linux/arch/arm/lib/backtrace.S
Ard Biesheuvel d4664b6c98 ARM: implement IRQ stacks
Now that we no longer rely on the stack pointer to access the current
task struct or thread info, we can implement support for IRQ stacks
cleanly as well.

Define a per-CPU IRQ stack and switch to this stack when taking an IRQ,
provided that we were not already using that stack in the interrupted
context. This is never the case for IRQs taken from user space, but ones
taken while running in the kernel could fire while one taken from user
space has not completed yet.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Marc Zyngier <maz@kernel.org>
Tested-by: Vladimir Murzin <vladimir.murzin@arm.com> # ARMv7M
2021-12-03 15:11:31 +01:00

132 lines
3.4 KiB
ArmAsm

/* SPDX-License-Identifier: GPL-2.0-only */
/*
* linux/arch/arm/lib/backtrace.S
*
* Copyright (C) 1995, 1996 Russell King
*
* 27/03/03 Ian Molton Clean up CONFIG_CPU
*/
#include <linux/kern_levels.h>
#include <linux/linkage.h>
#include <asm/assembler.h>
.text
@ fp is 0 or stack frame
#define frame r4
#define sv_fp r5
#define sv_pc r6
#define mask r7
#define offset r8
#define loglvl r9
ENTRY(c_backtrace)
#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
ret lr
ENDPROC(c_backtrace)
#else
stmfd sp!, {r4 - r9, lr} @ Save an extra register so we have a location...
movs frame, r0 @ if frame pointer is zero
beq no_frame @ we have no stack frames
mov loglvl, r2
tst r1, #0x10 @ 26 or 32-bit mode?
ARM( moveq mask, #0xfc000003 )
THUMB( moveq mask, #0xfc000000 )
THUMB( orreq mask, #0x03 )
movne mask, #0 @ mask for 32-bit
1: stmfd sp!, {pc} @ calculate offset of PC stored
ldr r0, [sp], #4 @ by stmfd for this CPU
adr r1, 1b
sub offset, r0, r1
/*
* Stack frame layout:
* optionally saved caller registers (r4 - r10)
* saved fp
* saved sp
* saved lr
* frame => saved pc
* optionally saved arguments (r0 - r3)
* saved sp => <next word>
*
* Functions start with the following code sequence:
* mov ip, sp
* stmfd sp!, {r0 - r3} (optional)
* corrected pc => stmfd sp!, {..., fp, ip, lr, pc}
*/
for_each_frame: tst frame, mask @ Check for address exceptions
bne no_frame
1001: ldr sv_pc, [frame, #0] @ get saved pc
1002: ldr sv_fp, [frame, #-12] @ get saved fp
sub sv_pc, sv_pc, offset @ Correct PC for prefetching
bic sv_pc, sv_pc, mask @ mask PC/LR for the mode
1003: ldr r2, [sv_pc, #-4] @ if stmfd sp!, {args} exists,
ldr r3, .Ldsi+4 @ adjust saved 'pc' back one
teq r3, r2, lsr #11 @ instruction
subne r0, sv_pc, #4 @ allow for mov
subeq r0, sv_pc, #8 @ allow for mov + stmia
ldr r1, [frame, #-4] @ get saved lr
mov r2, frame
bic r1, r1, mask @ mask PC/LR for the mode
mov r3, loglvl
bl dump_backtrace_entry
ldr r1, [sv_pc, #-4] @ if stmfd sp!, {args} exists,
ldr r3, .Ldsi+4
teq r3, r1, lsr #11
ldreq r0, [frame, #-8] @ get sp
subeq r0, r0, #4 @ point at the last arg
mov r2, loglvl
bleq dump_backtrace_stm @ dump saved registers
1004: ldr r1, [sv_pc, #0] @ if stmfd sp!, {..., fp, ip, lr, pc}
ldr r3, .Ldsi @ instruction exists,
teq r3, r1, lsr #11
subeq r0, frame, #16
mov r2, loglvl
bleq dump_backtrace_stm @ dump saved registers
teq sv_fp, #0 @ zero saved fp means
beq no_frame @ no further frames
cmp sv_fp, frame @ next frame must be
mov frame, sv_fp @ above the current frame
#ifdef CONFIG_IRQSTACKS
@
@ Kernel stacks may be discontiguous in memory. If the next
@ frame is below the previous frame, accept it as long as it
@ lives in kernel memory.
@
cmpls sv_fp, #PAGE_OFFSET
#endif
bhi for_each_frame
1006: adr r0, .Lbad
mov r1, loglvl
mov r2, frame
bl _printk
no_frame: ldmfd sp!, {r4 - r9, pc}
ENDPROC(c_backtrace)
.pushsection __ex_table,"a"
.align 3
.long 1001b, 1006b
.long 1002b, 1006b
.long 1003b, 1006b
.long 1004b, 1006b
.popsection
.Lbad: .asciz "%sBacktrace aborted due to bad frame pointer <%p>\n"
.align
.Ldsi: .word 0xe92dd800 >> 11 @ stmfd sp!, {... fp, ip, lr, pc}
.word 0xe92d0000 >> 11 @ stmfd sp!, {}
#endif