static int
mprotect_segments (char *base, const Elf_Phdr *from, const Elf_Phdr *to)
{
return mprotect (base + from->p_vaddr,
to->p_vaddr + to->p_memsz - from->p_vaddr,
segment_flags_to_prot (from->p_flags));
}
static int
map_segments (int fd, char **base,
const Elf_Phdr *from, const Elf_Phdr *to)
{
int prot = segment_flags_to_prot (from->p_flags);
char *ret;
ret = mmap (*base + from->p_vaddr,
to->p_offset + to->p_filesz - from->p_offset,
prot, MAP_PRIVATE, fd, from->p_offset);
if (ret == (char *) -1)
return 1;
if (!*base)
*base = ret;
return 0;
}
static SCM
load_thunk_from_memory (char *data, size_t len, int is_read_only)
#define FUNC_NAME "load-thunk-from-memory"
{
Elf_Ehdr *header;
Elf_Phdr *ph;
const char *err_msg = 0;
size_t n, alignment = 8;
int i;
int dynamic_segment = -1;
SCM init = SCM_BOOL_F, entry = SCM_BOOL_F;
char *frame_maps = 0;
if (len < sizeof *header)
ABORT ("object file too small");
header = (Elf_Ehdr*) data;
if ((err_msg = check_elf_header (header)))
goto cleanup;
if (header->e_phnum == 0)
ABORT ("no loadable segments");
n = header->e_phnum;
if (len < header->e_phoff + n * sizeof (Elf_Phdr))
ABORT ("object file too small");
ph = (Elf_Phdr*) (data + header->e_phoff);
/* Check that the segment table is sane. */
for (i = 0; i < n; i++)
{
if (ph[i].p_filesz != ph[i].p_memsz)
ABORT ("expected p_filesz == p_memsz");
if (!ph[i].p_flags)
ABORT ("expected nonzero segment flags");
if (ph[i].p_align < alignment)
{
if (ph[i].p_align % alignment)
ABORT ("expected new alignment to be multiple of old");
alignment = ph[i].p_align;
}
if (ph[i].p_type == PT_DYNAMIC)
{
if (dynamic_segment >= 0)
ABORT ("expected only one PT_DYNAMIC segment");
dynamic_segment = i;
continue;
}
if (ph[i].p_type != PT_LOAD)
ABORT ("unknown segment type");
if (i == 0)
{
if (ph[i].p_vaddr != 0)
ABORT ("first loadable vaddr is not 0");
}
else
{
if (ph[i].p_vaddr < ph[i-1].p_vaddr + ph[i-1].p_memsz)
ABORT ("overlapping segments");
if (ph[i].p_offset + ph[i].p_filesz > len)
ABORT ("segment beyond end of byte array");
}
}
if (dynamic_segment < 0)
ABORT ("no PT_DYNAMIC segment");
if (!IS_ALIGNED ((scm_t_uintptr) data, alignment))
ABORT ("incorrectly aligned base");
/* Allow writes to writable pages. */
if (is_read_only)
{
#ifdef HAVE_SYS_MMAN_H
for (i = 0; i < n; i++)
{
if (ph[i].p_type != PT_LOAD)
continue;
if (ph[i].p_flags == PF_R)
continue;
if (ph[i].p_align != 4096)
continue;
if (mprotect (data + ph[i].p_vaddr,
ph[i].p_memsz,
segment_flags_to_prot (ph[i].p_flags)))
goto cleanup;
}
#else
ABORT ("expected writable pages");
#endif
}
if ((err_msg = process_dynamic_segment (data, &ph[dynamic_segment],
&init, &entry, &frame_maps)))
goto cleanup;
if (scm_is_true (init))
scm_call_0 (init);
register_elf (data, len, frame_maps);
/* Finally! Return the thunk. */
return entry;
cleanup:
{
if (errno)
SCM_SYSERROR;
scm_misc_error (FUNC_NAME, err_msg ? err_msg : "error loading ELF file",
SCM_EOL);
}
}
