linux-kernel - [PATCH v2 4/7] x86/boot: Clear direction and interrupt flags in startup

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Date:   Sun,  2 Feb 2020 12:13:50 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>
Cc:     linux-efi@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 4/7] x86/boot: Clear direction and interrupt flags in startup_64

startup_32 already clears these flags on entry, do it in startup_64 as
well for consistency.

The direction flag in particular is not specified to be cleared in the
boot protocol documentation, and we currently call into C code
(paging_prepare) without explicitly clearing it.

Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
---
 arch/x86/boot/compressed/head_64.S | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 27eb2a6786db..69cc6c68741e 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -264,6 +264,9 @@ SYM_CODE_START(startup_64)
 	 * and command line.
 	 */
 
+	cld
+	cli
+
 	/* Setup data segments. */
 	xorl	%eax, %eax
 	movl	%eax, %ds
-- 
2.24.1