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ARMv6 and greater introduced a new instruction ("bx") which can be used
to return from function calls. Recent CPUs perform better when the
"bx lr" instruction is used rather than the "mov pc, lr" instruction,
and this sequence is strongly recommended to be used by the ARM
architecture manual (section A.4.1.1).
We provide a new macro "ret" with all its variants for the condition
code which will resolve to the appropriate instruction.
Rather than doing this piecemeal, and miss some instances, change all
the "mov pc" instances to use the new macro, with the exception of
the "movs" instruction and the kprobes code. This allows us to detect
the "mov pc, lr" case and fix it up - and also gives us the possibility
of deploying this for other registers depending on the CPU selection.
Reported-by: Will Deacon <will.deacon@arm.com>
Tested-by: Stephen Warren <swarren@nvidia.com> # Tegra Jetson TK1
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr> # mioa701_bootresume.S
Tested-by: Andrew Lunn <andrew@lunn.ch> # Kirkwood
Tested-by: Shawn Guo <shawn.guo@freescale.com>
Tested-by: Tony Lindgren <tony@atomide.com> # OMAPs
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com> # Armada XP, 375, 385
Acked-by: Sekhar Nori <nsekhar@ti.com> # DaVinci
Acked-by: Christoffer Dall <christoffer.dall@linaro.org> # kvm/hyp
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com> # PXA3xx
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> # Xen
Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> # ARMv7M
Tested-by: Simon Horman <horms+renesas@verge.net.au> # Shmobile
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
153 lines
3.7 KiB
ArmAsm
153 lines
3.7 KiB
ArmAsm
/*
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* linux/arch/arm/lib/backtrace.S
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*
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* Copyright (C) 1995, 1996 Russell King
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* 27/03/03 Ian Molton Clean up CONFIG_CPU
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*
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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.text
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@ fp is 0 or stack frame
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#define frame r4
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#define sv_fp r5
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#define sv_pc r6
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#define mask r7
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#define offset r8
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ENTRY(c_backtrace)
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#if !defined(CONFIG_FRAME_POINTER) || !defined(CONFIG_PRINTK)
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ret lr
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ENDPROC(c_backtrace)
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#else
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stmfd sp!, {r4 - r8, lr} @ Save an extra register so we have a location...
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movs frame, r0 @ if frame pointer is zero
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beq no_frame @ we have no stack frames
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tst r1, #0x10 @ 26 or 32-bit mode?
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ARM( moveq mask, #0xfc000003 )
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THUMB( moveq mask, #0xfc000000 )
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THUMB( orreq mask, #0x03 )
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movne mask, #0 @ mask for 32-bit
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1: stmfd sp!, {pc} @ calculate offset of PC stored
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ldr r0, [sp], #4 @ by stmfd for this CPU
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adr r1, 1b
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sub offset, r0, r1
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/*
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* Stack frame layout:
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* optionally saved caller registers (r4 - r10)
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* saved fp
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* saved sp
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* saved lr
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* frame => saved pc
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* optionally saved arguments (r0 - r3)
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* saved sp => <next word>
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*
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* Functions start with the following code sequence:
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* mov ip, sp
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* stmfd sp!, {r0 - r3} (optional)
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* corrected pc => stmfd sp!, {..., fp, ip, lr, pc}
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*/
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for_each_frame: tst frame, mask @ Check for address exceptions
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bne no_frame
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1001: ldr sv_pc, [frame, #0] @ get saved pc
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1002: ldr sv_fp, [frame, #-12] @ get saved fp
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sub sv_pc, sv_pc, offset @ Correct PC for prefetching
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bic sv_pc, sv_pc, mask @ mask PC/LR for the mode
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1003: ldr r2, [sv_pc, #-4] @ if stmfd sp!, {args} exists,
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ldr r3, .Ldsi+4 @ adjust saved 'pc' back one
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teq r3, r2, lsr #10 @ instruction
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subne r0, sv_pc, #4 @ allow for mov
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subeq r0, sv_pc, #8 @ allow for mov + stmia
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ldr r1, [frame, #-4] @ get saved lr
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mov r2, frame
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bic r1, r1, mask @ mask PC/LR for the mode
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bl dump_backtrace_entry
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ldr r1, [sv_pc, #-4] @ if stmfd sp!, {args} exists,
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ldr r3, .Ldsi+4
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teq r3, r1, lsr #11
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ldreq r0, [frame, #-8] @ get sp
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subeq r0, r0, #4 @ point at the last arg
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bleq .Ldumpstm @ dump saved registers
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1004: ldr r1, [sv_pc, #0] @ if stmfd sp!, {..., fp, ip, lr, pc}
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ldr r3, .Ldsi @ instruction exists,
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teq r3, r1, lsr #11
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subeq r0, frame, #16
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bleq .Ldumpstm @ dump saved registers
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teq sv_fp, #0 @ zero saved fp means
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beq no_frame @ no further frames
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cmp sv_fp, frame @ next frame must be
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mov frame, sv_fp @ above the current frame
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bhi for_each_frame
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1006: adr r0, .Lbad
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mov r1, frame
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bl printk
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no_frame: ldmfd sp!, {r4 - r8, pc}
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ENDPROC(c_backtrace)
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.pushsection __ex_table,"a"
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.align 3
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.long 1001b, 1006b
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.long 1002b, 1006b
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.long 1003b, 1006b
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.long 1004b, 1006b
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.popsection
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#define instr r4
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#define reg r5
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#define stack r6
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.Ldumpstm: stmfd sp!, {instr, reg, stack, r7, lr}
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mov stack, r0
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mov instr, r1
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mov reg, #10
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mov r7, #0
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1: mov r3, #1
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ARM( tst instr, r3, lsl reg )
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THUMB( lsl r3, reg )
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THUMB( tst instr, r3 )
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beq 2f
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add r7, r7, #1
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teq r7, #6
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moveq r7, #0
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adr r3, .Lcr
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addne r3, r3, #1 @ skip newline
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ldr r2, [stack], #-4
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mov r1, reg
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adr r0, .Lfp
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bl printk
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2: subs reg, reg, #1
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bpl 1b
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teq r7, #0
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adrne r0, .Lcr
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blne printk
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ldmfd sp!, {instr, reg, stack, r7, pc}
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.Lfp: .asciz " r%d:%08x%s"
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.Lcr: .asciz "\n"
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.Lbad: .asciz "Backtrace aborted due to bad frame pointer <%p>\n"
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.align
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.Ldsi: .word 0xe92dd800 >> 11 @ stmfd sp!, {... fp, ip, lr, pc}
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.word 0xe92d0000 >> 11 @ stmfd sp!, {}
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#endif
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