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x86/kexec: Use RIP relative addressing

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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
This commit is contained in:
Peter Zijlstra 2020-03-16 10:13:45 +01:00
parent f0f70adb78
commit fc8bd77d64
1 changed files with 1 additions and 4 deletions
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5
arch/x86/kernel/relocate_kernel_64.S
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@ -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