linux-kernel - [PATCH v5 06/27] arm64: Delay daif masking for user return

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Message-Id: <1535471497-38854-7-git-send-email-julien.thierry@arm.com>
Date:   Tue, 28 Aug 2018 16:51:16 +0100
From:   Julien Thierry <julien.thierry@....com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, daniel.thompson@...aro.org,
        joel@...lfernandes.org, marc.zyngier@....com, mark.rutland@....com,
        christoffer.dall@....com, james.morse@....com,
        catalin.marinas@....com, will.deacon@....com,
        Julien Thierry <julien.thierry@....com>
Subject: [PATCH v5 06/27] arm64: Delay daif masking for user return

Masking daif flags is done very early before returning to EL0.

Only toggle the interrupt masking while in the vector entry and mask daif
once in kernel_exit.

Signed-off-by: Julien Thierry <julien.thierry@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: James Morse <james.morse@....com>
---
 arch/arm64/kernel/entry.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 09dbea22..85ce06ac 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -259,9 +259,9 @@ alternative_else_nop_endif
 	.endm
 
 	.macro	kernel_exit, el
-	.if	\el != 0
 	disable_daif
 
+	.if	\el != 0
 	/* Restore the task's original addr_limit. */
 	ldr	x20, [sp, #S_ORIG_ADDR_LIMIT]
 	str	x20, [tsk, #TSK_TI_ADDR_LIMIT]
@@ -896,7 +896,7 @@ work_pending:
  * "slow" syscall return path.
  */
 ret_to_user:
-	disable_daif
+	disable_irq				// disable interrupts
 	ldr	x1, [tsk, #TSK_TI_FLAGS]
 	and	x2, x1, #_TIF_WORK_MASK
 	cbnz	x2, work_pending
-- 
1.9.1