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Commit a3ba87a6 authored by Rabin Vincent's avatar Rabin Vincent Committed by Russell King
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ARM: 6316/1: ftrace: add Thumb-2 support 



Fix the mcount routines to build and run on a kernel built with the
Thumb-2 instruction set by correcting the following errors using the
fixes suggested by Catalin Marinas:

 - Problem: The following assembler errors appear at the "adr r0,
   ftrace_stub" instruction:

   entry-common.S: Assembler messages:
   entry-common.S:179: Error: invalid immediate for address calculation (value = 0x00000004)

   Fix: The errors don't occur with a non-global symbol, so use one.

 - Problem: The "mov lr, pc" does not set the lsb when storing the pc in
   lr.  The called function returns with "bx lr", and the mode changes
   to ARM.

   Fix: Add a label on the return address and use "adr lr, BSYM(label)".

We don't modify the old mcount because it won't be built when using
Thumb-2.

Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarRabin Vincent <rabin@rab.in>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 72fa62fa

arch/arm/kernel/entry-common.S

+4 −2
Original line number Diff line number Diff line
@@ -167,7 +167,7 @@ ENTRY(__gnu_mcount_nc) 
	stmdb	sp!, {r0-r3, lr}

	ldr	r0, =ftrace_trace_function

	ldr	r2, [r0]

	adr	r0, ftrace_stub

	adr	r0, .Lftrace_stub

	cmp	r0, r2

	bne	gnu_trace

	ldmia	sp!, {r0-r3, ip, lr}
@@ -177,8 +177,9 @@ gnu_trace: 
	ldr	r1, [sp, #20]			@ lr of instrumented routine

	mov	r0, lr

	sub	r0, r0, #MCOUNT_INSN_SIZE

	mov	lr, pc

	adr	lr, BSYM(1f)

	mov	pc, r2

1:

	ldmia	sp!, {r0-r3, ip, lr}

	mov	pc, ip

ENDPROC(__gnu_mcount_nc)
@@ -213,6 +214,7 @@ ENDPROC(mcount) 
#endif /* CONFIG_DYNAMIC_FTRACE */



ENTRY(ftrace_stub)

.Lftrace_stub:

	mov	pc, lr

ENDPROC(ftrace_stub)