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Move malloc_{g,s}et_state to libc_malloc_debug

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These deprecated functions are only safe to call from
__malloc_initialize_hook and as a result, are not useful in the
general case.  Move the implementations to libc_malloc_debug so that
existing binaries that need it will now have to preload the debug DSO
to work correctly.

This also allows simplification of the core malloc implementation by
dropping all the undumping support code that was added to make
malloc_set_state work.

One known breakage is that of ancient emacs binaries that depend on
this.  They will now crash when running with this libc.  With
LD_BIND_NOW=1, it will terminate immediately because of not being able
to find malloc_set_state but with lazy binding it will crash in
unpredictable ways.  It will need a preloaded libc_malloc_debug.so so
that its initialization hook is executed to allow its malloc
implementation to work properly.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Siddhesh Poyarekar
2021-07-22 18:38:10 +05:30
parent b5bd5bfe88
commit 0552fd2c7d
64 changed files with 256 additions and 225 deletions
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55
malloc/malloc.c
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@ -1921,19 +1921,6 @@ static struct malloc_state main_arena =
.attached_threads = 1
};
/* These variables are used for undumping support. Chunked are marked
as using mmap, but we leave them alone if they fall into this
range. NB: The chunk size for these chunks only includes the
initial size field (of SIZE_SZ bytes), there is no trailing size
field (unlike with regular mmapped chunks). */
static mchunkptr dumped_main_arena_start; /* Inclusive. */
static mchunkptr dumped_main_arena_end; /* Exclusive. */
/* True if the pointer falls into the dumped arena. Use this after
chunk_is_mmapped indicates a chunk is mmapped. */
#define DUMPED_MAIN_ARENA_CHUNK(p) \
((p) >= dumped_main_arena_start && (p) < dumped_main_arena_end)
/* There is only one instance of the malloc parameters. */
static struct malloc_par mp_ =
@ -2083,7 +2070,7 @@ do_check_chunk (mstate av, mchunkptr p)
assert (prev_inuse (p));
}
}
else if (!DUMPED_MAIN_ARENA_CHUNK (p))
else
{
/* address is outside main heap */
if (contiguous (av) && av->top != initial_top (av))
@ -2948,11 +2935,6 @@ munmap_chunk (mchunkptr p)
assert (chunk_is_mmapped (p));
/* Do nothing if the chunk is a faked mmapped chunk in the dumped
main arena. We never free this memory. */
if (DUMPED_MAIN_ARENA_CHUNK (p))
return;
uintptr_t mem = (uintptr_t) chunk2mem (p);
uintptr_t block = (uintptr_t) p - prev_size (p);
size_t total_size = prev_size (p) + size;
@ -3275,8 +3257,7 @@ __libc_free (void *mem)
Dumped fake mmapped chunks do not affect the threshold. */
if (!mp_.no_dyn_threshold
&& chunksize_nomask (p) > mp_.mmap_threshold
&& chunksize_nomask (p) <= DEFAULT_MMAP_THRESHOLD_MAX
&& !DUMPED_MAIN_ARENA_CHUNK (p))
&& chunksize_nomask (p) <= DEFAULT_MMAP_THRESHOLD_MAX)
{
mp_.mmap_threshold = chunksize (p);
mp_.trim_threshold = 2 * mp_.mmap_threshold;
@ -3343,12 +3324,9 @@ __libc_realloc (void *oldmem, size_t bytes)
/* Little security check which won't hurt performance: the allocator
never wrapps around at the end of the address space. Therefore
we can exclude some size values which might appear here by
accident or by "design" from some intruder. We need to bypass
this check for dumped fake mmap chunks from the old main arena
because the new malloc may provide additional alignment. */
accident or by "design" from some intruder. */
if ((__builtin_expect ((uintptr_t) oldp > (uintptr_t) -oldsize, 0)
|| __builtin_expect (misaligned_chunk (oldp), 0))
&& !DUMPED_MAIN_ARENA_CHUNK (oldp))
|| __builtin_expect (misaligned_chunk (oldp), 0)))
malloc_printerr ("realloc(): invalid pointer");
if (!checked_request2size (bytes, &nb))
@ -3359,24 +3337,6 @@ __libc_realloc (void *oldmem, size_t bytes)
if (chunk_is_mmapped (oldp))
{
/* If this is a faked mmapped chunk from the dumped main arena,
always make a copy (and do not free the old chunk). */
if (DUMPED_MAIN_ARENA_CHUNK (oldp))
{
/* Must alloc, copy, free. */
void *newmem = __libc_malloc (bytes);
if (newmem == 0)
return NULL;
/* Copy as many bytes as are available from the old chunk
and fit into the new size. NB: The overhead for faked
mmapped chunks is only SIZE_SZ, not CHUNK_HDR_SZ as for
regular mmapped chunks. */
if (bytes > oldsize - SIZE_SZ)
bytes = oldsize - SIZE_SZ;
memcpy (newmem, oldmem, bytes);
return newmem;
}
void *newmem;
#if HAVE_MREMAP
@ -5056,12 +5016,7 @@ musable (void *mem)
p = mem2chunk (mem);
if (chunk_is_mmapped (p))
{
if (DUMPED_MAIN_ARENA_CHUNK (p))
result = chunksize (p) - SIZE_SZ;
else
result = chunksize (p) - CHUNK_HDR_SZ;
}
result = chunksize (p) - CHUNK_HDR_SZ;
else if (inuse (p))
result = memsize (p);