[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 06/17] xen: arm32: resync mem* with Linux v3.14-rc7
On 03/20/2014 03:45 PM, Ian Campbell wrote: > This pulls in the following Linux commits: > commit 455bd4c430b0c0a361f38e8658a0d6cb469942b5 > Author: Ivan Djelic <ivan.djelic@xxxxxxxxxx> > 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@xxxxxxxxxx> > Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxx> > Signed-off-by: Dirk Behme <dirk.behme@xxxxxxxxx> > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> > > commit 418df63adac56841ef6b0f1fcf435bc64d4ed177 > Author: Nicolas Pitre <nicolas.pitre@xxxxxxxxxx> > 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@xxxxxxxxxx> > Tested-by: Alexander Holler <holler@xxxxxxxxxxxxx> > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> > > Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx> Acked-by: Julien Grall <julien.grall@xxxxxxxxxx> -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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