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From: Mans Rullgard <mans@mansr.com>
Date: Sat, 16 Aug 2008 23:03:06 +0000 (+0100)
Subject: ARM: Workaround for erratum 451034
X-Git-Url: http://git.mansr.com/?p=linux-omap;a=commitdiff_plain;h=b84fa87873ffb68ad23930cf6cddeea8bec43ede
ARM: Workaround for erratum 451034
On Cortex-A8 r1p0 and r1p1, executing a NEON store with an integer
store in the store buffer, can cause a processor deadlock under
certain conditions.
Executing a DMB instruction before saving NEON/VFP registers and before
return to userspace makes it safe to run code which includes similar
counter-measures. Userspace code can still trigger the deadlock, so
a different workaround is required to safely run untrusted code.
See ARM Cortex-A8 Errata Notice (PR120-PRDC-008070) for full details.
Signed-off-by: Mans Rullgard <mans@mansr.com>
---
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index aa475d9..41d536e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1117,6 +1117,22 @@ config NEON
Say Y to include support code for NEON, the ARMv7 Advanced SIMD
Extension.
+config ARM_ERRATUM_451034
+ bool "Enable workaround for ARM erratum 451034"
+ depends on VFPv3
+ help
+ On Cortex-A8 r1p0 and r1p1, executing a NEON store with an integer
+ store in the store buffer, can cause a processor deadlock under
+ certain conditions.
+
+ See ARM Cortex-A8 Errata Notice (PR120-PRDC-008070) for full details.
+
+ Say Y to include a partial workaround.
+
+ WARNING: Even with this option enabled, userspace code can trigger
+ the deadlock. To safely run untrusted code, a different fix is
+ required.
+
endmenu
menu "Userspace binary formats"
diff --git a/arch/arm/include/asm/vfpmacros.h b/arch/arm/include/asm/vfpmacros.h
index 422f3cc..934798b 100644
--- a/arch/arm/include/asm/vfpmacros.h
+++ b/arch/arm/include/asm/vfpmacros.h
@@ -32,6 +32,9 @@
@ write all the working registers out of the VFP
.macro VFPFSTMIA, base, tmp
+#ifdef CONFIG_ARM_ERRATUM_451034
+ dmb
+#endif
#if __LINUX_ARM_ARCH__ < 6
STC p11, cr0, [\base],#33*4 @ FSTMIAX \base!, {d0-d15}
#else
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 060d7e2..9799a35 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -69,6 +69,10 @@ no_work_pending:
/* perform architecture specific actions before user return */
arch_ret_to_user r1, lr
+#ifdef CONFIG_ARM_ERRATUM_451034
+ dmb
+#endif
+
@ slow_restore_user_regs
ldr r1, [sp, #S_PSR] @ get calling cpsr
ldr lr, [sp, #S_PC]! @ get pc
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