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| author | James Morse <james.morse@arm.com> | 2015-12-15 12:21:25 +0100 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2015-12-15 18:09:08 +0100 |
| commit | 971c67ce37cfeeaf560e792a2c3bc21d8b67163a (patch) | |
| tree | dabce8d15638e66a8c351454e78e3f5bac6f6c2f /arch/arm64/kernel/entry.S | |
| parent | Merge branch 'aarch64/efi' into aarch64/for-next/core (diff) | |
| download | linux-971c67ce37cfeeaf560e792a2c3bc21d8b67163a.tar.xz linux-971c67ce37cfeeaf560e792a2c3bc21d8b67163a.zip | |
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>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 2284c296e3f7..0667fb7d8bb1 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -178,7 +178,7 @@ alternative_endif mrs \rd, sp_el0 .endm - .macro irq_stack_entry, dummy_lr + .macro irq_stack_entry mov x19, sp // preserve the original sp this_cpu_ptr irq_stack, x25, x26 @@ -196,10 +196,12 @@ alternative_endif add x26, x25, x26 mov sp, x26 - /* Add a dummy stack frame */ - stp x29, \dummy_lr, [sp, #-16]! // dummy stack frame + /* + * Add a dummy stack frame, this non-standard format is fixed up + * by unwind_frame() + */ + stp x29, x19, [sp, #-16]! mov x29, sp - stp x19, xzr, [sp, #-16]! 9998: .endm @@ -229,7 +231,7 @@ tsk .req x28 // current thread_info .macro irq_handler ldr_l x1, handle_arch_irq mov x0, sp - irq_stack_entry x22 + irq_stack_entry blr x1 irq_stack_exit .endm |