arm64: reduce stack use in irq_handler
authorJames Morse <james.morse@arm.com>
Tue, 15 Dec 2015 11:21:25 +0000 (11:21 +0000)
committerAlex Shi <alex.shi@linaro.org>
Wed, 11 May 2016 08:43:12 +0000 (16:43 +0800)
commita79c216b06b18f1545d55e8f238dd9b49896f347
tree2906855168b2726c86729df29f5a467ee08816c9
parent7ae24aa87b5b0c58d378b6fc8fb0d8e72fbfd81d
arm64: reduce stack use in irq_handler

The code for switching to irq_stack stores three pieces of information on
the stack, fp+lr, as a fake stack frame (that lets us walk back onto the
interrupted tasks stack frame), and the address of the struct pt_regs that
contains the register values from kernel entry. (which dump_backtrace()
will print in any stack trace).

To reduce this, we store fp, and the pointer to the struct pt_regs.
unwind_frame() can recognise this as the irq_stack dummy frame, (as it only
appears at the top of the irq_stack), and use the struct pt_regs values
to find the missing interrupted link-register.

Suggested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from commit 971c67ce37cfeeaf560e792a2c3bc21d8b67163a)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
arch/arm64/include/asm/irq.h
arch/arm64/kernel/entry.S
arch/arm64/kernel/stacktrace.c