[PATCH] ARM: vfp: Fix up exception location in Thumb mode

On Sat, Jan 15, 2011 at 03:38:16PM +0000, Catalin Marinas wrote:

On 14 January 2011 18:47, Russell King - ARM Linux
[off-list ref] wrote:

quoted

diff -u b/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S

--- b/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S

@@ -499,10 +499,11 @@

? ? ? ?blo ? ? __und_usr_unknown
?3: ? ? ldrht ? r0, [r4]
? ? ? ?add ? ? r2, r2, #2 ? ? ? ? ? ? ? ? ? ? ?@ r2 is PC + 2, make it PC + 4
- ? ? ? orr ? ? r0, r0, r5, lsl #16
+ ? ? ? str ? ? r2, [sp, #S_PC] ? ? ? ? ? ? ? ? @ it's a 2x16bit instr, update
+ ? ? ? orr ? ? r0, r0, r5, lsl #16 ? ? ? ? ? ? @ ?regs->ARM_pc
? ? ? ?@
? ? ? ?@ r0 = the two 16-bit Thumb instructions which caused the exception
- ? ? ? @ r2 = PC value for the following Thumb instruction (:= regs->ARM_pc+2)
+ ? ? ? @ r2 = PC value for the following Thumb instruction (:= regs->ARM_pc)
? ? ? ?@ r4 = PC value for the first 16-bit Thumb instruction
? ? ? ?@
?#else

Do we need to modify the VFP entry code to avoit the store to ARM_pc?

The one after the sub #4 instruction?

That's answered by the comments... "retry the instruction" and that
r2 = regs->ARM_pc in every case, and both r2 and regs->ARM_pc point
at the _following_ instruction...

I do hope this isn't a case that _more_ comments are making this more
confusing (which seems to be the way with documentation - the more
words you use, the more questions people have).  Maybe we should get
rid of all the comments instead?