diff mbox

[v2,05/27] x86: relocate_kernel - Adapt assembly for PIE support

Message ID 20180313205945.245105-6-thgarnie@google.com (mailing list archive)
State New, archived
Headers show

Commit Message

Thomas Garnier March 13, 2018, 8:59 p.m. UTC 
Change the assembly code to use only relative references of symbols for the
kernel to be PIE compatible.

Position Independent Executable (PIE) support will allow to extended the
KASLR randomization range below the -2G memory limit.

Signed-off-by: Thomas Garnier <thgarnie@google.com>
---
 arch/x86/kernel/relocate_kernel_64.S | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
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Patch

diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 11eda21eb697..a7227dfe1a2b 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -208,9 +208,11 @@  identity_mapped:
 	movq	%rax, %cr3
 	lea	PAGE_SIZE(%r8), %rsp
 	call	swap_pages
-	movq	$virtual_mapped, %rax
-	pushq	%rax
-	ret
+	jmp	*virtual_mapped_addr(%rip)
+
+	/* Absolute value for PIE support */
+virtual_mapped_addr:
+	.quad virtual_mapped
 
 virtual_mapped:
 	movq	RSP(%r8), %rsp