x86/boot/compressed: Move 32-bit entrypoint code into .text section

commit e2ab9eab32 upstream.

Move the code that stores the arguments passed to the EFI entrypoint
into the .text section, so that it can be moved into a separate
compilation unit in a subsequent patch.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20221122161017.2426828-3-ardb@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/x86/boot/compressed/head_64.S

@@ -303,24 +303,41 @@ SYM_FUNC_START(efi32_stub_entry)
 	popl	%ecx
 	popl	%edx
 	popl	%esi
+	jmp	efi32_entry
+SYM_FUNC_END(efi32_stub_entry)
 
+	.text
+/*
+ * This is the common EFI stub entry point for mixed mode.
+ *
+ * Arguments:	%ecx	image handle
+ * 		%edx	EFI system table pointer
+ *		%esi	struct bootparams pointer (or NULL when not using
+ *			the EFI handover protocol)
+ *
+ * Since this is the point of no return for ordinary execution, no registers
+ * are considered live except for the function parameters. [Note that the EFI
+ * stub may still exit and return to the firmware using the Exit() EFI boot
+ * service.]
+ */
+SYM_FUNC_START_LOCAL(efi32_entry)
 	call	1f
-1:	pop	%ebp
+1:	pop	%ebx
-	subl	$ rva(1b), %ebp
-
-	movl	%esi, rva(efi32_boot_args+8)(%ebp)
-SYM_INNER_LABEL(efi32_pe_stub_entry, SYM_L_LOCAL)
-	movl	%ecx, rva(efi32_boot_args)(%ebp)
-	movl	%edx, rva(efi32_boot_args+4)(%ebp)
-	movb	$0, rva(efi_is64)(%ebp)
 
 	/* Save firmware GDTR and code/data selectors */
-	sgdtl	rva(efi32_boot_gdt)(%ebp)
+	sgdtl	(efi32_boot_gdt - 1b)(%ebx)
-	movw	%cs, rva(efi32_boot_cs)(%ebp)
+	movw	%cs, (efi32_boot_cs - 1b)(%ebx)
-	movw	%ds, rva(efi32_boot_ds)(%ebp)
+	movw	%ds, (efi32_boot_ds - 1b)(%ebx)
 
 	/* Store firmware IDT descriptor */
-	sidtl	rva(efi32_boot_idt)(%ebp)
+	sidtl	(efi32_boot_idt - 1b)(%ebx)
+
+	/* Store boot arguments */
+	leal	(efi32_boot_args - 1b)(%ebx), %ebx
+	movl	%ecx, 0(%ebx)
+	movl	%edx, 4(%ebx)
+	movl	%esi, 8(%ebx)
+	movb	$0x0, 12(%ebx)          // efi_is64
 
 	/* Disable paging */
 	movl	%cr0, %eax
@@ -328,7 +345,8 @@ SYM_INNER_LABEL(efi32_pe_stub_entry, SYM_L_LOCAL)
 	movl	%eax, %cr0
 
 	jmp	startup_32
-SYM_FUNC_END(efi32_stub_entry)
+SYM_FUNC_END(efi32_entry)
+	__HEAD
 #endif
 
 	.code64
@@ -847,7 +865,9 @@ SYM_FUNC_START(efi32_pe_entry)
 	 */
 	subl	%esi, %ebx
 	movl	%ebx, rva(image_offset)(%ebp)	// save image_offset
-	jmp	efi32_pe_stub_entry
+	xorl	%esi, %esi
+	jmp	efi32_entry			// pass %ecx, %edx, %esi
+						// no other registers remain live
 
 2:	popl	%edi				// restore callee-save registers
 	popl	%ebx