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![]() Currently, it's possible to set the kernel to ignore alignment faults when changing the alignment fault handling mode at runtime via /proc/sys/alignment, even though this is undesirable on ARMv6 and above, where it can result in infinite spins where an un-fixed- up instruction repeatedly faults. In addition, the kernel clobbers any alignment mode specified on the command-line if running on ARMv6 or above. This patch factors out the necessary safety check into a couple of new helper functions, and checks and modifies the fault handling mode as appropriate on boot and on writes to /proc/cpu/alignment. Prior to ARMv6, the behaviour is unchanged. For ARMv6 and above, the behaviour changes as follows: * Attempting to ignore faults on ARMv6 results in the mode being forced to UM_FIXUP instead. A warning is printed if this happened as a result of a write to /proc/cpu/alignment. The user's UM_WARN bit (if present) is still honoured. * An alignment= argument from the kernel command-line is now honoured, except that the kernel will modify the specified mode as described above. This is allows modes such as UM_SIGNAL and UM_WARN to be active immediately from boot, which is useful for debugging purposes. Signed-off-by: Dave Martin <dave.martin@linaro.org> Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> |
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