| Message ID | 1395330365-9901-6-git-send-email-ian.campbell@citrix.com |
|---|---|
| State | Superseded |
| Headers | show |
On 03/20/2014 03:45 PM, Ian Campbell wrote: > This pulls in the following Linux commits: > commit 455bd4c430b0c0a361f38e8658a0d6cb469942b5 > Author: Ivan Djelic <ivan.djelic@parrot.com> > Date: Wed Mar 6 20:09:27 2013 +0100 > > ARM: 7668/1: fix memset-related crashes caused by recent GCC (4.7.2) optimi > > 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 *waite > { > 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; ca > 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 resul > 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> > > commit 418df63adac56841ef6b0f1fcf435bc64d4ed177 > Author: Nicolas Pitre <nicolas.pitre@linaro.org> > Date: Tue Mar 12 13:00:42 2013 +0100 > > ARM: 7670/1: fix the memset fix > > Commit 455bd4c430b0 ("ARM: 7668/1: fix memset-related crashes caused by > recent GCC (4.7.2) optimizations") attempted to fix a compliance issue > with the memset return value. However the memset itself became broken > by that patch for misaligned pointers. > > This fixes the above by branching over the entry code from the > misaligned fixup code to avoid reloading the original pointer. > > Also, because the function entry alignment is wrong in the Thumb mode > compilation, that fixup code is moved to the end. > > While at it, the entry instructions are slightly reworked to help dual > issue pipelines. > > Signed-off-by: Nicolas Pitre <nico@linaro.org> > Tested-by: Alexander Holler <holler@ahsoftware.de> > Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> > > Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Acked-by: Julien Grall <julien.grall@linaro.org>
diff --git a/xen/arch/arm/arm32/lib/memset.S b/xen/arch/arm/arm32/lib/memset.S index d2937a3..c8ab257 100644 --- a/xen/arch/arm/arm32/lib/memset.S +++ b/xen/arch/arm/arm32/lib/memset.S @@ -16,27 +16,15 @@ .text .align 5 - .word 0 - -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 - add r2, r2, r3 @ 1 (r2 = r2 - (4 - r3)) -/* - * The pointer is now aligned and the length is adjusted. Try doing the - * memset again. - */ ENTRY(memset) ands r3, r0, #3 @ 1 unaligned? - bne 1b @ 1 + mov ip, r0 @ preserve r0 as return value + bne 6f @ 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 +1: orr r1, r1, r1, lsl #8 orr r1, r1, r1, lsl #16 mov r3, r1 cmp r2, #16 @@ -45,29 +33,28 @@ 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 @@ -76,54 +63,63 @@ 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 + +6: subs r2, r2, #4 @ 1 do we have enough + blt 5b @ 1 bytes to align with? + cmp r3, #2 @ 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)) + b 1b ENDPROC(memset)
This pulls in the following Linux commits: commit 455bd4c430b0c0a361f38e8658a0d6cb469942b5 Author: Ivan Djelic <ivan.djelic@parrot.com> Date: Wed Mar 6 20:09:27 2013 +0100 ARM: 7668/1: fix memset-related crashes caused by recent GCC (4.7.2) optimi 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 *waite { 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; ca 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 resul 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> commit 418df63adac56841ef6b0f1fcf435bc64d4ed177 Author: Nicolas Pitre <nicolas.pitre@linaro.org> Date: Tue Mar 12 13:00:42 2013 +0100 ARM: 7670/1: fix the memset fix Commit 455bd4c430b0 ("ARM: 7668/1: fix memset-related crashes caused by recent GCC (4.7.2) optimizations") attempted to fix a compliance issue with the memset return value. However the memset itself became broken by that patch for misaligned pointers. This fixes the above by branching over the entry code from the misaligned fixup code to avoid reloading the original pointer. Also, because the function entry alignment is wrong in the Thumb mode compilation, that fixup code is moved to the end. While at it, the entry instructions are slightly reworked to help dual issue pipelines. Signed-off-by: Nicolas Pitre <nico@linaro.org> Tested-by: Alexander Holler <holler@ahsoftware.de> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Signed-off-by: Ian Campbell <ian.campbell@citrix.com> --- xen/arch/arm/arm32/lib/memset.S | 100 +++++++++++++++++++-------------------- 1 file changed, 48 insertions(+), 52 deletions(-)