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Subject[tip: core/objtool] x86/kexec: Use RIP relative addressing
The following commit has been merged into the core/objtool branch of tip:

Commit-ID: fc8bd77d6476d7733ace9e03093b4acaee6e0605
Gitweb: https://git.kernel.org/tip/fc8bd77d6476d7733ace9e03093b4acaee6e0605
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Mon, 16 Mar 2020 10:13:45 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 25 Mar 2020 18:28:27 +01:00

x86/kexec: Use RIP relative addressing

Normally identity_mapped is not visible to objtool, due to:

arch/x86/kernel/Makefile:OBJECT_FILES_NON_STANDARD_relocate_kernel_$(BITS).o := y

However, when we want to run objtool on vmlinux.o there is no hiding
it:

vmlinux.o: warning: objtool: .text+0x4c0f1: unsupported intra-function call

Replace the (i386 inspired) pattern:

call 1f
1: popq %r8
subq $(1b - relocate_kernel), %r8

With a x86_64 RIP-relative LEA:

leaq relocate_kernel(%rip), %r8

Suggested-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200324160924.143334345@infradead.org
---
arch/x86/kernel/relocate_kernel_64.S | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index ef3ba99..cc5c8b9 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -196,10 +196,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped)

/* get the re-entry point of the peer system */
movq 0(%rsp), %rbp
- call 1f
-1:
- popq %r8
- subq $(1b - relocate_kernel), %r8
+ leaq relocate_kernel(%rip), %r8
movq CP_PA_SWAP_PAGE(%r8), %r10
movq CP_PA_BACKUP_PAGES_MAP(%r8), %rdi
movq CP_PA_TABLE_PAGE(%r8), %rax
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