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| author | Mark Rutland <mark.rutland@arm.com> | 2020-11-30 14:59:40 +0300 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2020-11-30 15:11:37 +0300 |
| commit | ca1314d73eed493c49bb1932c60a8605530db2e4 (patch) | |
| tree | ecaaa97c87d5031f5ac6d4457ab832e8e2652953 | |
| parent | ff1712f953e27f0b0718762ec17d0adb15c9fd0b (diff) | |
| download | linux-ca1314d73eed493c49bb1932c60a8605530db2e4.tar.xz | |
arm64: syscall: exit userspace before unmasking exceptions
In el0_svc_common() we unmask exceptions before we call user_exit(), and
so there's a window where an IRQ or debug exception can be taken while
RCU is not watching. In do_debug_exception() we account for this in via
debug_exception_{enter,exit}(), but in the el1_irq asm we do not and we
call trace functions which rely on RCU before we have a guarantee that
RCU is watching.
Let's avoid this by having el0_svc_common() exit userspace before
unmasking exceptions, matching what we do for all other EL0 entry paths.
We can use user_exit_irqoff() to avoid the pointless save/restore of IRQ
flags while we're sure exceptions are masked in DAIF.
The workaround for Cortex-A76 erratum 1463225 may trigger a debug
exception before this point, but the debug code invoked in this case is
safe even when RCU is not watching.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201130115950.22492-2-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
| -rw-r--r-- | arch/arm64/kernel/syscall.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c index e4c0dadf0d92..13fe79f8e2db 100644 --- a/arch/arm64/kernel/syscall.c +++ b/arch/arm64/kernel/syscall.c @@ -120,8 +120,8 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, */ cortex_a76_erratum_1463225_svc_handler(); + user_exit_irqoff(); local_daif_restore(DAIF_PROCCTX); - user_exit(); if (system_supports_mte() && (flags & _TIF_MTE_ASYNC_FAULT)) { /* |