x86/boot/32: Extract efi_pe_entry() from startup_32()

The efi_pe_entry() body is somehow squashed into startup_32(). In the old days,
we forced startup_32() to start at offset 0x00 and efi_pe_entry() to start
at 0x10.

But this requirement was removed long time ago, in:

  99f857db8857 ("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_32() into a separate function, we do so and we separate it to two
functions as they are marked already: efi_pe_entry() + efi32_stub_entry().

We also annotate the functions appropriatelly by ENTRY+ENDPROC.

ABI offset is preserved:

  0000   128 FUNC    GLOBAL DEFAULT    6 startup_32
  0080    60 FUNC    GLOBAL DEFAULT    6 efi_pe_entry
  00bc    68 FUNC    GLOBAL DEFAULT    6 efi32_stub_entry

On the top-level, it looked like this:

	ENTRY(startup_32)
	#ifdef CONFIG_EFI_STUB		; start of inlined
		jmp     preferred_addr
	ENTRY(efi_pe_entry)
		... ; a lot of assembly (efi_pe_entry)
	ENTRY(efi32_stub_entry)
		... ; a lot of assembly (efi32_stub_entry)
		leal    preferred_addr(%eax), %eax
		jmp     *%eax
	preferred_addr:
	#endif				; end of inlined
		... ; a lot of assembly (startup_32)
	ENDPROC(startup_32)

And it is now converted into:

	ENTRY(startup_32)
		... ; a lot of assembly (startup_32)
	ENDPROC(startup_32)

	#ifdef CONFIG_EFI_STUB
	ENTRY(efi_pe_entry)
		... ; a lot of assembly (efi_pe_entry)
	ENDPROC(efi_pe_entry)

	ENTRY(efi32_stub_entry)
		... ; a lot of assembly (efi32_stub_entry)
		leal    startup_32(%eax), %eax
		jmp     *%eax
	ENDPROC(efi32_stub_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/20170824073327.4129-1-jslaby@suse.cz
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index d85b962..11c68cf 100644 (file)
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -61,71 +61,6 @@
 
        __HEAD
 ENTRY(startup_32)
-#ifdef CONFIG_EFI_STUB
-       jmp     preferred_addr
-
-       /*
-        * We don't need the return address, so set up the stack so
-        * efi_main() can find its arguments.
-        */
-ENTRY(efi_pe_entry)
-       add     $0x4, %esp
-
-       call    1f
-1:     popl    %esi
-       subl    $1b, %esi
-
-       popl    %ecx
-       movl    %ecx, efi32_config(%esi)        /* Handle */
-       popl    %ecx
-       movl    %ecx, efi32_config+8(%esi)      /* EFI System table pointer */
-
-       /* Relocate efi_config->call() */
-       leal    efi32_config(%esi), %eax
-       add     %esi, 40(%eax)
-       pushl   %eax
-
-       call    make_boot_params
-       cmpl    $0, %eax
-       je      fail
-       movl    %esi, BP_code32_start(%eax)
-       popl    %ecx
-       pushl   %eax
-       pushl   %ecx
-       jmp     2f              /* Skip efi_config initialization */
-
-ENTRY(efi32_stub_entry)
-       add     $0x4, %esp
-       popl    %ecx
-       popl    %edx
-
-       call    1f
-1:     popl    %esi
-       subl    $1b, %esi
-
-       movl    %ecx, efi32_config(%esi)        /* Handle */
-       movl    %edx, efi32_config+8(%esi)      /* EFI System table pointer */
-
-       /* Relocate efi_config->call() */
-       leal    efi32_config(%esi), %eax
-       add     %esi, 40(%eax)
-       pushl   %eax
-2:
-       call    efi_main
-       cmpl    $0, %eax
-       movl    %eax, %esi
-       jne     2f
-fail:
-       /* EFI init failed, so hang. */
-       hlt
-       jmp     fail
-2:
-       movl    BP_code32_start(%esi), %eax
-       leal    preferred_addr(%eax), %eax
-       jmp     *%eax
-
-preferred_addr:
-#endif
        cld
        /*
         * Test KEEP_SEGMENTS flag to see if the bootloader is asking
@@ -208,6 +143,70 @@ preferred_addr:
        jmp     *%eax
 ENDPROC(startup_32)
 
+#ifdef CONFIG_EFI_STUB
+/*
+ * We don't need the return address, so set up the stack so efi_main() can find
+ * its arguments.
+ */
+ENTRY(efi_pe_entry)
+       add     $0x4, %esp
+
+       call    1f
+1:     popl    %esi
+       subl    $1b, %esi
+
+       popl    %ecx
+       movl    %ecx, efi32_config(%esi)        /* Handle */
+       popl    %ecx
+       movl    %ecx, efi32_config+8(%esi)      /* EFI System table pointer */
+
+       /* Relocate efi_config->call() */
+       leal    efi32_config(%esi), %eax
+       add     %esi, 40(%eax)
+       pushl   %eax
+
+       call    make_boot_params
+       cmpl    $0, %eax
+       je      fail
+       movl    %esi, BP_code32_start(%eax)
+       popl    %ecx
+       pushl   %eax
+       pushl   %ecx
+       jmp     2f              /* Skip efi_config initialization */
+ENDPROC(efi_pe_entry)
+
+ENTRY(efi32_stub_entry)
+       add     $0x4, %esp
+       popl    %ecx
+       popl    %edx
+
+       call    1f
+1:     popl    %esi
+       subl    $1b, %esi
+
+       movl    %ecx, efi32_config(%esi)        /* Handle */
+       movl    %edx, efi32_config+8(%esi)      /* EFI System table pointer */
+
+       /* Relocate efi_config->call() */
+       leal    efi32_config(%esi), %eax
+       add     %esi, 40(%eax)
+       pushl   %eax
+2:
+       call    efi_main
+       cmpl    $0, %eax
+       movl    %eax, %esi
+       jne     2f
+fail:
+       /* EFI init failed, so hang. */
+       hlt
+       jmp     fail
+2:
+       movl    BP_code32_start(%esi), %eax
+       leal    startup_32(%eax), %eax
+       jmp     *%eax
+ENDPROC(efi32_stub_entry)
+#endif
+
        .text
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