3.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Will Deacon <will.deacon@xxxxxxx> commit 1059c6bf8534acda249e7e65c81e7696fb074dc1 upstream. When returning from a debug exception taken from EL1, we unmask debug exceptions after handling the exception. This is crucial for debug exceptions taken from EL0, so that any kernel work on the ret_to_user path can be debugged by kgdb. However, when returning back to EL1 the only thing left to do is to restore the original register state before the exception return. If single-step has been enabled by the debug exception handler, we will get stuck in an infinite debug exception loop, since we will take the step exception as soon as we unmask debug exceptions. This patch avoids unmasking debug exceptions on the debug exception return path when the exception was taken from EL1. Fixes: 2a2830703a23 (arm64: debug: avoid accessing mdscr_el1 on fault paths where possible) Reported-by: David Long <dave.long@xxxxxxxxxx> Reported-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> Signed-off-by: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/kernel/entry.S | 1 - 1 file changed, 1 deletion(-) --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -298,7 +298,6 @@ el1_dbg: mrs x0, far_el1 mov x2, sp // struct pt_regs bl do_debug_exception - enable_dbg kernel_exit 1 el1_inv: // TODO: add support for undefined instructions in kernel mode -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html