ref: 041d2d96655de6afaac6b20437df8897b03f6c92
dir: /src/libmach/elf64/elf64read.c/
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <scc/mach.h>
#include "../libmach.h"
#include "elf64.h"
static int
unpack_hdr(int order, unsigned char *buf, Elf_Ehdr *hdr)
{
int n;
n = unpack(order,
buf,
"'16sslqqqlssssss",
hdr->e_ident,
&hdr->e_type,
&hdr->e_machine,
&hdr->e_version,
&hdr->e_entry,
&hdr->e_phoff,
&hdr->e_shoff,
&hdr->e_flags,
&hdr->e_ehsize,
&hdr->e_phentsize,
&hdr->e_phnum,
&hdr->e_shentsize,
&hdr->e_shnum,
&hdr->e_shstrndx);
assert(n == ELFHSZ);
return n;
}
static int
unpack_phdr(int order, unsigned char *buf, Elf_Phdr *phdr)
{
int n;
n = unpack(order,
buf,
"llqqqqqq",
&phdr->p_type,
&phdr->p_flags,
&phdr->p_offset,
&phdr->p_vaddr,
&phdr->p_paddr,
&phdr->p_filesz,
&phdr->p_memsz,
&phdr->p_align);
assert(n == ELFPSZ);
return n;
}
static int
unpack_shdr(int order, unsigned char *buf, Elf_Shdr *shdr)
{
int n;
n = unpack(order,
buf,
"llqqqqllqq",
&shdr->sh_name,
&shdr->sh_type,
&shdr->sh_flags,
&shdr->sh_addr,
&shdr->sh_offset,
&shdr->sh_size,
&shdr->sh_link,
&shdr->sh_info,
&shdr->sh_addralign,
&shdr->sh_entsize);
assert(n == ELFSSZ);
return n;
}
static int
unpack_sym(int order, unsigned char *buf, Elf_Sym *sym)
{
int n;
n = unpack(order,
buf,
"lccsqq",
&sym->st_name,
&sym->st_info,
&sym->st_other,
&sym->st_shndx,
&sym->st_value,
&sym->st_size);
assert(n == ELFESZ);
return n;
}
static int
readhdr(Obj *obj, FILE *fp)
{
Elf64 *elf;
Elf_Ehdr *hdr;
unsigned char buf[ELFHSZ];
elf = obj->data;
hdr = &elf->hdr;
if (fread(buf, ELFHSZ, 1, fp) != 1)
return 0;
unpack_hdr(ORDER(obj->type), buf, hdr);
switch (hdr->e_type) {
case ET_REL:
case ET_EXEC:
case ET_DYN:
return 1;
default:
return 0;
}
}
static int
readphdr(Obj *obj, FILE *fp)
{
long long i;
Elf_Ehdr *hdr;
Elf_Phdr *phdr;
Elf64 *elf;
unsigned char buf[ELFPSZ];
elf = obj->data;
hdr = &elf->hdr;
if (hdr->e_phoff == 0 || hdr->e_phnum == 0)
return 1;
phdr = calloc(hdr->e_phnum, sizeof(*phdr));
if (!phdr)
return 0;
elf->phdr = phdr;
if (!objpos(obj, fp, hdr->e_phoff))
return 0;
for (i = 0; i < hdr->e_phnum; i++) {
if (fread(buf, ELFPSZ, 1, fp) != 1)
return 0;
unpack_phdr(ORDER(obj->type), buf, &phdr[i]);
}
return 1;
}
static int
readshdr(Obj *obj, FILE *fp)
{
long long i, nsec;
Elf_Ehdr *hdr;
Elf_Shdr *shdr;
Elf64 *elf;
unsigned char buf[ELFSSZ + ELFHSZ];
elf = obj->data;
hdr = &elf->hdr;
if (hdr->e_shoff == 0)
return 1;
if (!objpos(obj, fp, hdr->e_shoff))
return 0;
if (hdr->e_shnum != SHN_UNDEF) {
nsec = hdr->e_shnum;
} else {
Elf_Shdr sec0;
fpos_t pos;
fgetpos(fp, &pos);
fread(buf, ELFHSZ, 1, fp);
fsetpos(fp, &pos);
if (ferror(fp))
return 0;
unpack_shdr(ORDER(obj->type), buf, &sec0);
nsec = sec0.sh_size;
}
if (nsec > SIZE_MAX)
return 0;
shdr = calloc(nsec, sizeof(*shdr));
if (!shdr)
return 0;
elf->shdr = shdr;
elf->nsec = nsec;
for (i = 0; i < nsec; i++) {
if (fread(buf, ELFSSZ, 1, fp) != 1)
return 0;
unpack_shdr(ORDER(obj->type), buf, &shdr[i]);
if (shdr[i].sh_type == SHT_SYMTAB) {
/*
* elf supports multiple symbol table, but we don't
* care and we only support one, and we reject elf
* files with more of one symbol table.
*/
if (elf->symtab)
return 0;
elf->symtab = &shdr[i];
}
}
return 1;
}
static int
readsecstr(Obj *obj, FILE *fp)
{
long idx;
size_t siz;
char *str;
Elf_Shdr *shdr;
Elf64 *elf;
Elf_Ehdr *hdr;
elf = obj->data;
hdr = &elf->hdr;
idx = hdr->e_shstrndx;
if (idx == SHN_UNDEF)
return 0;
if (idx == SHN_XINDEX) {
if (hdr->e_shnum == 0)
return 0;
idx = elf->shdr[0].sh_link;
}
if (idx >= hdr->e_shnum)
return 0;
shdr = &elf->shdr[idx];
if (shdr->sh_size > SIZE_MAX)
return 0;
siz = shdr->sh_size;
if (siz == 0)
return 1;
str = malloc(siz);
if (!str)
return 0;
elf->strtbl[SEC_STRTBL] = str;
elf->strsiz[SEC_STRTBL] = siz;
if (!objpos(obj, fp, shdr->sh_offset))
return 0;
if (fread(str, siz, 1, fp) != 1)
return 0;
return 1;
}
static int
readsymstr(Obj *obj, FILE *fp)
{
long idx;
size_t siz;
char *str;
Elf64 *elf;
Elf_Shdr *shdr;
elf = obj->data;
if (!elf->symtab)
return 1;
idx = elf->symtab->sh_link;
if (idx >= elf->nsec)
return 0;
shdr = &elf->shdr[idx];
if (shdr->sh_size > SIZE_MAX)
return 0;
siz = shdr->sh_size;
if (siz == 0)
return 1;
str = malloc(siz);
if (!str)
return 0;
elf->strtbl[SYM_STRTBL] = str;
elf->strsiz[SYM_STRTBL] = siz;
if (!objpos(obj, fp, shdr->sh_offset))
return 0;
if (fread(str, siz, 1, fp) != 1)
return 0;
return 1;
}
static int
readsym(Obj *obj, FILE *fp)
{
long nsym, i;
int sec;
Elf64 *elf;
Elf_Sym *syms;
Elf_Shdr *shdr;
unsigned char buf[ELFSSZ];
elf = obj->data;
if (!elf->symtab)
return 1;
shdr = elf->symtab;
assert(shdr->sh_type == SHT_SYMTAB);
nsym = shdr->sh_size / shdr->sh_entsize;
if (nsym >= SIZE_MAX)
return 0;
syms = calloc(nsym, sizeof(*syms));
if (!syms)
return 0;
elf->syms = syms;
elf->nsym = nsym;
if (!objpos(obj, fp, shdr->sh_offset))
return 0;
for (i = 0; i < nsym; i++) {
if (fread(buf, ELFESZ, 1, fp) != 1)
return 0;
unpack_sym(ORDER(obj->type), buf, &syms[i]);
sec = syms[i].st_shndx;
switch (sec) {
case SHN_XINDEX:
/*
* Elf supports an extension mechanism to allow
* indexes bigger than 4 bytes. We don't care
* and we reject elf files using this feature.
*/
return 0;
case SHN_UNDEF:
case SHN_ABS:
case SHN_COMMON:
break;
default:
if (sec >= elf->nsec)
return 0;
break;
}
}
return 1;
}
int
elf64read(Obj *obj, FILE *fp)
{
if (!readhdr(obj, fp))
return -1;
if (!readphdr(obj, fp))
return -1;
if (!readshdr(obj, fp))
return -1;
if (!readsym(obj, fp))
return -1;
if (!readsecstr(obj, fp))
return -1;
if (!readsymstr(obj, fp))
return -1;
return 0;
}