| Message ID | 1411381144-3528-1-git-send-email-will.deacon@arm.com |
|---|---|
| State | Accepted |
| Commit | 1059c6bf8534acda249e7e65c81e7696fb074dc1 |
| Headers | show |
On Mon, Sep 22, 2014 at 11:19:04AM +0100, Will Deacon wrote: > 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. > > Cc: <stable@vger.kernel.org> Does it work better if I add: Fixes: 2a2830703a23 (arm64: debug: avoid accessing mdscr_el1 on fault paths where possible) Cc: <stable@vger.kernel.org> #3.16+
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index f0b5e5120a87..726b910fe6ec 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -324,7 +324,6 @@ 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
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. Cc: <stable@vger.kernel.org> Reported-by: David Long <dave.long@linaro.org> Reported-by: AKASHI Takahiro <takahiro.akashi@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com> --- arch/arm64/kernel/entry.S | 1 - 1 file changed, 1 deletion(-)