Re: [PATCH][2/6]Memory preserving reboot using kexec
From: Hariprasad Nellitheertha
Date: Wed Sep 15 2004 - 08:03:47 EST
Regards, Hari
--
Hariprasad Nellitheertha
Linux Technology Center
India Software Labs
IBM India, Bangalore
This patch contains the code that does the memory preserving reboot. It
copies over the first 640k into a backup region before handing over to
kexec. The second kernel will boot using only the backup region.
Signed off by Hariprasad Nellitheertha <hari@xxxxxxxxxx>
Signed off by Adam Litke <litke@xxxxxxxxxx>
---
linux-2.6.9-rc1-hari/arch/i386/Kconfig | 20 ++++++++
linux-2.6.9-rc1-hari/arch/i386/kernel/machine_kexec.c | 31 ++++++++++++
linux-2.6.9-rc1-hari/arch/i386/kernel/setup.c | 13 +++++
linux-2.6.9-rc1-hari/fs/proc/proc_misc.c | 25 ++++++++++
linux-2.6.9-rc1-hari/include/asm-i386/crash_dump.h | 44 ++++++++++++++++++
linux-2.6.9-rc1-hari/include/linux/bootmem.h | 1
linux-2.6.9-rc1-hari/include/linux/crash_dump.h | 28 +++++++++++
linux-2.6.9-rc1-hari/kernel/panic.c | 7 ++
linux-2.6.9-rc1-hari/mm/bootmem.c | 5 ++
9 files changed, 174 insertions(+)
diff -puN arch/i386/Kconfig~kd-reb-269rc1-mm5 arch/i386/Kconfig
--- linux-2.6.9-rc1/arch/i386/Kconfig~kd-reb-269rc1-mm5 2004-09-15 17:36:30.000000000 +0530
+++ linux-2.6.9-rc1-hari/arch/i386/Kconfig 2004-09-15 17:36:30.000000000 +0530
@@ -894,6 +894,26 @@ config KEXEC
support. As of this writing the exact hardware interface is
strongly in flux, so no good recommendation can be made.
+config CRASH_DUMP
+ bool "kernel crash dumps (EXPERIMENTAL)"
+ depends on KEXEC
+ help
+ Generate crash dump using kexec.
+
+config BACKUP_BASE
+ int "location of the crash dumps backup region"
+ depends on CRASH_DUMP
+ default 16
+ help
+ This is the location where the second kernel will boot from.
+
+config BACKUP_SIZE
+ int "Size of the crash dumps backup region"
+ depends on CRASH_DUMP
+ range 16 64
+ default 32
+ help
+ The size of the second kernel's memory.
endmenu
diff -puN arch/i386/kernel/setup.c~kd-reb-269rc1-mm5 arch/i386/kernel/setup.c
--- linux-2.6.9-rc1/arch/i386/kernel/setup.c~kd-reb-269rc1-mm5 2004-09-15 17:36:30.000000000 +0530
+++ linux-2.6.9-rc1-hari/arch/i386/kernel/setup.c 2004-09-15 17:36:30.000000000 +0530
@@ -39,6 +39,7 @@
#include <linux/efi.h>
#include <linux/init.h>
#include <linux/edd.h>
+#include <linux/crash_dump.h>
#include <video/edid.h>
#include <asm/e820.h>
#include <asm/mpspec.h>
@@ -57,6 +58,7 @@
unsigned long init_pg_tables_end __initdata = ~0UL;
int disable_pse __initdata = 0;
+unsigned int dump_enabled;
/*
* Machine setup..
@@ -708,6 +710,11 @@ static void __init parse_cmdline_early (
if (to != command_line)
to--;
if (!memcmp(from+7, "exactmap", 8)) {
+ /* If we are doing a crash dump, we
+ * still need to know the real mem
+ * size.
+ */
+ set_saved_max_pfn();
from += 8+7;
e820.nr_map = 0;
userdef = 1;
@@ -815,6 +822,9 @@ static void __init parse_cmdline_early (
if (c == ' ' && !memcmp(from, "highmem=", 8))
highmem_pages = memparse(from+8, &from) >> PAGE_SHIFT;
+ if (!memcmp(from, "dump", 4))
+ dump_enabled = 1;
+
c = *(from++);
if (!c)
break;
@@ -1102,6 +1112,9 @@ static unsigned long __init setup_memory
}
}
#endif
+
+ crash_reserve_bootmem();
+
return max_low_pfn;
}
#else
diff -puN /dev/null include/asm-i386/crash_dump.h
--- /dev/null 2003-01-30 15:54:37.000000000 +0530
+++ linux-2.6.9-rc1-hari/include/asm-i386/crash_dump.h 2004-09-15 17:36:30.000000000 +0530
@@ -0,0 +1,44 @@
+/* asm-i386/crash_dump.h */
+#include <linux/bootmem.h>
+
+extern unsigned int dump_enabled;
+
+void __crash_relocate_mem(unsigned long, unsigned long);
+unsigned long __init find_max_low_pfn(void);
+void __init find_max_pfn(void);
+
+extern unsigned int crashed;
+
+#ifdef CONFIG_CRASH_DUMP
+#define CRASH_BACKUP_BASE ((unsigned long)CONFIG_BACKUP_BASE * 0x100000)
+#define CRASH_BACKUP_SIZE ((unsigned long)CONFIG_BACKUP_SIZE * 0x100000)
+#define CRASH_RELOCATE_SIZE 0xa0000
+
+static inline void crash_relocate_mem(void)
+{
+ if (crashed)
+ __crash_relocate_mem(CRASH_BACKUP_BASE + CRASH_BACKUP_SIZE,
+ CRASH_RELOCATE_SIZE);
+}
+
+static inline void set_saved_max_pfn(void)
+{
+ find_max_pfn();
+ saved_max_pfn = find_max_low_pfn();
+}
+
+static inline void crash_reserve_bootmem(void)
+{
+ if (!dump_enabled) {
+ reserve_bootmem(0, CRASH_RELOCATE_SIZE);
+ reserve_bootmem(CRASH_BACKUP_BASE,
+ CRASH_BACKUP_SIZE + CRASH_RELOCATE_SIZE);
+ }
+}
+#else
+#define CRASH_BACKUP_BASE 0x6000000
+#define CRASH_BACKUP_SIZE 0x1000000
+#define crash_relocate_mem() do { } while(0)
+#define set_saved_max_pfn() do { } while(0)
+#define crash_reserve_bootmem() do { } while(0)
+#endif
diff -puN include/linux/bootmem.h~kd-reb-269rc1-mm5 include/linux/bootmem.h
--- linux-2.6.9-rc1/include/linux/bootmem.h~kd-reb-269rc1-mm5 2004-09-15 17:36:30.000000000 +0530
+++ linux-2.6.9-rc1-hari/include/linux/bootmem.h 2004-09-15 17:36:30.000000000 +0530
@@ -21,6 +21,7 @@ extern unsigned long min_low_pfn;
* highest page
*/
extern unsigned long max_pfn;
+extern unsigned long saved_max_pfn;
/*
* node_bootmem_map is a map pointer - the bits represent all physical
diff -puN /dev/null include/linux/crash_dump.h
--- /dev/null 2003-01-30 15:54:37.000000000 +0530
+++ linux-2.6.9-rc1-hari/include/linux/crash_dump.h 2004-09-15 17:36:30.000000000 +0530
@@ -0,0 +1,28 @@
+#include <linux/kexec.h>
+#include <linux/smp_lock.h>
+#include <linux/device.h>
+#include <asm/crash_dump.h>
+
+#ifdef CONFIG_CRASH_DUMP
+extern int crash_dump_on;
+static inline void crash_machine_kexec(void)
+{
+ struct kimage *image;
+
+ if ((!crash_dump_on) || (crashed))
+ return;
+
+ image = xchg(&kexec_image, 0);
+ if (image) {
+ crashed = 1;
+ device_shutdown();
+ printk(KERN_EMERG "kexec: opening parachute\n");
+ machine_kexec(image);
+ while (1);
+ } else {
+ printk(KERN_EMERG "kexec: No kernel image loaded!\n");
+ }
+}
+#else
+#define crash_machine_kexec() do { } while(0)
+#endif
diff -puN kernel/panic.c~kd-reb-269rc1-mm5 kernel/panic.c
--- linux-2.6.9-rc1/kernel/panic.c~kd-reb-269rc1-mm5 2004-09-15 17:36:30.000000000 +0530
+++ linux-2.6.9-rc1-hari/kernel/panic.c 2004-09-15 17:36:30.000000000 +0530
@@ -19,10 +19,14 @@
#include <linux/syscalls.h>
#include <linux/interrupt.h>
#include <linux/nmi.h>
+#include <linux/kexec.h>
+#include <linux/crash_dump.h>
int panic_timeout;
int panic_on_oops;
int tainted;
+unsigned int crashed;
+int crash_dump_on;
EXPORT_SYMBOL(panic_timeout);
@@ -62,6 +66,9 @@ NORET_TYPE void panic(const char * fmt,
printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
bust_spinlocks(0);
+ /* If we have crashed, perform a kexec reboot, for dump write-out */
+ crash_machine_kexec();
+
#ifdef CONFIG_SMP
smp_send_stop();
#endif
diff -puN mm/bootmem.c~kd-reb-269rc1-mm5 mm/bootmem.c
--- linux-2.6.9-rc1/mm/bootmem.c~kd-reb-269rc1-mm5 2004-09-15 17:36:30.000000000 +0530
+++ linux-2.6.9-rc1-hari/mm/bootmem.c 2004-09-15 17:36:30.000000000 +0530
@@ -27,6 +27,11 @@
unsigned long max_low_pfn;
unsigned long min_low_pfn;
unsigned long max_pfn;
+/*
+ * If we have booted due to a crash, max_pfn will be a very low value. We need
+ * to know the amount of memory that the previous kernel used.
+ */
+unsigned long saved_max_pfn;
EXPORT_SYMBOL(max_pfn); /* This is exported so
* dma_get_required_mask(), which uses
diff -puN fs/proc/proc_misc.c~kd-reb-269rc1-mm5 fs/proc/proc_misc.c
--- linux-2.6.9-rc1/fs/proc/proc_misc.c~kd-reb-269rc1-mm5 2004-09-15 17:36:30.000000000 +0530
+++ linux-2.6.9-rc1-hari/fs/proc/proc_misc.c 2004-09-15 17:36:30.000000000 +0530
@@ -44,6 +44,7 @@
#include <linux/jiffies.h>
#include <linux/sysrq.h>
#include <linux/vmalloc.h>
+#include <linux/crash_dump.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/io.h>
@@ -563,6 +564,25 @@ static struct file_operations proc_sysrq
};
#endif
+#ifdef CONFIG_CRASH_DUMP
+/*
+ * Enable kexec reboot upon panic; for dumping
+ */
+static ssize_t write_crash_dump_on(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ if (count) {
+ if (get_user(crash_dump_on, buf))
+ return -EFAULT;
+ }
+ return count;
+}
+
+static struct file_operations proc_crash_dump_on_operations = {
+ .write = write_crash_dump_on,
+};
+#endif
+
struct proc_dir_entry *proc_root_kcore;
static void create_seq_entry(char *name, mode_t mode, struct file_operations *f)
@@ -663,6 +683,11 @@ void __init proc_misc_init(void)
if (entry)
entry->proc_fops = &proc_sysrq_trigger_operations;
#endif
+#ifdef CONFIG_CRASH_DUMP
+ entry = create_proc_entry("kexec-dump", S_IWUSR, NULL);
+ if (entry)
+ entry->proc_fops = &proc_crash_dump_on_operations;
+#endif
#ifdef CONFIG_LOCKMETER
entry = create_proc_entry("lockmeter", S_IWUSR | S_IRUGO, NULL);
if (entry) {
diff -puN arch/i386/kernel/machine_kexec.c~kd-reb-269rc1-mm5 arch/i386/kernel/machine_kexec.c
--- linux-2.6.9-rc1/arch/i386/kernel/machine_kexec.c~kd-reb-269rc1-mm5 2004-09-15 17:36:30.000000000 +0530
+++ linux-2.6.9-rc1-hari/arch/i386/kernel/machine_kexec.c 2004-09-15 17:36:30.000000000 +0530
@@ -161,6 +161,30 @@ void machine_kexec_cleanup(struct kimage
}
/*
+ * We are going to do a memory preserving reboot. So, we copy over the
+ * first 640k of memory into a backup location. Though the second kernel
+ * boots from a different location, it still requires the first 640k.
+ * Hence this backup.
+ */
+void __crash_relocate_mem(unsigned long backup_addr, unsigned long backup_size)
+{
+ unsigned long pfn, pfn_max;
+ void *src_addr, *dest_addr;
+ struct page *page;
+
+ pfn_max = backup_size >> PAGE_SHIFT;
+ for (pfn = 0; pfn < pfn_max; pfn++) {
+ src_addr = phys_to_virt(pfn << PAGE_SHIFT);
+ dest_addr = backup_addr + src_addr;
+ if (!pfn_valid(pfn))
+ continue;
+ page = pfn_to_page(pfn);
+ if (PageReserved(page))
+ copy_page(dest_addr, src_addr);
+ }
+}
+
+/*
* Do not allocate memory (or fail in any way) in machine_kexec().
* We are past the point of no return, committed to rebooting now.
*/
@@ -180,6 +204,13 @@ void machine_kexec(struct kimage *image)
/* Set up an identity mapping for the reboot_code_buffer */
identity_map_page(reboot_code_buffer);
+ /*
+ * If we are here to do a crash dump, save the memory from
+ * 0-640k before we copy over the kexec kernel image. Otherwise
+ * our dump will show the wrong kernel entirely.
+ */
+ crash_relocate_mem();
+
/* copy it out */
memcpy((void *)reboot_code_buffer, relocate_new_kernel, relocate_new_kernel_size);
_