linux-kernel - [PATCH v11 04/11] x86/entry/64: Adapt assembly for PIE support

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Message-Id: <20200228000105.165012-5-thgarnie@chromium.org>
Date:   Thu, 27 Feb 2020 16:00:49 -0800
From:   Thomas Garnier <thgarnie@...omium.org>
To:     kernel-hardening@...ts.openwall.com
Cc:     kristen@...ux.intel.com, keescook@...omium.org,
        Thomas Garnier <thgarnie@...omium.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v11 04/11] x86/entry/64: Adapt assembly for PIE support

Change the assembly code to use only relative references of symbols for the
kernel to be PIE compatible.

Signed-off-by: Thomas Garnier <thgarnie@...omium.org>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
 arch/x86/entry/entry_64.S | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index f2bb91e87877..2c8200d35797 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1329,7 +1329,8 @@ SYM_CODE_START_LOCAL(error_entry)
 	movl	%ecx, %eax			/* zero extend */
 	cmpq	%rax, RIP+8(%rsp)
 	je	.Lbstep_iret
-	cmpq	$.Lgs_change, RIP+8(%rsp)
+	leaq	.Lgs_change(%rip), %rcx
+	cmpq	%rcx, RIP+8(%rsp)
 	jne	.Lerror_entry_done_lfence
 
 	/*
@@ -1529,10 +1530,10 @@ SYM_CODE_START(nmi)
 	 * resume the outer NMI.
 	 */
 
-	movq	$repeat_nmi, %rdx
+	leaq	repeat_nmi(%rip), %rdx
 	cmpq	8(%rsp), %rdx
 	ja	1f
-	movq	$end_repeat_nmi, %rdx
+	leaq	end_repeat_nmi(%rip), %rdx
 	cmpq	8(%rsp), %rdx
 	ja	nested_nmi_out
 1:
@@ -1586,7 +1587,8 @@ nested_nmi:
 	pushq	%rdx
 	pushfq
 	pushq	$__KERNEL_CS
-	pushq	$repeat_nmi
+	leaq	repeat_nmi(%rip), %rdx
+	pushq	%rdx
 
 	/* Put stack back */
 	addq	$(6*8), %rsp
@@ -1625,7 +1627,11 @@ first_nmi:
 	addq	$8, (%rsp)	/* Fix up RSP */
 	pushfq			/* RFLAGS */
 	pushq	$__KERNEL_CS	/* CS */
-	pushq	$1f		/* RIP */
+	pushq	$0		/* Space for RIP */
+	pushq	%rdx		/* Save RDX */
+	leaq	1f(%rip), %rdx	/* Put the address of 1f label into RDX */
+	movq    %rdx, 8(%rsp)   /* Store it in RIP field */
+	popq	%rdx		/* Restore RDX */
 	iretq			/* continues at repeat_nmi below */
 	UNWIND_HINT_IRET_REGS
 1:
-- 
2.25.1.481.gfbce0eb801-goog