From 08f87f769b595151be1afeff53e144f543faa614 Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Wed, 06 Dec 2023 09:51:13 +0000
Subject: [PATCH] add dts config

---
 kernel/arch/x86/platform/efi/efi_stub_32.S |  120 ++++++++++++++----------------------------------------------
 1 files changed, 28 insertions(+), 92 deletions(-)

diff --git a/kernel/arch/x86/platform/efi/efi_stub_32.S b/kernel/arch/x86/platform/efi/efi_stub_32.S
index ab2e91e..f3cfdb1 100644
--- a/kernel/arch/x86/platform/efi/efi_stub_32.S
+++ b/kernel/arch/x86/platform/efi/efi_stub_32.S
@@ -7,118 +7,54 @@
  */
 
 #include <linux/linkage.h>
+#include <linux/init.h>
+#include <asm/asm-offsets.h>
 #include <asm/page_types.h>
 
-/*
- * efi_call_phys(void *, ...) is a function with variable parameters.
- * All the callers of this function assure that all the parameters are 4-bytes.
- */
+	__INIT
+SYM_FUNC_START(efi_call_svam)
+	push	%ebp
+	movl	%esp, %ebp
+	push	%ebx
 
-/*
- * In gcc calling convention, EBX, ESP, EBP, ESI and EDI are all callee save.
- * So we'd better save all of them at the beginning of this function and restore
- * at the end no matter how many we use, because we can not assure EFI runtime
- * service functions will comply with gcc calling convention, too.
- */
-
-.text
-ENTRY(efi_call_phys)
-	/*
-	 * 0. The function can only be called in Linux kernel. So CS has been
-	 * set to 0x0010, DS and SS have been set to 0x0018. In EFI, I found
-	 * the values of these registers are the same. And, the corresponding
-	 * GDT entries are identical. So I will do nothing about segment reg
-	 * and GDT, but change GDT base register in prolog and epilog.
-	 */
+	push	16(%esp)
+	push	16(%esp)
+	push	%ecx
+	push	%edx
+	movl	%eax, %ebx		// &systab_phys->runtime
 
 	/*
-	 * 1. Now I am running with EIP = <physical address> + PAGE_OFFSET.
-	 * But to make it smoothly switch from virtual mode to flat mode.
-	 * The mapping of lower virtual memory has been created in prolog and
-	 * epilog.
+	 * Switch to the flat mapped alias of this routine, by jumping to the
+	 * address of label '1' after subtracting PAGE_OFFSET from it.
 	 */
 	movl	$1f, %edx
 	subl	$__PAGE_OFFSET, %edx
 	jmp	*%edx
 1:
 
-	/*
-	 * 2. Now on the top of stack is the return
-	 * address in the caller of efi_call_phys(), then parameter 1,
-	 * parameter 2, ..., param n. To make things easy, we save the return
-	 * address of efi_call_phys in a global variable.
-	 */
-	popl	%edx
-	movl	%edx, saved_return_addr
-	/* get the function pointer into ECX*/
-	popl	%ecx
-	movl	%ecx, efi_rt_function_ptr
-	movl	$2f, %edx
-	subl	$__PAGE_OFFSET, %edx
-	pushl	%edx
-
-	/*
-	 * 3. Clear PG bit in %CR0.
-	 */
+	/* disable paging */
 	movl	%cr0, %edx
 	andl	$0x7fffffff, %edx
 	movl	%edx, %cr0
-	jmp	1f
-1:
 
-	/*
-	 * 4. Adjust stack pointer.
-	 */
+	/* convert the stack pointer to a flat mapped address */
 	subl	$__PAGE_OFFSET, %esp
 
-	/*
-	 * 5. Call the physical function.
-	 */
-	jmp	*%ecx
+	/* call the EFI routine */
+	movl	(%eax), %eax
+	call	*EFI_svam(%eax)
 
-2:
-	/*
-	 * 6. After EFI runtime service returns, control will return to
-	 * following instruction. We'd better readjust stack pointer first.
-	 */
-	addl	$__PAGE_OFFSET, %esp
+	/* grab the virtually remapped EFI runtime services table pointer */
+	movl	(%ebx), %ecx
+	movl	36(%esp), %edx		// &efi.runtime
+	movl	%ecx, (%edx)
 
-	/*
-	 * 7. Restore PG bit
-	 */
+	/* re-enable paging */
 	movl	%cr0, %edx
 	orl	$0x80000000, %edx
 	movl	%edx, %cr0
-	jmp	1f
-1:
-	/*
-	 * 8. Now restore the virtual mode from flat mode by
-	 * adding EIP with PAGE_OFFSET.
-	 */
-	movl	$1f, %edx
-	jmp	*%edx
-1:
 
-	/*
-	 * 9. Balance the stack. And because EAX contain the return value,
-	 * we'd better not clobber it.
-	 */
-	leal	efi_rt_function_ptr, %edx
-	movl	(%edx), %ecx
-	pushl	%ecx
-
-	/*
-	 * 10. Push the saved return address onto the stack and return.
-	 */
-	leal	saved_return_addr, %edx
-	movl	(%edx), %ecx
-	pushl	%ecx
-	ret
-ENDPROC(efi_call_phys)
-.previous
-
-.data
-saved_return_addr:
-	.long 0
-efi_rt_function_ptr:
-	.long 0
+	movl	16(%esp), %ebx
+	leave
+	RET
+SYM_FUNC_END(efi_call_svam)

--
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