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#include <camellia/execbuf.h>
#include <camellia/flags.h>
#include <camellia/syscalls.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "elf.h"
#include <elfload.h>
void elf_execf(FILE *f, char **argv, char **envp) {
size_t ret;
void *buf;
long buflen;
fseek(f, 0, SEEK_END);
buflen = ftell(f);
if (buflen < 0) return; /* errno set by fseek */
buf = malloc(buflen);
// TODO don't read the entire file into memory
fseek(f, 0, SEEK_SET);
if (!buf) return;
ret = fread(buf, buflen, 1, f);
fclose(f);
if (ret == 1) {
elf_exec(buf, argv, envp);
}
free(buf);
}
static bool valid_ehdr(const struct Elf64_Ehdr *h) {
return h->e_ident[0] == 0x7f
&& h->e_ident[1] == 'E'
&& h->e_ident[2] == 'L'
&& h->e_ident[3] == 'F'
&& h->e_machine == EM_X86_64
&& h->e_version == 1;
}
static bool load_phdr(const void *elf, void *exebase, size_t idx) {
const struct Elf64_Ehdr *ehdr = elf;
const struct Elf64_Phdr *phdr = elf + ehdr->e_phoff + idx * ehdr->e_phentsize;
if (phdr->p_type == PT_DYNAMIC) return true;
if (phdr->p_type != PT_LOAD) {
printf("unknown type %x\n", phdr->p_type);
return false;
}
// TODO overlap check
// TODO don't ignore flags
_sys_memflag(exebase + phdr->p_vaddr, phdr->p_memsz, MEMFLAG_PRESENT);
// TODO check that filesz <= memsz
memcpy(exebase + phdr->p_vaddr, elf + phdr->p_offset, phdr->p_filesz);
return true;
}
static size_t elf_spread(const void *elf) {
const struct Elf64_Ehdr *ehdr = elf;
uintptr_t high = 0, low = ~0;
for (size_t phi = 0; phi < ehdr->e_phnum; phi++) {
const struct Elf64_Phdr *phdr = elf + ehdr->e_phoff + phi * ehdr->e_phentsize;
if (high < phdr->p_vaddr + phdr->p_memsz)
high = phdr->p_vaddr + phdr->p_memsz;
if (low > phdr->p_vaddr)
low = phdr->p_vaddr;
}
return high - low;
}
static void *memdup(const void *orig, size_t len) {
void *n = malloc(len);
if (n) memcpy(n, orig, len);
return n;
}
static const char *default_argv[] = {NULL};
/* frees memory outside of [low; low + len] and jumps to *entry
* also sets up main's stack */
void _freejmp_chstack(void *entry, void *low, size_t len, const char **argv, char **envp, void *stack); // elfload.s
_Noreturn void execbuf_chstack(void *stack, void __user *buf, size_t len);
void _freejmp(void *entry, void *low, size_t imglen, const char **argv, char **envp) {
// TODO error checking
// although i guess it's fine for it to crash
// also TODO just alloc a new stack
void *stack = (void*)~0;
struct execdata ed;
size_t argv_len;
size_t cwd_len = absolutepath(NULL, NULL, 0);
if (!argv) argv = default_argv;
ed.argc = 0;
while (argv[ed.argc]) ed.argc++;
argv_len = (ed.argc+1) * sizeof(char *);
/* make a copy of argv, so it doesn't get overridden
* if it overlaps with the new stack. */
argv = memdup(argv, argv_len);
for (int i = 0; i < ed.argc; i++) {
argv[i] = strdup(argv[i]);
}
ed.cwd = malloc(cwd_len);
getcwd(ed.cwd, cwd_len);
stack -= argv_len;
ed.argv = stack;
for (int i = 0; i < ed.argc; i++) {
size_t len = strlen(argv[i]) + 1;
stack -= len;
memcpy(stack, argv[i], len);
ed.argv[i] = stack;
}
ed.argv[ed.argc] = NULL;
/* push cwd */
stack -= cwd_len;
memcpy(stack, ed.cwd, cwd_len);
ed.cwd = stack;
stack -= sizeof ed;
memcpy(stack, &ed, sizeof ed);
uintptr_t high = (uintptr_t)low + imglen;
uint64_t buf[] = {
EXECBUF_SYSCALL, _SYS_MEMFLAG, 0, (uintptr_t)low, 0, 0, 0,
EXECBUF_SYSCALL, _SYS_MEMFLAG, high, ~0 - 0xF000 - high, 0, 0, 0,
EXECBUF_JMP, (uintptr_t)entry,
};
execbuf_chstack(stack, buf, sizeof buf);
}
static void *elf_loadmem(struct Elf64_Ehdr *ehdr) {
void *exebase;
size_t spread = elf_spread(ehdr);
switch (ehdr->e_type) {
case ET_EXEC:
exebase = (void*)0;
break;
case ET_DYN:
exebase = _sys_memflag((void*)0x1000, spread, MEMFLAG_FINDFREE);
if (!exebase)
return NULL;
break;
default:
return NULL;
}
for (size_t phi = 0; phi < ehdr->e_phnum; phi++) {
if (!load_phdr((void*)ehdr, exebase, phi)) {
_sys_memflag(exebase, spread, 0);
return NULL;
}
}
return exebase;
}
void elf_exec(void *base, char **argv, char **envp) {
struct Elf64_Ehdr *ehdr = base;
if (!valid_ehdr(ehdr)) return;
void *exebase = elf_loadmem(ehdr);
if (!exebase) return;
void *newstack = _sys_memflag((void*)0x11000, 0x1000, MEMFLAG_FINDFREE | MEMFLAG_PRESENT) + 0x1000 - 8;
if (!newstack) return;
_freejmp_chstack(exebase + ehdr->e_entry, exebase, elf_spread(ehdr) + 0x1000, (const char**)argv, envp, newstack);
}
void *elf_partialexec(void *base) {
struct Elf64_Ehdr *ehdr = base;
if (!valid_ehdr(ehdr)) return NULL;
void *exebase = elf_loadmem(ehdr);
if (!exebase) return NULL;
return exebase + ehdr->e_entry;
}
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