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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
Download Patch File Download Diff File Expand all files Collapse all files

173
malloc/malloc.c
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@ -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
{