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#include <merror.h>
#include <elf.h>
#include <melf.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include "sim.h"
#define SEC_ALIGN 0x1000
struct load_state {
FILE *file;
int fd;
uint32_t file_sz;
Elf32_Phdr *phdr;
uint32_t phdr_len;
Elf32_Ehdr ehdr;
};
static int assert_ehdr(const void *const given, const void *const assert,
size_t size)
{
if (memcmp(given, assert, size) == 0)
return M_SUCCESS;
ERROR("invalid elf ehdr");
return M_ERROR;
}
static int load_ehdr(struct simulator *sim, struct load_state *state)
{
Elf32_Ehdr ehdr;
fseek(state->file, 0, SEEK_SET);
if (fread(&ehdr, sizeof(Elf32_Ehdr), 1, state->file) != 1) {
ERROR("cannot load ehdr");
return M_ERROR;
}
/**
* Compare each "static" value in the ehdr and make sure it
* is what it should be. If not throw and error and eventually
* return.
*/
Elf32_Ehdr baseline = MIPS_ELF_EHDR;
baseline.e_type = B16(ET_EXEC);
#define EHDR_ASSERT(name, size) \
if (res == M_SUCCESS) \
res |= assert_ehdr(&baseline.e_##name, \
&ehdr.e_##name, size) \
// ignore abi ver
ehdr.e_ident[EI_ABIVERSION] = 0x00;
int res = 0;
EHDR_ASSERT(ident, EI_NIDENT);
EHDR_ASSERT(type, sizeof(Elf32_Half));
EHDR_ASSERT(machine, sizeof(Elf32_Half));
EHDR_ASSERT(version, sizeof(Elf32_Word));
// EHDR_ASSERT(flags, sizeof(Elf32_Word));
EHDR_ASSERT(ehsize, sizeof(Elf32_Half));
EHDR_ASSERT(phentsize, sizeof(Elf32_Half));
EHDR_ASSERT(shentsize, sizeof(Elf32_Half));
#undef EHDR_ASSERT
if (res)
return M_ERROR;
state->ehdr = ehdr;
sim->entry = B32(ehdr.e_entry);
return M_SUCCESS;
}
static int load_phdr(struct load_state *state)
{
Elf32_Phdr *phdr = NULL;
uint32_t off = B32(state->ehdr.e_phoff);
uint16_t len = B16(state->ehdr.e_phnum);
if (BOUND_CHK(state->file_sz, len, off)) {
ERROR("elf phdr location invalid");
return M_ERROR;
}
phdr = malloc(sizeof(Elf32_Phdr) * len);
if (phdr == NULL) {
PERROR("cannot alloc");
return M_ERROR;
}
fseek(state->file, off, SEEK_SET);
if (fread(phdr, sizeof(Elf32_Phdr), len, state->file) != len) {
free(phdr);
PERROR("cannot read phdr");
return M_ERROR;
}
state->phdr = phdr;
state->phdr_len = len;
return M_SUCCESS;
}
static int load_segment(struct simulator *sim,
struct load_state *state, Elf32_Phdr *hdr)
{
uint32_t off = B32(hdr->p_offset);
uint32_t len = B32(hdr->p_filesz);
uint32_t is_text = B32(hdr->p_flags) & PF_X;
if (BOUND_CHK(state->file_sz, len, off)) {
ERROR("segment location invalid");
return M_ERROR;
}
uintptr_t addr = 0;
uint32_t add = 0;
if (len % SEC_ALIGN) {
add = SEC_ALIGN - (len % SEC_ALIGN);
len += add;
}
if (is_text) {
addr = sim->text_max;
sim->text_max += len;
} else {
addr = sim->data_max;
sim->data_max += len;
}
bool read = B32(hdr->p_flags) & PF_R;
bool write = B32(hdr->p_flags) & PF_W;
uint32_t prot = 0;
if (read)
prot |= PROT_READ;
if (write)
prot |= PROT_WRITE;
void *res = mmap((void*)addr, len, prot, MAP_PRIVATE | MAP_FIXED,
state->fd, off);
if ((uintptr_t)res != addr) {
PERROR("failed to map executable");
return M_ERROR;
}
return M_SUCCESS;
}
static int load_memory(struct simulator *sim, struct load_state *state)
{
uint32_t base = 0;
for (uint32_t i = 0; i < state->phdr_len; i++) {
Elf32_Phdr *hdr = NULL;
uint32_t min = UINT32_MAX;
if (B32(state->phdr[i].p_filesz) < 1)
continue;
// we need to load segments in order
for (uint32_t j = 0; j < state->phdr_len; j++) {
Elf32_Phdr *temp = &state->phdr[j];
uint32_t off = B32(temp->p_offset);
uint32_t len = B32(temp->p_filesz);
if (len < 1)
continue;
if (off <= base)
continue;
if (off >= min)
continue;
min = off;
hdr = temp;
}
base = min;
if (hdr == NULL) {
ERROR("invalid elf phdr");
return M_ERROR;
}
if (load_segment(sim, state, hdr))
return M_ERROR;
}
return M_SUCCESS;
}
int sim_load_file(struct simulator *sim) {
struct load_state state;
state.file = fopen(sim->args->executable, "r");
if (state.file == NULL) {
PERROR("cannot read '%s'", state.file);
return M_ERROR;
}
state.fd = fileno(state.file);
// get filesize
fseek(state.file, 0, SEEK_END);
state.file_sz = ftell(state.file);
state.phdr = NULL;
int res = M_SUCCESS;
if (res == M_SUCCESS)
res = load_ehdr(sim, &state);
if (res == M_SUCCESS)
res = load_phdr(&state);
if (res == M_SUCCESS)
res = load_memory(sim, &state);
if (state.phdr)
free(state.phdr);
fclose(state.file);
return res;
}
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