[PATCH] kexec: x86 kexec core

This is the i386 implementation of kexec.

Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/Kconfig

@@ -953,6 +953,23 @@ config PHYSICAL_START
 
 	  Don't change this unless you know what you are doing.
 
+config KEXEC
+	bool "kexec system call (EXPERIMENTAL)"
+	depends on EXPERIMENTAL
+	help
+	  kexec is a system call that implements the ability to shutdown your
+	  current kernel, and to start another kernel.  It is like a reboot
+	  but it is indepedent of the system firmware.   And like a reboot
+	  you can start any kernel with it, not just Linux.
+
+	  The name comes from the similiarity to the exec system call.
+
+	  It is an ongoing process to be certain the hardware in a machine
+	  is properly shutdown, so do not be surprised if this code does not
+	  initially work for you.  It may help to enable device hotplugging
+	  support.  As of this writing the exact hardware interface is
+	  strongly in flux, so no good recommendation can be made.
+
 endmenu
 
 

arch/i386/kernel/Makefile

@@ -24,6 +24,7 @@ obj-$(CONFIG_X86_MPPARSE)	+= mpparse.o
 obj-$(CONFIG_X86_LOCAL_APIC)	+= apic.o nmi.o
 obj-$(CONFIG_X86_IO_APIC)	+= io_apic.o
 obj-$(CONFIG_X86_REBOOTFIXUPS)	+= reboot_fixups.o
+obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o crash.o
 obj-$(CONFIG_X86_NUMAQ)		+= numaq.o
 obj-$(CONFIG_X86_SUMMIT_NUMA)	+= summit.o
 obj-$(CONFIG_KPROBES)		+= kprobes.o

arch/i386/kernel/crash.c

@@ -0,0 +1,42 @@
+/*
+ * Architecture specific (i386) functions for kexec based crash dumps.
+ *
+ * Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
+ *
+ * Copyright (C) IBM Corporation, 2004. All rights reserved.
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/smp.h>
+#include <linux/irq.h>
+#include <linux/reboot.h>
+#include <linux/kexec.h>
+#include <linux/irq.h>
+#include <linux/delay.h>
+#include <linux/elf.h>
+#include <linux/elfcore.h>
+
+#include <asm/processor.h>
+#include <asm/hardirq.h>
+#include <asm/nmi.h>
+#include <asm/hw_irq.h>
+
+#define MAX_NOTE_BYTES 1024
+typedef u32 note_buf_t[MAX_NOTE_BYTES/4];
+
+note_buf_t crash_notes[NR_CPUS];
+
+void machine_crash_shutdown(void)
+{
+	/* This function is only called after the system
+	 * has paniced or is otherwise in a critical state.
+	 * The minimum amount of code to allow a kexec'd kernel
+	 * to run successfully needs to happen here.
+	 *
+	 * In practice this means shooting down the other cpus in
+	 * an SMP system.
+	 */
+}

arch/i386/kernel/machine_kexec.c

@@ -0,0 +1,220 @@
+/*
+ * machine_kexec.c - handle transition of Linux booting another kernel
+ * Copyright (C) 2002-2005 Eric Biederman  <ebiederm@xmission.com>
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2.  See the file COPYING for more details.
+ */
+
+#include <linux/mm.h>
+#include <linux/kexec.h>
+#include <linux/delay.h>
+#include <asm/pgtable.h>
+#include <asm/pgalloc.h>
+#include <asm/tlbflush.h>
+#include <asm/mmu_context.h>
+#include <asm/io.h>
+#include <asm/apic.h>
+#include <asm/cpufeature.h>
+
+static inline unsigned long read_cr3(void)
+{
+	unsigned long cr3;
+	asm volatile("movl %%cr3,%0": "=r"(cr3));
+	return cr3;
+}
+
+#define PAGE_ALIGNED __attribute__ ((__aligned__(PAGE_SIZE)))
+
+#define L0_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
+#define L1_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
+#define L2_ATTR (_PAGE_PRESENT)
+
+#define LEVEL0_SIZE (1UL << 12UL)
+
+#ifndef CONFIG_X86_PAE
+#define LEVEL1_SIZE (1UL << 22UL)
+static u32 pgtable_level1[1024] PAGE_ALIGNED;
+
+static void identity_map_page(unsigned long address)
+{
+	unsigned long level1_index, level2_index;
+	u32 *pgtable_level2;
+
+	/* Find the current page table */
+	pgtable_level2 = __va(read_cr3());
+
+	/* Find the indexes of the physical address to identity map */
+	level1_index = (address % LEVEL1_SIZE)/LEVEL0_SIZE;
+	level2_index = address / LEVEL1_SIZE;
+
+	/* Identity map the page table entry */
+	pgtable_level1[level1_index] = address | L0_ATTR;
+	pgtable_level2[level2_index] = __pa(pgtable_level1) | L1_ATTR;
+
+	/* Flush the tlb so the new mapping takes effect.
+	 * Global tlb entries are not flushed but that is not an issue.
+	 */
+	load_cr3(pgtable_level2);
+}
+
+#else
+#define LEVEL1_SIZE (1UL << 21UL)
+#define LEVEL2_SIZE (1UL << 30UL)
+static u64 pgtable_level1[512] PAGE_ALIGNED;
+static u64 pgtable_level2[512] PAGE_ALIGNED;
+
+static void identity_map_page(unsigned long address)
+{
+	unsigned long level1_index, level2_index, level3_index;
+	u64 *pgtable_level3;
+
+	/* Find the current page table */
+	pgtable_level3 = __va(read_cr3());
+
+	/* Find the indexes of the physical address to identity map */
+	level1_index = (address % LEVEL1_SIZE)/LEVEL0_SIZE;
+	level2_index = (address % LEVEL2_SIZE)/LEVEL1_SIZE;
+	level3_index = address / LEVEL2_SIZE;
+
+	/* Identity map the page table entry */
+	pgtable_level1[level1_index] = address | L0_ATTR;
+	pgtable_level2[level2_index] = __pa(pgtable_level1) | L1_ATTR;
+	set_64bit(&pgtable_level3[level3_index], __pa(pgtable_level2) | L2_ATTR);
+
+	/* Flush the tlb so the new mapping takes effect.
+	 * Global tlb entries are not flushed but that is not an issue.
+	 */
+	load_cr3(pgtable_level3);
+}
+#endif
+
+
+static void set_idt(void *newidt, __u16 limit)
+{
+	unsigned char curidt[6];
+
+	/* ia32 supports unaliged loads & stores */
+	(*(__u16 *)(curidt)) = limit;
+	(*(__u32 *)(curidt +2)) = (unsigned long)(newidt);
+
+	__asm__ __volatile__ (
+		"lidt %0\n"
+		: "=m" (curidt)
+		);
+};
+
+
+static void set_gdt(void *newgdt, __u16 limit)
+{
+	unsigned char curgdt[6];
+
+	/* ia32 supports unaligned loads & stores */
+	(*(__u16 *)(curgdt)) = limit;
+	(*(__u32 *)(curgdt +2)) = (unsigned long)(newgdt);
+
+	__asm__ __volatile__ (
+		"lgdt %0\n"
+		: "=m" (curgdt)
+		);
+};
+
+static void load_segments(void)
+{
+#define __STR(X) #X
+#define STR(X) __STR(X)
+
+	__asm__ __volatile__ (
+		"\tljmp $"STR(__KERNEL_CS)",$1f\n"
+		"\t1:\n"
+		"\tmovl $"STR(__KERNEL_DS)",%eax\n"
+		"\tmovl %eax,%ds\n"
+		"\tmovl %eax,%es\n"
+		"\tmovl %eax,%fs\n"
+		"\tmovl %eax,%gs\n"
+		"\tmovl %eax,%ss\n"
+		);
+#undef STR
+#undef __STR
+}
+
+typedef asmlinkage NORET_TYPE void (*relocate_new_kernel_t)(
+	unsigned long indirection_page, unsigned long reboot_code_buffer,
+	unsigned long start_address, unsigned int has_pae) ATTRIB_NORET;
+
+const extern unsigned char relocate_new_kernel[];
+extern void relocate_new_kernel_end(void);
+const extern unsigned int relocate_new_kernel_size;
+
+/*
+ * A architecture hook called to validate the
+ * proposed image and prepare the control pages
+ * as needed.  The pages for KEXEC_CONTROL_CODE_SIZE
+ * have been allocated, but the segments have yet
+ * been copied into the kernel.
+ *
+ * Do what every setup is needed on image and the
+ * reboot code buffer to allow us to avoid allocations
+ * later.
+ *
+ * Currently nothing.
+ */
+int machine_kexec_prepare(struct kimage *image)
+{
+	return 0;
+}
+
+/*
+ * Undo anything leftover by machine_kexec_prepare
+ * when an image is freed.
+ */
+void machine_kexec_cleanup(struct kimage *image)
+{
+}
+
+/*
+ * Do not allocate memory (or fail in any way) in machine_kexec().
+ * We are past the point of no return, committed to rebooting now.
+ */
+NORET_TYPE void machine_kexec(struct kimage *image)
+{
+	unsigned long page_list;
+	unsigned long reboot_code_buffer;
+	relocate_new_kernel_t rnk;
+
+	/* Interrupts aren't acceptable while we reboot */
+	local_irq_disable();
+
+	/* Compute some offsets */
+	reboot_code_buffer = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
+	page_list = image->head;
+
+	/* Set up an identity mapping for the reboot_code_buffer */
+	identity_map_page(reboot_code_buffer);
+
+	/* copy it out */
+	memcpy((void *)reboot_code_buffer, relocate_new_kernel, relocate_new_kernel_size);
+
+	/* The segment registers are funny things, they are
+	 * automatically loaded from a table, in memory wherever you
+	 * set them to a specific selector, but this table is never
+	 * accessed again you set the segment to a different selector.
+	 *
+	 * The more common model is are caches where the behide
+	 * the scenes work is done, but is also dropped at arbitrary
+	 * times.
+	 *
+	 * I take advantage of this here by force loading the
+	 * segments, before I zap the gdt with an invalid value.
+	 */
+	load_segments();
+	/* The gdt & idt are now invalid.
+	 * If you want to load them you must set up your own idt & gdt.
+	 */
+	set_gdt(phys_to_virt(0),0);
+	set_idt(phys_to_virt(0),0);
+
+	/* now call it */
+	rnk = (relocate_new_kernel_t) reboot_code_buffer;
+	(*rnk)(page_list, reboot_code_buffer, image->start, cpu_has_pae);
+}