diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2017-01-18 17:23:41 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-26 08:23:50 +0100 |
| commit | 8323d0555fe332e35d052d7c1185d299bd8724d9 (patch) | |
| tree | 404cbbae43a6ea6c1b6b71240663a7934afde3a9 /arch/arm64 | |
| parent | 6e65a4c698cf8a296f042ab3b9d7b459564ffcd9 (diff) | |
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')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 2 | ||||
| -rw-r--r-- | arch/arm64/kernel/traps.c | 28 |
2 files changed, 25 insertions, 5 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 5a3753d09e20..bd14849beb73 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -562,7 +562,7 @@ 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) diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index e9b9b5364393..ca7f0ac5f708 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -434,16 +434,33 @@ const char *esr_get_class_string(u32 esr) } /* - * bad_mode handles the impossible case in the exception vector. + * bad_mode handles the impossible case in the exception vector. This is always + * fatal. */ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr) { - siginfo_t info; - void __user *pc = (void __user *)instruction_pointer(regs); console_verbose(); pr_crit("Bad mode in %s handler detected, code 0x%08x -- %s\n", handler[reason], esr, esr_get_class_string(esr)); + + die("Oops - bad mode", regs, 0); + local_irq_disable(); + panic("bad mode"); +} + +/* + * bad_el0_sync handles unexpected, but potentially recoverable synchronous + * exceptions taken from EL0. Unlike bad_mode, this returns. + */ +asmlinkage void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr) +{ + siginfo_t info; + void __user *pc = (void __user *)instruction_pointer(regs); + console_verbose(); + + pr_crit("Bad EL0 synchronous exception detected on CPU%d, code 0x%08x -- %s\n", + smp_processor_id(), esr, esr_get_class_string(esr)); __show_regs(regs); info.si_signo = SIGILL; @@ -451,7 +468,10 @@ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr) info.si_code = ILL_ILLOPC; info.si_addr = pc; - arm64_notify_die("Oops - bad mode", regs, &info, 0); + current->thread.fault_address = 0; + current->thread.fault_code = 0; + + force_sig_info(info.si_signo, &info, current); } void __pte_error(const char *file, int line, unsigned long val) |