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| author | Rabin Vincent <rabin@rab.in> | 2014-05-24 20:38:01 +0400 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-05-26 02:44:27 +0400 |
| commit | 483a6c9d447f625b991fa04a1530493d893984db (patch) | |
| tree | 1b7396010f4ddc8dc31e57cd05a5e6601493076f /arch/arm/kernel/entry-header.S | |
| parent | fbebf59778600488147744cdf7d7c20d22531025 (diff) | |
| download | linux-483a6c9d447f625b991fa04a1530493d893984db.tar.xz | |
ARM: 8064/1: fix v7-M signal return
According to the ARM ARM, the behaviour is UNPREDICTABLE if the PC read
from the exception return stack is not half word aligned. See the
pseudo code for ExceptionReturn() and PopStack().
The signal handler's address has the bit 0 set, and setup_return()
directly writes this to regs->ARM_pc. Current hardware happens to
discard this bit, but QEMU's emulation doesn't and this makes processes
crash. Mask out bit 0 before the exception return in order to get
predictable behaviour.
Fixes: 19c4d593f0b4 ("ARM: ARMv7-M: Add support for exception handling")
Cc: stable@kernel.org
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/kernel/entry-header.S')
| -rw-r--r-- | arch/arm/kernel/entry-header.S | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm/kernel/entry-header.S b/arch/arm/kernel/entry-header.S index 1420725142ca..efb208de75ec 100644 --- a/arch/arm/kernel/entry-header.S +++ b/arch/arm/kernel/entry-header.S @@ -132,6 +132,10 @@ orrne r5, V7M_xPSR_FRAMEPTRALIGN biceq r5, V7M_xPSR_FRAMEPTRALIGN + @ ensure bit 0 is cleared in the PC, otherwise behaviour is + @ unpredictable + bic r4, #1 + @ write basic exception frame stmdb r2!, {r1, r3-r5} ldmia sp, {r1, r3-r5} |