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Message-Id: <43b8a8153855d9af17029fcfcadebd8d4b14b7c4.1184181208.git.hpa@zytor.com>
Date: Wed, 11 Jul 2007 12:18:53 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: torvalds@...ux-foundation.org, andi@...stfloor.org,
linux-kernel@...r.kernel.org
Cc: "H. Peter Anvin" <hpa@...or.com>
Subject: [x86 setup 28/33] Code for actual protected-mode entry
From: H. Peter Anvin <hpa@...or.com>
This is the code which actually does the switch to protected mode,
including all preparation. It is also responsible for invoking the
boot loader hooks, if present.
Signed-off-by: H. Peter Anvin <hpa@...or.com>
---
arch/i386/boot/pm.c | 170 +++++++++++++++++++++++++++++++++++++++++++++++
arch/i386/boot/pmjump.S | 54 +++++++++++++++
2 files changed, 224 insertions(+), 0 deletions(-)
create mode 100644 arch/i386/boot/pm.c
create mode 100644 arch/i386/boot/pmjump.S
diff --git a/arch/i386/boot/pm.c b/arch/i386/boot/pm.c
new file mode 100644
index 0000000..3fa53e1
--- /dev/null
+++ b/arch/i386/boot/pm.c
@@ -0,0 +1,170 @@
+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ * Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ * This file is part of the Linux kernel, and is made available under
+ * the terms of the GNU General Public License version 2.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * arch/i386/boot/pm.c
+ *
+ * Prepare the machine for transition to protected mode.
+ */
+
+#include "boot.h"
+#include <asm/segment.h>
+
+/*
+ * Invoke the realmode switch hook if present; otherwise
+ * disable all interrupts.
+ */
+static void realmode_switch_hook(void)
+{
+ if (boot_params.hdr.realmode_swtch) {
+ asm volatile("lcallw *%0"
+ : : "m" (boot_params.hdr.realmode_swtch)
+ : "eax", "ebx", "ecx", "edx");
+ } else {
+ asm volatile("cli");
+ outb(0x80, 0x70); /* Disable NMI */
+ io_delay();
+ }
+}
+
+/*
+ * A zImage kernel is loaded at 0x10000 but wants to run at 0x1000.
+ * A bzImage kernel is loaded and runs at 0x100000.
+ */
+static void move_kernel_around(void)
+{
+ /* Note: rely on the compile-time option here rather than
+ the LOADED_HIGH flag. The Qemu kernel loader unconditionally
+ sets the loadflags to zero. */
+#ifndef __BIG_KERNEL__
+ u16 dst_seg, src_seg;
+ u32 syssize;
+
+ dst_seg = 0x1000 >> 4;
+ src_seg = 0x10000 >> 4;
+ syssize = boot_params.hdr.syssize; /* Size in 16-byte paragraphs */
+
+ while (syssize) {
+ int paras = (syssize >= 0x1000) ? 0x1000 : syssize;
+ int dwords = paras << 2;
+
+ asm volatile("pushw %%es ; "
+ "pushw %%ds ; "
+ "movw %1,%%es ; "
+ "movw %2,%%ds ; "
+ "xorw %%di,%%di ; "
+ "xorw %%si,%%si ; "
+ "rep;movsl ; "
+ "popw %%ds ; "
+ "popw %%es"
+ : "+c" (dwords)
+ : "rm" (dst_seg), "rm" (src_seg)
+ : "esi", "edi");
+
+ syssize -= paras;
+ dst_seg += paras;
+ src_seg += paras;
+ }
+#endif
+}
+
+/*
+ * Disable all interrupts at the legacy PIC.
+ */
+static void mask_all_interrupts(void)
+{
+ outb(0xff, 0xa1); /* Mask all interrupts on the seconday PIC */
+ io_delay();
+ outb(0xfb, 0x21); /* Mask all but cascade on the primary PIC */
+ io_delay();
+}
+
+/*
+ * Reset IGNNE# if asserted in the FPU.
+ */
+static void reset_coprocessor(void)
+{
+ outb(0, 0xf0);
+ io_delay();
+ outb(0, 0xf1);
+ io_delay();
+}
+
+/*
+ * Set up the GDT
+ */
+#define GDT_ENTRY(flags,base,limit) \
+ (((u64)(base & 0xff000000) << 32) | \
+ ((u64)flags << 40) | \
+ ((u64)(limit & 0x00ff0000) << 32) | \
+ ((u64)(base & 0x00ffff00) << 16) | \
+ ((u64)(limit & 0x0000ffff)))
+
+struct gdt_ptr {
+ u16 len;
+ u32 ptr;
+} __attribute__((packed));
+
+static void setup_gdt(void)
+{
+ /* There are machines which are known to not boot with the GDT
+ being 8-byte unaligned. Intel recommends 16 byte alignment. */
+ static const u64 boot_gdt[] __attribute__((aligned(16))) = {
+ /* CS: code, read/execute, 4 GB, base 0 */
+ [GDT_ENTRY_BOOT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
+ /* DS: data, read/write, 4 GB, base 0 */
+ [GDT_ENTRY_BOOT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
+ };
+ struct gdt_ptr gdt;
+
+ gdt.len = sizeof(boot_gdt)-1;
+ gdt.ptr = (u32)&boot_gdt + (ds() << 4);
+
+ asm volatile("lgdtl %0" : : "m" (gdt));
+}
+
+/*
+ * Set up the IDT
+ */
+static void setup_idt(void)
+{
+ static const struct gdt_ptr null_idt = {0, 0};
+ asm volatile("lidtl %0" : : "m" (null_idt));
+}
+
+/*
+ * Actual invocation sequence
+ */
+void go_to_protected_mode(void)
+{
+ /* Hook before leaving real mode, also disables interrupts */
+ realmode_switch_hook();
+
+ /* Move the kernel/setup to their final resting places */
+ move_kernel_around();
+
+ /* Enable the A20 gate */
+ if (enable_a20()) {
+ puts("A20 gate not responding, unable to boot...\n");
+ die();
+ }
+
+ /* Reset coprocessor (IGNNE#) */
+ reset_coprocessor();
+
+ /* Mask all interrupts in the PIC */
+ mask_all_interrupts();
+
+ /* Actual transition to protected mode... */
+ setup_idt();
+ setup_gdt();
+ protected_mode_jump(boot_params.hdr.code32_start,
+ (u32)&boot_params + (ds() << 4));
+}
diff --git a/arch/i386/boot/pmjump.S b/arch/i386/boot/pmjump.S
new file mode 100644
index 0000000..2e55923
--- /dev/null
+++ b/arch/i386/boot/pmjump.S
@@ -0,0 +1,54 @@
+/* ----------------------------------------------------------------------- *
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ * Copyright 2007 rPath, Inc. - All Rights Reserved
+ *
+ * This file is part of the Linux kernel, and is made available under
+ * the terms of the GNU General Public License version 2.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * arch/i386/boot/pmjump.S
+ *
+ * The actual transition into protected mode
+ */
+
+#include <asm/boot.h>
+#include <asm/segment.h>
+
+ .text
+
+ .globl protected_mode_jump
+ .type protected_mode_jump, @function
+
+ .code16
+
+/*
+ * void protected_mode_jump(u32 entrypoint, u32 bootparams);
+ */
+protected_mode_jump:
+ xorl %ebx, %ebx # Flag to indicate this is a boot
+ movl %edx, %esi # Pointer to boot_params table
+ movl %eax, 2f # Patch ljmpl instruction
+ jmp 1f # Short jump to flush instruction q.
+
+1:
+ movw $__BOOT_DS, %cx
+
+ movl %cr0, %edx
+ orb $1, %dl # Protected mode (PE) bit
+ movl %edx, %cr0
+
+ movw %cx, %ds
+ movw %cx, %es
+ movw %cx, %fs
+ movw %cx, %gs
+ movw %cx, %ss
+
+ # Jump to the 32-bit entrypoint
+ .byte 0x66, 0xea # ljmpl opcode
+2: .long 0 # offset
+ .word __BOOT_CS # segment
+
+ .size protected_mode_jump, .-protected_mode_jump
--
1.5.2.2
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