Optimize __memset_chk, __memcpy_chk. DO NOT MERGE.
This change creates assembler versions of __memcpy_chk/__memset_chk
that is implemented in the memcpy/memset assembler code. This change
avoids an extra call to memcpy/memset, instead allowing a simple fall
through to occur from the chk code into the body of the real
implementation.
Testing:
- Ran the libc_test on __memcpy_chk/__memset_chk on all nexus devices.
- Wrote a small test executable that has three calls to __memcpy_chk and
three calls to __memset_chk. First call dest_len is length + 1. Second
call dest_len is length. Third call dest_len is length - 1.
Verified that the first two calls pass, and the third fails. Examined
the logcat output on all nexus devices to verify that the fortify
error message was sent properly.
- I benchmarked the new __memcpy_chk and __memset_chk on all systems. For
__memcpy_chk and large copies, the savings is relatively small (about 1%).
For small copies, the savings is large on cortex-a15/krait devices
(between 5% to 30%).
For cortex-a9 and small copies, the speed up is present, but relatively
small (about 3% to 5%).
For __memset_chk and large copies, the savings is also small (about 1%).
However, all processors show larger speed-ups on small copies (about 30% to
100%).
Bug: 9293744
Merge from internal master.
(cherry-picked from 7c860db0747f6276a6e43984d43f8fa5181ea936)
Change-Id: I916ad305e4001269460ca6ebd38aaa0be8ac7f52
diff --git a/libc/arch-arm/cortex-a9/bionic/memset.S b/libc/arch-arm/cortex-a9/bionic/memset.S
index b58aa45..d011430 100644
--- a/libc/arch-arm/cortex-a9/bionic/memset.S
+++ b/libc/arch-arm/cortex-a9/bionic/memset.S
@@ -28,6 +28,7 @@
#include <machine/cpu-features.h>
#include <machine/asm.h>
+#include "libc_events.h"
/*
* This code assumes it is running on a processor that supports all arm v7
@@ -36,9 +37,28 @@
.fpu neon
+ENTRY(__memset_chk)
+ cmp r2, r3
+ bls done
+
+ ldr r0, error_message
+ ldr r1, error_code
+1:
+ add r0, pc
+ bl __fortify_chk_fail
+error_code:
+ .word BIONIC_EVENT_MEMSET_BUFFER_OVERFLOW
+error_message:
+ .word error_string-(1b+8)
+
+END(__memset_chk)
+
ENTRY(bzero)
mov r2, r1
mov r1, #0
+
+done:
+ // Fall through to memset...
END(bzero)
/* memset() returns its first argument. */
@@ -150,3 +170,7 @@
ldmfd sp!, {r0, r4-r7, lr}
bx lr
END(memset)
+
+ .data
+error_string:
+ .string "memset buffer overflow"