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authorMark Rutland <mark.rutland@arm.com>2017-01-18 18:23:41 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2017-01-19 16:38:22 +0100
commit7d9e8f71b989230bc613d121ca38507d34ada849 (patch)
treec21ba216304132dfc9e92ebe3720627b9d21beea /arch/arm64/kernel/entry.S
parentarm64/ptrace: Reject attempts to set incomplete hardware breakpoint fields (diff)
downloadlinux-7d9e8f71b989230bc613d121ca38507d34ada849.tar.xz
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arm64: avoid returning from bad_mode
Generally, taking an unexpected exception should be a fatal event, and bad_mode is intended to cater for this. However, it should be possible to contain unexpected synchronous exceptions from EL0 without bringing the kernel down, by sending a SIGILL to the task. We tried to apply this approach in commit 9955ac47f4ba1c95 ("arm64: don't kill the kernel on a bad esr from el0"), by sending a signal for any bad_mode call resulting from an EL0 exception. However, this also applies to other unexpected exceptions, such as SError and FIQ. The entry paths for these exceptions branch to bad_mode without configuring the link register, and have no kernel_exit. Thus, if we take one of these exceptions from EL0, bad_mode will eventually return to the original user link register value. This patch fixes this by introducing a new bad_el0_sync handler to cater for the recoverable case, and restoring bad_mode to its original state, whereby it calls panic() and never returns. The recoverable case branches to bad_el0_sync with a bl, and returns to userspace via the usual ret_to_user mechanism. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Fixes: 9955ac47f4ba1c95 ("arm64: don't kill the kernel on a bad esr from el0") Reported-by: Mark Salter <msalter@redhat.com> Cc: Will Deacon <will.deacon@arm.com> Cc: stable@vger.kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
-rw-r--r--arch/arm64/kernel/entry.S2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 923841ffe4a9..43512d4d7df2 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -683,7 +683,7 @@ el0_inv:
mov x0, sp
mov x1, #BAD_SYNC
mov x2, x25
- bl bad_mode
+ bl bad_el0_sync
b ret_to_user
ENDPROC(el0_sync)