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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 <user/lib/elf.h>
#include <user/lib/elfload.h>
void elf_execf(FILE *f, char **argv, char **envp) {
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 && fread(buf, 1, buflen, f))
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
_syscall_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;
}
/* 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, 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 len, char **argv, char **envp) {
void *stack = (void*)~0;
size_t *stack_w;
int argc = 0;
if (argv) {
size_t len;
for (int i = 0; argv[i]; i++) {
len = strlen(argv[i]) + 1; // including the null byte
stack -= len;
memcpy(stack, argv[i], len);
argv[i] = stack;
argc++;
}
len = sizeof(char*) * argc;
stack -= len;
memcpy(stack, argv, len);
argv = stack;
}
stack_w = stack;
*--stack_w = (uintptr_t)envp;
*--stack_w = (uintptr_t)argv;
*--stack_w = argc;
uintptr_t high = (uintptr_t)low + len;
uint64_t buf[] = {
EXECBUF_SYSCALL, _SYSCALL_MEMFLAG, 0, (uintptr_t)low, 0, 0, 0,
EXECBUF_SYSCALL, _SYSCALL_MEMFLAG, high, ~0 - 0xF000 - high, 0, 0, 0,
EXECBUF_JMP, (uintptr_t)entry,
};
execbuf_chstack(stack_w, 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 = _syscall_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)) {
_syscall_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 = _syscall_memflag((void*)0x1000, 0x1000, MEMFLAG_FINDFREE | MEMFLAG_PRESENT);
if (!newstack) return;
_freejmp_chstack(exebase + ehdr->e_entry, exebase, elf_spread(ehdr) + 0x1000, 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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