kexec_load(2) — Linux manual pages

Linux manual pages	Section 2: System Calls

Name

kexec_load — load a new kernel for later execution

Synopsis

#include <linux/kexec.h>

`long kexec_load(`	unsigned long `entry`,
	unsigned long `nr_segments`,
	struct kexec_segment *`segments`,
	unsigned long `flags)`;

	Note
	There is no glibc wrapper for this system call; see NOTES.

DESCRIPTION

The kexec_load() system call loads a new kernel that can be executed later by reboot(2).

The flags argument is a mask whose high-order bits control the operation of the call. The following values can be specified in flags:

KEXEC_ON_CRASH (since Linux 2.6.13): Execute the new kernel automatically on a system crash.
KEXEC_PRESERVE_CONTEXT (since Linux 2.6.27): Preserve the system hardware and software states before executing the new kernel. This could be used for system suspend. This flag is available only if the kernel was configured with CONFIG_KEXEC_JUMP, and is effective only if nr_segments is greater than 0.

The low-order bits of flags contain the architecture of the to-be-executed kernel. Specify (OR) the constant KEXEC_ARCH_DEFAULT to use the current architecture, or one of the following architecture constants KEXEC_ARCH_386, KEXEC_ARCH_X86_64, KEXEC_ARCH_PPC, KEXEC_ARCH_PPC64, KEXEC_ARCH_IA_64, KEXEC_ARCH_ARM, KEXEC_ARCH_S390, KEXEC_ARCH_SH, KEXEC_ARCH_MIPS, and KEXEC_ARCH_MIPS_LE. The architecture must be executable on the CPU of the system.

The entry argument is the physical entry address in the kernel image. The nr_segments argument is the number of segments pointed to by the segments pointer. The segments argument is an array of kexec_segment structures which define the kernel layout:

struct kexec_segment {

void * buf;
/* Buffer in user space */

size_t bufsz;
/* Buffer length in user space */

void * mem;
/* Physical address of kernel */

size_t memsz;
/* Physical address length */

};

The kernel image defined by segments is copied from the calling process into previously reserved memory.

RETURN VALUE

On success, kexec_load() returns 0. On error, −1 is returned and errno is set to indicate the error.

ERRORS

EBUSY: Another crash kernel is already being loaded or a crash kernel is already in use.
EINVAL: flags is invalid; or nr_segments is too large
EPERM: The caller does not have the CAP_SYS_BOOT capability.

VERSIONS

The kexec_load() system call first appeared in Linux 2.6.13.

CONFORMING TO

This system call is Linux-specific.

NOTES

Currently, there is no glibc support for kexec_load(). Call it using syscall(2).

The required constants are in the Linux kernel source file linux/kexec.h, which is not currently exported to glibc. Therefore, these constants must be defined manually.

This system call is available only if the kernel was configured with CONFIG_KEXEC.

COLOPHON

This page is part of release 3.52 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man−pages/.

  Copyright (C) 2010 Intel Corporation
Author: Andi Kleen

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struct	kexec_segment {
	void	*	`buf`;	/* Buffer in user space */
	size_t		`bufsz`;	/* Buffer length in user space */
	void	*	`mem`;	/* Physical address of kernel */
	size_t		`memsz`;	/* Physical address length */
};