+++ /dev/null
-From 455bd4c430b0c0a361f38e8658a0d6cb469942b5 Mon Sep 17 00:00:00 2001
-From: Ivan Djelic <ivan.djelic@parrot.com>
-Date: Wed, 6 Mar 2013 20:09:27 +0100
-Subject: [PATCH] ARM: 7668/1: fix memset-related crashes caused by recent GCC
- (4.7.2) optimizations
-
-Recent GCC versions (e.g. GCC-4.7.2) perform optimizations based on
-assumptions about the implementation of memset and similar functions.
-The current ARM optimized memset code does not return the value of
-its first argument, as is usually expected from standard implementations.
-
-For instance in the following function:
-
-void debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter)
-{
- memset(waiter, MUTEX_DEBUG_INIT, sizeof(*waiter));
- waiter->magic = waiter;
- INIT_LIST_HEAD(&waiter->list);
-}
-
-compiled as:
-
-800554d0 <debug_mutex_lock_common>:
-800554d0: e92d4008 push {r3, lr}
-800554d4: e1a00001 mov r0, r1
-800554d8: e3a02010 mov r2, #16 ; 0x10
-800554dc: e3a01011 mov r1, #17 ; 0x11
-800554e0: eb04426e bl 80165ea0 <memset>
-800554e4: e1a03000 mov r3, r0
-800554e8: e583000c str r0, [r3, #12]
-800554ec: e5830000 str r0, [r3]
-800554f0: e5830004 str r0, [r3, #4]
-800554f4: e8bd8008 pop {r3, pc}
-
-GCC assumes memset returns the value of pointer 'waiter' in register r0; causing
-register/memory corruptions.
-
-This patch fixes the return value of the assembly version of memset.
-It adds a 'mov' instruction and merges an additional load+store into
-existing load/store instructions.
-For ease of review, here is a breakdown of the patch into 4 simple steps:
-
-Step 1
-======
-Perform the following substitutions:
-ip -> r8, then
-r0 -> ip,
-and insert 'mov ip, r0' as the first statement of the function.
-At this point, we have a memset() implementation returning the proper result,
-but corrupting r8 on some paths (the ones that were using ip).
-
-Step 2
-======
-Make sure r8 is saved and restored when (! CALGN(1)+0) == 1:
-
-save r8:
-- str lr, [sp, #-4]!
-+ stmfd sp!, {r8, lr}
-
-and restore r8 on both exit paths:
-- ldmeqfd sp!, {pc} @ Now <64 bytes to go.
-+ ldmeqfd sp!, {r8, pc} @ Now <64 bytes to go.
-(...)
- tst r2, #16
- stmneia ip!, {r1, r3, r8, lr}
-- ldr lr, [sp], #4
-+ ldmfd sp!, {r8, lr}
-
-Step 3
-======
-Make sure r8 is saved and restored when (! CALGN(1)+0) == 0:
-
-save r8:
-- stmfd sp!, {r4-r7, lr}
-+ stmfd sp!, {r4-r8, lr}
-
-and restore r8 on both exit paths:
- bgt 3b
-- ldmeqfd sp!, {r4-r7, pc}
-+ ldmeqfd sp!, {r4-r8, pc}
-(...)
- tst r2, #16
- stmneia ip!, {r4-r7}
-- ldmfd sp!, {r4-r7, lr}
-+ ldmfd sp!, {r4-r8, lr}
-
-Step 4
-======
-Rewrite register list "r4-r7, r8" as "r4-r8".
-
-Signed-off-by: Ivan Djelic <ivan.djelic@parrot.com>
-Reviewed-by: Nicolas Pitre <nico@linaro.org>
-Signed-off-by: Dirk Behme <dirk.behme@gmail.com>
-Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
----
- arch/arm/lib/memset.S | 85 ++++++++++++++++++++++++++-------------------------
- 1 file changed, 44 insertions(+), 41 deletions(-)
-
---- a/arch/arm/lib/memset.S
-+++ b/arch/arm/lib/memset.S
-@@ -19,9 +19,9 @@
- 1: subs r2, r2, #4 @ 1 do we have enough
- blt 5f @ 1 bytes to align with?
- cmp r3, #2 @ 1
-- strltb r1, [r0], #1 @ 1
-- strleb r1, [r0], #1 @ 1
-- strb r1, [r0], #1 @ 1
-+ strltb r1, [ip], #1 @ 1
-+ strleb r1, [ip], #1 @ 1
-+ strb r1, [ip], #1 @ 1
- add r2, r2, r3 @ 1 (r2 = r2 - (4 - r3))
- /*
- * The pointer is now aligned and the length is adjusted. Try doing the
-@@ -29,10 +29,14 @@
- */
-
- ENTRY(memset)
-- ands r3, r0, #3 @ 1 unaligned?
-+/*
-+ * Preserve the contents of r0 for the return value.
-+ */
-+ mov ip, r0
-+ ands r3, ip, #3 @ 1 unaligned?
- bne 1b @ 1
- /*
-- * we know that the pointer in r0 is aligned to a word boundary.
-+ * we know that the pointer in ip is aligned to a word boundary.
- */
- orr r1, r1, r1, lsl #8
- orr r1, r1, r1, lsl #16
-@@ -43,29 +47,28 @@ ENTRY(memset)
- #if ! CALGN(1)+0
-
- /*
-- * We need an extra register for this loop - save the return address and
-- * use the LR
-+ * We need 2 extra registers for this loop - use r8 and the LR
- */
-- str lr, [sp, #-4]!
-- mov ip, r1
-+ stmfd sp!, {r8, lr}
-+ mov r8, r1
- mov lr, r1
-
- 2: subs r2, r2, #64
-- stmgeia r0!, {r1, r3, ip, lr} @ 64 bytes at a time.
-- stmgeia r0!, {r1, r3, ip, lr}
-- stmgeia r0!, {r1, r3, ip, lr}
-- stmgeia r0!, {r1, r3, ip, lr}
-+ stmgeia ip!, {r1, r3, r8, lr} @ 64 bytes at a time.
-+ stmgeia ip!, {r1, r3, r8, lr}
-+ stmgeia ip!, {r1, r3, r8, lr}
-+ stmgeia ip!, {r1, r3, r8, lr}
- bgt 2b
-- ldmeqfd sp!, {pc} @ Now <64 bytes to go.
-+ ldmeqfd sp!, {r8, pc} @ Now <64 bytes to go.
- /*
- * No need to correct the count; we're only testing bits from now on
- */
- tst r2, #32
-- stmneia r0!, {r1, r3, ip, lr}
-- stmneia r0!, {r1, r3, ip, lr}
-+ stmneia ip!, {r1, r3, r8, lr}
-+ stmneia ip!, {r1, r3, r8, lr}
- tst r2, #16
-- stmneia r0!, {r1, r3, ip, lr}
-- ldr lr, [sp], #4
-+ stmneia ip!, {r1, r3, r8, lr}
-+ ldmfd sp!, {r8, lr}
-
- #else
-
-@@ -74,54 +77,54 @@ ENTRY(memset)
- * whole cache lines at once.
- */
-
-- stmfd sp!, {r4-r7, lr}
-+ stmfd sp!, {r4-r8, lr}
- mov r4, r1
- mov r5, r1
- mov r6, r1
- mov r7, r1
-- mov ip, r1
-+ mov r8, r1
- mov lr, r1
-
- cmp r2, #96
-- tstgt r0, #31
-+ tstgt ip, #31
- ble 3f
-
-- and ip, r0, #31
-- rsb ip, ip, #32
-- sub r2, r2, ip
-- movs ip, ip, lsl #(32 - 4)
-- stmcsia r0!, {r4, r5, r6, r7}
-- stmmiia r0!, {r4, r5}
-- tst ip, #(1 << 30)
-- mov ip, r1
-- strne r1, [r0], #4
-+ and r8, ip, #31
-+ rsb r8, r8, #32
-+ sub r2, r2, r8
-+ movs r8, r8, lsl #(32 - 4)
-+ stmcsia ip!, {r4, r5, r6, r7}
-+ stmmiia ip!, {r4, r5}
-+ tst r8, #(1 << 30)
-+ mov r8, r1
-+ strne r1, [ip], #4
-
- 3: subs r2, r2, #64
-- stmgeia r0!, {r1, r3-r7, ip, lr}
-- stmgeia r0!, {r1, r3-r7, ip, lr}
-+ stmgeia ip!, {r1, r3-r8, lr}
-+ stmgeia ip!, {r1, r3-r8, lr}
- bgt 3b
-- ldmeqfd sp!, {r4-r7, pc}
-+ ldmeqfd sp!, {r4-r8, pc}
-
- tst r2, #32
-- stmneia r0!, {r1, r3-r7, ip, lr}
-+ stmneia ip!, {r1, r3-r8, lr}
- tst r2, #16
-- stmneia r0!, {r4-r7}
-- ldmfd sp!, {r4-r7, lr}
-+ stmneia ip!, {r4-r7}
-+ ldmfd sp!, {r4-r8, lr}
-
- #endif
-
- 4: tst r2, #8
-- stmneia r0!, {r1, r3}
-+ stmneia ip!, {r1, r3}
- tst r2, #4
-- strne r1, [r0], #4
-+ strne r1, [ip], #4
- /*
- * When we get here, we've got less than 4 bytes to zero. We
- * may have an unaligned pointer as well.
- */
- 5: tst r2, #2
-- strneb r1, [r0], #1
-- strneb r1, [r0], #1
-+ strneb r1, [ip], #1
-+ strneb r1, [ip], #1
- tst r2, #1
-- strneb r1, [r0], #1
-+ strneb r1, [ip], #1
- mov pc, lr
- ENDPROC(memset)
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