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ARM: 7440/1: kprobes: only test 'sub pc, pc, #1b-2b+8-2' on ARMv6 

'sub pc, pc, #1b-2b+8-2' results in address<1:0> == '10'.

sub pc, pc, #const (== ADR pc, #const) performs an interworking branch
(BXWritePC()) on ARMv7+ and a simple branch (BranchWritePC()) on earlier
versions.

In ARM state, BXWritePC() is UNPREDICTABLE when address<1:0> == '10'.

In ARM state on ARMv6+, BranchWritePC() ignores address<1:0>.  Before
ARMv6, BranchWritePC() is UNPREDICTABLE if address<1:0> != '00'

So the instruction is UNPREDICTABLE both before and after v6.

Acked-by: Jon Medhurst <tixy@yxit.co.uk>
Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Rabin Vincent 2012-07-04 07:37:37 +01:00 committed by Russell King
parent fdeb8e35fd
commit f8b435bb91
1 changed files with 2 additions and 2 deletions
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4
arch/arm/kernel/kprobes-test-arm.c
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@ -187,8 +187,8 @@ void kprobe_arm_test_cases(void)
TEST_BF_R ("mov pc, r",0,2f,"")
TEST_BF_RR("mov pc, r",0,2f,", asl r",1,0,"")
TEST_BB( "sub pc, pc, #1b-2b+8")
#if __LINUX_ARM_ARCH__ >= 6
TEST_BB( "sub pc, pc, #1b-2b+8-2") /* UNPREDICTABLE before ARMv6 */
#if __LINUX_ARM_ARCH__ == 6 && !defined(CONFIG_CPU_V7)
TEST_BB( "sub pc, pc, #1b-2b+8-2") /* UNPREDICTABLE before and after ARMv6 */
#endif
TEST_BB_R( "sub pc, pc, r",14, 1f-2f+8,"")
TEST_BB_R( "rsb pc, r",14,1f-2f+8,", pc")