From 9b55613f42e8d40d5c9ccb8970bde6af4764b2ab Mon Sep 17 00:00:00 2001 From: Russell King Date: Fri, 11 Sep 2015 16:44:02 +0100 Subject: ARM: fix Thumb2 signal handling when ARMv6 is enabled When a kernel is built covering ARMv6 to ARMv7, we omit to clear the IT state when entering a signal handler. This can cause the first few instructions to be conditionally executed depending on the parent context. In any case, the original test for >= ARMv7 is broken - ARMv6 can have Thumb-2 support as well, and an ARMv6T2 specific build would omit this code too. Relax the test back to ARMv6 or greater. This results in us always clearing the IT state bits in the PSR, even on CPUs where these bits are reserved. However, they're reserved for the IT state, so this should cause no harm. Cc: Fixes: d71e1352e240 ("Clear the IT state when invoking a Thumb-2 signal handler") Acked-by: Tony Lindgren Tested-by: H. Nikolaus Schaller Tested-by: Grazvydas Ignotas Signed-off-by: Russell King --- arch/arm/kernel/signal.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) (limited to 'arch/arm/kernel/signal.c') diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index 423663e23791..586eef26203d 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -343,12 +343,17 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig, */ thumb = handler & 1; -#if __LINUX_ARM_ARCH__ >= 7 +#if __LINUX_ARM_ARCH__ >= 6 /* - * Clear the If-Then Thumb-2 execution state - * ARM spec requires this to be all 000s in ARM mode - * Snapdragon S4/Krait misbehaves on a Thumb=>ARM - * signal transition without this. + * Clear the If-Then Thumb-2 execution state. ARM spec + * requires this to be all 000s in ARM mode. Snapdragon + * S4/Krait misbehaves on a Thumb=>ARM signal transition + * without this. + * + * We must do this whenever we are running on a Thumb-2 + * capable CPU, which includes ARMv6T2. However, we elect + * to do this whenever we're on an ARMv6 or later CPU for + * simplicity. */ cpsr &= ~PSR_IT_MASK; #endif -- cgit v1.2.1 From 12fc7306e6ffae4e86680892f2286063d7d6eae7 Mon Sep 17 00:00:00 2001 From: Russell King Date: Wed, 16 Sep 2015 11:08:49 +0100 Subject: ARM: get rid of needless #if in signal handling code Remove the #if statement which caused trouble for kernels that support both ARMv6 and ARMv7. Older architectures do not implement these bits, so it should be safe to always clear them. Signed-off-by: Russell King --- arch/arm/kernel/signal.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'arch/arm/kernel/signal.c') diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index 586eef26203d..29e5dc70bb41 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -343,7 +343,6 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig, */ thumb = handler & 1; -#if __LINUX_ARM_ARCH__ >= 6 /* * Clear the If-Then Thumb-2 execution state. ARM spec * requires this to be all 000s in ARM mode. Snapdragon @@ -352,11 +351,10 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig, * * We must do this whenever we are running on a Thumb-2 * capable CPU, which includes ARMv6T2. However, we elect - * to do this whenever we're on an ARMv6 or later CPU for - * simplicity. + * to always do this to simplify the code; this field is + * marked UNK/SBZP for older architectures. */ cpsr &= ~PSR_IT_MASK; -#endif if (thumb) { cpsr |= PSR_T_BIT; -- cgit v1.2.1