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authorRussell King - ARM Linux <linux@arm.linux.org.uk>2011-07-12 01:25:43 +0400
committerEric Miao <eric.y.miao@gmail.com>2011-07-12 15:42:40 +0400
commita4841e39f7ca85ee2a40803ebac6221c6d8822c0 (patch)
treee65f29a84302d63823b0554ec4c3299d0b8b6948 /arch/arm/include/asm/irq.h
parentfe0d42203cb5616eeff68b14576a0f7e2dd56625 (diff)
downloadlinux-a4841e39f7ca85ee2a40803ebac6221c6d8822c0.tar.xz
ARM: introduce handle_IRQ() not to dump exception stack
On Mon, Jul 11, 2011 at 3:52 PM, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote: ... > The __exception annotation on a function causes this to happen: > > [<c002406c>] (asm_do_IRQ+0x6c/0x8c) from [<c0024b84>] > (__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 <rmk+kernel@arm.linux.org.uk> Signed-off-by: Eric Miao <eric.y.miao@gmail.com>
Diffstat (limited to 'arch/arm/include/asm/irq.h')
-rw-r--r--arch/arm/include/asm/irq.h1
1 files changed, 1 insertions, 0 deletions
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