[BZ,20628] make mallinfo saturating
Commit Message
"Carlos O'Donell" <carlos@redhat.com> writes:
> DJ, Care to make a version 2 of the patch?
Version 2. Changed some of the counters to larger types and tested those
too, which took about 130Gb of virtual memory and lots of waiting...
[BZ #20628]
* malloc/malloc.c (int_mallinfo): Use saturating add instead of
overflow to collect statistics into a fixed "int" container.
Comments
On 10/04/2016 01:04 PM, DJ Delorie wrote:
> +/* Saturated add - add ADD to SUM. If the result exceeds the range of
> + "int", set SUM to UINT_MAX instead ((int)-1). Assumes ADD and SUM
> + are positive. The published ABI prevents us from bumping "int" to
> + a larger type. */
> +#define SAT_ADD(SUM, ADD) \
> + ({ INTERNAL_SIZE_T tmp = (INTERNAL_SIZE_T)(SUM) + (INTERNAL_SIZE_T)(ADD); SUM = (tmp > UINT_MAX) ? -1 : tmp; })
> +
> +/* Likewise, but assign ADD to SUM. */
> +#define SAT_SET(SUM, ADD) \
> + ({ SUM = ((INTERNAL_SIZE_T)(ADD) > UINT_MAX) ? -1 : (ADD); })
These don't look right, as INTERNAL_SIZE_T might not be wider than int,
which means the + in SAT_ADD will wrap around before SAT_ADD gets a
chance to check for overflow. Also, if SUM is INT_MIN then SAT_ADD(SUM,
1) should set it to INT_MIN + 1, but that doesn't happen when
INTERNAL_SIZE_T is wider than int.
How about something like the following instead?
#define MIN(a, b) ((a)<(b)?(a):(b))
/* Return the sum of the unsigned int A and the nonnegative integer B.
If the result is not representable as an unsigned int, return
UINT_MAX.
B's type may be any integer type. */
#define UINT_SATURATED_ADD(a, b) \
({ unsigned a1 = a, b1 = MIN (b, UINT_MAX), sum1 = a1 + b1; \
sum1 < a1 ? UINT_MAX : sum1; })
and then set 'm->smblks = UINT_SATURATED_ADD (m->sm_blks, nfastblocks);'
and 'm->hblks = UINT_SATURATED_ADD (0, mp_.n_mmaps);', etc.
@@ -224,6 +224,7 @@
#include <unistd.h>
#include <stdio.h> /* needed for malloc_stats */
#include <errno.h>
+#include <limits.h>
#include <shlib-compat.h>
@@ -4594,8 +4595,8 @@ int_mallinfo (mstate av, struct mallinfo *m)
mchunkptr p;
INTERNAL_SIZE_T avail;
INTERNAL_SIZE_T fastavail;
- int nblocks;
- int nfastblocks;
+ INTERNAL_SIZE_T nblocks;
+ INTERNAL_SIZE_T nfastblocks;
/* Ensure initialization */
if (av->top == 0)
@@ -4633,18 +4634,29 @@ int_mallinfo (mstate av, struct mallinfo *m)
}
}
- m->smblks += nfastblocks;
- m->ordblks += nblocks;
- m->fordblks += avail;
- m->uordblks += av->system_mem - avail;
- m->arena += av->system_mem;
- m->fsmblks += fastavail;
+/* Saturated add - add ADD to SUM. If the result exceeds the range of
+ "int", set SUM to UINT_MAX instead ((int)-1). Assumes ADD and SUM
+ are positive. The published ABI prevents us from bumping "int" to
+ a larger type. */
+#define SAT_ADD(SUM, ADD) \
+ ({ INTERNAL_SIZE_T tmp = (INTERNAL_SIZE_T)(SUM) + (INTERNAL_SIZE_T)(ADD); SUM = (tmp > UINT_MAX) ? -1 : tmp; })
+
+/* Likewise, but assign ADD to SUM. */
+#define SAT_SET(SUM, ADD) \
+ ({ SUM = ((INTERNAL_SIZE_T)(ADD) > UINT_MAX) ? -1 : (ADD); })
+
+ SAT_ADD (m->smblks, nfastblocks);
+ SAT_ADD (m->ordblks, nblocks);
+ SAT_ADD (m->fordblks, avail);
+ SAT_ADD (m->uordblks, av->system_mem - avail);
+ SAT_ADD (m->arena, av->system_mem);
+ SAT_ADD (m->fsmblks, fastavail);
if (av == &main_arena)
{
- m->hblks = mp_.n_mmaps;
- m->hblkhd = mp_.mmapped_mem;
- m->usmblks = 0;
- m->keepcost = chunksize (av->top);
+ SAT_SET (m->hblks, mp_.n_mmaps);
+ SAT_SET (m->hblkhd, mp_.mmapped_mem);
+ SAT_SET (m->usmblks, 0);
+ SAT_SET (m->keepcost, chunksize (av->top));
}
}