From a4841e39f7ca85ee2a40803ebac6221c6d8822c0 Mon Sep 17 00:00:00 2001 From: Russell King - ARM Linux Date: Mon, 11 Jul 2011 22:25:43 +0100 Subject: ARM: introduce handle_IRQ() not to dump exception stack On Mon, Jul 11, 2011 at 3:52 PM, Russell King - ARM Linux wrote: ... > The __exception annotation on a function causes this to happen: > > [] (asm_do_IRQ+0x6c/0x8c) from [] > (__irq_svc+0x44/0xcc) > Exception stack(0xc3897c78 to 0xc3897cc0) > 7c60: 4022d320 4022e000 > 7c80: 08000075 00001000 c32273c0 c03ce1c0 c2b49b78 4022d000 c2b420b4 00000001 > 7ca0: 00000000 c3897cfc 00000000 c3897cc0 c00afc54 c002edd8 00000013 ffffffff > > Where that stack dump represents the pt_regs for the exception which > happened. Any function found in while unwinding will cause this to > be printed. > > If you insert a C function between the IRQ assembly and asm_do_IRQ, > the > dump you get from asm_do_IRQ will be the stack for your function, > not > the pt_regs. That makes the feature useless. > When __irq_svc - or any of the other exception handling assembly code - calls the C code, the stack pointer will be pointing at the pt_regs structure. All the entry points into C code from the exception handling code are marked with __exception or __exception_irq_enter to indicate that they are one of the functions which has pt_regs above them. Normally, when you've entered asm_do_IRQ() you will have this stack layout (higher address towards top): pt_regs asm_do_IRQ frame If you insert a C function between the exception assembly code and asm_do_IRQ, you end up with this stack layout instead: pt_regs your function frame asm_do_IRQ frame This means when we unwind, we'll get to asm_do_IRQ, and rather than dumping out the pt_regs, we'll dump out your functions stack frame instead, because that's what is above the asm_do_IRQ stack frame rather than the expected pt_regs structure. The fix is to introduce handle_IRQ() for no exception stack dump, so it can be called with MULTI_IRQ_HANDLER is selected and a C function is between the assembly code and the actual IRQ handling code. Signed-off-by: Russell King Signed-off-by: Eric Miao --- arch/arm/include/asm/irq.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/arm/include/asm/irq.h') diff --git a/arch/arm/include/asm/irq.h b/arch/arm/include/asm/irq.h index 2721a5814cb9..5a526afb5f18 100644 --- a/arch/arm/include/asm/irq.h +++ b/arch/arm/include/asm/irq.h @@ -23,6 +23,7 @@ struct pt_regs; extern void migrate_irqs(void); extern void asm_do_IRQ(unsigned int, struct pt_regs *); +void handle_IRQ(unsigned int, struct pt_regs *); void init_IRQ(void); #endif -- cgit v1.2.3