[PATCH] kexec: add kexec syscalls

This patch introduces the architecture independent implementation the
sys_kexec_load, the compat_sys_kexec_load system calls.

Kexec on panic support has been integrated into the core patch and is
relatively clean.

In addition the hopefully architecture independent option
crashkernel=size@location has been docuemented.  It's purpose is to reserve
space for the panic kernel to live, and where no DMA transfer will ever be
setup to access.
Signed-off-by: NEric Biederman <ebiederm@xmission.com>
Signed-off-by: NAlexander Nyberg <alexn@telia.com>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Documentation/kernel-parameters.txt

@@ -358,6 +358,10 @@ running once the system is up.
 	cpia_pp=	[HW,PPT]
 			Format: { parport<nr> | auto | none }
 
+	crashkernel=nn[KMG]@ss[KMG]
+			[KNL] Reserve a chunk of physical memory to
+			hold a kernel to switch to with kexec on panic.
+
 	cs4232=		[HW,OSS]
 			Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
 

MAINTAINERS

@@ -1330,6 +1330,16 @@ M:	rml@novell.com
 L:	linux-kernel@vger.kernel.org
 S:	Maintained
 
+KEXEC
+P:	Eric Biederman
+P:	Randy Dunlap
+M:	ebiederm@xmission.com
+M:	rddunlap@osdl.org
+W:	http://www.xmission.com/~ebiederm/files/kexec/
+L:	linux-kernel@vger.kernel.org
+L:	fastboot@osdl.org
+S:	Maintained
+
 LANMEDIA WAN CARD DRIVER
 P:	Andrew Stanley-Jones
 M:	asj@lanmedia.com

include/linux/kexec.h

+#ifndef LINUX_KEXEC_H
+#define LINUX_KEXEC_H
+
+#ifdef CONFIG_KEXEC
+#include <linux/types.h>
+#include <linux/list.h>
+#include <linux/linkage.h>
+#include <linux/compat.h>
+#include <asm/kexec.h>
+
+/* Verify architecture specific macros are defined */
+
+#ifndef KEXEC_SOURCE_MEMORY_LIMIT
+#error KEXEC_SOURCE_MEMORY_LIMIT not defined
+#endif
+
+#ifndef KEXEC_DESTINATION_MEMORY_LIMIT
+#error KEXEC_DESTINATION_MEMORY_LIMIT not defined
+#endif
+
+#ifndef KEXEC_CONTROL_MEMORY_LIMIT
+#error KEXEC_CONTROL_MEMORY_LIMIT not defined
+#endif
+
+#ifndef KEXEC_CONTROL_CODE_SIZE
+#error KEXEC_CONTROL_CODE_SIZE not defined
+#endif
+
+#ifndef KEXEC_ARCH
+#error KEXEC_ARCH not defined
+#endif
+
+/*
+ * This structure is used to hold the arguments that are used when loading
+ * kernel binaries.
+ */
+
+typedef unsigned long kimage_entry_t;
+#define IND_DESTINATION  0x1
+#define IND_INDIRECTION  0x2
+#define IND_DONE         0x4
+#define IND_SOURCE       0x8
+
+#define KEXEC_SEGMENT_MAX 8
+struct kexec_segment {
+	void __user *buf;
+	size_t bufsz;
+	unsigned long mem;	/* User space sees this as a (void *) ... */
+	size_t memsz;
+};
+
+#ifdef CONFIG_COMPAT
+struct compat_kexec_segment {
+	compat_uptr_t buf;
+	compat_size_t bufsz;
+	compat_ulong_t mem;	/* User space sees this as a (void *) ... */
+	compat_size_t memsz;
+};
+#endif
+
+struct kimage {
+	kimage_entry_t head;
+	kimage_entry_t *entry;
+	kimage_entry_t *last_entry;
+
+	unsigned long destination;
+
+	unsigned long start;
+	struct page *control_code_page;
+
+	unsigned long nr_segments;
+	struct kexec_segment segment[KEXEC_SEGMENT_MAX];
+
+	struct list_head control_pages;
+	struct list_head dest_pages;
+	struct list_head unuseable_pages;
+
+	/* Address of next control page to allocate for crash kernels. */
+	unsigned long control_page;
+
+	/* Flags to indicate special processing */
+	unsigned int type : 1;
+#define KEXEC_TYPE_DEFAULT 0
+#define KEXEC_TYPE_CRASH   1
+};
+
+
+
+/* kexec interface functions */
+extern NORET_TYPE void machine_kexec(struct kimage *image) ATTRIB_NORET;
+extern int machine_kexec_prepare(struct kimage *image);
+extern void machine_kexec_cleanup(struct kimage *image);
+extern asmlinkage long sys_kexec_load(unsigned long entry,
+	unsigned long nr_segments, struct kexec_segment __user *segments,
+	unsigned long flags);
+#ifdef CONFIG_COMPAT
+extern asmlinkage long compat_sys_kexec_load(unsigned long entry,
+	unsigned long nr_segments, struct compat_kexec_segment __user *segments,
+	unsigned long flags);
+#endif
+extern struct page *kimage_alloc_control_pages(struct kimage *image, unsigned int order);
+extern void crash_kexec(void);
+extern struct kimage *kexec_image;
+
+#define KEXEC_ON_CRASH  0x00000001
+#define KEXEC_ARCH_MASK 0xffff0000
+
+/* These values match the ELF architecture values.
+ * Unless there is a good reason that should continue to be the case.
+ */
+#define KEXEC_ARCH_DEFAULT ( 0 << 16)
+#define KEXEC_ARCH_386     ( 3 << 16)
+#define KEXEC_ARCH_X86_64  (62 << 16)
+#define KEXEC_ARCH_PPC     (20 << 16)
+#define KEXEC_ARCH_PPC64   (21 << 16)
+#define KEXEC_ARCH_IA_64   (50 << 16)
+
+#define KEXEC_FLAGS    (KEXEC_ON_CRASH)  /* List of defined/legal kexec flags */
+
+/* Location of a reserved region to hold the crash kernel.
+ */
+extern struct resource crashk_res;
+
+#else /* !CONFIG_KEXEC */
+static inline void crash_kexec(void) { }
+#endif /* CONFIG_KEXEC */
+#endif /* LINUX_KEXEC_H */

include/linux/reboot.h

@@ -51,6 +51,9 @@ extern void machine_restart(char *cmd);
 extern void machine_halt(void);
 extern void machine_power_off(void);
 
+extern void machine_shutdown(void);
+extern void machine_crash_shutdown(void);
+
 #endif
 
 #endif /* _LINUX_REBOOT_H */

include/linux/syscalls.h

@@ -159,8 +159,9 @@ asmlinkage long sys_shutdown(int, int);
 asmlinkage long sys_reboot(int magic1, int magic2, unsigned int cmd,
 				void __user *arg);
 asmlinkage long sys_restart_syscall(void);
-asmlinkage long sys_kexec_load(void *entry, unsigned long nr_segments,
-			struct kexec_segment *segments, unsigned long flags);
+asmlinkage long sys_kexec_load(unsigned long entry,
+	unsigned long nr_segments, struct kexec_segment __user *segments,
+	unsigned long flags);
 
 asmlinkage long sys_exit(int error_code);
 asmlinkage void sys_exit_group(int error_code);

kernel/Makefile

@@ -17,6 +17,7 @@ obj-$(CONFIG_MODULES) += module.o
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_PM) += power/
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
+obj-$(CONFIG_KEXEC) += kexec.o
 obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_CPUSETS) += cpuset.o
 obj-$(CONFIG_IKCONFIG) += configs.o

kernel/panic.c

@@ -18,6 +18,7 @@
 #include <linux/sysrq.h>
 #include <linux/interrupt.h>
 #include <linux/nmi.h>
+#include <linux/kexec.h>
 
 int panic_timeout;
 int panic_on_oops;
@@ -63,6 +64,13 @@ NORET_TYPE void panic(const char * fmt, ...)
         unsigned long caller = (unsigned long) __builtin_return_address(0);
 #endif
 
+	/*
+	 * It's possible to come here directly from a panic-assertion and not
+	 * have preempt disabled. Some functions called from here want
+	 * preempt to be disabled. No point enabling it later though...
+	 */
+	preempt_disable();
+
 	bust_spinlocks(1);
 	va_start(args, fmt);
 	vsnprintf(buf, sizeof(buf), fmt, args);
@@ -70,7 +78,19 @@ NORET_TYPE void panic(const char * fmt, ...)
 	printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
 	bust_spinlocks(0);
 
+	/*
+	 * If we have crashed and we have a crash kernel loaded let it handle
+	 * everything else.
+	 * Do we want to call this before we try to display a message?
+	 */
+	crash_kexec();
+
 #ifdef CONFIG_SMP
+	/*
+	 * Note smp_send_stop is the usual smp shutdown function, which
+	 * unfortunately means it may not be hardened to work in a panic
+	 * situation.
+	 */
 	smp_send_stop();
 #endif
 
@@ -79,8 +99,7 @@ NORET_TYPE void panic(const char * fmt, ...)
 	if (!panic_blink)
 		panic_blink = no_blink;
 
-	if (panic_timeout > 0)
-	{
+	if (panic_timeout > 0) {
 		/*
 	 	 * Delay timeout seconds before rebooting the machine. 
 		 * We can't use the "normal" timers since we just panicked..

kernel/sys.c

@@ -16,6 +16,8 @@
 #include <linux/init.h>
 #include <linux/highuid.h>
 #include <linux/fs.h>
+#include <linux/kernel.h>
+#include <linux/kexec.h>
 #include <linux/workqueue.h>
 #include <linux/device.h>
 #include <linux/key.h>
@@ -439,6 +441,24 @@ asmlinkage long sys_reboot(int magic1, int magic2, unsigned int cmd, void __user
 		machine_restart(buffer);
 		break;
 
+#ifdef CONFIG_KEXEC
+	case LINUX_REBOOT_CMD_KEXEC:
+	{
+		struct kimage *image;
+		image = xchg(&kexec_image, 0);
+		if (!image) {
+			unlock_kernel();
+			return -EINVAL;
+		}
+		notifier_call_chain(&reboot_notifier_list, SYS_RESTART, NULL);
+		system_state = SYSTEM_RESTART;
+		device_shutdown();
+		printk(KERN_EMERG "Starting new kernel\n");
+		machine_shutdown();
+		machine_kexec(image);
+		break;
+	}
+#endif
 #ifdef CONFIG_SOFTWARE_SUSPEND
 	case LINUX_REBOOT_CMD_SW_SUSPEND:
 		{

kernel/sys_ni.c

@@ -18,6 +18,8 @@ cond_syscall(sys_acct);
 cond_syscall(sys_lookup_dcookie);
 cond_syscall(sys_swapon);
 cond_syscall(sys_swapoff);
+cond_syscall(sys_kexec_load);
+cond_syscall(compat_sys_kexec_load);
 cond_syscall(sys_init_module);
 cond_syscall(sys_delete_module);
 cond_syscall(sys_socketpair);