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authorMark Rutland <mark.rutland@arm.com>2017-01-18 17:23:41 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-01-26 08:23:50 +0100
commit8323d0555fe332e35d052d7c1185d299bd8724d9 (patch)
tree404cbbae43a6ea6c1b6b71240663a7934afde3a9
parent6e65a4c698cf8a296f042ab3b9d7b459564ffcd9 (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>
-rw-r--r--arch/arm64/kernel/entry.S2
-rw-r--r--arch/arm64/kernel/traps.c28
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)