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>
This commit is contained in:
parent
ff1712f953
commit
ca1314d73e
|
@ -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)) {
|
||||
/*
|
||||
|
|
Loading…
Reference in New Issue