Re: [PATCH][2/6]Memory preserving reboot using kexec
From: Hariprasad Nellitheertha
Date: Tue Aug 17 2004 - 07:17:22 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 CRASH_BACKUP_SIZE amount of memory into a backup
region before handing over to kexec.
Signed off by Hariprasad Nellitheertha <hari@xxxxxxxxxx>
Signed off by Adam Litke <litke@xxxxxxxxxx>
---
linux-2.6.8.1-hari/arch/i386/Kconfig | 22 +++++++++++
linux-2.6.8.1-hari/arch/i386/kernel/machine_kexec.c | 31 +++++++++++++++
linux-2.6.8.1-hari/arch/i386/kernel/setup.c | 11 +++++
linux-2.6.8.1-hari/include/asm-i386/crash_dump.h | 39 ++++++++++++++++++++
linux-2.6.8.1-hari/include/linux/bootmem.h | 1
linux-2.6.8.1-hari/include/linux/crash_dump.h | 27 +++++++++++++
linux-2.6.8.1-hari/kernel/panic.c | 6 +++
linux-2.6.8.1-hari/mm/bootmem.c | 5 ++
8 files changed, 142 insertions(+)
diff -puN arch/i386/Kconfig~kd-reb-268 arch/i386/Kconfig
--- linux-2.6.8.1/arch/i386/Kconfig~kd-reb-268 2004-08-17 17:04:35.000000000 +0530
+++ linux-2.6.8.1-hari/arch/i386/Kconfig 2004-08-17 17:05:03.000000000 +0530
@@ -865,6 +865,28 @@ config REGPARM
generate incorrect output with certain kernel constructs when
-mregparm=3 is used.
+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 128
+ help
+ Offset of backup region in terms of MB. Change this if you want
+ to modify the location of the crash dumps backup region.
+
+config BACKUP_SIZE
+ int "Size of the crash dumps backup region"
+ depends on CRASH_DUMP
+ range 16 64
+ default 16
+ help
+ The size of the backup region, in MB. This is also the size of the
+ memory that will be used to boot the second kernel after a crash.
endmenu
diff -puN arch/i386/kernel/machine_kexec.c~kd-reb-268 arch/i386/kernel/machine_kexec.c
--- linux-2.6.8.1/arch/i386/kernel/machine_kexec.c~kd-reb-268 2004-08-17 17:04:35.000000000 +0530
+++ linux-2.6.8.1-hari/arch/i386/kernel/machine_kexec.c 2004-08-17 17:05:03.000000000 +0530
@@ -9,6 +9,7 @@
#include <linux/mm.h>
#include <linux/kexec.h>
#include <linux/delay.h>
+#include <linux/crash_dump.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
@@ -16,6 +17,7 @@
#include <asm/io.h>
#include <asm/apic.h>
#include <asm/cpufeature.h>
+#include <asm/hw_irq.h>
static void set_idt(void *newidt, __u16 limit)
@@ -76,6 +78,28 @@ const extern unsigned int relocate_new_k
extern void use_mm(struct mm_struct *mm);
/*
+ * We are going to do a memory preserving reboot. So, we copy over the
+ * first xxMB of memory into a backup location.
+ */
+void __relocate_base_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.
*/
@@ -94,6 +118,13 @@ void machine_kexec(struct kimage *image)
reboot_code_buffer = page_to_pfn(image->reboot_code_pages) << PAGE_SHIFT;
indirection_page = image->head & PAGE_MASK;
+ /*
+ * If we are here to do a crash dump, save the memory from
+ * 0-16MB before we copy over the kexec kernel image. Otherwise
+ * our dump will show the wrong kernel entirely.
+ */
+ relocate_base_mem();
+
/* copy it out */
memcpy((void *)reboot_code_buffer, relocate_new_kernel, relocate_new_kernel_size);
diff -puN arch/i386/kernel/setup.c~kd-reb-268 arch/i386/kernel/setup.c
--- linux-2.6.8.1/arch/i386/kernel/setup.c~kd-reb-268 2004-08-17 17:04:35.000000000 +0530
+++ linux-2.6.8.1-hari/arch/i386/kernel/setup.c 2004-08-17 17:05:03.000000000 +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>
@@ -56,6 +57,7 @@
unsigned long init_pg_tables_end __initdata = ~0UL;
int disable_pse __initdata = 0;
+unsigned int dump_enabled;
/*
* Machine setup..
@@ -347,6 +349,9 @@ static void __init limit_regions(unsigne
}
}
}
+ /* If we are doing a crash dump, we still need to know the real mem size*/
+ set_saved_max_pfn();
+
for (i = 0; i < e820.nr_map; i++) {
if (e820.map[i].type == E820_RAM) {
current_addr = e820.map[i].addr + e820.map[i].size;
@@ -809,6 +814,9 @@ 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;
@@ -1082,6 +1090,9 @@ 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-2.6.8.1-hari/include/asm-i386/crash_dump.h 2004-08-17 17:05:03.000000000 +0530
@@ -0,0 +1,39 @@
+/* asm-i386/crash_dump.h */
+#include <linux/bootmem.h>
+
+extern unsigned int dump_enabled;
+
+unsigned long __init find_max_low_pfn(void);
+void __init find_max_pfn(void);
+void __relocate_base_mem(unsigned long, unsigned long);
+
+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)
+
+static inline void relocate_base_mem(void)
+{
+ if (crashed)
+ __relocate_base_mem(CRASH_BACKUP_BASE, CRASH_BACKUP_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(CRASH_BACKUP_BASE, CRASH_BACKUP_SIZE);
+}
+#else
+#define CRASH_BACKUP_BASE 0x08000000
+#define CRASH_BACKUP_SIZE 0x01000000
+static inline void relocate_base_mem(void) {}
+static inline void set_saved_max_pfn(void) {}
+static inline void crash_reserve_bootmem(void) {}
+#endif
diff -puN include/linux/bootmem.h~kd-reb-268 include/linux/bootmem.h
--- linux-2.6.8.1/include/linux/bootmem.h~kd-reb-268 2004-08-17 17:04:36.000000000 +0530
+++ linux-2.6.8.1-hari/include/linux/bootmem.h 2004-08-17 17:05:03.000000000 +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-2.6.8.1-hari/include/linux/crash_dump.h 2004-08-17 17:05:03.000000000 +0530
@@ -0,0 +1,27 @@
+#include <linux/kexec.h>
+#include <linux/smp_lock.h>
+#include <linux/device.h>
+#include <asm/crash_dump.h>
+
+#ifdef CONFIG_CRASH_DUMP
+static inline void crash_machine_kexec(void)
+{
+ struct kimage *image;
+
+ if (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
+static inline void crash_machine_kexec(void) {}
+#endif
diff -puN kernel/panic.c~kd-reb-268 kernel/panic.c
--- linux-2.6.8.1/kernel/panic.c~kd-reb-268 2004-08-17 17:04:36.000000000 +0530
+++ linux-2.6.8.1-hari/kernel/panic.c 2004-08-17 17:05:03.000000000 +0530
@@ -19,10 +19,13 @@
#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;
EXPORT_SYMBOL(panic_timeout);
@@ -68,6 +71,9 @@ NORET_TYPE void panic(const char * fmt,
sys_sync();
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-268 mm/bootmem.c
--- linux-2.6.8.1/mm/bootmem.c~kd-reb-268 2004-08-17 17:04:36.000000000 +0530
+++ linux-2.6.8.1-hari/mm/bootmem.c 2004-08-17 17:05:03.000000000 +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
_