-.\" Hey Emacs! This file is -*- nroff -*- source.
-.\"
-.\" Copyright (C) 2010 Intel Corporation
-.\" Author: Andi Kleen
+.\" Copyright (C) 2010 Intel Corporation, Author: Andi Kleen
+.\" and Copyright 2014, Vivek Goyal <vgoyal@redhat.com>
+.\" and Copyright (c) 2015, Michael Kerrisk <mtk.manpages@gmail.com>
.\"
+.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
-.TH KEXEC_LOAD 2 2010-11-04 "Linux" "Linux Programmer's Manual"
+.\" %%%LICENSE_END
+.\"
+.TH KEXEC_LOAD 2 2015-02-01 "Linux" "Linux Programmer's Manual"
.SH NAME
-kexec_load \- load a new kernel for later execution
+kexec_load, kexec_file_load \- load a new kernel for later execution
.SH SYNOPSIS
+.nf
.B #include <linux/kexec.h>
-.br
+
.BI "long kexec_load(unsigned long " entry ", unsigned long " nr_segments ","
-.br
.BI " struct kexec_segment *" segments \
", unsigned long " flags ");"
+
+.BI "long kexec_file_load(int " kernel_fd ", int " initrd_fd ","
+.br
+.BI " unsigned long " cmdline_len \
+", const char *" cmdline ","
+.BI " unsigned long " flags ");"
+
+.fi
+.IR Note :
+There are no glibc wrappers for these system calls; see NOTES.
.SH DESCRIPTION
The
.BR kexec_load ()
.PP
The
.I flags
-argument is a mask whose high-order bits control the operation of the call.
+argument is a bit mask that controls the operation of the call.
The following values can be specified in
.IR flags :
.TP
.BR KEXEC_ON_CRASH " (since Linux 2.6.13)"
Execute the new kernel automatically on a system crash.
-.\" FIXME figure out how this is really used
+This "crash kernel" is loaded into an area of reserved memory that
+is determined at boot time using the
+.I craskkernel
+kernel command-line parameter.
+The location of this reserved memory is exported to user space via the
+.I /proc/iomem
+file, in an entry labeled "Crash kernel".
+A user-space application can parse this file and prepare a list of
+segments (see below) that specify this reserved memory as destination.
+If this flag is specified, the kernel checks that the
+target segments specified in
+.I segments
+fall within the reserved region.
.TP
-.BR KEXEC_PRESERVE_CONTEXT " (since Linux 2.7.27)"
+.BR 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 only available if the kernel was configured with
+This flag is available only if the kernel was configured with
.BR CONFIG_KEXEC_JUMP ,
-and is only effective if
+and is effective only if
.I nr_segments
is greater than 0.
.PP
-The low-order bits of
+The high-order bits (corresponding to the mask 0xffff0000) of
.I flags
contain the architecture of the to-be-executed kernel.
Specify (OR) the constant
to use the current architecture,
or one of the following architecture constants
.BR KEXEC_ARCH_386 ,
+.BR KEXEC_ARCH_68K ,
.BR KEXEC_ARCH_X86_64 ,
.BR KEXEC_ARCH_PPC ,
.BR KEXEC_ARCH_PPC64 ,
.I nr_segments
argument is the number of segments pointed to by the
.I segments
-pointer.
+pointer;
+the kernel imposes an (arbitrary) limit of 16 on the number of segments.
The
.I segments
argument is an array of
.fi
.in
.PP
-.\" FIXME elaborate on the following:
The kernel image defined by
.I segments
-is copied from the calling process into previously reserved memory.
-.SH RETURN VALUE
-On success,
+is copied from the calling process into
+the kernel either in regular
+memory or in reserved memory (if
+.BR KEXEC_ON_CRASH
+is set).
+The kernel first performs various sanity checks on the
+information passed in
+.IR segments .
+If these checks pass, the kernel copies the segment data to kernel memory.
+Each segment specified in
+.I segments
+is copied as follows:
+.IP * 3
+.I buf
+and
+.I bufsz
+identify a memory region in the caller's virtual address space
+that is the source of the copy.
+The value in
+.I bufsz
+may not exceed the value in the
+.I memsz
+field.
+.IP *
+.I mem
+and
+.I memsz
+specify a physical address range that is the target of the copy.
+The values specified in both fields must be multiples of
+the system page size.
+.IP *
+.I bufsz
+bytes are copied from the source buffer to the target kernel buffer.
+If
+.I bufsz
+is less than
+.IR memsz ,
+then the excess bytes in the kernel buffer are zeroed out.
+.PP
+In case of a normal kexec (i.e., the
+.BR KEXEC_ON_CRASH
+flag is not set), the segment data is loaded in any available memory
+and is moved to the final destination at kexec reboot time (e.g., when the
+.BR kexec (8)
+command is executed with the
+.I \-e
+option).
+
+In case of kexec on panic (i.e., the
+.BR KEXEC_ON_CRASH
+flag is set), the segment data is
+loaded to reserved memory at the time of the call, and, after a crash,
+the kexec mechanism simply passes control to that kernel.
+
+The
.BR kexec_load ()
-returns 0.
-On error, -1 is returned and
+system call is available only if the kernel was configured with
+.BR CONFIG_KEXEC .
+.SS kexec_file_load()
+The
+.BR kexec_file_load ()
+system call is similar to
+.BR kexec_load (),
+but it takes a different set of arguments.
+It reads the kernel to be loaded from the file referred to by the descriptor
+.IR kernel_fd ,
+and the initrd (initial RAM disk)
+to be loaded from file referred to by the descriptor
+.IR initrd_fd .
+The
+.IR cmdline
+argument is a pointer to a buffer containing the command line
+for the new kernel.
+The
+.IR cmdline_len
+argument specifies size of the buffer.
+The last byte in the buffer must be a null byte (\(aq\\0\(aq).
+
+The
+.IR flags
+argument is a bit mask which modifies the behavior of the call.
+The following values can be specified in
+.IR flags :
+.TP
+.BR KEXEC_FILE_UNLOAD
+Unload the currently loaded kernel.
+.TP
+.BR KEXEC_FILE_ON_CRASH
+Load the new kernel in the memory region reserved for the crash kernel
+(as for
+.BR KEXEC_ON_CRASH).
+This kernel is booted if the currently running kernel crashes.
+.TP
+.BR KEXEC_FILE_NO_INITRAMFS
+Loading initrd/initramfs is optional.
+Specify this flag if no initramfs is being loaded.
+If this flag is set, the value passed in
+.IR initrd_fd
+is ignored.
+.PP
+The
+.BR kexec_file_load ()
+.\" See also http://lwn.net/Articles/603116/
+system call was added to provide support for systems
+where "kexec" loading should be restricted to
+only kernels that are signed.
+This system call is available only if the kernel was configured with
+.BR CONFIG_KEXEC_FILE .
+.SH RETURN VALUE
+On success, these system calls returns 0.
+On error, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
+.B EADDRNOTAVAIL
+.\" See kernel/kexec.::sanity_check_segment_list in the 3.19 kernel source
+The
+.B KEXEC_ON_CRASH
+flags was specified, but the region specified by the
+.I mem
+and
+.I memsz
+fields of one of the
+.I segments
+entries lies outside the range of memory reserved for the crash kernel.
+.TP
+.B EADDRNOTAVAIL
+The value in a
+.I mem
+or
+.I memsz
+field in one of the
+.I segments
+entries is not a multiple of the system page size.
+.TP
+.B EBADF
+.I kernel_fd
+or
+.I initrd_fd
+is not a valid file descriptor.
+.TP
.B EBUSY
Another crash kernel is already being loaded
or a crash kernel is already in use.
.TP
.B EINVAL
.I flags
-is invalid; or
+is invalid.
+.TP
+.B EINVAL
+The value of a
+.I bufsz
+field in one of the
+.I segments
+entries exceeds the value in the corresponding
+.I memsz
+field.
+.TP
+.B EINVAL
.IR nr_segments
-is too large
-.\" KEXEC_SEGMENT_MAX == 16
+exceeds
+.BR KEXEC_SEGMENT_MAX
+(16).
+.TP
+.B EINVAL
+Two or more of the kernel target buffers overlap.
+.TP
+.B EINVAL
+The value in
+.I cmdline[cmdline_len-1]
+is not \(aq\\0\(aq.
+.TP
+.B EINVAL
+The file referred to by
+.I kernel_fd
+or
+.I initrd_fd
+is empty (length zero).
+.TP
+.B ENOMEM
+Could not allocate memory.
+.TP
+.B ENOEXEC
+.I kernel_fd
+does not refer to an open file, or the kernel can't load this file.
+Currently, the file must be a bzImage and contain an x86 kernel that
+is loadable above 4GiB in memory (see the kernel source file
+.IR Documentation/x86/boot.txt ).
.TP
.B EPERM
The caller does not have the
The
.BR kexec_load ()
system call first appeared in Linux 2.6.13.
+The
+.BR kexec_file_load ()
+system call first appeared in Linux 3.17.
.SH CONFORMING TO
-This system call is Linux-specific.
+These system calls are Linux-specific.
.SH NOTES
-Currently, there is no glibc support for
-.BR kexec_load ().
-Call it using
+Currently, there is no glibc support for these system calls.
+Call them using
.BR syscall (2).
-.PP
-The required constants are in the kernel source file
-.IR linux/kexec.h ,
-which is not currently exported to glibc.
-.\" FIXME Andi submitted a patch for this.
-.\" Check if it got accepted later.
-Therefore, these constants must be defined manually.
-
-This system call is only available if the kernel was configured with
-.BR CONFIG_KEXEC .
.SH SEE ALSO
.BR reboot (2),
-.BR syscall (2)
+.BR syscall (2),
+.BR kexec (8)
+
+The kernel source files
+.IR Documentation/kdump/kdump.txt
+and
+.IR Documentation/kernel-parameters.txt .
+.SH COLOPHON
+This page is part of release 3.79 of the Linux
+.I man-pages
+project.
+A description of the project,
+information about reporting bugs,
+and the latest version of this page,
+can be found at
+\%http://www.kernel.org/doc/man\-pages/.
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