Commit fc8bd77d authored Mar 16, 2020 by Peter Zijlstra

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

parent f0f70adb

arch/x86/kernel/relocate_kernel_64.S

+1 −4

Original line number	Diff line number	Diff line
		@@ -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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