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-rw-r--r--arch/x86/boot/pmjump.S75
1 files changed, 75 insertions, 0 deletions
diff --git a/arch/x86/boot/pmjump.S b/arch/x86/boot/pmjump.S
new file mode 100644
index 0000000000..cbec8bd084
--- /dev/null
+++ b/arch/x86/boot/pmjump.S
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+/* SPDX-License-Identifier: GPL-2.0-only */
+/* ----------------------------------------------------------------------- *
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ * Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * The actual transition into protected mode
+ */
+
+#include <asm/boot.h>
+#include <asm/processor-flags.h>
+#include <asm/segment.h>
+#include <linux/linkage.h>
+
+ .text
+ .code16
+
+/*
+ * void protected_mode_jump(u32 entrypoint, u32 bootparams);
+ */
+SYM_FUNC_START_NOALIGN(protected_mode_jump)
+ movl %edx, %esi # Pointer to boot_params table
+
+ xorl %ebx, %ebx
+ movw %cs, %bx
+ shll $4, %ebx
+ addl %ebx, 2f
+ jmp 1f # Short jump to serialize on 386/486
+1:
+
+ movw $__BOOT_DS, %cx
+ movw $__BOOT_TSS, %di
+
+ movl %cr0, %edx
+ orb $X86_CR0_PE, %dl # Protected mode
+ movl %edx, %cr0
+
+ # Transition to 32-bit mode
+ .byte 0x66, 0xea # ljmpl opcode
+2: .long .Lin_pm32 # offset
+ .word __BOOT_CS # segment
+SYM_FUNC_END(protected_mode_jump)
+
+ .code32
+ .section ".text32","ax"
+SYM_FUNC_START_LOCAL_NOALIGN(.Lin_pm32)
+ # Set up data segments for flat 32-bit mode
+ movl %ecx, %ds
+ movl %ecx, %es
+ movl %ecx, %fs
+ movl %ecx, %gs
+ movl %ecx, %ss
+ # The 32-bit code sets up its own stack, but this way we do have
+ # a valid stack if some debugging hack wants to use it.
+ addl %ebx, %esp
+
+ # Set up TR to make Intel VT happy
+ ltr %di
+
+ # Clear registers to allow for future extensions to the
+ # 32-bit boot protocol
+ xorl %ecx, %ecx
+ xorl %edx, %edx
+ xorl %ebx, %ebx
+ xorl %ebp, %ebp
+ xorl %edi, %edi
+
+ # Set up LDTR to make Intel VT happy
+ lldt %cx
+
+ jmpl *%eax # Jump to the 32-bit entrypoint
+SYM_FUNC_END(.Lin_pm32)