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| author | Mark Rutland <mark.rutland@arm.com> | 2017-01-18 17:23:41 (GMT) |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-26 07:24:40 (GMT) |
| commit | de327948c009792ea49b07139c21e3a953137344 (patch) | |
| tree | 2f57318f545e86e2ce69f39751590c3562b50402 /arch/arm64/kernel/entry.S | |
| parent | 71c49649551460f484c97f79c4fd51728ae55495 (diff) | |
| download | linux-de327948c009792ea49b07139c21e3a953137344.tar.xz | |
arm64: avoid returning from bad_mode
commit 7d9e8f71b989230bc613d121ca38507d34ada849 upstream.
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>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 223d54a..79b0fe2 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -624,7 +624,7 @@ 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) |