Some malloc tests compare pointers meaning to compare addresses.
On AArch64, the 64-bit value of the pointer may contain metadata
along with the values of the address.
In order to correctly compare addresses, we add new function for
AArch64 target that will use the AArch64 64 SUBP (subtract pointer)
instruction when it is available. This instruction uses the 56-bit
addresses ignoring top-byte metadata.
Best implementation is selected using ifunc resolver.
On other targets and also on AArch64 when MTE is not available this
function defaults to PTR_DIFF defined in libc-pointer-arith.h.
Three malloc tests are modified accordingly:
- tst-memalign-2.c
- tst-memalign-3.c
- tst-realloc.c
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
#include <unistd.h>
#include <array_length.h>
#include <libc-pointer-arith.h>
+#include <support/address-diff.h>
#include <support/check.h>
#include "tst-malloc-aux.h"
/* 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);
+ TEST_VERIFY (support_address_diff (
+ tcache_allocs[i].ptr1, tcache_allocs[i].ptr2) == 0);
free (tcache_allocs[i].ptr2);
-
- TEST_VERIFY (tcache_allocs[i].ptr1 == tcache_allocs[i].ptr2);
}
/* Test for non-head tcache hits. This exercises the memalign
count = 0;
for (i = 0; i < 10; ++ i)
- if (ptr[i] == p)
+ if (support_address_diff (ptr[i], p) == 0)
++ count;
free (p);
TEST_VERIFY (count > 0);
{
int ok = 0;
for (j = 0; j < LN; ++ j)
- if (large_allocs[i].ptr1 == large_allocs[j].ptr2)
+ if (support_address_diff (large_allocs[i].ptr1, large_allocs[j].ptr2)
+ == 0)
ok = 1;
if (ok == 1)
count ++;
#include <unistd.h>
#include <array_length.h>
#include <libc-pointer-arith.h>
+#include <support/address-diff.h>
#include <support/check.h>
#include <support/xthread.h>
#include "tst-malloc-aux.h"
/* 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);
+ TEST_VERIFY (support_address_diff (
+ tcache_allocs[i].ptr1, tcache_allocs[i].ptr2) == 0);
free (tcache_allocs[i].ptr2);
-
- TEST_VERIFY (tcache_allocs[i].ptr1 == tcache_allocs[i].ptr2);
}
/* Test for non-head tcache hits. */
count = 0;
for (i = 0; i < 10; ++ i)
- if (ptr[i] == p)
+ if (support_address_diff (ptr[i], p) == 0)
++ count;
free (p);
TEST_VERIFY (count > 0);
{
int ok = 0;
for (j = 0; j < LN; ++ j)
- if (large_allocs[i].ptr1 == large_allocs[j].ptr2)
+ if (support_address_diff (large_allocs[i].ptr1, large_allocs[j].ptr2)
+ == 0)
ok = 1;
if (ok == 1)
count ++;
#include <string.h>
#include <libc-diag.h>
#include <support/check.h>
+#include <support/address-diff.h>
#include "tst-malloc-aux.h"
size_t newsz = malloc_usable_size (p);
printf ("size: %zu, usable size: %zu, extra: %zu\n",
sz, newsz, newsz - sz);
- uintptr_t oldp = (uintptr_t) p;
+ void *oldp = p;
void *new_p = realloc (p, newsz);
- if ((uintptr_t) new_p != oldp)
+ if (support_address_diff (new_p, oldp) != 0)
FAIL_EXIT1 ("Expanding (%zu bytes) to usable size (%zu) moved block",
sz, newsz);
free (new_p);
xwrite \
# libsupport-routines
-libsupport-static-only-routines := $(libsupport-routines)
+libsupport-static-only-routines = $(libsupport-routines) $(libsupport-sysdep_routines)
# Only build one variant of the library.
libsupport-inhibit-o := .os
ifeq ($(build-shared),yes)
--- /dev/null
+/* Support functions for pointer arithmetic.
+ Copyright (C) 2026 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/>. */
+
+#ifndef _POINTER_ARITH_H
+#define _POINTER_ARITH_H 1
+
+#include <stddef.h>
+
+/* Returns difference in bytes between addresses of two pointers. */
+ptrdiff_t support_address_diff (const void *lhs, const void *rhs);
+
+#endif /* _POINTER_ARITH_H */
ifeq ($(subdir),malloc)
sysdep_malloc_debug_routines = __mtag_tag_zero_region __mtag_tag_region
endif # malloc directory
+
+ifeq ($(subdir),support)
+libsupport-sysdep_routines += \
+ support-address-diff \
+ # libsupport-sysdep_routines
+endif
--- /dev/null
+/* Support functions for pointer arithmetic for AArch64.
+ Copyright (C) 2026 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 "address-diff.h"
+
+#include <sys/ifunc.h>
+#include <sys/auxv.h>
+#include <libc-pointer-arith.h>
+
+static ptrdiff_t
+address_diff_mte (const void *lhs, const void *rhs)
+{
+ register const void *x0 asm ("x0") = lhs;
+ register const void *x1 asm ("x1") = rhs;
+ asm (".inst 0x9ac10000 /* subp x0, x0, x1 */" : "+r" (x0) : "r" (x1));
+ return (ptrdiff_t)x0;
+}
+
+static ptrdiff_t
+address_diff_generic (const void *lhs, const void *rhs)
+{
+ return PTR_DIFF (lhs, rhs);
+}
+
+static void * __attribute__ ((unused))
+address_diff_resolver (unsigned long a0, const unsigned long *a1)
+{
+ unsigned long hwcap2 = __ifunc_hwcap (_IFUNC_ARG_AT_HWCAP2, a0, a1);
+ if (hwcap2 & HWCAP2_MTE)
+ return (void *)address_diff_mte;
+ return (void *)address_diff_generic;
+}
+
+ptrdiff_t support_address_diff (const void *lhs, const void *rhs)
+__attribute__ ((ifunc ("address_diff_resolver")));
ifeq ($(subdir),misc)
sysdep_routines += hugepages
endif
+
+ifeq ($(subdir),support)
+libsupport-sysdep_routines += \
+ support-address-diff \
+ # libsupport-sysdep_routines
+endif
--- /dev/null
+/* Support functions for pointer arithmetic.
+ Copyright (C) 2026 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 "address-diff.h"
+
+#include <libc-pointer-arith.h>
+
+ptrdiff_t support_address_diff (const void *lhs, const void *rhs)
+{
+ return PTR_DIFF (lhs, rhs);
+}
projects / thirdparty / glibc.git / commitdiff
