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From: Szabolcs Nagy <szabolcs.nagy@arm.com>
To: libc-alpha@sourceware.org, Richard.Earnshaw@arm.com,
	DJ Delorie <dj@redhat.com>
Subject: [PATCH 09/16] malloc: Only support zeroing and not arbitrary memset with mtag
Date: Thu,  4 Mar 2021 16:32:45 +0000	[thread overview]
Message-ID: <4b85579387c095e4dbcc044042aa0f2dfdbd3a18.1614874816.git.szabolcs.nagy@arm.com> (raw)
In-Reply-To: <cover.1614874816.git.szabolcs.nagy@arm.com>

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.
---
 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 caf34843f7..9002d51d7b 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 d3ab37a40a..259070cfad 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 3c202888a4..74d398bba5 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 979cbb743e..f58402ccf9 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 e8fc236b6c..4743e873f1 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
-- 
2.17.1


  parent reply	other threads:[~2021-03-04 16:33 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-04 16:30 [PATCH 00/16] memory tagging improvements Szabolcs Nagy
2021-03-04 16:30 ` [PATCH 01/16] malloc: Fix a realloc crash with heap tagging [BZ 27468] Szabolcs Nagy
2021-03-05  0:15   ` DJ Delorie
2021-03-05 12:01     ` Szabolcs Nagy
2021-03-05 18:42       ` DJ Delorie
2021-03-05 20:51   ` DJ Delorie
2021-03-04 16:30 ` [PATCH 02/16] Remove PR_TAGGED_ADDR_ENABLE from sys/prctl.h Szabolcs Nagy
2021-03-26 11:29   ` Szabolcs Nagy
2021-04-13  8:37     ` Szabolcs Nagy
2021-04-13 21:32       ` DJ Delorie
2021-03-04 16:31 ` [PATCH 03/16] malloc: Move MTAG_MMAP_FLAGS definition Szabolcs Nagy
2021-03-05  1:07   ` DJ Delorie
2021-03-04 16:31 ` [PATCH 04/16] malloc: Simplify __mtag_tag_new_usable Szabolcs Nagy
2021-03-05  0:20   ` DJ Delorie
2021-03-05 12:24     ` Szabolcs Nagy
2021-03-05 18:52   ` DJ Delorie
2021-03-04 16:31 ` [PATCH 05/16] malloc: Avoid taggig mmaped memory on free Szabolcs Nagy
2021-03-05  1:01   ` DJ Delorie
2021-03-04 16:31 ` [PATCH 06/16] malloc: Ensure the generic mtag hooks are not used Szabolcs Nagy
2021-03-05  1:05   ` DJ Delorie
2021-03-05 12:44     ` Szabolcs Nagy
2021-03-05 20:30   ` DJ Delorie
2021-03-04 16:32 ` [PATCH 07/16] malloc: Refactor TAG_ macros to avoid indirection Szabolcs Nagy
2021-03-05  0:28   ` DJ Delorie
2021-03-04 16:32 ` [PATCH 08/16] malloc: Use global flag instead of function pointer dispatch for mtag Szabolcs Nagy
2021-03-05  0:46   ` DJ Delorie
2021-03-05 12:53     ` Szabolcs Nagy
2021-03-04 16:32 ` Szabolcs Nagy [this message]
2021-03-05  0:49   ` [PATCH 09/16] malloc: Only support zeroing and not arbitrary memset with mtag DJ Delorie
2021-03-04 16:33 ` [PATCH 10/16] malloc: Change calloc when tagging is disabled Szabolcs Nagy
2021-03-05  1:06   ` DJ Delorie
2021-03-04 16:33 ` [PATCH 11/16] malloc: Use branches instead of mtag_granule_mask Szabolcs Nagy
2021-03-05 21:00   ` DJ Delorie
2021-03-04 16:33 ` [PATCH 12/16] malloc: Use mtag_enabled instead of USE_MTAG Szabolcs Nagy
2021-03-05  0:56   ` DJ Delorie
2021-03-04 16:34 ` [PATCH 13/16] aarch64: inline __libc_mtag_address_get_tag Szabolcs Nagy
2021-03-04 16:34 ` [PATCH 14/16] aarch64: inline __libc_mtag_new_tag Szabolcs Nagy
2021-03-04 16:34 ` [PATCH 15/16] aarch64: Optimize __libc_mtag_tag_region Szabolcs Nagy
2021-03-04 16:34 ` [PATCH 16/16] aarch64: Optimize __libc_mtag_tag_zero_region Szabolcs Nagy

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