From c076a0bc698c537f72c33bad2925f4e3da59d23c Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Fri, 29 Jan 2021 17:07:28 +0000 Subject: [PATCH] malloc: Only support zeroing and not arbitrary memset with mtag The memset api is suboptimal and does not provide much benefit. Memory tagging only needs a zeroing memset (and only for memory that's sized and aligned to multiples of the tag granule), so change the internal api and the target hooks accordingly. This is to simplify the implementation of the target hook. Reviewed-by: DJ Delorie --- malloc/malloc.c | 17 ++++++++--------- sysdeps/aarch64/Makefile | 2 +- ...g_memset_tag.S => __mtag_tag_zero_region.S} | 18 +++++++----------- sysdeps/aarch64/libc-mtag.h | 4 ++-- sysdeps/generic/libc-mtag.h | 6 +++--- 5 files changed, 21 insertions(+), 26 deletions(-) rename sysdeps/aarch64/{__mtag_memset_tag.S => __mtag_tag_zero_region.S} (82%) diff --git a/malloc/malloc.c b/malloc/malloc.c index 9c3981febe4..9cfea1f8785 100644 --- a/malloc/malloc.c +++ b/malloc/malloc.c @@ -413,12 +413,11 @@ void *(*__morecore)(ptrdiff_t) = __default_morecore; operations can continue to be used. Support macros are used to do this: - void *tag_new_memset (void *ptr, int, val, size_t size) + void *tag_new_zero_region (void *ptr, size_t size) - Has the same interface as memset(), but additionally allocates a - new tag, colors the memory with that tag and returns a pointer that - is correctly colored for that location. The non-tagging version - will simply call memset. + Allocates a new tag, colors the memory with that tag, zeros the + memory and returns a pointer that is correctly colored for that + location. The non-tagging version will simply call memset with 0. void *tag_region (void *ptr, size_t size) @@ -458,11 +457,11 @@ tag_region (void *ptr, size_t size) } static __always_inline void * -tag_new_memset (void *ptr, int val, size_t size) +tag_new_zero_region (void *ptr, size_t size) { if (__glibc_unlikely (mtag_enabled)) - return __libc_mtag_memset_with_tag (__libc_mtag_new_tag (ptr), val, size); - return memset (ptr, val, size); + return __libc_mtag_tag_zero_region (__libc_mtag_new_tag (ptr), size); + return memset (ptr, 0, size); } /* Defined later. */ @@ -3679,7 +3678,7 @@ __libc_calloc (size_t n, size_t elem_size) regardless of MORECORE_CLEARS, so we zero the whole block while doing so. */ #ifdef USE_MTAG - return tag_new_memset (mem, 0, CHUNK_AVAILABLE_SIZE (p) - CHUNK_HDR_SZ); + return tag_new_zero_region (mem, CHUNK_AVAILABLE_SIZE (p) - CHUNK_HDR_SZ); #else INTERNAL_SIZE_T csz = chunksize (p); diff --git a/sysdeps/aarch64/Makefile b/sysdeps/aarch64/Makefile index d3ab37a40ac..259070cfad9 100644 --- a/sysdeps/aarch64/Makefile +++ b/sysdeps/aarch64/Makefile @@ -41,7 +41,7 @@ endif ifeq ($(subdir),misc) sysdep_headers += sys/ifunc.h sysdep_routines += __mtag_address_get_tag \ - __mtag_memset_tag \ + __mtag_tag_zero_region \ __mtag_new_tag \ __mtag_tag_region diff --git a/sysdeps/aarch64/__mtag_memset_tag.S b/sysdeps/aarch64/__mtag_tag_zero_region.S similarity index 82% rename from sysdeps/aarch64/__mtag_memset_tag.S rename to sysdeps/aarch64/__mtag_tag_zero_region.S index 3c202888a45..74d398bba52 100644 --- a/sysdeps/aarch64/__mtag_memset_tag.S +++ b/sysdeps/aarch64/__mtag_tag_zero_region.S @@ -20,9 +20,6 @@ #ifdef USE_MTAG -/* Use the same register names and assignments as memset. */ -#include "memset-reg.h" - .arch armv8.5-a .arch_extension memtag @@ -31,16 +28,15 @@ /* FIXME: This is a minimal implementation. We could do much better than this for large values of COUNT. */ -ENTRY(__libc_mtag_memset_with_tag) +#define dstin x0 +#define count x1 +#define dst x2 - and valw, valw, 255 - orr valw, valw, valw, lsl 8 - orr valw, valw, valw, lsl 16 - orr val, val, val, lsl 32 - mov dst, dstin +ENTRY(__libc_mtag_tag_zero_region) + mov dst, dstin L(loop): - stgp val, val, [dst], #16 + stzg dst, [dst], #16 subs count, count, 16 bne L(loop) #if 0 @@ -49,5 +45,5 @@ L(loop): ldg dstin, [dstin] // Recover the tag created (might be untagged). #endif ret -END (__libc_mtag_memset_with_tag) +END (__libc_mtag_tag_zero_region) #endif /* USE_MTAG */ diff --git a/sysdeps/aarch64/libc-mtag.h b/sysdeps/aarch64/libc-mtag.h index 979cbb743ea..f58402ccf94 100644 --- a/sysdeps/aarch64/libc-mtag.h +++ b/sysdeps/aarch64/libc-mtag.h @@ -39,8 +39,8 @@ void *__libc_mtag_tag_region (const void *, size_t) */ void *__libc_mtag_tag_region (void *, size_t); -/* Optimized equivalent to __libc_mtag_tag_region followed by memset. */ -void *__libc_mtag_memset_with_tag (void *, int, size_t); +/* Optimized equivalent to __libc_mtag_tag_region followed by memset to 0. */ +void *__libc_mtag_tag_zero_region (void *, size_t); /* Convert address P to a pointer that is tagged correctly for that location. diff --git a/sysdeps/generic/libc-mtag.h b/sysdeps/generic/libc-mtag.h index e8fc236b6cf..4743e873f10 100644 --- a/sysdeps/generic/libc-mtag.h +++ b/sysdeps/generic/libc-mtag.h @@ -44,12 +44,12 @@ __libc_mtag_tag_region (void *p, size_t n) return p; } -/* Optimized equivalent to __libc_mtag_tag_region followed by memset. */ +/* Optimized equivalent to __libc_mtag_tag_region followed by memset to 0. */ static inline void * -__libc_mtag_memset_with_tag (void *p, int c, size_t n) +__libc_mtag_tag_zero_region (void *p, size_t n) { __libc_mtag_link_error (); - return memset (p, c, n); + return memset (p, 0, n); } /* Convert address P to a pointer that is tagged correctly for that -- 2.39.5