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Commit d68133b5 authored by Rabin Vincent's avatar Rabin Vincent Committed by Russell King
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ARM: 7299/1: ftrace: clear zero bit in reported IPs for Thumb-2 



The dynamic ftrace ops startup test currently fails on Thumb-2 kernels:

 Testing tracer function: PASSED
 Testing dynamic ftrace: PASSED
 Testing dynamic ftrace ops #1: (0 0 0 0 0) FAILED!

This is because while the addresses in the mcount records do not have
the zero bit set, the IP reported by the mcount call does have it set
(because it is copied from the LR).  This mismatch causes the ops
filtering in ftrace_ops_list_func() to not call the relevant tracers.

Fix this by clearing the zero bit before adjusting the LR for the mcount
instruction size.  Also, combine the mov+sub into a single sub
instruction.

Acked-by: default avatarDave Martin <dave.martin@linaro.org>
Signed-off-by: default avatarRabin Vincent <rabin@rab.in>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 34ae6c96

arch/arm/kernel/entry-common.S

+9 −6
Original line number Diff line number Diff line
@@ -149,6 +149,11 @@ ENDPROC(ret_from_fork) 
#endif

#endif



.macro mcount_adjust_addr rd, rn

	bic	\rd, \rn, #1		@ clear the Thumb bit if present

	sub	\rd, \rd, #MCOUNT_INSN_SIZE

.endm



.macro __mcount suffix

	mcount_enter

	ldr	r0, =ftrace_trace_function
@@ -173,8 +178,7 @@ ENDPROC(ret_from_fork) 
	mcount_exit



1: 	mcount_get_lr	r1			@ lr of instrumented func

	mov	r0, lr				@ instrumented function

	sub	r0, r0, #MCOUNT_INSN_SIZE

	mcount_adjust_addr	r0, lr		@ instrumented function

	adr	lr, BSYM(2f)

	mov	pc, r2

2:	mcount_exit
@@ -184,8 +188,7 @@ ENDPROC(ret_from_fork) 
	mcount_enter



	mcount_get_lr	r1			@ lr of instrumented func

	mov	r0, lr				@ instrumented function

	sub	r0, r0, #MCOUNT_INSN_SIZE

	mcount_adjust_addr	r0, lr		@ instrumented function



	.globl ftrace_call\suffix

ftrace_call\suffix:
@@ -205,11 +208,11 @@ ftrace_graph_call\suffix: 
#ifdef CONFIG_DYNAMIC_FTRACE

	@ called from __ftrace_caller, saved in mcount_enter

	ldr	r1, [sp, #16]		@ instrumented routine (func)

	mcount_adjust_addr	r1, r1

#else

	@ called from __mcount, untouched in lr

	mov	r1, lr			@ instrumented routine (func)

	mcount_adjust_addr	r1, lr	@ instrumented routine (func)

#endif

	sub	r1, r1, #MCOUNT_INSN_SIZE

	mov	r2, fp			@ frame pointer

	bl	prepare_ftrace_return

	mcount_exit