[RFC PATCH v2 07/45] arm64: entry: mask DAIF before returning from C EL1 handlers

[Vladimir Murzin]

From: Ada Couprie Diaz <ada.coupriediaz at arm.com>

Most EL1 exceptions already call local_daif_mask() before returning,
with the exception of debug exception handlers which do not change
DAIF, and the IRQ/FIQ/Error handlers.

However, DAIF get masked in kernel_exit() in all cases when returning
from EL1 C handlers anyway.

Move this masking from assembly to C by calling local_daif_mask()
before irqentry_nmi_exit(). Unlike the raw DAIF masking helper,
local_daif_mask() invokes trace_hardirqs_off(), so it must execute
while RCU is still watching.

Remove the disable_daif assembly macro, as this was its only use.

Signed-off-by: Ada Couprie Diaz <ada.coupriediaz at arm.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
---
 arch/arm64/include/asm/assembler.h | 4 ----
 arch/arm64/kernel/entry-common.c   | 2 ++
 arch/arm64/kernel/entry.S          | 4 ----
 3 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index effae53e9739..0b58b550e8dc 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -34,10 +34,6 @@
 	wx\n	.req	w\n
 	.endr
 
-	.macro disable_daif
-	msr	daifset, #0xf
-	.endm
-
 /*
  * Save/restore interrupts.
  */
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index ceb4eb11232a..2be42d7f4eaa 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -495,6 +495,7 @@ static __always_inline void __el1_pnmi(struct pt_regs *regs,
 
 	state = irqentry_nmi_enter(regs);
 	do_interrupt_handler(regs, handler);
+	local_daif_mask();
 	irqentry_nmi_exit(regs, state);
 }
 
@@ -540,6 +541,7 @@ asmlinkage void noinstr el1h_64_error_handler(struct pt_regs *regs)
 	local_daif_restore(DAIF_ERRCTX);
 	state = irqentry_nmi_enter(regs);
 	do_serror(regs, esr);
+	local_daif_mask();
 	irqentry_nmi_exit(regs, state);
 }
 
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index e0db14e9c843..f63049ac32dc 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -333,10 +333,6 @@ alternative_else_nop_endif
 	.endm
 
 	.macro	kernel_exit, el
-	.if	\el != 0
-	disable_daif
-	.endif
-
 #ifdef CONFIG_ARM64_PSEUDO_NMI
 alternative_if_not ARM64_HAS_GIC_PRIO_MASKING
 	b	.Lskip_pmr_restore\@
-- 
2.34.1