vaddr - FIXED_HIGHER_HALF_OFFSET_64;
}
} else if (ranges) {
// Drop lower half
continue;
}
if (!fully_virtual) {
load_addr += slide;
}
uint64_t this_top = load_addr + phdr.p_memsz;
if (top) {
if (this_top > *top) {
*top = this_top;
}
}
uint64_t mem_base, mem_size;
if (ranges) {
mem_base = load_addr & ~(phdr.p_align - 1);
mem_size = this_top - mem_base;
} else {
mem_base = load_addr;
mem_size = phdr.p_memsz;
}
if (!fully_virtual &&
((higher_half == true && this_top > 0x80000000)
|| !memmap_alloc_range((size_t)mem_base, (size_t)mem_size, alloc_type, true, false, simulation, false))) {
if (simulation == false || ++try_count == max_simulated_tries) {
panic(true, "elf: Failed to allocate necessary memory range (%X-%X)", mem_base, mem_base + mem_size);
}
if (!kaslr) {
slide += max_align;
}
goto again;
}
if (simulation) {
continue;
}
memcpy((void *)(uintptr_t)load_addr, elf + (phdr.p_offset), phdr.p_filesz);
size_t to_zero = (size_t)(phdr.p_memsz - phdr.p_filesz);
if (to_zero) {
void *ptr = (void *)(uintptr_t)(load_addr + phdr.p_filesz);
memset(ptr, 0, to_zero);
}
if (elf64_apply_relocations(elf, &hdr, (void *)(uintptr_t)load_addr, phdr.p_vaddr, phdr.p_memsz, slide)) {
panic(true, "elf: Failed to apply relocations");
}
}
if (simulation) {
simulation = false;
goto final;
}
if (fully_virtual) {
*virtual_base += slide;
}
*entry_point = entry + slide;
if (_slide)
*_slide = slide;
if (ranges_count != NULL && ranges != NULL) {
elf64_get_ranges(elf, slide, ranges, ranges_count);
}
return 0;
}
int elf32_load(uint8_t *elf, uint32_t *entry_point, uint32_t *top, uint32_t alloc_type) {
struct elf32_hdr hdr;
memcpy(&hdr, elf + (0), sizeof(struct elf32_hdr));
if (strncmp((char *)hdr.ident, "\177ELF", 4)) {
printv("elf: Not a valid ELF file.\n");
return -1;
}
if (hdr.ident[EI_DATA] != BITS_LE) {
printv("elf: Not a Little-endian ELF file.\n");
return -1;
}
if (hdr.machine != ARCH_X86_32) {
printv("elf: Not an x86_32 ELF file.\n");
return -1;
}
uint32_t entry = hdr.entry;
bool entry_adjusted = false;
if (top)
*top = 0;
if (hdr.phdr_size < sizeof(struct elf32_phdr)) {
panic(true, "elf: phdr_size < sizeof(struct elf32_phdr)");
}
for (uint16_t i = 0; i < hdr.ph_num; i++) {
struct elf32_phdr phdr;
memcpy(&phdr, elf + (hdr.phoff + i * hdr.phdr_size),
sizeof(struct elf32_phdr));
if (phdr.p_type != PT_LOAD)
continue;
// Sanity checks
if (phdr.p_filesz > phdr.p_memsz) {
panic(true, "elf: p_filesz > p_memsz");
}
if (top) {
uint32_t this_top = phdr.p_paddr + 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, true, false, false);
memcpy((void *)(uintptr_t)phdr.p_paddr, elf + (phdr.p_offset), phdr.p_filesz);
size_t to_zero = (size_t)(phdr.p_memsz - phdr.p_filesz);
if (to_zero) {
void *ptr = (void *)(uintptr_t)(phdr.p_paddr + phdr.p_filesz);
memset(ptr, 0, to_zero);
}
if (!entry_adjusted && entry >= phdr.p_vaddr && entry < (phdr.p_vaddr + phdr.p_memsz)) {
entry -= phdr.p_vaddr;
entry += phdr.p_paddr;
entry_adjusted = true;
}
}
*entry_point = entry;
return 0;
}
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