2013-12-18 Andrew Hunter <ahh@google.com>
+ * sysdeps/generic/ldsodefs.h (__signal_safe_memalign): New prototype.
+ (__signal_safe_malloc, __signal_safe_free): Likewise.
+ (__signal_safe_realloc, __signal_safe_calloc): Likewise.
+ * elf/dl-misc.c (__signal_safe_allocator_header): New struct.
+ (__signal_safe_memalign, __signal_safe_malloc): New function.
+ (__signal_safe_free, __signal_safe_realloc): Likewise.
+ (__signal_safe_calloc): Likewise.
+ * elf/dl-tls.c (allocate_dtv, _dl_clear_dtv): Call signal-safe
+ functions.
+ (_dl_deallocate_tls, _dl_update_slotinfo): Likewise.
+
+2013-12-18 Andrew Hunter <ahh@google.com>
+
* elf/Versions (ld): Add _dl_clear_dtv.
* sysdeps/generic/ldsodefs.h (_dl_clear_dtv): New prototype.
* elf/dl-tls.c (_dl_clear_dtv): New function.
#include <assert.h>
#include <fcntl.h>
#include <ldsodefs.h>
+#include <libc-symbols.h>
#include <limits.h>
#include <link.h>
#include <stdarg.h>
return *low;
}
+
+/* To support accessing TLS variables from signal handlers, we need an
+ async signal safe memory allocator. These routines are never
+ themselves invoked reentrantly (all calls to them are surrounded by
+ signal masks) but may be invoked concurrently from many threads.
+ The current implementation is not particularly performant nor space
+ efficient, but it will be used rarely (and only in binaries that use
+ dlopen.) The API matches that of malloc() and friends. */
+
+struct __signal_safe_allocator_header
+{
+ size_t size;
+ void *start;
+};
+
+void *weak_function
+__signal_safe_memalign (size_t boundary, size_t size)
+{
+ struct __signal_safe_allocator_header *header;
+ if (boundary < sizeof (*header))
+ boundary = sizeof (*header);
+
+ /* Boundary must be a power of two. */
+ if (boundary & (boundary - 1) == 0)
+ return NULL;
+
+ size_t pg = GLRO (dl_pagesize);
+ size_t padded_size;
+ if (boundary <= pg)
+ {
+ /* We'll get a pointer certainly aligned to boundary, so just
+ add one more boundary-sized chunk to hold the header. */
+ padded_size = roundup (size, boundary) + boundary;
+ }
+ else
+ {
+ /* If we want K pages aligned to a J-page boundary, K+J+1 pages
+ contains at least one such region that isn't directly at the start
+ (so we can place the header.) This is wasteful, but you're the one
+ who wanted 64K-aligned TLS. */
+ padded_size = roundup (size, pg) + boundary + pg;
+ }
+
+
+ size_t actual_size = roundup (padded_size, pg);
+ void *actual = mmap (NULL, actual_size, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+ if (actual == MAP_FAILED)
+ return NULL;
+
+ if (boundary <= pg)
+ {
+ header = actual + boundary - sizeof (*header);
+ }
+ else
+ {
+ intptr_t actual_pg = ((intptr_t) actual) / pg;
+ intptr_t boundary_pg = boundary / pg;
+ intptr_t start_pg = actual_pg + boundary_pg;
+ start_pg -= start_pg % boundary_pg;
+ if (start_pg > (actual_pg + 1))
+ {
+ int ret = munmap (actual, (start_pg - actual_pg - 1) * pg);
+ assert (ret == 0);
+ actual = (void *) ((start_pg - 1) * pg);
+ }
+ char *start = (void *) (start_pg * pg);
+ header = start - sizeof (*header);
+
+ }
+ header->size = actual_size;
+ header->start = actual;
+ void *ptr = header;
+ ptr += sizeof (*header);
+ if (((intptr_t) ptr) % boundary != 0)
+ _dl_fatal_printf ("__signal_safe_memalign produced incorrect alignment\n");
+ return ptr;
+}
+
+void * weak_function
+__signal_safe_malloc (size_t size)
+{
+ return __signal_safe_memalign (1, size);
+}
+
+void weak_function
+__signal_safe_free (void *ptr)
+{
+ if (ptr == NULL)
+ return;
+
+ struct __signal_safe_allocator_header *header = ((char *) ptr) - sizeof (*header);
+ int ret = munmap (header->start, header->size);
+
+ assert (ret == 0);
+}
+
+void * weak_function
+__signal_safe_realloc (void *ptr, size_t size)
+{
+ if (size == 0)
+ {
+ __signal_safe_free (ptr);
+ return NULL;
+ }
+ if (ptr == NULL)
+ return __signal_safe_malloc (size);
+
+ struct __signal_safe_allocator_header *header = ((char *) ptr) - sizeof (*header);
+ size_t old_size = header->size;
+ if (old_size - sizeof (*header) >= size)
+ return ptr;
+
+ void *new_ptr = __signal_safe_malloc (size);
+ if (new_ptr == NULL)
+ return NULL;
+
+ memcpy (new_ptr, ptr, old_size);
+ __signal_safe_free (ptr);
+
+ return new_ptr;
+}
+
+void * weak_function
+__signal_safe_calloc (size_t nmemb, size_t size)
+{
+ void *ptr = __signal_safe_malloc (nmemb * size);
+ if (ptr == NULL)
+ return NULL;
+ return memset (ptr, 0, nmemb * size);
+}
initial set of modules. This should avoid in most cases expansions
of the dtv. */
dtv_length = GL(dl_tls_max_dtv_idx) + DTV_SURPLUS;
- dtv = calloc (dtv_length + 2, sizeof (dtv_t));
+ dtv = __signal_safe_calloc (dtv_length + 2, sizeof (dtv_t));
if (dtv != NULL)
{
/* This is the initial length of the dtv. */
for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
if (! dtv[1 + cnt].pointer.is_static
&& dtv[1 + cnt].pointer.val != TLS_DTV_UNALLOCATED)
- free (dtv[1 + cnt].pointer.val);
+ __signal_safe_free (dtv[1 + cnt].pointer.val);
memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t));
}
for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
if (! dtv[1 + cnt].pointer.is_static
&& dtv[1 + cnt].pointer.val != TLS_DTV_UNALLOCATED)
- free (dtv[1 + cnt].pointer.val);
+ __signal_safe_free (dtv[1 + cnt].pointer.val);
/* The array starts with dtv[-1]. */
if (dtv != GL(dl_initial_dtv))
- free (dtv - 1);
+ __signal_safe_free (dtv - 1);
if (dealloc_tcb)
{
allocate_and_init (struct link_map *map)
{
void *newp;
-
- newp = __libc_memalign (map->l_tls_align, map->l_tls_blocksize);
+ newp = __signal_safe_memalign (map->l_tls_align, map->l_tls_blocksize);
if (newp == NULL)
oom ();
if (gen <= dtv[0].counter)
continue;
+ size_t modid = total + cnt;
+
/* If there is no map this means the entry is empty. */
struct link_map *map = listp->slotinfo[cnt].map;
if (map == NULL)
{
/* If this modid was used at some point the memory
might still be allocated. */
- if (! dtv[total + cnt].pointer.is_static
- && dtv[total + cnt].pointer.val != TLS_DTV_UNALLOCATED)
+ if (dtv[-1].counter >= modid
+ && !dtv[modid].pointer.is_static
+ && dtv[modid].pointer.val != TLS_DTV_UNALLOCATED)
{
- free (dtv[total + cnt].pointer.val);
- dtv[total + cnt].pointer.val = TLS_DTV_UNALLOCATED;
+ __signal_safe_free (dtv[modid].pointer.val);
+ dtv[modid].pointer.val = TLS_DTV_UNALLOCATED;
}
continue;
}
+ assert (modid == map->l_tls_modid);
/* Check whether the current dtv array is large enough. */
- size_t modid = map->l_tls_modid;
- assert (total + cnt == modid);
if (dtv[-1].counter < modid)
{
/* Reallocate the dtv. */
{
/* This is the initial dtv that was allocated
during rtld startup using the dl-minimal.c
- malloc instead of the real malloc. We can't
+ malloc instead of the real allocator. We can't
free it, we have to abandon the old storage. */
- newp = malloc ((2 + newsize) * sizeof (dtv_t));
+ newp = __signal_safe_malloc (
+ (2 + newsize) * sizeof (dtv_t));
if (newp == NULL)
oom ();
memcpy (newp, &dtv[-1], (2 + oldsize) * sizeof (dtv_t));
}
else
{
- newp = realloc (&dtv[-1],
+ newp = __signal_safe_realloc (&dtv[-1],
(2 + newsize) * sizeof (dtv_t));
if (newp == NULL)
oom ();
deallocate even if it is this dtv entry we are
supposed to load. The reason is that we call
memalign and not malloc. */
- free (dtv[modid].pointer.val);
+ __signal_safe_free (dtv[modid].pointer.val);
/* This module is loaded dynamically- We defer memory
allocation. */
extern void _dl_clear_dtv (dtv_t *dtv) internal_function;
rtld_hidden_proto (_dl_clear_dtv)
+extern void *__signal_safe_memalign (size_t boundary, size_t size);
+extern void *__signal_safe_malloc (size_t size);
+extern void __signal_safe_free (void *ptr);
+extern void *__signal_safe_realloc (void *ptr, size_t size);
+extern void *__signal_safe_calloc (size_t nmemb, size_t size);
+
/* Deallocate memory allocated with _dl_allocate_tls. */
extern void _dl_deallocate_tls (void *tcb, bool dealloc_tcb) internal_function;
rtld_hidden_proto (_dl_deallocate_tls)
projects / platform / upstream / glibc.git / commitdiff