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