Move efi32_pe_entry() into the .text section, so that it can be moved
out of head_64.S and into a separate compilation unit in a subsequent
patch.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/boot/compressed/head_64.S | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index b51f0e107c2e..9ae6ddccd3ef 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -757,7 +757,7 @@ SYM_DATA(efi_is64, .byte 1)
 #define BS32_handle_protocol	88 // offsetof(efi_boot_services_32_t, handle_protocol)
 #define LI32_image_base		32 // offsetof(efi_loaded_image_32_t, image_base)
 
-	__HEAD
+	.text
 	.code32
 SYM_FUNC_START(efi32_pe_entry)
 /*
@@ -779,12 +779,11 @@ SYM_FUNC_START(efi32_pe_entry)
 
 	call	1f
 1:	pop	%ebx
-	subl	$ rva(1b), %ebx
 
 	/* Get the loaded image protocol pointer from the image handle */
 	leal	-4(%ebp), %eax
 	pushl	%eax				// &loaded_image
-	leal	rva(loaded_image_proto)(%ebx), %eax
+	leal	(loaded_image_proto - 1b)(%ebx), %eax
 	pushl	%eax				// pass the GUID address
 	pushl	8(%ebp)				// pass the image handle
 
@@ -813,13 +812,13 @@ SYM_FUNC_START(efi32_pe_entry)
 	movl	12(%ebp), %edx			// sys_table
 	movl	-4(%ebp), %esi			// loaded_image
 	movl	LI32_image_base(%esi), %esi	// loaded_image->image_base
-	movl	%ebx, %ebp			// startup_32 for efi32_pe_stub_entry
+	leal	(startup_32 - 1b)(%ebx), %ebp	// runtime address of startup_32
 	/*
 	 * We need to set the image_offset variable here since startup_32() will
 	 * use it before we get to the 64-bit efi_pe_entry() in C code.
 	 */
-	subl	%esi, %ebx
-	movl	%ebx, rva(image_offset)(%ebp)	// save image_offset
+	subl	%esi, %ebp			// calculate image_offset
+	movl	%ebp, (image_offset - 1b)(%ebx)	// save image_offset
 	xorl	%esi, %esi
 	jmp	efi32_entry
 
-- 
2.35.1

On Wed, Sep 21, 2022 at 04:54:10PM +0200, Ard Biesheuvel wrote:
>  	/*
>  	 * We need to set the image_offset variable here since startup_32() will
>  	 * use it before we get to the 64-bit efi_pe_entry() in C code.
>  	 */
> -	subl	%esi, %ebx
> -	movl	%ebx, rva(image_offset)(%ebp)	// save image_offset
> +	subl	%esi, %ebp			// calculate image_offset
> +	movl	%ebp, (image_offset - 1b)(%ebx)	// save image_offset

All looks ok, just one question: what was the reason for that
image_offset thing?

I see:

1887c9b653f9 ("efi/x86: Decompress at start of PE image load address")

It says that if the kernel is loaded as a PE executable using
LoadImage() we don't know where that image will be loaded each time so
we're saving that offset for later when relocating (or not) the kernel?

All part of those improvements:

https://lore.kernel.org/all/20200301230537.2247550-1-nivedita@alum.mit.edu/

Am I close?

I.e., that image_offset is purely a kernel thing and not something EFI
LoadImage's inner workings mandate...? It doesn't seem so from where I'm
standing but lemme doublecheck still.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

On Thu, 17 Nov 2022 at 16:57, Borislav Petkov <bp@alien8.de> wrote:
>
> On Wed, Sep 21, 2022 at 04:54:10PM +0200, Ard Biesheuvel wrote:
> >       /*
> >        * We need to set the image_offset variable here since startup_32() will
> >        * use it before we get to the 64-bit efi_pe_entry() in C code.
> >        */
> > -     subl    %esi, %ebx
> > -     movl    %ebx, rva(image_offset)(%ebp)   // save image_offset
> > +     subl    %esi, %ebp                      // calculate image_offset
> > +     movl    %ebp, (image_offset - 1b)(%ebx) // save image_offset
>
> All looks ok, just one question: what was the reason for that
> image_offset thing?
>
> I see:
>
> 1887c9b653f9 ("efi/x86: Decompress at start of PE image load address")
>
> It says that if the kernel is loaded as a PE executable using
> LoadImage() we don't know where that image will be loaded each time so
> we're saving that offset for later when relocating (or not) the kernel?
>
> All part of those improvements:
>
> https://lore.kernel.org/all/20200301230537.2247550-1-nivedita@alum.mit.edu/
>
> Am I close?
>

Yes.

The x86 boot protocol does not require that the setup data block comes
right before the image, it just receives the address in %esi

When doing PE boot, this is guaranteed, and so we can reuse the memory
before the image.

> I.e., that image_offset is purely a kernel thing and not something EFI
> LoadImage's inner workings mandate...? It doesn't seem so from where I'm
> standing but lemme doublecheck still.
>

No this has nothing do with the EFI in particular, only with how the
x86 boot image is constructed and wrapped into a PE/COFF executable.

On Thu, Nov 17, 2022 at 05:06:37PM +0100, Ard Biesheuvel wrote:
> No this has nothing do with the EFI in particular, only with how the
> x86 boot image is constructed and wrapped into a PE/COFF executable.

Ok, thanks.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette