linux-kernel - [PATCH v1 2/8] x86/entry/clearregs: Add infrastructure to clear registers

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Message-Id: <20180110010328.22163-3-andi@firstfloor.org>
Date:   Tue,  9 Jan 2018 17:03:22 -0800
From:   Andi Kleen <andi@...stfloor.org>
To:     tglx@...utronix.de
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        torvalds@...ux-foundation.org, dwmw@...zon.co.uk, pjt@...gle.com,
        luto@...nel.org, peterz@...radead.org, thomas.lendacky@....com,
        tim.c.chen@...ux.intel.com, gregkh@...ux-foundation.org,
        dave.hansen@...el.com, jikos@...nel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH v1 2/8] x86/entry/clearregs: Add infrastructure to clear registers

From: Andi Kleen <ak@...ux.intel.com>

Add 64bit assembler macros to clear registers on kernel entry.
Used in followon patches.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 arch/x86/entry/calling.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 45a63e00a6af..9444e7623185 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -172,6 +172,34 @@ For 32-bit we have the following conventions - kernel is built with
 	.byte 0xf1
 	.endm
 
+	.macro CLEAR_R11_TO_R15
+	xorq %r15, %r15
+	xorq %r14, %r14
+	xorq %r13, %r13
+	xorq %r12, %r12
+	xorq %r11, %r11
+	.endm
+
+	.macro CLEAR_R8_TO_R15
+	CLEAR_R11_TO_R15
+	xorq %r10, %r10
+	xorq %r9, %r9
+	xorq %r8, %r8
+	.endm
+
+	.macro CLEAR_ALL_REGS
+	CLEAR_R8_TO_R15
+	xorl %eax, %eax
+	xorl %ebx, %ebx
+	xorl %ecx, %ecx
+	xorl %edx, %edx
+	xorl %esi, %esi
+	xorl %edi, %edi
+#ifndef CONFIG_FRAME_POINTER
+	xorl %ebp, %ebp
+#endif
+	.endm
+
 /*
  * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
  * frame pointer is replaced with an encoded pointer to pt_regs.  The encoding
-- 
2.14.3