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malloc: set NON_MAIN_ARENA flag for reclaimed memalign chunk (BZ #30101)

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Based on these comments in malloc.c:

   size field is or'ed with NON_MAIN_ARENA if the chunk was obtained
   from a non-main arena.  This is only set immediately before handing
   the chunk to the user, if necessary.

   The NON_MAIN_ARENA flag is never set for unsorted chunks, so it
   does not have to be taken into account in size comparisons.

When we pull a chunk off the unsorted list (or any list) we need to
make sure that flag is set properly before returning the chunk.

Use the rounded-up size for chunk_ok_for_memalign()

Do not scan the arena for reusable chunks if there's no arena.

Account for chunk overhead when determining if a chunk is a reuse
candidate.

mcheck interferes with memalign, so skip mcheck variants of
memalign tests.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
DJ Delorie 2023-04-03 17:33:03 -04:00
parent 8895a99c10
commit e5524ef335
4 changed files with 276 additions and 90 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
malloc/Makefile
View File

@ -43,7 +43,8 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
tst-tcfree1 tst-tcfree2 tst-tcfree3 \
tst-safe-linking \
tst-mallocalign1 \
tst-memalign-2
tst-memalign-2 \
tst-memalign-3
tests-static := \
tst-interpose-static-nothread \
@ -71,7 +72,7 @@ test-srcs = tst-mtrace
# with MALLOC_CHECK_=3 because they expect a specific failure.
tests-exclude-malloc-check = tst-malloc-check tst-malloc-usable \
tst-mxfast tst-safe-linking \
tst-compathooks-off tst-compathooks-on tst-memalign-2
tst-compathooks-off tst-compathooks-on tst-memalign-2 tst-memalign-3
# Run all tests with MALLOC_CHECK_=3
tests-malloc-check = $(filter-out $(tests-exclude-malloc-check) \
@ -116,6 +117,8 @@ tests-exclude-mcheck = tst-mallocstate \
tst-malloc-usable-tunables \
tst-malloc_info \
tst-compathooks-off tst-compathooks-on \
tst-memalign-2 \
tst-memalign-3 \
tst-mxfast
tests-mcheck = $(filter-out $(tests-exclude-mcheck) $(tests-static), $(tests))

173
malloc/malloc.c
View File

@ -4974,13 +4974,13 @@ _int_realloc (mstate av, mchunkptr oldp, INTERNAL_SIZE_T oldsize,
/* Returns 0 if the chunk is not and does not contain the requested
aligned sub-chunk, else returns the amount of "waste" from
trimming. BYTES is the *user* byte size, not the chunk byte
trimming. NB is the *chunk* byte size, not the user byte
size. */
static size_t
chunk_ok_for_memalign (mchunkptr p, size_t alignment, size_t bytes)
chunk_ok_for_memalign (mchunkptr p, size_t alignment, size_t nb)
{
void *m = chunk2mem (p);
INTERNAL_SIZE_T size = memsize (p);
INTERNAL_SIZE_T size = chunksize (p);
void *aligned_m = m;
if (__glibc_unlikely (misaligned_chunk (p)))
@ -4997,12 +4997,12 @@ chunk_ok_for_memalign (mchunkptr p, size_t alignment, size_t bytes)
/* If it's a perfect fit, it's an exception to the return value rule
(we would return zero waste, which looks like "not usable"), so
handle it here by returning a small non-zero value instead. */
if (size == bytes && front_extra == 0)
if (size == nb && front_extra == 0)
return 1;
/* If the block we need fits in the chunk, calculate total waste. */
if (size > bytes + front_extra)
return size - bytes;
if (size > nb + front_extra)
return size - nb;
/* Can't use this chunk. */
return 0;
@ -5048,94 +5048,97 @@ _int_memalign (mstate av, size_t alignment, size_t bytes)
and unlikely to meet our alignment requirements. We have not done
any experimentation with searching for aligned fastbins. */
int first_bin_index;
int first_largebin_index;
int last_bin_index;
if (in_smallbin_range (nb))
first_bin_index = smallbin_index (nb);
else
first_bin_index = largebin_index (nb);
if (in_smallbin_range (nb * 2))
last_bin_index = smallbin_index (nb * 2);
else
last_bin_index = largebin_index (nb * 2);
first_largebin_index = largebin_index (MIN_LARGE_SIZE);
int victim_index; /* its bin index */
for (victim_index = first_bin_index;
victim_index < last_bin_index;
victim_index ++)
if (av != NULL)
{
victim = NULL;
int first_bin_index;
int first_largebin_index;
int last_bin_index;
if (victim_index < first_largebin_index)
{
/* Check small bins. Small bin chunks are doubly-linked despite
being the same size. */
if (in_smallbin_range (nb))
first_bin_index = smallbin_index (nb);
else
first_bin_index = largebin_index (nb);
mchunkptr fwd; /* misc temp for linking */
mchunkptr bck; /* misc temp for linking */
if (in_smallbin_range (nb * 2))
last_bin_index = smallbin_index (nb * 2);
else
last_bin_index = largebin_index (nb * 2);
bck = bin_at (av, victim_index);
fwd = bck->fd;
while (fwd != bck)
first_largebin_index = largebin_index (MIN_LARGE_SIZE);
int victim_index; /* its bin index */
for (victim_index = first_bin_index;
victim_index < last_bin_index;
victim_index ++)
{
if (chunk_ok_for_memalign (fwd, alignment, bytes) > 0)
{
victim = fwd;
victim = NULL;
/* Unlink it */
victim->fd->bk = victim->bk;
victim->bk->fd = victim->fd;
break;
if (victim_index < first_largebin_index)
{
/* Check small bins. Small bin chunks are doubly-linked despite
being the same size. */
mchunkptr fwd; /* misc temp for linking */
mchunkptr bck; /* misc temp for linking */
bck = bin_at (av, victim_index);
fwd = bck->fd;
while (fwd != bck)
{
if (chunk_ok_for_memalign (fwd, alignment, nb) > 0)
{
victim = fwd;
/* Unlink it */
victim->fd->bk = victim->bk;
victim->bk->fd = victim->fd;
break;
}
fwd = fwd->fd;
}
}
else
{
/* Check large bins. */
mchunkptr fwd; /* misc temp for linking */
mchunkptr bck; /* misc temp for linking */
mchunkptr best = NULL;
size_t best_size = 0;
bck = bin_at (av, victim_index);
fwd = bck->fd;
while (fwd != bck)
{
int extra;
if (chunksize (fwd) < nb)
break;
extra = chunk_ok_for_memalign (fwd, alignment, nb);
if (extra > 0
&& (extra <= best_size || best == NULL))
{
best = fwd;
best_size = extra;
}
fwd = fwd->fd;
}
victim = best;
if (victim != NULL)
{
unlink_chunk (av, victim);
break;
}
}
fwd = fwd->fd;
if (victim != NULL)
break;
}
}
else
{
/* Check large bins. */
mchunkptr fwd; /* misc temp for linking */
mchunkptr bck; /* misc temp for linking */
mchunkptr best = NULL;
size_t best_size = 0;
bck = bin_at (av, victim_index);
fwd = bck->fd;
while (fwd != bck)
{
int extra;
if (chunksize (fwd) < nb)
break;
extra = chunk_ok_for_memalign (fwd, alignment, bytes);
if (extra > 0
&& (extra <= best_size || best == NULL))
{
best = fwd;
best_size = extra;
}
fwd = fwd->fd;
}
victim = best;
if (victim != NULL)
{
unlink_chunk (av, victim);
break;
}
}
if (victim != NULL)
break;
}
/* Strategy: find a spot within that chunk that meets the alignment
request, and then possibly free the leading and trailing space.
@ -5147,6 +5150,8 @@ _int_memalign (mstate av, size_t alignment, size_t bytes)
p = victim;
m = chunk2mem (p);
set_inuse (p);
if (av != &main_arena)
set_non_main_arena (p);
}
else
{

13
malloc/tst-memalign-2.c
View File

@ -33,9 +33,10 @@ typedef struct TestCase {
} TestCase;
static TestCase tcache_allocs[] = {
{ 24, 8, NULL, NULL },
{ 24, 16, NULL, NULL },
{ 128, 32, NULL, NULL }
{ 24, 32, NULL, NULL },
{ 24, 64, NULL, NULL },
{ 128, 128, NULL, NULL },
{ 500, 128, NULL, NULL }
};
#define TN array_length (tcache_allocs)
@ -70,11 +71,15 @@ do_test (void)
for (i = 0; i < TN; ++ i)
{
size_t sz2;
tcache_allocs[i].ptr1 = memalign (tcache_allocs[i].alignment, tcache_allocs[i].size);
CHECK (tcache_allocs[i].ptr1, tcache_allocs[i].alignment);
sz2 = malloc_usable_size (tcache_allocs[i].ptr1);
free (tcache_allocs[i].ptr1);
/* This should return the same chunk as was just free'd. */
tcache_allocs[i].ptr2 = memalign (tcache_allocs[i].alignment, tcache_allocs[i].size);
tcache_allocs[i].ptr2 = memalign (tcache_allocs[i].alignment, sz2);
CHECK (tcache_allocs[i].ptr2, tcache_allocs[i].alignment);
free (tcache_allocs[i].ptr2);

173
malloc/tst-memalign-3.c Normal file
View File

@ -0,0 +1,173 @@
/* Test for memalign chunk reuse.
Copyright (C) 2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <malloc.h>
#include <stdio.h>
#include <pthread.h>
#include <string.h>
#include <unistd.h>
#include <array_length.h>
#include <libc-pointer-arith.h>
#include <support/check.h>
#include <support/xthread.h>
typedef struct TestCase {
size_t size;
size_t alignment;
void *ptr1;
void *ptr2;
} TestCase;
static TestCase tcache_allocs[] = {
{ 24, 32, NULL, NULL },
{ 24, 64, NULL, NULL },
{ 128, 128, NULL, NULL },
{ 500, 128, NULL, NULL }
};
#define TN array_length (tcache_allocs)
static TestCase large_allocs[] = {
{ 23450, 64, NULL, NULL },
{ 23450, 64, NULL, NULL },
{ 23550, 64, NULL, NULL },
{ 23550, 64, NULL, NULL },
{ 23650, 64, NULL, NULL },
{ 23650, 64, NULL, NULL },
{ 33650, 64, NULL, NULL },
{ 33650, 64, NULL, NULL }
};
#define LN array_length (large_allocs)
void *p;
/* Sanity checks, ancillary to the actual test. */
#define CHECK(p,a) \
if (p == NULL || !PTR_IS_ALIGNED (p, a)) \
FAIL_EXIT1 ("NULL or misaligned memory detected.\n");
static void *
mem_test (void *closure)
{
int i;
int j;
int count;
void *ptr[10];
void *p;
/* TCache test. */
for (i = 0; i < TN; ++ i)
{
size_t sz2;
tcache_allocs[i].ptr1 = memalign (tcache_allocs[i].alignment, tcache_allocs[i].size);
CHECK (tcache_allocs[i].ptr1, tcache_allocs[i].alignment);
sz2 = malloc_usable_size (tcache_allocs[i].ptr1);
free (tcache_allocs[i].ptr1);
/* This should return the same chunk as was just free'd. */
tcache_allocs[i].ptr2 = memalign (tcache_allocs[i].alignment, sz2);
CHECK (tcache_allocs[i].ptr2, tcache_allocs[i].alignment);
free (tcache_allocs[i].ptr2);
TEST_VERIFY (tcache_allocs[i].ptr1 == tcache_allocs[i].ptr2);
}
/* Test for non-head tcache hits. */
for (i = 0; i < array_length (ptr); ++ i)
{
if (i == 4)
{
ptr[i] = memalign (64, 256);
CHECK (ptr[i], 64);
}
else
{
ptr[i] = malloc (256);
CHECK (ptr[i], 4);
}
}
for (i = 0; i < array_length (ptr); ++ i)
free (ptr[i]);
p = memalign (64, 256);
CHECK (p, 64);
count = 0;
for (i = 0; i < 10; ++ i)
if (ptr[i] == p)
++ count;
free (p);
TEST_VERIFY (count > 0);
/* Large bins test. */
for (i = 0; i < LN; ++ i)
{
large_allocs[i].ptr1 = memalign (large_allocs[i].alignment, large_allocs[i].size);
CHECK (large_allocs[i].ptr1, large_allocs[i].alignment);
/* Keep chunks from combining by fragmenting the heap. */
p = malloc (512);
CHECK (p, 4);
}
for (i = 0; i < LN; ++ i)
free (large_allocs[i].ptr1);
/* Force the unsorted bins to be scanned and moved to small/large
bins. */
p = malloc (60000);
for (i = 0; i < LN; ++ i)
{
large_allocs[i].ptr2 = memalign (large_allocs[i].alignment, large_allocs[i].size);
CHECK (large_allocs[i].ptr2, large_allocs[i].alignment);
}
count = 0;
for (i = 0; i < LN; ++ i)
{
int ok = 0;
for (j = 0; j < LN; ++ j)
if (large_allocs[i].ptr1 == large_allocs[j].ptr2)
ok = 1;
if (ok == 1)
count ++;
}
/* The allocation algorithm is complicated outside of the memalign
logic, so just make sure it's working for most of the
allocations. This avoids possible boundary conditions with
empty/full heaps. */
TEST_VERIFY (count > LN / 2);
return 0;
}
static int
do_test (void)
{
pthread_t p;
p = xpthread_create (NULL, mem_test, NULL);
xpthread_join (p);
return 0;
}
#include <support/test-driver.c>