diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2017-01-23 18:28:50 +0000 |
|---|---|---|
| committer | Mister Oyster <oysterized@gmail.com> | 2017-04-11 10:57:49 +0200 |
| commit | 2de5b1ee69fe5e6477e753d59845d05b2c3e1034 (patch) | |
| tree | 74a6c537129fa62afc3f52b3abada83900792d20 /arch/arm64/kernel | |
| parent | 44d530b73c641619938041707e2003cf846850ae (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>
Cc: stable@vger.kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Diffstat (limited to 'arch/arm64/kernel')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 2 | ||||
| -rw-r--r-- | arch/arm64/kernel/traps.c | 25 |
2 files changed, 22 insertions, 5 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index e9fa68252..499d1667d 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -621,7 +621,7 @@ el0_inv: mov x0, sp mov x1, #BAD_SYNC mrs x2, esr_el1 - b bad_mode + b bad_el0_sync ENDPROC(el0_sync) .align 6 diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 807f7f045..a38990183 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -431,12 +431,11 @@ int register_async_abort_handler(void (*fn)(struct pt_regs *regs, void *), void #endif /* - * 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(); #ifdef CONFIG_MEDIATEK_SOLUTION @@ -450,6 +449,24 @@ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr) #endif pr_crit("Bad mode in %s handler detected, code 0x%08x\n", handler[reason], 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\n", + smp_processor_id(), esr); __show_regs(regs); info.si_signo = SIGILL; @@ -457,7 +474,7 @@ 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); + force_sig_info(info.si_signo, &info, current); } void __pte_error(const char *file, int line, unsigned long val) |