[PATCH] support: add support_ptr_after_free

[Andreas Schwab]

On Mai 06 2026, Yury Khrustalev wrote:

> diff --git a/sysdeps/aarch64/support-use-after-free.c b/sysdeps/aarch64/support-use-after-free.c
> new file mode 100644
> index 0000000000..eff5ff7c9a
> --- /dev/null
> +++ b/sysdeps/aarch64/support-use-after-free.c
> @@ -0,0 +1,47 @@
> +/* Support functions testing malloc: aarch64 version.
> +   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 "test-pointer.h"
> +
> +#include <sys/ifunc.h>
> +#include <sys/auxv.h>
> +
> +/* This version clears bits 59:56 (4 bits) to remove possible
> +   MTE tag from the pointer without trying to access memory
> +   that this pointer points to.  */
> +static void *ptr_after_free_mte (void *ptr)
> +{
> +  return (void *)((uintptr_t)ptr & ~(0xfull << 56ull));
> +}
> +
> +static void *ptr_after_free_generic (void *ptr)
> +{
> +  return ptr;
> +}
> +
> +static void * __attribute__ ((unused))
> +ptr_after_free_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 *)ptr_after_free_mte;
> +  return (void *)ptr_after_free_generic;
> +}
> +
> +void *support_ptr_after_free (void *ptr)
> +__attribute__ ((ifunc ("ptr_after_free_resolver")));
> \ No newline at end of file

Please add the newline.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."