minix/lib/libexec/exec_elf.c
Ben Gras 53002f6f6c recognize and execute dynamically linked executables
. generalize libexec slightly to get some more necessary information
	  from ELF files, e.g. the interpreter
	. execute dynamically linked executables when exec()ed by VFS
	. switch to netbsd variant of elf32.h exclusively, solves some
	  conflicting headers
2012-04-16 00:41:42 +00:00

245 lines
6.6 KiB
C

#define _SYSTEM 1
#include <minix/type.h>
#include <minix/const.h>
#include <sys/param.h>
#include <assert.h>
#include <unistd.h>
#include <errno.h>
#include <libexec.h>
#include <string.h>
#include <machine/elf.h>
/* For verbose logging */
#define ELF_DEBUG 0
/* Support only 32-bit ELF objects */
#define __ELF_WORD_SIZE 32
#define SECTOR_SIZE 512
static int check_header(const Elf_Ehdr *hdr);
static int elf_sane(const Elf_Ehdr *hdr)
{
if (check_header(hdr) != OK) {
return 0;
}
if((hdr->e_type != ET_EXEC) && (hdr->e_type != ET_DYN)) {
return 0;
}
if ((hdr->e_phoff > SECTOR_SIZE) ||
(hdr->e_phoff + hdr->e_phentsize * hdr->e_phnum) > SECTOR_SIZE) {
#if ELF_DEBUG
printf("peculiar phoff\n");
#endif
return 0;
}
return 1;
}
static int elf_ph_sane(const Elf_Phdr *phdr)
{
if (rounddown((uintptr_t)phdr, sizeof(Elf_Addr)) != (uintptr_t)phdr) {
return 0;
}
return 1;
}
static int elf_unpack(const char *exec_hdr,
int hdr_len, const Elf_Ehdr **hdr, const Elf_Phdr **phdr)
{
*hdr = (const Elf_Ehdr *)exec_hdr;
if(!elf_sane(*hdr)) {
#if ELF_DEBUG
printf("elf_sane failed\n");
#endif
return ENOEXEC;
}
*phdr = (const Elf_Phdr *)(exec_hdr + (*hdr)->e_phoff);
if(!elf_ph_sane(*phdr)) {
#if ELF_DEBUG
printf("elf_ph_sane failed\n");
#endif
return ENOEXEC;
}
#if 0
if((int)((*phdr) + (*hdr)->e_phnum) >= hdr_len) return ENOEXEC;
#endif
return OK;
}
int read_header_elf(
const char *exec_hdr, /* executable header */
int hdr_len, /* significant bytes in exec_hdr */
vir_bytes *text_vaddr, /* text virtual address */
phys_bytes *text_paddr, /* text physical address */
vir_bytes *text_filebytes, /* text segment size (in the file) */
vir_bytes *text_membytes, /* text segment size (in memory) */
vir_bytes *data_vaddr, /* data virtual address */
phys_bytes *data_paddr, /* data physical address */
vir_bytes *data_filebytes, /* data segment size (in the file) */
vir_bytes *data_membytes, /* data segment size (in memory) */
vir_bytes *pc, /* program entry point (initial PC) */
off_t *text_offset, /* file offset to text segment */
off_t *data_offset /* file offset to data segment */
)
{
const Elf_Ehdr *hdr = NULL;
const Elf_Phdr *phdr = NULL;
unsigned long seg_filebytes, seg_membytes;
int e, i = 0;
*text_vaddr = *text_paddr = 0;
*text_filebytes = *text_membytes = 0;
*data_vaddr = *data_paddr = 0;
*data_filebytes = *data_membytes = 0;
*pc = *text_offset = *data_offset = 0;
if((e=elf_unpack(exec_hdr, hdr_len, &hdr, &phdr)) != OK) {
#if ELF_DEBUG
printf("elf_unpack failed\n");
#endif
return e;
}
#if ELF_DEBUG
printf("Program header file offset (phoff): %ld\n", hdr->e_phoff);
printf("Section header file offset (shoff): %ld\n", hdr->e_shoff);
printf("Program header entry size (phentsize): %d\n", hdr->e_phentsize);
printf("Program header entry num (phnum): %d\n", hdr->e_phnum);
printf("Section header entry size (shentsize): %d\n", hdr->e_shentsize);
printf("Section header entry num (shnum): %d\n", hdr->e_shnum);
printf("Section name strings index (shstrndx): %d\n", hdr->e_shstrndx);
printf("Entry Point: 0x%lx\n", hdr->e_entry);
#endif
for (i = 0; i < hdr->e_phnum; i++) {
switch (phdr[i].p_type) {
case PT_LOAD:
if (phdr[i].p_memsz == 0)
break;
seg_filebytes = phdr[i].p_filesz;
seg_membytes = round_page(phdr[i].p_memsz + phdr[i].p_vaddr -
trunc_page(phdr[i].p_vaddr));
if (hdr->e_entry >= phdr[i].p_vaddr &&
hdr->e_entry < (phdr[i].p_vaddr + phdr[i].p_memsz)) {
*text_vaddr = phdr[i].p_vaddr;
*text_paddr = phdr[i].p_paddr;
*text_filebytes = seg_filebytes;
*text_membytes = seg_membytes;
*pc = (vir_bytes)hdr->e_entry;
*text_offset = phdr[i].p_offset;
} else {
*data_vaddr = phdr[i].p_vaddr;
*data_paddr = phdr[i].p_paddr;
*data_filebytes = seg_filebytes;
*data_membytes = seg_membytes;
*data_offset = phdr[i].p_offset;
}
break;
default:
break;
}
}
#if ELF_DEBUG
printf("Text vaddr: 0x%lx\n", *text_vaddr);
printf("Text paddr: 0x%lx\n", *text_paddr);
printf("Text filebytes: 0x%lx\n", *text_filebytes);
printf("Text membytes: 0x%lx\n", *text_membytes);
printf("Data vaddr: 0x%lx\n", *data_vaddr);
printf("Data paddr: 0x%lx\n", *data_paddr);
printf("Data filebyte: 0x%lx\n", *data_filebytes);
printf("Data membytes: 0x%lx\n", *data_membytes);
printf("PC: 0x%lx\n", *pc);
printf("Text offset: 0x%lx\n", *text_offset);
printf("Data offset: 0x%lx\n", *data_offset);
#endif
return OK;
}
#define IS_ELF(ehdr) ((ehdr).e_ident[EI_MAG0] == ELFMAG0 && \
(ehdr).e_ident[EI_MAG1] == ELFMAG1 && \
(ehdr).e_ident[EI_MAG2] == ELFMAG2 && \
(ehdr).e_ident[EI_MAG3] == ELFMAG3)
static int check_header(const Elf_Ehdr *hdr)
{
if (!IS_ELF(*hdr) ||
hdr->e_ident[EI_DATA] != ELF_TARG_DATA ||
hdr->e_ident[EI_VERSION] != EV_CURRENT ||
hdr->e_phentsize != sizeof(Elf_Phdr) ||
hdr->e_version != ELF_TARG_VER)
return ENOEXEC;
return OK;
}
int elf_phdr(const char *exec_hdr, int hdr_len, vir_bytes *ret_phdr)
{
const Elf_Ehdr *hdr = NULL;
const Elf_Phdr *phdr = NULL;
int e, i, have_computed_phdr = 1;
if((e=elf_unpack(exec_hdr, hdr_len, &hdr, &phdr)) != OK) return e;
for (i = 0; i < hdr->e_phnum; i++) {
switch (phdr[i].p_type) {
case PT_LOAD:
/* compute phdr based on this heuristic, to be used
* if there is no PT_PHDR
*/
if(phdr[i].p_offset == 0) {
*ret_phdr = phdr[i].p_vaddr + hdr->e_phoff;
have_computed_phdr = 1;
}
break;
case PT_PHDR:
*ret_phdr = phdr[i].p_vaddr;
return OK;
default:
break;;
}
}
if(have_computed_phdr) return OK;
return ENOENT;
}
/* Return >0 if there is an ELF interpreter (i.e. it is a dynamically linked
* executable) and we could extract it successfully.
* Return 0 if there isn't one.
* Return <0 on error.
*/
int elf_has_interpreter(const char *exec_hdr, /* executable header */
int hdr_len, char *interp, int maxsz)
{
const Elf_Ehdr *hdr = NULL;
const Elf_Phdr *phdr = NULL;
int e, i;
if((e=elf_unpack(exec_hdr, hdr_len, &hdr, &phdr)) != OK) return e;
for (i = 0; i < hdr->e_phnum; i++) {
switch (phdr[i].p_type) {
case PT_INTERP:
if(!interp) return 1;
if(phdr[i].p_filesz >= maxsz)
return -1;
if(phdr[i].p_offset + phdr[i].p_filesz >= hdr_len)
return -1;
memcpy(interp, exec_hdr + phdr[i].p_offset, phdr[i].p_filesz);
interp[phdr[i].p_filesz] = '\0';
return 1;
default:
continue;
}
}
return 0;
}