/* 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(char *exec_hdr, /* executable header */
int hdr_len, char *interp, int maxsz)
{
Elf_Ehdr *hdr = NULL;
Elf_Phdr *phdr = NULL;
int e, i;
if((e=elf_unpack(exec_hdr, hdr_len, &hdr, &phdr)) != OK) return 0;
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;
}
int libexec_load_elf(struct exec_info *execi)
{
Elf_Ehdr *hdr = NULL;
Elf_Phdr *phdr = NULL;
int e, i = 0;
int first = 1;
vir_bytes startv = 0, stacklow;
assert(execi != NULL);
assert(execi->hdr != NULL);
if((e=elf_unpack(execi->hdr, execi->hdr_len, &hdr, &phdr)) != OK) {
return e;
}
/* this function can load the dynamic linker, but that
* shouldn't require an interpreter itself.
*/
i = elf_has_interpreter(execi->hdr, execi->hdr_len, NULL, 0);
if(i > 0) {
return ENOEXEC;
}
execi->stack_size = roundup(execi->stack_size, PAGE_SIZE);
execi->stack_high = rounddown(execi->stack_high, PAGE_SIZE);
stacklow = execi->stack_high - execi->stack_size;
assert(execi->copymem);
assert(execi->clearmem);
assert(execi->allocmem_prealloc_cleared);
assert(execi->allocmem_prealloc_junk);
assert(execi->allocmem_ondemand);
for (i = 0; i < hdr->e_phnum; i++) {
Elf_Phdr *ph = &phdr[i];
off_t file_limit = ph->p_offset + ph->p_filesz;
/* sanity check binary before wiping out the target process */
if(execi->filesize < file_limit) {
return ENOEXEC;
}
}
if(execi->clearproc) execi->clearproc(execi);
for (i = 0; i < hdr->e_phnum; i++) {
vir_bytes seg_membytes, page_offset, p_vaddr, vaddr;
vir_bytes chunk, vfileend, vmemend;
off_t foffset, fbytes;
Elf_Phdr *ph = &phdr[i];
int try_mmap = 1;
u16_t clearend = 0;
int pagechunk;
int mmap_prot = PROT_READ;
if(!(ph->p_flags & PF_R)) {
printf("libexec: warning: unreadable segment\n");
}
if(ph->p_flags & PF_W) {
mmap_prot |= PROT_WRITE;
#if ELF_DEBUG
printf("libexec: adding PROT_WRITE\n");
#endif
} else {
#if ELF_DEBUG
printf("libexec: not adding PROT_WRITE\n");
#endif
}
if (ph->p_type != PT_LOAD || ph->p_memsz == 0) continue;
if((ph->p_vaddr % PAGE_SIZE) != (ph->p_offset % PAGE_SIZE)) {
printf("libexec: unaligned ELF program?\n");
try_mmap = 0;
}
if(!execi->memmap) {
try_mmap = 0;
}
foffset = ph->p_offset;
fbytes = ph->p_filesz;
vaddr = p_vaddr = ph->p_vaddr + execi->load_offset;
seg_membytes = ph->p_memsz;
page_offset = vaddr % PAGE_SIZE;
vaddr -= page_offset;
foffset -= page_offset;
seg_membytes += page_offset;
fbytes += page_offset;
vfileend = p_vaddr + ph->p_filesz;
/* if there's usable memory after the file end, we have
* to tell VM to clear the memory part of the page when it's
* mapped in
*/
if((pagechunk = (vfileend % PAGE_SIZE))
&& ph->p_filesz < ph->p_memsz) {
clearend = PAGE_SIZE - pagechunk;
}
seg_membytes = roundup(seg_membytes, PAGE_SIZE);
fbytes = roundup(fbytes, PAGE_SIZE);
if(first || startv > vaddr) startv = vaddr;
first = 0;
if ((ph->p_flags & PF_X) != 0 && execi->text_size < seg_membytes)
execi->text_size = seg_membytes;
else
execi->data_size = seg_membytes;
if(try_mmap && execi->memmap(execi, vaddr, fbytes, foffset, clearend, mmap_prot) == OK) {
#if ELF_DEBUG
printf("libexec: mmap 0x%lx-0x%lx done, clearend 0x%x\n",
vaddr, vaddr+fbytes, clearend);
#endif
if(seg_membytes > fbytes) {
int rem_mem = seg_membytes - fbytes;;
vir_bytes remstart = vaddr + fbytes;
if(execi->allocmem_ondemand(execi,
remstart, rem_mem) != OK) {
printf("libexec: mmap extra mem failed\n");
return ENOMEM;
}
#if ELF_DEBUG
else printf("libexec: allocated 0x%lx-0x%lx\n",
remstart, remstart+rem_mem);
#endif
}
} else {
/* make us some memory */
if(execi->allocmem_prealloc_junk(execi, vaddr, seg_membytes) != OK) {
if(execi->clearproc) execi->clearproc(execi);
return ENOMEM;
}
#if ELF_DEBUG
printf("mmapped 0x%lx-0x%lx\n", vaddr, vaddr+seg_membytes);
#endif
/* Copy executable section into it */
if(execi->copymem(execi, ph->p_offset, p_vaddr, ph->p_filesz) != OK) {
if(execi->clearproc) execi->clearproc(execi);
return ENOMEM;
}
#if ELF_DEBUG
printf("copied 0x%lx-0x%lx\n", p_vaddr, p_vaddr+ph->p_filesz);
#endif
/* Clear remaining bits */
vmemend = vaddr + seg_membytes;
if((chunk = p_vaddr - vaddr) > 0) {
#if ELF_DEBUG
printf("start clearing 0x%lx-0x%lx\n", vaddr, vaddr+chunk);
#endif
execi->clearmem(execi, vaddr, chunk);
}
if((chunk = vmemend - vfileend) > 0) {
#if ELF_DEBUG
printf("end clearing 0x%lx-0x%lx\n", vfileend, vaddr+chunk);
#endif
execi->clearmem(execi, vfileend, chunk);
}
}
}
/* Make it a stack */
if(execi->allocmem_ondemand(execi, stacklow, execi->stack_size) != OK) {
if(execi->clearproc) execi->clearproc(execi);
return ENOMEM;
}
#if ELF_DEBUG
printf("stack mmapped 0x%lx-0x%lx\n", stacklow, stacklow+execi->stack_size);
#endif
/* record entry point and lowest load vaddr for caller */
execi->pc = hdr->e_entry + execi->load_offset;
execi->load_base = startv;
return OK;
}
int libexec_load_elf(struct exec_info *execi)
{
Elf_Ehdr *hdr = NULL;
Elf_Phdr *phdr = NULL;
int e, i = 0;
int first = 1;
vir_bytes startv = 0, stacklow;
assert(execi != NULL);
assert(execi->hdr != NULL);
if((e=elf_unpack(execi->hdr, execi->hdr_len, &hdr, &phdr)) != OK) {
printf("libexec_load_elf: elf_unpack failed\n");
return e;
}
/* this function can load the dynamic linker, but that
* shouldn't require an interpreter itself.
*/
i = elf_has_interpreter(execi->hdr, execi->hdr_len, NULL, 0);
if(i > 0) {
return ENOEXEC;
}
execi->stack_size = roundup(execi->stack_size, PAGE_SIZE);
execi->stack_high = rounddown(execi->stack_high, PAGE_SIZE);
stacklow = execi->stack_high - execi->stack_size;
assert(execi->copymem);
assert(execi->clearmem);
assert(execi->allocmem_prealloc);
assert(execi->allocmem_ondemand);
if(execi->clearproc) execi->clearproc(execi);
for (i = 0; i < hdr->e_phnum; i++) {
vir_bytes seg_membytes, page_offset, p_vaddr, vaddr;
vir_bytes chunk, vfileend, vmemend;
Elf_Phdr *ph = &phdr[i];
if (ph->p_type != PT_LOAD || ph->p_memsz == 0) continue;
vaddr = p_vaddr = ph->p_vaddr + execi->load_offset;
seg_membytes = ph->p_memsz;
page_offset = vaddr % PAGE_SIZE;
vaddr -= page_offset;
seg_membytes += page_offset;
seg_membytes = roundup(seg_membytes, PAGE_SIZE);
if(first || startv > vaddr) startv = vaddr;
first = 0;
/* make us some memory */
if(execi->allocmem_prealloc(execi, vaddr, seg_membytes) != OK) {
if(execi->clearproc) execi->clearproc(execi);
return ENOMEM;
}
#if ELF_DEBUG
printf("mmapped 0x%lx-0x%lx\n", vaddr, vaddr+seg_membytes);
#endif
/* Copy executable section into it */
if(execi->copymem(execi, ph->p_offset, p_vaddr, ph->p_filesz) != OK) {
if(execi->clearproc) execi->clearproc(execi);
return ENOMEM;
}
#if ELF_DEBUG
printf("copied 0x%lx-0x%lx\n", p_vaddr, p_vaddr+ph->p_filesz);
#endif
/* Clear remaining bits */
vfileend = p_vaddr + ph->p_filesz;
vmemend = vaddr + seg_membytes;
if((chunk = p_vaddr - vaddr) > 0) {
#if ELF_DEBUG
printf("start clearing 0x%lx-0x%lx\n", vaddr, vaddr+chunk);
#endif
execi->clearmem(execi, vaddr, chunk);
}
if((chunk = vmemend - vfileend) > 0) {
#if ELF_DEBUG
printf("end clearing 0x%lx-0x%lx\n", vfileend, vaddr+chunk);
#endif
execi->clearmem(execi, vfileend, chunk);
}
}
/* Make it a stack */
if(execi->allocmem_ondemand(execi, stacklow, execi->stack_size) != OK) {
if(execi->clearproc) execi->clearproc(execi);
return ENOMEM;
}
#if ELF_DEBUG
printf("stack mmapped 0x%lx-0x%lx\n", stacklow, stacklow+execi->stack_size);
#endif
/* record entry point and lowest load vaddr for caller */
execi->pc = hdr->e_entry + execi->load_offset;
execi->load_base = startv;
return OK;
}
