[PATCH v5 1/1] malloc: aarch64: Add ifuncs for malloc functions
Adhemerval Zanella Netto
adhemerval.zanella@linaro.org
Mon Jun 8 17:17:39 GMT 2026
On 04/06/26 11:23, Yury Khrustalev wrote:
> Introduce ifuncs and resolvers for functions pertinent to the
> malloc interface on the AArch64 target: malloc, calloc, free,
> realloc, memalign, valloc, pvalloc, posix_memalign, aligned_alloc,
> free_sized, free_aligned_sized, malloc_usable_size.
>
> A target can define the USE_MULTIARCH_MALLOC macro. In this case
> it must provide alternative aliases for the malloc functions that
> point to the ifuncs.
>
> This implementation respects the --disable-multi-arch configure
> flag. If multi-arch support is disabled, the generic aliases
> are used on aarch64.
>
> This patch contains aarch64-specific resolvers. At this moment they
> return core implementations but in the future they can be changed
> to support for features, e.g. to handle memory tagging.
Patch looks good, some comments below.
> ---
> malloc/malloc-internal.h | 3 +
> malloc/malloc.c | 48 +++++++++++---
> sysdeps/aarch64/multiarch/Makefile | 10 ++-
> sysdeps/aarch64/multiarch/malloc-ifuncs.c | 80 +++++++++++++++++++++++
> sysdeps/aarch64/multiarch/malloc-ifuncs.h | 61 +++++++++++++++++
> sysdeps/generic/malloc-ifuncs.h | 35 ++++++++++
> 6 files changed, 227 insertions(+), 10 deletions(-)
> create mode 100644 sysdeps/aarch64/multiarch/malloc-ifuncs.c
> create mode 100644 sysdeps/aarch64/multiarch/malloc-ifuncs.h
> create mode 100644 sysdeps/generic/malloc-ifuncs.h
>
> diff --git a/malloc/malloc-internal.h b/malloc/malloc-internal.h
> index a6340bfd88..04ebe93ad8 100644
> --- a/malloc/malloc-internal.h
> +++ b/malloc/malloc-internal.h
> @@ -24,6 +24,9 @@
> #include <malloc-size.h>
> #include <hugepages.h>
> #include <calloc-clear-memory.h>
> +#if defined(USE_MULTIARCH)
> +# include <malloc-ifuncs.h>
> +#endif
>
> /* Called in the parent process before a fork. */
> void __malloc_fork_lock_parent (void) attribute_hidden;
> diff --git a/malloc/malloc.c b/malloc/malloc.c
> index 6ce76cb4df..9a2e796f0e 100644
> --- a/malloc/malloc.c
> +++ b/malloc/malloc.c
> @@ -499,6 +499,7 @@ libc_hidden_proto (__libc_free)
> set to zero.
> */
> void* __libc_calloc(size_t, size_t);
> +libc_hidden_proto (__libc_calloc)
>
> /*
> realloc(void* p, size_t n)
> @@ -551,6 +552,7 @@ libc_hidden_proto (__libc_memalign)
> size of the system. If the pagesize is unknown, 4096 is used.
> */
> void* __libc_valloc(size_t);
> +libc_hidden_proto (__libc_valloc)
>
>
>
> @@ -585,6 +587,7 @@ struct mallinfo __libc_mallinfo(void);
> round up n to nearest pagesize.
> */
> void* __libc_pvalloc(size_t);
> +libc_hidden_proto (__libc_pvalloc)
>
> /*
> malloc_trim(size_t pad);
> @@ -628,6 +631,7 @@ int __malloc_trim(size_t);
>
> */
> size_t __malloc_usable_size(void*);
> +libc_hidden_proto (__malloc_usable_size)
>
> /*
> malloc_stats();
> @@ -657,6 +661,7 @@ void __malloc_stats(void);
> POSIX wrapper like memalign(), checking for validity of size.
> */
> int __posix_memalign(void **, size_t, size_t);
> +libc_hidden_proto (__posix_memalign)
> #endif /* IS_IN (libc) */
>
> /*
> @@ -3315,8 +3320,11 @@ libc_hidden_def (__libc_memalign)
>
> /* For ISO C17. */
> void *
> -weak_function
> -aligned_alloc (size_t alignment, size_t bytes)
> +__aligned_alloc (size_t alignment, size_t bytes);
> +libc_hidden_proto (__aligned_alloc)
> +
> +void *
> +__aligned_alloc (size_t alignment, size_t bytes)
> {
> /* Starting with ISO C17 the standard requires an error for alignments
> that are not supported. Only integral powers of 2 are valid. */
> @@ -3328,11 +3336,15 @@ aligned_alloc (size_t alignment, size_t bytes)
>
> return _mid_memalign (alignment, bytes);
> }
> +libc_hidden_def (__aligned_alloc)
>
> /* For ISO C23. */
> void
> -weak_function
> -free_sized (void *ptr, __attribute_maybe_unused__ size_t size)
> +__free_sized (void *ptr, __attribute_maybe_unused__ size_t size);
> +libc_hidden_proto (__free_sized)
> +
> +void
> +__free_sized (void *ptr, __attribute_maybe_unused__ size_t size)
> {
> /* We do not perform validation that size is the same as the original
> requested size at this time. We leave that to the sanitizers. We
> @@ -3341,11 +3353,16 @@ free_sized (void *ptr, __attribute_maybe_unused__ size_t size)
>
> free (ptr);
> }
> +libc_hidden_def (__free_sized)
>
> /* For ISO C23. */
> void
> -weak_function
> -free_aligned_sized (void *ptr, __attribute_maybe_unused__ size_t alignment,
> +__free_aligned_sized (void *ptr, __attribute_maybe_unused__ size_t alignment,
> + __attribute_maybe_unused__ size_t size);
> +libc_hidden_proto (__free_aligned_sized)
> +
> +void
> +__free_aligned_sized (void *ptr, __attribute_maybe_unused__ size_t alignment,
> __attribute_maybe_unused__ size_t size)
> {
> /* We do not perform validation that size and alignment is the same as
> @@ -3355,6 +3372,7 @@ free_aligned_sized (void *ptr, __attribute_maybe_unused__ size_t alignment,
>
> free (ptr);
> }
> +libc_hidden_def (__free_aligned_sized)
>
> static void *
> _mid_memalign (size_t alignment, size_t bytes)
> @@ -3403,6 +3421,7 @@ __libc_valloc (size_t bytes)
> {
> return _mid_memalign (GLRO (dl_pagesize), bytes);
> }
> +libc_hidden_def (__libc_valloc)
>
> void *
> __libc_pvalloc (size_t bytes)
> @@ -3420,6 +3439,7 @@ __libc_pvalloc (size_t bytes)
>
> return _mid_memalign (pagesize, rounded_bytes & -pagesize);
> }
> +libc_hidden_def (__libc_pvalloc)
>
> static void * __attribute_noinline__
> __libc_calloc2 (size_t sz)
> @@ -3541,6 +3561,7 @@ __libc_calloc (size_t n, size_t elem_size)
> #endif
> return __libc_calloc2 (bytes);
> }
> +libc_hidden_def (__libc_calloc)
> #endif /* IS_IN (libc) */
>
> /*
> @@ -4537,6 +4558,7 @@ __malloc_usable_size (void *m)
> return 0;
> return musable (m);
> }
> +libc_hidden_def (__malloc_usable_size)
> #endif /* IS_IN (libc) */
>
> /*
> @@ -5064,6 +5086,7 @@ __posix_memalign (void **memptr, size_t alignment, size_t size)
> *memptr = mem;
> return 0;
> }
> +libc_hidden_def (__posix_memalign)
> #endif /* IS_IN (libc) */
>
>
> @@ -5226,6 +5249,9 @@ __malloc_info (int options, FILE *fp)
> }
>
> #if IS_IN (libc)
> +
> +/* See sysdeps/generic/malloc-ifuncs.h for details. */
> +# if !defined (USE_MULTIARCH_MALLOC)
> strong_alias (__libc_malloc, malloc)
> strong_alias (__libc_realloc, realloc)
> strong_alias (__libc_free, free)
> @@ -5235,6 +5261,10 @@ weak_alias (__posix_memalign, posix_memalign)
> weak_alias (__libc_valloc, valloc)
> weak_alias (__libc_pvalloc, pvalloc)
> weak_alias (__malloc_usable_size, malloc_usable_size)
> +weak_alias (__aligned_alloc, aligned_alloc)
> +weak_alias (__free_sized, free_sized)
> +weak_alias (__free_aligned_sized, free_aligned_sized)
> +#endif /* !USE_MULTIARCH_MALLOC */
>
> weak_alias (__malloc_info, malloc_info)
> weak_alias (__libc_mallinfo, mallinfo)
> @@ -5244,9 +5274,11 @@ weak_alias (__malloc_stats, malloc_stats)
> weak_alias (__malloc_trim, malloc_trim)
> #endif /* IS_IN (libc) */
>
> -#if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_26)
> +#if !defined (USE_MULTIARCH_MALLOC)
> +# if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_26)
> compat_symbol (libc, __libc_free, cfree, GLIBC_2_0);
> -#endif
> +# endif
> +#endif /* !USE_MULTIARCH_MALLOC */
>
> /* ------------------------------------------------------------
> History:
> diff --git a/sysdeps/aarch64/multiarch/Makefile b/sysdeps/aarch64/multiarch/Makefile
> index 38952655b1..a8a03a0491 100644
> --- a/sysdeps/aarch64/multiarch/Makefile
> +++ b/sysdeps/aarch64/multiarch/Makefile
> @@ -18,5 +18,11 @@ sysdep_routines += \
> memset_zva64 \
> strlen_asimd \
> strlen_generic \
> -# sysdep_routines
> -endif
> + # sysdep_routines
> +endif # ifeq ($(subdir),string)
> +
> +ifeq ($(subdir),malloc)
> +sysdep_routines += \
> + malloc-ifuncs \
> + # sysdep_routines
> +endif # ifeq ($(subdir),malloc)
> diff --git a/sysdeps/aarch64/multiarch/malloc-ifuncs.c b/sysdeps/aarch64/multiarch/malloc-ifuncs.c
> new file mode 100644
> index 0000000000..e475f43a31
> --- /dev/null
> +++ b/sysdeps/aarch64/multiarch/malloc-ifuncs.c
> @@ -0,0 +1,80 @@
> +/* Code for ifunc resolvers for 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/>. */
> +
> +#if IS_IN (libc)
> +
> +#include <stdint.h>
> +#include <init-arch.h>
> +#include <shlib-compat.h>
> +#include <malloc-ifuncs.h>
> +
> +libc_ifunc_hidden (__libc_malloc, __libc_malloc_redirect,
> + __libc_malloc)
> +strong_alias (__libc_malloc_redirect, malloc)
> +
> +libc_ifunc_hidden (__libc_calloc, __libc_calloc_redirect,
> + __libc_calloc)
> +weak_alias (__libc_calloc_redirect, calloc)
> +
> +libc_ifunc_hidden (__libc_memalign, __libc_memalign_redirect,
> + __libc_memalign)
> +weak_alias (__libc_memalign_redirect, memalign)
> +
> +libc_ifunc_hidden (__libc_valloc, __libc_valloc_redirect,
> + __libc_valloc)
> +weak_alias (__libc_valloc_redirect, valloc)
> +
> +libc_ifunc_hidden (__libc_pvalloc, __libc_pvalloc_redirect,
> + __libc_pvalloc)
> +weak_alias (__libc_pvalloc_redirect, pvalloc)
> +
> +libc_ifunc_hidden (__libc_realloc, __libc_realloc_redirect,
> + __libc_realloc)
> +strong_alias (__libc_realloc_redirect, realloc)
> +
> +libc_ifunc_hidden (__libc_free, __libc_free_redirect,
> + __libc_free)
> +strong_alias (__libc_free_redirect, free)
> +
> +libc_ifunc_hidden (__malloc_usable_size, __malloc_usable_size_redirect,
> + __malloc_usable_size)
> +weak_alias (__malloc_usable_size_redirect, malloc_usable_size)
> +
> +libc_ifunc_hidden (__posix_memalign, __posix_memalign_redirect,
> + __posix_memalign)
> +weak_alias (__posix_memalign_redirect, posix_memalign)
> +
> +libc_ifunc_hidden (__aligned_alloc, __aligned_alloc_redirect,
> + __aligned_alloc)
> +weak_alias (__aligned_alloc_redirect, aligned_alloc)
> +
> +libc_ifunc_hidden (__free_sized, __free_sized_redirect,
> + __free_sized)
> +weak_alias (__free_sized_redirect, free_sized)
> +
> +libc_ifunc_hidden (__free_aligned_sized, __free_aligned_sized_redirect,
> + __free_aligned_sized)
> +weak_alias (__free_aligned_sized_redirect, free_aligned_sized)
> +
> +#endif /* IS_IN (libc) */
> +
> +#ifdef SHARED
> +# if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_26)
The SHLIB_COMPAT already handles SHARED (it is declared as 0 for !SHARED),
so no need to handle it here.
> +compat_symbol (libc, __libc_free_redirect, cfree, GLIBC_2_0);
> +# endif
> +#endif
> diff --git a/sysdeps/aarch64/multiarch/malloc-ifuncs.h b/sysdeps/aarch64/multiarch/malloc-ifuncs.h
> new file mode 100644
> index 0000000000..4b510ef004
> --- /dev/null
> +++ b/sysdeps/aarch64/multiarch/malloc-ifuncs.h
> @@ -0,0 +1,61 @@
> +/* Definitions for ifunc resolvers for 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/>. */
> +
> +#ifndef _AARCH64_MALLOC_IFUNCS_H
> +#define _AARCH64_MALLOC_IFUNCS_H
> +
> +#define USE_MULTIARCH_MALLOC 1
> +
> +#include <stddef.h>
> +#include <sys/cdefs.h>
> +
> +/* Core implementations of malloc functions. An ifunc resolver must
> + use these implementations as a fallback option. Other implementations
> + may internally call these core functions. */
> +void *__libc_malloc (size_t);
> +libc_hidden_proto (__libc_malloc)
> +void *__libc_calloc (size_t, size_t);
> +libc_hidden_proto (__libc_calloc)
> +void *__libc_memalign (size_t, size_t);
> +libc_hidden_proto (__libc_memalign)
> +void *__libc_valloc (size_t);
> +libc_hidden_proto (__libc_valloc)
> +void *__libc_pvalloc (size_t);
> +libc_hidden_proto (__libc_pvalloc)
> +void *__libc_realloc (void *, size_t);
> +libc_hidden_proto (__libc_realloc)
> +void __libc_free (void *);
> +libc_hidden_proto (__libc_free)
> +size_t __malloc_usable_size (void *);
> +libc_hidden_proto (__malloc_usable_size)
> +
> +/* For additions of POSIX. */
> +int __posix_memalign (void **, size_t, size_t);
> +libc_hidden_proto (__posix_memalign)
> +
> +/* For ISO C17. */
> +void *__aligned_alloc (size_t, size_t);
> +libc_hidden_proto (__aligned_alloc)
> +
> +/* For ISO C23. */
> +void __free_sized (void *, size_t);
> +libc_hidden_proto (__free_sized)
> +void __free_aligned_sized (void *, size_t, size_t);
> +libc_hidden_proto (__free_aligned_sized)
The malloc-internal.h already has libc_hidden_proto for calloc and others,
I think there is no need to duplicate here on the aarch64-specific code.
> +
> +#endif /* _AARCH64_MALLOC_IFUNCS_H */
> diff --git a/sysdeps/generic/malloc-ifuncs.h b/sysdeps/generic/malloc-ifuncs.h
> new file mode 100644
> index 0000000000..3bb6e60ba1
> --- /dev/null
> +++ b/sysdeps/generic/malloc-ifuncs.h
> @@ -0,0 +1,35 @@
> +/* Definitions for ifunc resolvers for malloc: generic 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/>. */
> +
> +#ifndef _GENERIC_MALLOC_IFUNCS_H
> +#define _GENERIC_MALLOC_IFUNCS_H
> +
> +/* Targets should define this macro if they provide ifuncs for
> + malloc functions. When USE_MULTIARCH_MALLOC is defined, the
> + following functions should be implemented via ifuncs:
> +
> + malloc, calloc, free, realloc
> + memalign, valloc, pvalloc
> + posix_memalign
> + malloc_usable_size
> + aligned_alloc, free_sized, free_aligned_sized
> +
> +*/
> +#undef USE_MULTIARCH_MALLOC
I think the new way is to have internal defines being either being 0
(disable) or 1 (enable). This helps catch issues where the defined should
set, but the not case is wrongly used.
So I would suggest to define
#define USE_MULTIARCH_MALLOC 0
here and use "if USE_MULTIARCH_MALLOC" or "if !USE_MULTIARCH_MALLOC"
in the malloc code.
> +
> +#endif /* GENERIC_MALLOC_IFUNCS_H */
s/GENERIC_MALLOC_IFUNCS_H/_GENERIC_MALLOC_IFUNCS_H
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