linux-kernel - [PATCH v10 03/11] x86: relocate_kernel

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Message-Id: <20191205000957.112719-4-thgarnie@chromium.org>
Date:   Wed,  4 Dec 2019 16:09:40 -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>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Allison Randal <allison@...utok.net>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Jiri Slaby <jslaby@...e.cz>, linux-kernel@...r.kernel.org
Subject: [PATCH v10 03/11] x86: relocate_kernel - Adapt assembly for PIE support

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

Position Independent Executable (PIE) support will allow to extend the
KASLR randomization range below 0xffffffff80000000.

Signed-off-by: Thomas Garnier <thgarnie@...omium.org>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
 arch/x86/kernel/relocate_kernel_64.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index ef3ba99068d3..c294339df5ef 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -206,7 +206,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)
 	movq	%rax, %cr3
 	lea	PAGE_SIZE(%r8), %rsp
 	call	swap_pages
-	movq	$virtual_mapped, %rax
+	movabsq	$virtual_mapped, %rax
 	pushq	%rax
 	ret
 SYM_CODE_END(identity_mapped)
-- 
2.24.0.393.g34dc348eaf-goog