Re: [RFC PATCH] ARM: Add imprecise abort enable/disable macro

From: Fabrice Gasnier
Date: Mon Feb 10 2014 - 08:36:46 EST


On 02/10/2014 10:00 AM, Ben Dooks wrote:
On 10/02/14 08:50, Fabrice Gasnier wrote:
On 02/07/2014 06:09 PM, Will Deacon wrote:
On Fri, Feb 07, 2014 at 04:19:15PM +0000, Fabrice GASNIER wrote:
This patch adds imprecise abort enable/disable macros.
It also enables imprecise aborts when starting kernel.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
---
arch/arm/include/asm/irqflags.h | 33
+++++++++++++++++++++++++++++++++
arch/arm/kernel/smp.c | 1 +
arch/arm/kernel/traps.c | 4 ++++
3 files changed, 38 insertions(+)

diff --git a/arch/arm/include/asm/irqflags.h
b/arch/arm/include/asm/irqflags.h
index 3b763d6..82e3834 100644
--- a/arch/arm/include/asm/irqflags.h
+++ b/arch/arm/include/asm/irqflags.h
@@ -51,6 +51,9 @@ static inline void arch_local_irq_disable(void)
#define local_fiq_enable() __asm__("cpsie f @ __stf" : : :
"memory", "cc")
#define local_fiq_disable() __asm__("cpsid f @ __clf" : : :
"memory", "cc")
+
+#define local_abt_enable() __asm__("cpsie a @ __sta" : : :
"memory", "cc")
+#define local_abt_disable() __asm__("cpsid a @ __cla" : : :
"memory", "cc")
#else
/*
@@ -130,6 +133,36 @@ static inline void arch_local_irq_disable(void)
: "memory", "cc"); \
})
+/*
+ * Enable Aborts
+ */
+#define local_abt_enable() \
+ ({ \
+ unsigned long temp; \
+ __asm__ __volatile__( \
+ "mrs %0, cpsr @ sta\n" \
+" bic %0, %0, %1\n" \
+" msr cpsr_c, %0" \
+ : "=r" (temp) \
+ : "r" (PSR_A_BIT) \
Can you use "i" instead of a register for this constant?
Hi,

Sure, I will change it in a future patch.

+ : "memory", "cc"); \
You don't need the "cc" clobber.
That surprises me: I think "orr" and "bic" instruction might change N
and Z bits, depending on the result.
So shouldn't "cc" be placed here ?
I also see that it is used in local_fiq_enable/disable macros just
above, that are similar:

No, only if they have the S flag set on the instruction (ORRS,BICS)


Thank you for pointing that out!


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