path: root/arch/arm/kernel/entry-armv.S
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authorArun K S <arunks.linux@gmail.com>2014-05-19 11:43:00 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2014-05-30 01:12:28 +0100
commit3780f7ab4928bc05897a7e30cf102c20045823ef (patch)
tree3e22925b12809797822781ea3b9c39db5642e678 /arch/arm/kernel/entry-armv.S
parent8a87411b649c6082aebea613e84dcb3f174f72fb (diff)
ARM: 8062/1: Modify ldrt fixup handler to re-execute the userspace instruction
We will reach fixup handler when one thread(say cpu0) caused an undefined exception, while another thread(say cpu1) is unmmaping the page. Fixup handler returns to the next userspace instruction which has caused the undef execption, rather than going to the same instruction. ARM ARM says that after undefined exception, the PC will be pointing to the next instruction. ie +4 offset in case of ARM and +2 in case of Thumb And there is no correction offset passed to vector_stub in case of undef exception. File: arch/arm/kernel/entry-armv.S +1085 vector_stub und, UND_MODE During an undefined exception, in normal scenario(ie when ldrt instruction does not cause an abort) after resorting the context in VFP hardware, the PC is modified as show below before jumping to ret_from_exception which is in r9. File: arch/arm/vfp/vfphw.S +169 @ The context stored in the VFP hardware is up to date with this thread vfp_hw_state_valid: tst r1, #FPEXC_EX bne process_exception @ might as well handle the pending @ exception before retrying branch @ out before setting an FPEXC that @ stops us reading stuff VFPFMXR FPEXC, r1 @ Restore FPEXC last sub r2, r2, #4 @ Retry current instruction - if Thumb str r2, [sp, #S_PC] @ mode it's two 16-bit instructions, @ else it's one 32-bit instruction, so @ always subtract 4 from the following @ instruction address. But if ldrt results in an abort, we reach the fixup handler and return to ret_from_execption without correcting the pc. This patch modifes the fixup handler to re-execute the same instruction which caused undefined execption. Signed-off-by: Vinayak Menon <vinayakm.list@gmail.com> Signed-off-by: Arun KS <getarunks@gmail.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/entry-armv.S')
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 5fc897cf409b..0ffdec8eceb7 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -489,7 +489,8 @@ ENDPROC(__und_usr)
.pushsection .fixup, "ax"
.align 2
-4: mov pc, r9
+4: str r4, [sp, #S_PC] @ retry current instruction
+ mov pc, r9
.pushsection __ex_table,"a"
.long 1b, 4b