x86/boot/64: Extract efi_pe_entry() from startup_64()

Similarly to the 32-bit code, efi_pe_entry body() is somehow squashed into
startup_64().

In the old days, we forced startup_64() to start at offset 0x200 and efi_pe_entry()
to start at 0x210. But this requirement was removed long time ago, in:

  99f857db88 ("x86, build: Dynamically find entry points in compressed startup code")

The way it is now makes the code less readable and illogical. Given
we can now safely extract the inlined efi_pe_entry() body from
startup_64() into a separate function, we do so.

We also annotate the function appropriatelly by ENTRY+ENDPROC.

ABI offsets are preserved:

  0000000000000000 T startup_32
  0000000000000200 T startup_64
  0000000000000390 T efi64_stub_entry

On the top-level, it looked like:

	.org 0x200
	ENTRY(startup_64)
	#ifdef CONFIG_EFI_STUB		; start of inlined
		jmp     preferred_addr
	GLOBAL(efi_pe_entry)
		... ; a lot of assembly (efi_pe_entry)
		leaq    preferred_addr(%rax), %rax
		jmp     *%rax
	preferred_addr:
	#endif				; end of inlined
		... ; a lot of assembly (startup_64)
	ENDPROC(startup_64)

And it is now converted into:

	.org 0x200
	ENTRY(startup_64)
		... ; a lot of assembly (startup_64)
	ENDPROC(startup_64)

	#ifdef CONFIG_EFI_STUB
	ENTRY(efi_pe_entry)
		... ; a lot of assembly (efi_pe_entry)
		leaq    startup_64(%rax), %rax
		jmp     *%rax
	ENDPROC(efi_pe_entry)
	#endif

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: ard.biesheuvel@linaro.org
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20170824073327.4129-2-jslaby@suse.cz
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/boot/compressed/head_64.S

@@ -243,65 +243,6 @@ ENTRY(startup_64)
 	 * that maps our entire kernel(text+data+bss+brk), zero page
 	 * and command line.
 	 */
-#ifdef CONFIG_EFI_STUB
-	/*
-	 * The entry point for the PE/COFF executable is efi_pe_entry, so
-	 * only legacy boot loaders will execute this jmp.
-	 */
-	jmp	preferred_addr
-
-ENTRY(efi_pe_entry)
-	movq	%rcx, efi64_config(%rip)	/* Handle */
-	movq	%rdx, efi64_config+8(%rip) /* EFI System table pointer */
-
-	leaq	efi64_config(%rip), %rax
-	movq	%rax, efi_config(%rip)
-
-	call	1f
-1:	popq	%rbp
-	subq	$1b, %rbp
-
-	/*
-	 * Relocate efi_config->call().
-	 */
-	addq	%rbp, efi64_config+40(%rip)
-
-	movq	%rax, %rdi
-	call	make_boot_params
-	cmpq	$0,%rax
-	je	fail
-	mov	%rax, %rsi
-	leaq	startup_32(%rip), %rax
-	movl	%eax, BP_code32_start(%rsi)
-	jmp	2f		/* Skip the relocation */
-
-handover_entry:
-	call	1f
-1:	popq	%rbp
-	subq	$1b, %rbp
-
-	/*
-	 * Relocate efi_config->call().
-	 */
-	movq	efi_config(%rip), %rax
-	addq	%rbp, 40(%rax)
-2:
-	movq	efi_config(%rip), %rdi
-	call	efi_main
-	movq	%rax,%rsi
-	cmpq	$0,%rax
-	jne	2f
-fail:
-	/* EFI init failed, so hang. */
-	hlt
-	jmp	fail
-2:
-	movl	BP_code32_start(%esi), %eax
-	leaq	preferred_addr(%rax), %rax
-	jmp	*%rax
-
-preferred_addr:
-#endif
 
 	/* Setup data segments. */
 	xorl	%eax, %eax
@@ -413,6 +354,59 @@ lvl5:
 	jmp	*%rax
 
 #ifdef CONFIG_EFI_STUB
+
+/* The entry point for the PE/COFF executable is efi_pe_entry. */
+ENTRY(efi_pe_entry)
+	movq	%rcx, efi64_config(%rip)	/* Handle */
+	movq	%rdx, efi64_config+8(%rip) /* EFI System table pointer */
+
+	leaq	efi64_config(%rip), %rax
+	movq	%rax, efi_config(%rip)
+
+	call	1f
+1:	popq	%rbp
+	subq	$1b, %rbp
+
+	/*
+	 * Relocate efi_config->call().
+	 */
+	addq	%rbp, efi64_config+40(%rip)
+
+	movq	%rax, %rdi
+	call	make_boot_params
+	cmpq	$0,%rax
+	je	fail
+	mov	%rax, %rsi
+	leaq	startup_32(%rip), %rax
+	movl	%eax, BP_code32_start(%rsi)
+	jmp	2f		/* Skip the relocation */
+
+handover_entry:
+	call	1f
+1:	popq	%rbp
+	subq	$1b, %rbp
+
+	/*
+	 * Relocate efi_config->call().
+	 */
+	movq	efi_config(%rip), %rax
+	addq	%rbp, 40(%rax)
+2:
+	movq	efi_config(%rip), %rdi
+	call	efi_main
+	movq	%rax,%rsi
+	cmpq	$0,%rax
+	jne	2f
+fail:
+	/* EFI init failed, so hang. */
+	hlt
+	jmp	fail
+2:
+	movl	BP_code32_start(%esi), %eax
+	leaq	startup_64(%rax), %rax
+	jmp	*%rax
+ENDPROC(efi_pe_entry)
+
 	.org 0x390
 ENTRY(efi64_stub_entry)
 	movq	%rdi, efi64_config(%rip)	/* Handle */