static Elf_Ehdr *
get_elf_header(int fd, const char *path)
{
Elf_Ehdr *hdr;
/* DragonFly mmap does not have MAP_PREFAULT_READ */
hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE, fd, 0);
if (hdr == (Elf_Ehdr *)MAP_FAILED) {
_rtld_error("%s: read error: %s", path, rtld_strerror(errno));
return (NULL);
}
/* Make sure the file is valid */
if (!IS_ELF(*hdr)) {
_rtld_error("%s: invalid file format", path);
goto error;
}
if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
_rtld_error("%s: unsupported file layout", path);
goto error;
}
if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
hdr->e_version != EV_CURRENT) {
_rtld_error("%s: unsupported file version", path);
goto error;
}
if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
_rtld_error("%s: unsupported file type", path);
goto error;
}
if (hdr->e_machine != ELF_TARG_MACH) {
_rtld_error("%s: unsupported machine", path);
goto error;
}
/*
* We rely on the program header being in the first page. This is
* not strictly required by the ABI specification, but it seems to
* always true in practice. And, it simplifies things considerably.
*/
if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
_rtld_error(
"%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
goto error;
}
if (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) >
(size_t)PAGE_SIZE) {
_rtld_error("%s: program header too large", path);
goto error;
}
return (hdr);
error:
munmap(hdr, PAGE_SIZE);
return (NULL);
}
int
lm_init(char *libmap_override)
{
struct stat st;
char *lm_map, *p;
int fd;
dbg("lm_init(\"%s\")", libmap_override);
TAILQ_INIT(&lmp_head);
fd = open(_PATH_LIBMAP_CONF, O_RDONLY);
if (fd == -1) {
dbg("lm_init: open(\"%s\") failed, %s", _PATH_LIBMAP_CONF,
rtld_strerror(errno));
goto override;
}
/*
* Map a shared object into memory. The "fd" argument is a file descriptor,
* which must be open on the object and positioned at its beginning.
* The "path" argument is a pathname that is used only for error messages.
*
* The return value is a pointer to a newly-allocated Obj_Entry structure
* for the shared object. Returns NULL on failure.
*/
Obj_Entry *
map_object(int fd, const char *path, const struct stat *sb)
{
Obj_Entry *obj;
Elf_Ehdr *hdr;
int i;
Elf_Phdr *phdr;
Elf_Phdr *phlimit;
Elf_Phdr **segs;
int nsegs;
Elf_Phdr *phdyn;
Elf_Phdr *phinterp;
Elf_Phdr *phtls;
caddr_t mapbase;
caddr_t shlib_base;
size_t mapsize;
Elf_Addr base_vaddr;
Elf_Addr base_vlimit;
caddr_t base_addr;
Elf_Off data_offset;
Elf_Addr data_vaddr;
Elf_Addr data_vlimit;
caddr_t data_addr;
int data_prot;
int data_flags;
Elf_Addr clear_vaddr;
caddr_t clear_addr;
caddr_t clear_page;
Elf_Addr phdr_vaddr;
size_t nclear, phsize;
Elf_Addr bss_vaddr;
Elf_Addr bss_vlimit;
caddr_t bss_addr;
Elf_Word stack_flags;
Elf_Addr relro_page;
size_t relro_size;
Elf_Addr note_start;
Elf_Addr note_end;
hdr = get_elf_header(fd, path);
if (hdr == NULL)
return (NULL);
if (__ld_sharedlib_base) {
shlib_base = (void *)(intptr_t)strtoul(__ld_sharedlib_base, NULL, 0);
} else {
shlib_base = NULL;
}
/*
* Scan the program header entries, and save key information.
*
* We expect that the loadable segments are ordered by load address.
*/
phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff);
phsize = hdr->e_phnum * sizeof (phdr[0]);
phlimit = phdr + hdr->e_phnum;
nsegs = -1;
phdyn = phinterp = phtls = NULL;
phdr_vaddr = 0;
relro_page = 0;
relro_size = 0;
note_start = 0;
note_end = 0;
segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W;
while (phdr < phlimit) {
switch (phdr->p_type) {
case PT_INTERP:
phinterp = phdr;
break;
case PT_LOAD:
segs[++nsegs] = phdr;
if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) {
_rtld_error("%s: PT_LOAD segment %d not page-aligned",
path, nsegs);
goto error;
}
break;
case PT_PHDR:
phdr_vaddr = phdr->p_vaddr;
phsize = phdr->p_memsz;
break;
case PT_DYNAMIC:
phdyn = phdr;
break;
case PT_TLS:
phtls = phdr;
break;
case PT_GNU_STACK:
stack_flags = phdr->p_flags;
break;
case PT_GNU_RELRO:
relro_page = phdr->p_vaddr;
relro_size = phdr->p_memsz;
break;
case PT_NOTE:
if (phdr->p_offset > PAGE_SIZE ||
phdr->p_offset + phdr->p_filesz > PAGE_SIZE)
break;
note_start = (Elf_Addr)(char *)hdr + phdr->p_offset;
note_end = note_start + phdr->p_filesz;
break;
}
++phdr;
}
if (phdyn == NULL) {
_rtld_error("%s: object is not dynamically-linked", path);
goto error;
}
if (nsegs < 0) {
_rtld_error("%s: too few PT_LOAD segments", path);
goto error;
}
/*
* Map the entire address space of the object, to stake out our
* contiguous region, and to establish the base address for relocation.
*/
base_vaddr = trunc_page(segs[0]->p_vaddr);
base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
mapsize = base_vlimit - base_vaddr;
base_addr = (caddr_t) base_vaddr;
if (base_addr == NULL && shlib_base) {
size_t limit = 1024 * 256 * 1024;
size_t offset;
for (offset = 0; offset < limit; offset += 256 * 1024) {
mapbase = mmap(shlib_base + offset, mapsize,
PROT_NONE,
MAP_ANON | MAP_PRIVATE | MAP_NOCORE |
MAP_TRYFIXED,
-1, 0);
if (mapbase != MAP_FAILED)
break;
}
} else {
mapbase = mmap(base_addr, mapsize,
PROT_NONE,
MAP_ANON | MAP_PRIVATE | MAP_NOCORE,
-1, 0);
}
if (mapbase == (caddr_t) -1) {
_rtld_error("%s: mmap of entire address space failed: %s",
path, rtld_strerror(errno));
goto error;
}
if (base_addr != NULL && mapbase != base_addr) {
_rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
path, base_addr, mapbase);
goto error1;
}
for (i = 0; i <= nsegs; i++) {
/* Overlay the segment onto the proper region. */
data_offset = trunc_page(segs[i]->p_offset);
data_vaddr = trunc_page(segs[i]->p_vaddr);
data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz);
data_addr = mapbase + (data_vaddr - base_vaddr);
data_prot = convert_prot(segs[i]->p_flags);
data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
if (mmap(data_addr, data_vlimit - data_vaddr, data_prot,
data_flags, fd, data_offset) == (caddr_t) -1) {
_rtld_error("%s: mmap of data failed: %s", path,
rtld_strerror(errno));
goto error1;
}
/* Do BSS setup */
if (segs[i]->p_filesz != segs[i]->p_memsz) {
/* Clear any BSS in the last page of the segment. */
clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
clear_addr = mapbase + (clear_vaddr - base_vaddr);
clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr);
if ((nclear = data_vlimit - clear_vaddr) > 0) {
/* Make sure the end of the segment is writable */
if ((data_prot & PROT_WRITE) == 0 && -1 ==
mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) {
_rtld_error("%s: mprotect failed: %s", path,
rtld_strerror(errno));
goto error1;
}
memset(clear_addr, 0, nclear);
/*
* reset the data protection back, enable the segment to be
* coredumped since we modified it.
*/
if ((data_prot & PROT_WRITE) == 0) {
madvise(clear_page, PAGE_SIZE, MADV_CORE);
mprotect(clear_page, PAGE_SIZE, data_prot);
}
}
/* Overlay the BSS segment onto the proper region. */
bss_vaddr = data_vlimit;
bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz);
bss_addr = mapbase + (bss_vaddr - base_vaddr);
if (bss_vlimit > bss_vaddr) { /* There is something to do */
if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot,
data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) {
_rtld_error("%s: mmap of bss failed: %s", path,
rtld_strerror(errno));
goto error1;
}
}
}
if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff &&
(data_vlimit - data_vaddr + data_offset) >=
(hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) {
phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset;
}
}
obj = obj_new();
if (sb != NULL) {
obj->dev = sb->st_dev;
obj->ino = sb->st_ino;
}
obj->mapbase = mapbase;
obj->mapsize = mapsize;
obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
base_vaddr;
obj->vaddrbase = base_vaddr;
obj->relocbase = mapbase - base_vaddr;
obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
if (hdr->e_entry != 0)
obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry);
if (phdr_vaddr != 0) {
obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr);
} else {
obj->phdr = malloc(phsize);
if (obj->phdr == NULL) {
obj_free(obj);
_rtld_error("%s: cannot allocate program header", path);
goto error1;
}
memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize);
obj->phdr_alloc = true;
}
obj->phsize = phsize;
if (phinterp != NULL)
obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr);
if (phtls != NULL) {
tls_dtv_generation++;
obj->tlsindex = ++tls_max_index;
obj->tlssize = phtls->p_memsz;
obj->tlsalign = phtls->p_align;
obj->tlsinitsize = phtls->p_filesz;
obj->tlsinit = mapbase + phtls->p_vaddr;
}
obj->stack_flags = stack_flags;
if (relro_size) {
obj->relro_page = obj->relocbase + trunc_page(relro_page);
obj->relro_size = round_page(relro_size);
}
if (note_start < note_end)
digest_notes(obj, note_start, note_end);
munmap(hdr, PAGE_SIZE);
return (obj);
error1:
munmap(mapbase, mapsize);
error:
munmap(hdr, PAGE_SIZE);
return (NULL);
}
