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recognize and execute dynamically linked executables

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. 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
This commit is contained in:
Ben Gras
2012-04-03 15:52:25 +02:00
parent 927b9ef243
commit 53002f6f6c
21 changed files with 540 additions and 477 deletions
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154
lib/libexec/exec_elf.c
View File

@@ -7,6 +7,8 @@
#include <unistd.h>
#include <errno.h>
#include <libexec.h>
#include <string.h>
#include <machine/elf.h>
/* For verbose logging */
#define ELF_DEBUG 0
@@ -16,10 +18,63 @@
#define SECTOR_SIZE 512
static int __elfN(check_header)(const Elf_Ehdr *hdr);
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) */
@@ -36,7 +91,7 @@ int read_header_elf(
const Elf_Ehdr *hdr = NULL;
const Elf_Phdr *phdr = NULL;
unsigned long seg_filebytes, seg_membytes;
int i = 0;
int e, i = 0;
*text_vaddr = *text_paddr = 0;
*text_filebytes = *text_membytes = 0;
@@ -44,27 +99,12 @@ int read_header_elf(
*data_filebytes = *data_membytes = 0;
*pc = *text_offset = *data_offset = 0;
hdr = (const Elf_Ehdr *)exec_hdr;
if (__elfN(check_header)(hdr) != OK || (hdr->e_type != ET_EXEC))
{
return ENOEXEC;
}
if ((hdr->e_phoff > SECTOR_SIZE) ||
(hdr->e_phoff + hdr->e_phentsize * hdr->e_phnum) > SECTOR_SIZE) {
return ENOEXEC;
}
phdr = (const Elf_Phdr *)(exec_hdr + hdr->e_phoff);
if (
#ifdef __NBSD_LIBC
rounddown((uintptr_t)phdr, sizeof(Elf_Addr)) != (uintptr_t)phdr
#else
!_minix_aligned(hdr->e_phoff, Elf_Addr)
if((e=elf_unpack(exec_hdr, hdr_len, &hdr, &phdr)) != OK) {
#if ELF_DEBUG
printf("elf_unpack failed\n");
#endif
) {
return ENOEXEC;
}
return e;
}
#if ELF_DEBUG
printf("Program header file offset (phoff): %ld\n", hdr->e_phoff);
@@ -124,7 +164,12 @@ int read_header_elf(
return OK;
}
static int __elfN(check_header)(const Elf_Ehdr *hdr)
#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 ||
@@ -135,3 +180,66 @@ static int __elfN(check_header)(const Elf_Ehdr *hdr)
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;
}