-.\" 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
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
-.TH KEXEC_LOAD 2 2014-08-19 "Linux" "Linux Programmer's Manual"
+.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 is no glibc wrapper for this system call; see NOTES.
+There are no glibc wrappers for these system calls; see NOTES.
.SH DESCRIPTION
The
.BR kexec_load ()
.TP
.BR KEXEC_ON_CRASH " (since Linux 2.6.13)"
Execute the new kernel automatically on a system crash.
-.\" FIXME Explain in more detail how KEXEC_ON_CRASH is actually 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 2.6.27)"
Preserve the system hardware and
.fi
.in
.PP
-.\" FIXME Explain the details of how the kernel image defined by segments
-.\" is copied from the calling process into previously reserved memory.
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.
+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 Linux 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 available only 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 3.75 of the Linux
+This page is part of release 3.79 of the Linux
.I man-pages
project.
A description of the project,
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