mirror of https://github.com/mkerrisk/man-pages
224 lines
6.3 KiB
Groff
224 lines
6.3 KiB
Groff
.\" Copyright (C) 2010 Intel Corporation, Author: Andi Kleen
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.\" and Copyright 2014, Vivek Goyal <vgoyal@redhat.com>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.TH KEXEC_LOAD 2 2014-08-19 "Linux" "Linux Programmer's Manual"
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.SH NAME
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kexec_load, kexec_file_load \- load a new kernel for later execution
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.SH SYNOPSIS
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.nf
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.B #include <linux/kexec.h>
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.BI "long kexec_load(unsigned long " entry ", unsigned long " nr_segments ","
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.BI " struct kexec_segment *" segments \
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", unsigned long " flags ");"
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.BI "long kexec_file_load(int " kernel_fd ", int " initrd_fd ","
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.br
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.BI " unsigned long " cmdline_len \
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", const char *" cmdline ","
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.BI " unsigned long " flags ");"
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.fi
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.IR Note :
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There are no glibc wrappers for these system calls; see NOTES.
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.SH DESCRIPTION
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The
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.BR kexec_load ()
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system call loads a new kernel that can be executed later by
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.BR reboot (2).
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.PP
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The
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.I flags
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argument is a bit mask that controls the operation of the call.
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The following values can be specified in
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.IR flags :
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.TP
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.BR KEXEC_ON_CRASH " (since Linux 2.6.13)"
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Execute the new kernel automatically on a system crash.
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.\" FIXME Explain in more detail how KEXEC_ON_CRASH is actually used
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.TP
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.BR KEXEC_PRESERVE_CONTEXT " (since Linux 2.6.27)"
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Preserve the system hardware and
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software states before executing the new kernel.
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This could be used for system suspend.
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This flag is available only if the kernel was configured with
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.BR CONFIG_KEXEC_JUMP ,
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and is effective only if
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.I nr_segments
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is greater than 0.
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.PP
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The high-order bits (corresponding to the mask 0xffff0000) of
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.I flags
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contain the architecture of the to-be-executed kernel.
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Specify (OR) the constant
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.B KEXEC_ARCH_DEFAULT
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to use the current architecture,
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or one of the following architecture constants
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.BR KEXEC_ARCH_386 ,
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.BR KEXEC_ARCH_68K ,
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.BR KEXEC_ARCH_X86_64 ,
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.BR KEXEC_ARCH_PPC ,
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.BR KEXEC_ARCH_PPC64 ,
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.BR KEXEC_ARCH_IA_64 ,
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.BR KEXEC_ARCH_ARM ,
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.BR KEXEC_ARCH_S390 ,
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.BR KEXEC_ARCH_SH ,
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.BR KEXEC_ARCH_MIPS ,
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and
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.BR KEXEC_ARCH_MIPS_LE .
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The architecture must be executable on the CPU of the system.
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The
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.I entry
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argument is the physical entry address in the kernel image.
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The
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.I nr_segments
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argument is the number of segments pointed to by the
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.I segments
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pointer;
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the kernel imposes an (arbitrary) limit of 16 on the number of segments.
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The
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.I segments
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argument is an array of
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.I kexec_segment
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structures which define the kernel layout:
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.in +4n
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.nf
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struct kexec_segment {
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void *buf; /* Buffer in user space */
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size_t bufsz; /* Buffer length in user space */
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void *mem; /* Physical address of kernel */
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size_t memsz; /* Physical address length */
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};
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.fi
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.in
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.PP
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.\" FIXME Explain the details of how the kernel image defined by segments
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.\" is copied from the calling process into previously reserved memory.
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The kernel image defined by
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.I segments
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is copied from the calling process into previously reserved memory.
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The
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.BR kexec_load ()
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system call is available only if the kernel was configured with
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.BR CONFIG_KEXEC .
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.SS kexec_file_load()
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The
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.BR kexec_file_load ()
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system call is similar to
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.BR kexec_load (),
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but it takes a different set of arguments.
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It reads the kernel to be loaded from the file referred to by the descriptor
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.IR kernel_fd ,
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and the initrd (initial RAM disk)
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to be loaded from file referred to by the descriptor
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.IR initrd_fd .
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The
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.IR cmdline
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argument is a pointer to a string containing the command line
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for the new kernel; the
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.IR cmdline_len
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argument specifies the length of the string in
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.IR cmdline .
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The
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.IR flags
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argument is a bit mask which modifies the behavior of the call.
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The following values can be specified in
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.IR flags :
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.TP
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.BR KEXEC_FILE_UNLOAD
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Unload the currently loaded kernel.
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.TP
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.BR KEXEC_FILE_ON_CRASH
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Load the new kernel in the memory region reserved for the crash kernel.
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This kernel is booted if the currently running kernel crashes.
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.TP
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.BR KEXEC_FILE_NO_INITRAMFS
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Loading initrd/initramfs is optional.
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Specify this flag if no initramfs is being loaded.
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If this flag is set, the value passed in
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.IR initrd_fd
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is ignored.
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.PP
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The
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.BR kexec_file_load ()
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.\" See also http://lwn.net/Articles/603116/
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system call was added to provide support for systems
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where "kexec" loading should be restricted to
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only kernels that are signed.
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This system call is available only if the kernel was configured with
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.BR CONFIG_KEXEC_FILE .
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.SH RETURN VALUE
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On success, these system calls returns 0.
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On error, \-1 is returned and
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.I errno
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is set to indicate the error.
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.SH ERRORS
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.TP
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.B EBUSY
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Another crash kernel is already being loaded
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or a crash kernel is already in use.
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.TP
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.B EINVAL
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.I flags
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is invalid; or
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.IR nr_segments
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is too large
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.\" KEXEC_SEGMENT_MAX == 16
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.TP
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.B ENOEXEC
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.I kernel_fd
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does not refer to an open file, or the kernel can't load this file.
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.TP
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.B EPERM
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The caller does not have the
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.BR CAP_SYS_BOOT
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capability.
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.SH VERSIONS
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The
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.BR kexec_load ()
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system call first appeared in Linux 2.6.13.
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The
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.BR kexec_file_load ()
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system call first appeared in Linux 3.17.
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.SH CONFORMING TO
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These system calls are Linux-specific.
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.SH NOTES
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Currently, there is no glibc support for these system calls.
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Call them using
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.BR syscall (2).
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.SH SEE ALSO
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.BR reboot (2),
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.BR syscall (2),
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.BR kexec (8)
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The kernel source files
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.IR Documentation/kdump/kdump.txt
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and
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.IR Documentation/kernel-parameters.txt .
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