[PATCH] kexec: x86_64 kexec implementation

This is the x86_64 implementation of machine kexec.  32bit compatibility
support has been implemented, and machine_kexec has been enhanced to not care
about the changing internal kernel paget table structures.

From: Alexander Nyberg <alexn@dsv.su.se>

      build fix

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

6 files changed, 445 insertions, 1 deletions

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 56c02cf6397d..d09437b5c48f 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -380,6 +380,23 @@ 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.
+
 config SECCOMP
         bool "Enable seccomp to safely compute untrusted bytecode"
         depends on PROC_FS
diff --git a/arch/x86_64/ia32/ia32entry.S b/arch/x86_64/ia32/ia32entry.S
index f3ca0db85b5b..cc935427d532 100644
--- a/arch/x86_64/ia32/ia32entry.S
+++ b/arch/x86_64/ia32/ia32entry.S
@@ -589,7 +589,7 @@ ia32_sys_call_table:
         .quad compat_sys_mq_timedreceive        /* 280 */
         .quad compat_sys_mq_notify
         .quad compat_sys_mq_getsetattr
-        .quad quiet_ni_syscall          /* reserved for kexec */
+        .quad compat_sys_kexec_load     /* reserved for kexec */
         .quad compat_sys_waitid
         .quad quiet_ni_syscall          /* sys_altroot */
         .quad sys_add_key
diff --git a/arch/x86_64/kernel/Makefile b/arch/x86_64/kernel/Makefile
index 5ca4a4598fda..48f9e2c19cd6 100644
--- a/arch/x86_64/kernel/Makefile
+++ b/arch/x86_64/kernel/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_SMP)		+= smp.o smpboot.o trampoline.o
 obj-$(CONFIG_X86_LOCAL_APIC)    += apic.o  nmi.o
 obj-$(CONFIG_X86_IO_APIC)       += io_apic.o mpparse.o \
                 genapic.o genapic_cluster.o genapic_flat.o
+obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o crash.o
 obj-$(CONFIG_PM)                += suspend.o
 obj-$(CONFIG_SOFTWARE_SUSPEND)  += suspend_asm.o
 obj-$(CONFIG_CPU_FREQ)          += cpufreq/
diff --git a/arch/x86_64/kernel/crash.c b/arch/x86_64/kernel/crash.c
new file mode 100644
index 000000000000..7caf8a49d0cb
--- /dev/null
+++ b/arch/x86_64/kernel/crash.c
@@ -0,0 +1,38 @@
+/*
+ * Architecture specific (x86_64) 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 <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.
+         */
+}
diff --git a/arch/x86_64/kernel/machine_kexec.c b/arch/x86_64/kernel/machine_kexec.c
new file mode 100644
index 000000000000..200b5993f8d9
--- /dev/null
+++ b/arch/x86_64/kernel/machine_kexec.c
@@ -0,0 +1,245 @@
+/*
+ * 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 <linux/string.h>
+#include <linux/reboot.h>
+#include <asm/pda.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>
+#include <asm/hw_irq.h>
+
+#define LEVEL0_SIZE (1UL << 12UL)
+#define LEVEL1_SIZE (1UL << 21UL)
+#define LEVEL2_SIZE (1UL << 30UL)
+#define LEVEL3_SIZE (1UL << 39UL)
+#define LEVEL4_SIZE (1UL << 48UL)
+
+#define L0_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
+#define L1_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_PSE)
+#define L2_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
+#define L3_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
+
+static void init_level2_page(
+        u64 *level2p, unsigned long addr)
+{
+        unsigned long end_addr;
+        addr &= PAGE_MASK;
+        end_addr = addr + LEVEL2_SIZE;
+        while(addr < end_addr) {
+                *(level2p++) = addr | L1_ATTR;
+                addr += LEVEL1_SIZE;
+        }
+}
+
+static int init_level3_page(struct kimage *image,
+        u64 *level3p, unsigned long addr, unsigned long last_addr)
+{
+        unsigned long end_addr;
+        int result;
+        result = 0;
+        addr &= PAGE_MASK;
+        end_addr = addr + LEVEL3_SIZE;
+        while((addr < last_addr) && (addr < end_addr)) {
+                struct page *page;
+                u64 *level2p;
+                page = kimage_alloc_control_pages(image, 0);
+                if (!page) {
+                        result = -ENOMEM;
+                        goto out;
+                }
+                level2p = (u64 *)page_address(page);
+                init_level2_page(level2p, addr);
+                *(level3p++) = __pa(level2p) | L2_ATTR;
+                addr += LEVEL2_SIZE;
+        }
+        /* clear the unused entries */
+        while(addr < end_addr) {
+                *(level3p++) = 0;
+                addr += LEVEL2_SIZE;
+        }
+out:
+        return result;
+}
+
+
+static int init_level4_page(struct kimage *image,
+        u64 *level4p, unsigned long addr, unsigned long last_addr)
+{
+        unsigned long end_addr;
+        int result;
+        result = 0;
+        addr &= PAGE_MASK;
+        end_addr = addr + LEVEL4_SIZE;
+        while((addr < last_addr) && (addr < end_addr)) {
+                struct page *page;
+                u64 *level3p;
+                page = kimage_alloc_control_pages(image, 0);
+                if (!page) {
+                        result = -ENOMEM;
+                        goto out;
+                }
+                level3p = (u64 *)page_address(page);
+                result = init_level3_page(image, level3p, addr, last_addr);
+                if (result) {
+                        goto out;
+                }
+                *(level4p++) = __pa(level3p) | L3_ATTR;
+                addr += LEVEL3_SIZE;
+        }
+        /* clear the unused entries */
+        while(addr < end_addr) {
+                *(level4p++) = 0;
+                addr += LEVEL3_SIZE;
+        }
+ out:
+        return result;
+}
+
+
+static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
+{
+        u64 *level4p;
+        level4p = (u64 *)__va(start_pgtable);
+        return init_level4_page(image, level4p, 0, end_pfn << PAGE_SHIFT);
+}
+
+static void set_idt(void *newidt, u16 limit)
+{
+        unsigned char curidt[10];
+
+        /* x86-64 supports unaliged loads & stores */
+        (*(u16 *)(curidt)) = limit;
+        (*(u64 *)(curidt +2)) = (unsigned long)(newidt);
+
+        __asm__ __volatile__ (
+                "lidt %0\n"
+                : "=m" (curidt)
+                );
+};
+
+
+static void set_gdt(void *newgdt, u16 limit)
+{
+        unsigned char curgdt[10];
+
+        /* x86-64 supports unaligned loads & stores */
+        (*(u16 *)(curgdt)) = limit;
+        (*(u64 *)(curgdt +2)) = (unsigned long)(newgdt);
+
+        __asm__ __volatile__ (
+                "lgdt %0\n"
+                : "=m" (curgdt)
+                );
+};
+
+static void load_segments(void)
+{
+        __asm__ __volatile__ (
+                "\tmovl $"STR(__KERNEL_DS)",%eax\n"
+                "\tmovl %eax,%ds\n"
+                "\tmovl %eax,%es\n"
+                "\tmovl %eax,%ss\n"
+                "\tmovl %eax,%fs\n"
+                "\tmovl %eax,%gs\n"
+                );
+#undef STR
+#undef __STR
+}
+
+typedef NORET_TYPE void (*relocate_new_kernel_t)(
+        unsigned long indirection_page, unsigned long control_code_buffer,
+        unsigned long start_address, unsigned long pgtable) ATTRIB_NORET;
+
+const extern unsigned char relocate_new_kernel[];
+const extern unsigned long relocate_new_kernel_size;
+
+int machine_kexec_prepare(struct kimage *image)
+{
+        unsigned long start_pgtable, control_code_buffer;
+        int result;
+
+        /* Calculate the offsets */
+        start_pgtable       = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
+        control_code_buffer = start_pgtable + 4096UL;
+
+        /* Setup the identity mapped 64bit page table */
+        result = init_pgtable(image, start_pgtable);
+        if (result) {
+                return result;
+        }
+
+        /* Place the code in the reboot code buffer */
+        memcpy(__va(control_code_buffer), relocate_new_kernel, relocate_new_kernel_size);
+
+        return 0;
+}
+
+void machine_kexec_cleanup(struct kimage *image)
+{
+        return;
+}
+
+/*
+ * 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 control_code_buffer;
+        unsigned long start_pgtable;
+        relocate_new_kernel_t rnk;
+
+        /* Interrupts aren't acceptable while we reboot */
+        local_irq_disable();
+
+        /* Calculate the offsets */
+        page_list           = image->head;
+        start_pgtable       = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
+        control_code_buffer = start_pgtable + 4096UL;
+
+        /* Set the low half of the page table to my identity mapped
+         * page table for kexec.  Leave the high half pointing at the
+         * kernel pages.   Don't bother to flush the global pages
+         * as that will happen when I fully switch to my identity mapped
+         * page table anyway.
+         */
+        memcpy(__va(read_cr3()), __va(start_pgtable), PAGE_SIZE/2);
+        __flush_tlb();
+
+
+        /* 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 unless you set the segment to a different selector.
+         *
+         * The more common model 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) control_code_buffer;
+        (*rnk)(page_list, control_code_buffer, image->start, start_pgtable);
+}
diff --git a/arch/x86_64/kernel/relocate_kernel.S b/arch/x86_64/kernel/relocate_kernel.S
new file mode 100644
index 000000000000..d24fa9b72a2b
--- /dev/null
+++ b/arch/x86_64/kernel/relocate_kernel.S
@@ -0,0 +1,143 @@
+/*
+ * relocate_kernel.S - put the kernel image in place to boot
+ * 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/linkage.h>
+
+        /*
+         * Must be relocatable PIC code callable as a C function, that once
+         * it starts can not use the previous processes stack.
+         */
+        .globl relocate_new_kernel
+        .code64
+relocate_new_kernel:
+        /* %rdi page_list
+         * %rsi reboot_code_buffer
+         * %rdx start address
+         * %rcx page_table
+         * %r8  arg5
+         * %r9  arg6
+         */
+
+        /* zero out flags, and disable interrupts */
+        pushq $0
+        popfq
+
+        /* set a new stack at the bottom of our page... */
+        lea   4096(%rsi), %rsp
+
+        /* store the parameters back on the stack */
+        pushq   %rdx /* store the start address */
+
+        /* Set cr0 to a known state:
+         * 31 1 == Paging enabled
+         * 18 0 == Alignment check disabled
+         * 16 0 == Write protect disabled
+         * 3  0 == No task switch
+         * 2  0 == Don't do FP software emulation.
+         * 0  1 == Proctected mode enabled
+         */
+        movq    %cr0, %rax
+        andq    $~((1<<18)|(1<<16)|(1<<3)|(1<<2)), %rax
+        orl     $((1<<31)|(1<<0)), %eax
+        movq    %rax, %cr0
+
+        /* Set cr4 to a known state:
+         * 10 0 == xmm exceptions disabled
+         * 9  0 == xmm registers instructions disabled
+         * 8  0 == performance monitoring counter disabled
+         * 7  0 == page global disabled
+         * 6  0 == machine check exceptions disabled
+         * 5  1 == physical address extension enabled
+         * 4  0 == page size extensions disabled
+         * 3  0 == Debug extensions disabled
+         * 2  0 == Time stamp disable (disabled)
+         * 1  0 == Protected mode virtual interrupts disabled
+         * 0  0 == VME disabled
+         */
+
+        movq    $((1<<5)), %rax
+        movq    %rax, %cr4
+
+        jmp 1f
+1:
+
+        /* Switch to the identity mapped page tables,
+         * and flush the TLB.
+        */
+        movq    %rcx, %cr3
+
+        /* Do the copies */
+        movq    %rdi, %rcx      /* Put the page_list in %rcx */
+        xorq    %rdi, %rdi
+        xorq    %rsi, %rsi
+        jmp     1f
+
+0:      /* top, read another word for the indirection page */
+
+        movq    (%rbx), %rcx
+        addq    $8,     %rbx
+1:
+        testq   $0x1,   %rcx  /* is it a destination page? */
+        jz      2f
+        movq    %rcx,   %rdi
+        andq    $0xfffffffffffff000, %rdi
+        jmp     0b
+2:
+        testq   $0x2,   %rcx  /* is it an indirection page? */
+        jz      2f
+        movq    %rcx,   %rbx
+        andq    $0xfffffffffffff000, %rbx
+        jmp     0b
+2:
+        testq   $0x4,   %rcx  /* is it the done indicator? */
+        jz      2f
+        jmp     3f
+2:
+        testq   $0x8,   %rcx  /* is it the source indicator? */
+        jz      0b            /* Ignore it otherwise */
+        movq    %rcx,   %rsi  /* For ever source page do a copy */
+        andq    $0xfffffffffffff000, %rsi
+
+        movq    $512,   %rcx
+        rep ; movsq
+        jmp     0b
+3:
+
+        /* To be certain of avoiding problems with self-modifying code
+         * I need to execute a serializing instruction here.
+         * So I flush the TLB by reloading %cr3 here, it's handy,
+         * and not processor dependent.
+         */
+        movq    %cr3, %rax
+        movq    %rax, %cr3
+
+        /* set all of the registers to known values */
+        /* leave %rsp alone */
+
+        xorq    %rax, %rax
+        xorq    %rbx, %rbx
+        xorq    %rcx, %rcx
+        xorq    %rdx, %rdx
+        xorq    %rsi, %rsi
+        xorq    %rdi, %rdi
+        xorq    %rbp, %rbp
+        xorq    %r8,  %r8
+        xorq    %r9,  %r9
+        xorq    %r10, %r9
+        xorq    %r11, %r11
+        xorq    %r12, %r12
+        xorq    %r13, %r13
+        xorq    %r14, %r14
+        xorq    %r15, %r15
+
+        ret
+relocate_new_kernel_end:
+
+        .globl relocate_new_kernel_size
+relocate_new_kernel_size:
+        .quad relocate_new_kernel_end - relocate_new_kernel