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dynlink.c
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#define _GNU_SOURCE
#define SYSCALL_NO_TLS 1
#include <stdlib.h>
#include <stdarg.h>
#include <stddef.h>
#include <string.h>
#include <unistd.h>
#include <stdint.h>
#include <elf.h>
#include <sys/mman.h>
#include <limits.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
#include <link.h>
#include <setjmp.h>
#include <pthread.h>
#include <ctype.h>
#include <dlfcn.h>
#include <semaphore.h>
#include <sys/membarrier.h>
#include "pthread_impl.h"
#include "fork_impl.h"
#include "libc.h"
#include "dynlink.h"
static size_t ldso_page_size;
/* libc.h may have defined a macro for dynamic PAGE_SIZE already, but
* PAGESIZE is only defined if it's constant for the arch. */
#ifndef PAGESIZE
#undef PAGE_SIZE
#define PAGE_SIZE ldso_page_size
#endif
#define malloc __libc_malloc
#define calloc __libc_calloc
#define realloc __libc_realloc
#define free __libc_free
static void error_impl(const char *, ...);
static void error_noop(const char *, ...);
static void (*error)(const char *, ...) = error_noop;
#define MAXP2(a,b) (-(-(a)&-(b)))
#define ALIGN(x,y) ((x)+(y)-1 & -(y))
#define container_of(p,t,m) ((t*)((char *)(p)-offsetof(t,m)))
#define countof(a) ((sizeof (a))/(sizeof (a)[0]))
struct debug {
int ver;
void *head;
void (*bp)(void);
int state;
void *base;
};
struct td_index {
size_t args[2];
struct td_index *next;
};
struct dso {
#if DL_FDPIC
struct fdpic_loadmap *loadmap;
#else
unsigned char *base;
#endif
char *name;
size_t *dynv;
struct dso *next, *prev;
Phdr *phdr;
int phnum;
size_t phentsize;
Sym *syms;
Elf_Symndx *hashtab;
uint32_t *ghashtab;
int16_t *versym;
char *strings;
struct dso *syms_next, *lazy_next;
size_t *lazy, lazy_cnt;
unsigned char *map;
size_t map_len;
dev_t dev;
ino_t ino;
char relocated;
char constructed;
char kernel_mapped;
char mark;
char bfs_built;
char runtime_loaded;
struct dso **deps, *needed_by;
size_t ndeps_direct;
size_t next_dep;
pthread_t ctor_visitor;
char *rpath_orig, *rpath;
struct tls_module tls;
size_t tls_id;
size_t relro_start, relro_end;
uintptr_t *new_dtv;
unsigned char *new_tls;
struct td_index *td_index;
struct dso *fini_next;
char *shortname;
#if DL_FDPIC
unsigned char *base;
#else
struct fdpic_loadmap *loadmap;
#endif
struct funcdesc {
void *addr;
size_t *got;
} *funcdescs;
size_t *got;
char buf[];
};
struct symdef {
Sym *sym;
struct dso *dso;
};
typedef void (*stage3_func)(size_t *, size_t *);
// in ldso_rcrt1.c
typedef void (*stage4_func)(size_t * /* sp */);
static struct builtin_tls {
char c;
struct pthread pt;
void *space[16];
} builtin_tls[1];
#define MIN_TLS_ALIGN offsetof(struct builtin_tls, pt)
/* To support initial-exec TLS for dynamically loaded libraries via
* dlopen(), we pre-allocate some TLS entries of a static size,
* then try to use them for dynamic TLS entries at run-time.
* Note that the size-per-entry is based on empiric testing of some
* system libraries that use TLS + some margin. */
#define TLS_STATIC_RESERVE_COUNT 16u
#define TLS_STATIC_RESERVE_SIZE_PER_ENTRY 256u
#define ADDEND_LIMIT 4096
static size_t *saved_addends, *apply_addends_to;
static struct dso ldso;
static struct dso *head, *tail, *fini_head, *syms_tail, *lazy_head;
static char *env_path, *sys_path;
static unsigned long long gencnt;
static int runtime;
static int ldd_mode;
static int ldso_fail;
static int noload;
static int shutting_down;
static jmp_buf *rtld_fail;
static pthread_rwlock_t lock;
static struct debug debug;
static struct tls_module *tls_tail;
static size_t tls_cnt, tls_offset, tls_align = MIN_TLS_ALIGN;
static size_t static_tls_cnt;
static size_t static_tls_size;
static pthread_mutex_t init_fini_lock;
static pthread_cond_t ctor_cond;
static struct dso *builtin_deps[2];
static struct dso *const no_deps[1];
static struct dso *builtin_ctor_queue[4];
static struct dso **main_ctor_queue;
static struct fdpic_loadmap *app_loadmap;
static struct fdpic_dummy_loadmap app_dummy_loadmap;
struct debug *_dl_debug_addr = &debug;
extern weak hidden char __ehdr_start[];
extern hidden int __malloc_replaced;
hidden void (*const __init_array_start)(void)=0, (*const __fini_array_start)(void)=0;
extern hidden void (*const __init_array_end)(void), (*const __fini_array_end)(void);
weak_alias(__init_array_start, __init_array_end);
weak_alias(__fini_array_start, __fini_array_end);
static int dl_strcmp(const char *l, const char *r)
{
for (; *l==*r && *l; l++, r++);
return *(unsigned char *)l - *(unsigned char *)r;
}
#define strcmp(l,r) dl_strcmp(l,r)
/* Compute load address for a virtual address in a given dso. */
#if DL_FDPIC
static void *laddr(const struct dso *p, size_t v)
{
size_t j=0;
if (!p->loadmap) return p->base + v;
for (j=0; v-p->loadmap->segs[j].p_vaddr >= p->loadmap->segs[j].p_memsz; j++);
return (void *)(v - p->loadmap->segs[j].p_vaddr + p->loadmap->segs[j].addr);
}
static void *laddr_pg(const struct dso *p, size_t v)
{
size_t j=0;
size_t pgsz = PAGE_SIZE;
if (!p->loadmap) return p->base + v;
for (j=0; ; j++) {
size_t a = p->loadmap->segs[j].p_vaddr;
size_t b = a + p->loadmap->segs[j].p_memsz;
a &= -pgsz;
b += pgsz-1;
b &= -pgsz;
if (v-a<b-a) break;
}
return (void *)(v - p->loadmap->segs[j].p_vaddr + p->loadmap->segs[j].addr);
}
static void (*fdbarrier(void *p))()
{
void (*fd)();
__asm__("" : "=r"(fd) : "0"(p));
return fd;
}
#define fpaddr(p, v) fdbarrier((&(struct funcdesc){ \
laddr(p, v), (p)->got }))
#else
#define laddr(p, v) (void *)((p)->base + (v))
#define laddr_pg(p, v) laddr(p, v)
#define fpaddr(p, v) ((void (*)())laddr(p, v))
#endif
static void decode_vec(size_t *v, size_t *a, size_t cnt)
{
size_t i;
for (i=0; i<cnt; i++) a[i] = 0;
for (; v[0]; v+=2) if (v[0]-1<cnt-1) {
if (v[0] < 8*sizeof(long))
a[0] |= 1UL<<v[0];
a[v[0]] = v[1];
}
}
static int search_vec(size_t *v, size_t *r, size_t key)
{
for (; v[0]!=key; v+=2)
if (!v[0]) return 0;
*r = v[1];
return 1;
}
static uint32_t sysv_hash(const char *s0)
{
const unsigned char *s = (void *)s0;
uint_fast32_t h = 0;
while (*s) {
h = 16*h + *s++;
h ^= h>>24 & 0xf0;
}
return h & 0xfffffff;
}
static uint32_t gnu_hash(const char *s0)
{
const unsigned char *s = (void *)s0;
uint_fast32_t h = 5381;
for (; *s; s++)
h += h*32 + *s;
return h;
}
static Sym *sysv_lookup(const char *s, uint32_t h, struct dso *dso)
{
size_t i;
Sym *syms = dso->syms;
Elf_Symndx *hashtab = dso->hashtab;
char *strings = dso->strings;
for (i=hashtab[2+h%hashtab[0]]; i; i=hashtab[2+hashtab[0]+i]) {
if ((!dso->versym || dso->versym[i] >= 0)
&& (!strcmp(s, strings+syms[i].st_name)))
return syms+i;
}
return 0;
}
static Sym *gnu_lookup(uint32_t h1, uint32_t *hashtab, struct dso *dso, const char *s)
{
uint32_t nbuckets = hashtab[0];
uint32_t *buckets = hashtab + 4 + hashtab[2]*(sizeof(size_t)/4);
uint32_t i = buckets[h1 % nbuckets];
if (!i) return 0;
uint32_t *hashval = buckets + nbuckets + (i - hashtab[1]);
for (h1 |= 1; ; i++) {
uint32_t h2 = *hashval++;
if ((h1 == (h2|1)) && (!dso->versym || dso->versym[i] >= 0)
&& !strcmp(s, dso->strings + dso->syms[i].st_name))
return dso->syms+i;
if (h2 & 1) break;
}
return 0;
}
static Sym *gnu_lookup_filtered(uint32_t h1, uint32_t *hashtab, struct dso *dso, const char *s, uint32_t fofs, size_t fmask)
{
const size_t *bloomwords = (const void *)(hashtab+4);
size_t f = bloomwords[fofs & (hashtab[2]-1)];
if (!(f & fmask)) return 0;
f >>= (h1 >> hashtab[3]) % (8 * sizeof f);
if (!(f & 1)) return 0;
return gnu_lookup(h1, hashtab, dso, s);
}
#define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON | 1<<STT_TLS)
#define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK | 1<<STB_GNU_UNIQUE)
#ifndef ARCH_SYM_REJECT_UND
#define ARCH_SYM_REJECT_UND(s) 0
#endif
#if defined(__GNUC__)
__attribute__((always_inline))
#endif
static inline struct symdef find_sym2(struct dso *dso, const char *s, int need_def, int use_deps)
{
uint32_t h = 0, gh = gnu_hash(s), gho = gh / (8*sizeof(size_t)), *ght;
size_t ghm = 1ul << gh % (8*sizeof(size_t));
struct symdef def = {0};
struct dso **deps = use_deps ? dso->deps : 0;
for (; dso; dso=use_deps ? *deps++ : dso->syms_next) {
Sym *sym;
if ((ght = dso->ghashtab)) {
sym = gnu_lookup_filtered(gh, ght, dso, s, gho, ghm);
} else {
if (!h) h = sysv_hash(s);
sym = sysv_lookup(s, h, dso);
}
if (!sym) continue;
if (!sym->st_shndx)
if (need_def || (sym->st_info&0xf) == STT_TLS
|| ARCH_SYM_REJECT_UND(sym))
continue;
if (!sym->st_value)
if ((sym->st_info&0xf) != STT_TLS)
continue;
if (!(1<<(sym->st_info&0xf) & OK_TYPES)) continue;
if (!(1<<(sym->st_info>>4) & OK_BINDS)) continue;
def.sym = sym;
def.dso = dso;
break;
}
return def;
}
static struct symdef find_sym(struct dso *dso, const char *s, int need_def)
{
return find_sym2(dso, s, need_def, 0);
}
static struct symdef get_lfs64(const char *name)
{
const char *p;
static const char lfs64_list[] =
"aio_cancel\0aio_error\0aio_fsync\0aio_read\0aio_return\0"
"aio_suspend\0aio_write\0alphasort\0creat\0fallocate\0"
"fgetpos\0fopen\0freopen\0fseeko\0fsetpos\0fstat\0"
"fstatat\0fstatfs\0fstatvfs\0ftello\0ftruncate\0ftw\0"
"getdents\0getrlimit\0glob\0globfree\0lio_listio\0"
"lockf\0lseek\0lstat\0mkostemp\0mkostemps\0mkstemp\0"
"mkstemps\0mmap\0nftw\0open\0openat\0posix_fadvise\0"
"posix_fallocate\0pread\0preadv\0prlimit\0pwrite\0"
"pwritev\0readdir\0scandir\0sendfile\0setrlimit\0"
"stat\0statfs\0statvfs\0tmpfile\0truncate\0versionsort\0"
"__fxstat\0__fxstatat\0__lxstat\0__xstat\0fcntl\0";
if (!strcmp(name, "readdir64_r"))
return find_sym(&ldso, "readdir_r", 1);
size_t l = strnlen(name, 18);
if (l<2 || name[l-2]!='6' || name[l-1]!='4' || name[l])
goto nomatch;
for (p=lfs64_list; *p; p++) {
if (!strncmp(name, p, l-2) && !p[l-2])
return find_sym(&ldso, p, 1);
while (*p) p++;
}
nomatch:
return (struct symdef){ 0 };
}
static void do_relocs(struct dso *dso, size_t *rel, size_t rel_size, size_t stride)
{
unsigned char *base = dso->base;
Sym *syms = dso->syms;
char *strings = dso->strings;
Sym *sym;
const char *name;
void *ctx;
int type;
int sym_index;
struct symdef def;
size_t *reloc_addr;
size_t sym_val;
size_t tls_val;
size_t addend;
int skip_relative = 0, reuse_addends = 0, save_slot = 0;
if (dso == &ldso) {
/* Only ldso's REL table needs addend saving/reuse. */
if (rel == apply_addends_to)
reuse_addends = 1;
skip_relative = 1;
}
for (; rel_size; rel+=stride, rel_size-=stride*sizeof(size_t)) {
if (skip_relative && IS_RELATIVE(rel[1], dso->syms)) continue;
type = R_TYPE(rel[1]);
if (type == REL_NONE) continue;
reloc_addr = laddr(dso, rel[0]);
if (stride > 2) {
addend = rel[2];
} else if (type==REL_GOT || type==REL_PLT|| type==REL_COPY) {
addend = 0;
} else if (reuse_addends) {
/* Save original addend in stage 2 where the dso
* chain consists of just ldso; otherwise read back
* saved addend since the inline one was clobbered. */
if (head==&ldso)
saved_addends[save_slot] = *reloc_addr;
addend = saved_addends[save_slot++];
} else {
addend = *reloc_addr;
}
sym_index = R_SYM(rel[1]);
if (sym_index) {
sym = syms + sym_index;
name = strings + sym->st_name;
ctx = type==REL_COPY ? head->syms_next : head;
def = (sym->st_info>>4) == STB_LOCAL
? (struct symdef){ .dso = dso, .sym = sym }
: find_sym(ctx, name, type==REL_PLT);
if (!def.sym) def = get_lfs64(name);
if (!def.sym && (sym->st_shndx != SHN_UNDEF
|| sym->st_info>>4 != STB_WEAK)) {
if (dso->lazy && (type==REL_PLT || type==REL_GOT)) {
dso->lazy[3*dso->lazy_cnt+0] = rel[0];
dso->lazy[3*dso->lazy_cnt+1] = rel[1];
dso->lazy[3*dso->lazy_cnt+2] = addend;
dso->lazy_cnt++;
continue;
}
error("Error relocating %s: %s: symbol not found",
dso->name, name);
if (runtime) longjmp(*rtld_fail, 1);
continue;
}
} else {
sym = 0;
def.sym = 0;
def.dso = dso;
}
sym_val = def.sym ? (size_t)laddr(def.dso, def.sym->st_value) : 0;
tls_val = def.sym ? def.sym->st_value : 0;
if ((type == REL_TPOFF || type == REL_TPOFF_NEG)
&& def.dso->tls_id > static_tls_cnt) {
__builtin_debugtrap();
error("Error relocating %s: %s: initial-exec TLS "
"resolves to dynamic definition in %s",
dso->name, name, def.dso->name);
longjmp(*rtld_fail, 1);
}
switch(type) {
case REL_OFFSET:
addend -= (size_t)reloc_addr;
case REL_SYMBOLIC:
case REL_GOT:
case REL_PLT:
*reloc_addr = sym_val + addend;
break;
case REL_USYMBOLIC:
memcpy(reloc_addr, &(size_t){sym_val + addend}, sizeof(size_t));
break;
case REL_RELATIVE:
*reloc_addr = (size_t)base + addend;
break;
case REL_SYM_OR_REL:
if (sym) *reloc_addr = sym_val + addend;
else *reloc_addr = (size_t)base + addend;
break;
case REL_COPY:
memcpy(reloc_addr, (void *)sym_val, sym->st_size);
break;
case REL_OFFSET32:
*(uint32_t *)reloc_addr = sym_val + addend
- (size_t)reloc_addr;
break;
case REL_FUNCDESC:
*reloc_addr = def.sym ? (size_t)(def.dso->funcdescs
+ (def.sym - def.dso->syms)) : 0;
break;
case REL_FUNCDESC_VAL:
if ((sym->st_info&0xf) == STT_SECTION) *reloc_addr += sym_val;
else *reloc_addr = sym_val;
reloc_addr[1] = def.sym ? (size_t)def.dso->got : 0;
break;
case REL_DTPMOD:
*reloc_addr = def.dso->tls_id;
break;
case REL_DTPOFF:
*reloc_addr = tls_val + addend - DTP_OFFSET;
break;
#ifdef TLS_ABOVE_TP
case REL_TPOFF:
*reloc_addr = tls_val + def.dso->tls.offset + TPOFF_K + addend;
break;
#else
case REL_TPOFF:
*reloc_addr = tls_val - def.dso->tls.offset + addend;
break;
case REL_TPOFF_NEG:
*reloc_addr = def.dso->tls.offset - tls_val + addend;
break;
#endif
case REL_TLSDESC:
if (stride<3) addend = reloc_addr[!TLSDESC_BACKWARDS];
if (def.dso->tls_id > static_tls_cnt) {
struct td_index *new = malloc(sizeof *new);
if (!new) {
error(
"Error relocating %s: cannot allocate TLSDESC for %s",
dso->name, sym ? name : "(local)" );
longjmp(*rtld_fail, 1);
}
new->next = dso->td_index;
dso->td_index = new;
new->args[0] = def.dso->tls_id;
new->args[1] = tls_val + addend - DTP_OFFSET;
reloc_addr[0] = (size_t)__tlsdesc_dynamic;
reloc_addr[1] = (size_t)new;
} else {
reloc_addr[0] = (size_t)__tlsdesc_static;
#ifdef TLS_ABOVE_TP
reloc_addr[1] = tls_val + def.dso->tls.offset
+ TPOFF_K + addend;
#else
reloc_addr[1] = tls_val - def.dso->tls.offset
+ addend;
#endif
}
/* Some archs (32-bit ARM at least) invert the order of
* the descriptor members. Fix them up here. */
if (TLSDESC_BACKWARDS) {
size_t tmp = reloc_addr[0];
reloc_addr[0] = reloc_addr[1];
reloc_addr[1] = tmp;
}
break;
case REL_IRELATIVE:
*reloc_addr = (size_t)base + addend;
*reloc_addr = ((size_t(*)(void))*reloc_addr)();
break;
default:
error("Error relocating %s: unsupported relocation type %d",
dso->name, type);
if (runtime) longjmp(*rtld_fail, 1);
continue;
}
}
}
static void do_relr_relocs(struct dso *dso, size_t *relr, size_t relr_size)
{
if (dso == &ldso) return; /* self-relocation was done in _dlstart */
unsigned char *base = dso->base;
size_t *reloc_addr;
for (; relr_size; relr++, relr_size-=sizeof(size_t))
if ((relr[0]&1) == 0) {
reloc_addr = laddr(dso, relr[0]);
*reloc_addr++ += (size_t)base;
} else {
int i = 0;
for (size_t bitmap=relr[0]; (bitmap>>=1); i++)
if (bitmap&1)
reloc_addr[i] += (size_t)base;
reloc_addr += 8*sizeof(size_t)-1;
}
}
static void redo_lazy_relocs()
{
struct dso *p = lazy_head, *next;
lazy_head = 0;
for (; p; p=next) {
next = p->lazy_next;
size_t size = p->lazy_cnt*3*sizeof(size_t);
p->lazy_cnt = 0;
do_relocs(p, p->lazy, size, 3);
if (p->lazy_cnt) {
p->lazy_next = lazy_head;
lazy_head = p;
} else {
free(p->lazy);
p->lazy = 0;
p->lazy_next = 0;
}
}
}
/* A huge hack: to make up for the wastefulness of shared libraries
* needing at least a page of dirty memory even if they have no global
* data, we reclaim the gaps at the beginning and end of writable maps
* and "donate" them to the heap. */
static void reclaim(struct dso *dso, size_t start, size_t end)
{
if (start >= dso->relro_start && start < dso->relro_end) start = dso->relro_end;
if (end >= dso->relro_start && end < dso->relro_end) end = dso->relro_start;
if (start >= end) return;
char *base = laddr_pg(dso, start);
__malloc_donate(base, base+(end-start));
}
static void reclaim_gaps(struct dso *dso)
{
Phdr *ph = dso->phdr;
size_t phcnt = dso->phnum;
for (; phcnt--; ph=(void *)((char *)ph+dso->phentsize)) {
if (ph->p_type!=PT_LOAD) continue;
if ((ph->p_flags&(PF_R|PF_W))!=(PF_R|PF_W)) continue;
if (ph->p_memsz == 0) continue;
reclaim(dso, ph->p_vaddr & -PAGE_SIZE, ph->p_vaddr);
reclaim(dso, ph->p_vaddr+ph->p_memsz,
ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE);
}
}
static ssize_t read_loop(int fd, void *p, size_t n)
{
for (size_t i=0; i<n; ) {
ssize_t l = read(fd, (char *)p+i, n-i);
if (l<0) {
if (errno==EINTR) continue;
else return -1;
}
if (l==0) return i;
i += l;
}
return n;
}
static void *mmap_fixed(void *p, size_t n, int prot, int flags, int fd, off_t off)
{
static int no_map_fixed;
char *q;
if (!n) return p;
if (!no_map_fixed) {
q = mmap(p, n, prot, flags|MAP_FIXED, fd, off);
if (!DL_NOMMU_SUPPORT || q != MAP_FAILED || errno != EINVAL)
return q;
no_map_fixed = 1;
}
/* Fallbacks for MAP_FIXED failure on NOMMU kernels. */
if (flags & MAP_ANONYMOUS) {
memset(p, 0, n);
return p;
}
ssize_t r;
if (lseek(fd, off, SEEK_SET) < 0) return MAP_FAILED;
for (q=p; n; q+=r, off+=r, n-=r) {
r = read(fd, q, n);
if (r < 0 && errno != EINTR) return MAP_FAILED;
if (!r) {
memset(q, 0, n);
break;
}
}
return p;
}
static void unmap_library(struct dso *dso)
{
if (dso->loadmap) {
size_t i;
for (i=0; i<dso->loadmap->nsegs; i++) {
if (!dso->loadmap->segs[i].p_memsz)
continue;
munmap((void *)dso->loadmap->segs[i].addr,
dso->loadmap->segs[i].p_memsz);
}
free(dso->loadmap);
} else if (dso->map && dso->map_len) {
munmap(dso->map, dso->map_len);
}
}
static void *map_library(int fd, struct dso *dso)
{
Ehdr buf[(896+sizeof(Ehdr))/sizeof(Ehdr)];
void *allocated_buf=0;
size_t phsize;
size_t addr_min=SIZE_MAX, addr_max=0, map_len;
size_t this_min, this_max;
size_t nsegs = 0;
off_t off_start;
Ehdr *eh;
Phdr *ph, *ph0;
unsigned prot;
unsigned char *map=MAP_FAILED, *base;
size_t dyn=0;
size_t tls_image=0;
size_t i;
ssize_t l = read(fd, buf, sizeof buf);
eh = buf;
if (l<0) return 0;
if (l<sizeof *eh || (eh->e_type != ET_DYN && eh->e_type != ET_EXEC))
goto noexec;
phsize = eh->e_phentsize * eh->e_phnum;
if (phsize > sizeof buf - sizeof *eh) {
allocated_buf = malloc(phsize);
if (!allocated_buf) return 0;
l = pread(fd, allocated_buf, phsize, eh->e_phoff);
if (l < 0) goto error;
if (l != phsize) goto noexec;
ph = ph0 = allocated_buf;
} else if (eh->e_phoff + phsize > l) {
l = pread(fd, buf+1, phsize, eh->e_phoff);
if (l < 0) goto error;
if (l != phsize) goto noexec;
ph = ph0 = (void *)(buf + 1);
} else {
ph = ph0 = (void *)((char *)buf + eh->e_phoff);
}
for (i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
if (ph->p_type == PT_DYNAMIC) {
dyn = ph->p_vaddr;
} else if (ph->p_type == PT_TLS) {
tls_image = ph->p_vaddr;
dso->tls.align = ph->p_align;
dso->tls.len = ph->p_filesz;
dso->tls.size = ph->p_memsz;
} else if (ph->p_type == PT_GNU_RELRO) {
dso->relro_start = ph->p_vaddr & -PAGE_SIZE;
dso->relro_end = (ph->p_vaddr + ph->p_memsz) & -PAGE_SIZE;
} else if (ph->p_type == PT_GNU_STACK) {
if (!runtime && ph->p_memsz > __default_stacksize) {
__default_stacksize =
ph->p_memsz < DEFAULT_STACK_MAX ?
ph->p_memsz : DEFAULT_STACK_MAX;
}
}
if (ph->p_type != PT_LOAD) continue;
nsegs++;
if (ph->p_vaddr < addr_min) {
addr_min = ph->p_vaddr;
off_start = ph->p_offset;
prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
((ph->p_flags&PF_X) ? PROT_EXEC : 0));
}
if (ph->p_vaddr+ph->p_memsz > addr_max) {
addr_max = ph->p_vaddr+ph->p_memsz;
}
}
if (!dyn) goto noexec;
if (DL_FDPIC && !(eh->e_flags & FDPIC_CONSTDISP_FLAG)) {
dso->loadmap = calloc(1, sizeof *dso->loadmap
+ nsegs * sizeof *dso->loadmap->segs);
if (!dso->loadmap) goto error;
dso->loadmap->nsegs = nsegs;
for (ph=ph0, i=0; i<nsegs; ph=(void *)((char *)ph+eh->e_phentsize)) {
if (ph->p_type != PT_LOAD) continue;
prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
((ph->p_flags&PF_X) ? PROT_EXEC : 0));
map = mmap(0, ph->p_memsz + (ph->p_vaddr & PAGE_SIZE-1),
prot, MAP_PRIVATE,
fd, ph->p_offset & -PAGE_SIZE);
if (map == MAP_FAILED) {
unmap_library(dso);
goto error;
}
dso->loadmap->segs[i].addr = (size_t)map +
(ph->p_vaddr & PAGE_SIZE-1);
dso->loadmap->segs[i].p_vaddr = ph->p_vaddr;
dso->loadmap->segs[i].p_memsz = ph->p_memsz;
i++;
if (prot & PROT_WRITE) {
size_t brk = (ph->p_vaddr & PAGE_SIZE-1)
+ ph->p_filesz;
size_t pgbrk = brk + PAGE_SIZE-1 & -PAGE_SIZE;
size_t pgend = brk + ph->p_memsz - ph->p_filesz
+ PAGE_SIZE-1 & -PAGE_SIZE;
if (pgend > pgbrk && mmap_fixed(map+pgbrk,
pgend-pgbrk, prot,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS,
-1, off_start) == MAP_FAILED)
goto error;
memset(map + brk, 0, pgbrk-brk);
}
}
map = (void *)dso->loadmap->segs[0].addr;
map_len = 0;
goto done_mapping;
}
addr_max += PAGE_SIZE-1;
addr_max &= -PAGE_SIZE;
addr_min &= -PAGE_SIZE;
off_start &= -PAGE_SIZE;
map_len = addr_max - addr_min + off_start;
/* The first time, we map too much, possibly even more than
* the length of the file. This is okay because we will not
* use the invalid part; we just need to reserve the right
* amount of virtual address space to map over later. */
map = DL_NOMMU_SUPPORT
? mmap((void *)addr_min, map_len, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
: mmap((void *)addr_min, map_len, prot,
MAP_PRIVATE, fd, off_start);
if (map==MAP_FAILED) goto error;
dso->map = map;
dso->map_len = map_len;
/* If the loaded file is not relocatable and the requested address is
* not available, then the load operation must fail. */
if (eh->e_type != ET_DYN && addr_min && map!=(void *)addr_min) {
errno = EBUSY;
goto error;
}
base = map - addr_min;
dso->phdr = 0;
dso->phnum = 0;
for (ph=ph0, i=eh->e_phnum; i; i--, ph=(void *)((char *)ph+eh->e_phentsize)) {
if (ph->p_type != PT_LOAD) continue;
/* Check if the programs headers are in this load segment, and
* if so, record the address for use by dl_iterate_phdr. */
if (!dso->phdr && eh->e_phoff >= ph->p_offset
&& eh->e_phoff+phsize <= ph->p_offset+ph->p_filesz) {
dso->phdr = (void *)(base + ph->p_vaddr
+ (eh->e_phoff-ph->p_offset));
dso->phnum = eh->e_phnum;
dso->phentsize = eh->e_phentsize;
}
this_min = ph->p_vaddr & -PAGE_SIZE;
this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE;
off_start = ph->p_offset & -PAGE_SIZE;
prot = (((ph->p_flags&PF_R) ? PROT_READ : 0) |
((ph->p_flags&PF_W) ? PROT_WRITE: 0) |
((ph->p_flags&PF_X) ? PROT_EXEC : 0));
/* Reuse the existing mapping for the lowest-address LOAD */
if ((ph->p_vaddr & -PAGE_SIZE) != addr_min || DL_NOMMU_SUPPORT)
if (mmap_fixed(base+this_min, this_max-this_min, prot, MAP_PRIVATE|MAP_FIXED, fd, off_start) == MAP_FAILED)
goto error;
if (ph->p_memsz > ph->p_filesz && (ph->p_flags&PF_W)) {
size_t brk = (size_t)base+ph->p_vaddr+ph->p_filesz;
size_t pgbrk = brk+PAGE_SIZE-1 & -PAGE_SIZE;
memset((void *)brk, 0, pgbrk-brk & PAGE_SIZE-1);
if (pgbrk-(size_t)base < this_max && mmap_fixed((void *)pgbrk, (size_t)base+this_max-pgbrk, prot, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) == MAP_FAILED)
goto error;
}
}
for (i=0; ((size_t *)(base+dyn))[i]; i+=2)
if (((size_t *)(base+dyn))[i]==DT_TEXTREL) {
if (mprotect(map, map_len, PROT_READ|PROT_WRITE|PROT_EXEC)
&& errno != ENOSYS)
goto error;
break;
}
done_mapping:
dso->base = base;
dso->dynv = laddr(dso, dyn);
if (dso->tls.size) dso->tls.image = laddr(dso, tls_image);
free(allocated_buf);
return map;
noexec:
errno = ENOEXEC;
error:
if (map!=MAP_FAILED) unmap_library(dso);
free(allocated_buf);
return 0;
}
static int path_open(const char *name, const char *s, char *buf, size_t buf_size)
{
size_t l;
int fd;
for (;;) {
s += strspn(s, ":\n");
l = strcspn(s, ":\n");
if (l-1 >= INT_MAX) return -1;
if (snprintf(buf, buf_size, "%.*s/%s", (int)l, s, name) < buf_size) {
if ((fd = open(buf, O_RDONLY|O_CLOEXEC))>=0) return fd;
switch (errno) {
case ENOENT:
case ENOTDIR:
case EACCES:
case ENAMETOOLONG:
break;
default:
/* Any negative value but -1 will inhibit
* futher path search. */
return -2;
}
}
s += l;
}
}
static int fixup_rpath(struct dso *p, char *buf, size_t buf_size)
{
size_t n, l;
const char *s, *t, *origin;
char *d;
if (p->rpath || !p->rpath_orig) return 0;
if (!strchr(p->rpath_orig, '$')) {
p->rpath = p->rpath_orig;
return 0;
}
n = 0;
s = p->rpath_orig;
while ((t=strchr(s, '$'))) {
if (strncmp(t, "$ORIGIN", 7) && strncmp(t, "${ORIGIN}", 9))
return 0;
s = t+1;
n++;
}
if (n > SSIZE_MAX/PATH_MAX) return 0;
if (p->kernel_mapped) {
/* $ORIGIN searches cannot be performed for the main program
* when it is suid/sgid/AT_SECURE. This is because the
* pathname is under the control of the caller of execve.
* For libraries, however, $ORIGIN can be processed safely
* since the library's pathname came from a trusted source
* (either system paths or a call to dlopen). */
if (libc.secure)
return 0;
l = readlink("/proc/self/exe", buf, buf_size);
if (l == -1) switch (errno) {
case ENOENT:
case ENOTDIR:
case EACCES:
return 0;
default:
return -1;
}
if (l >= buf_size)
return 0;
buf[l] = 0;
origin = buf;
} else {
origin = p->name;
}
t = strrchr(origin, '/');
if (t) {
l = t-origin;
} else {
/* Normally p->name will always be an absolute or relative
* pathname containing at least one '/' character, but in the
* case where ldso was invoked as a command to execute a
* program in the working directory, app.name may not. Fix. */
origin = ".";
l = 1;
}
/* Disallow non-absolute origins for suid/sgid/AT_SECURE. */
if (libc.secure && *origin != '/')
return 0;
p->rpath = malloc(strlen(p->rpath_orig) + n*l + 1);
if (!p->rpath) return -1;
d = p->rpath;
s = p->rpath_orig;
while ((t=strchr(s, '$'))) {
memcpy(d, s, t-s);
d += t-s;
memcpy(d, origin, l);
d += l;
/* It was determined previously that the '$' is followed
* either by "ORIGIN" or "{ORIGIN}". */
s = t + 7 + 2*(t[1]=='{');
}
strcpy(d, s);
return 0;
}
static void decode_dyn(struct dso *p)
{
size_t dyn[DYN_CNT];
decode_vec(p->dynv, dyn, DYN_CNT);
p->syms = laddr(p, dyn[DT_SYMTAB]);
p->strings = laddr(p, dyn[DT_STRTAB]);
if (dyn[0]&(1<<DT_HASH))
p->hashtab = laddr(p, dyn[DT_HASH]);
if (dyn[0]&(1<<DT_RPATH))
p->rpath_orig = p->strings + dyn[DT_RPATH];
if (dyn[0]&(1<<DT_RUNPATH))
p->rpath_orig = p->strings + dyn[DT_RUNPATH];