Merging upstream version 6.8.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 331 insertions, 0 deletions

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+.\" 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>
+.\"
+.\" SPDX-License-Identifier: Linux-man-pages-copyleft
+.\"
+.TH kexec_load 2 2024-05-02 "Linux man-pages (unreleased)"
+.SH NAME
+kexec_load, kexec_file_load \- load a new kernel for later execution
+.SH LIBRARY
+Standard C library
+.RI ( libc ", " \-lc )
+.SH SYNOPSIS
+.nf
+.BR "#include <linux/kexec.h>" "      /* Definition of " KEXEC_* " constants */"
+.BR "#include <sys/syscall.h>" "      /* Definition of " SYS_* " constants */"
+.B #include <unistd.h>
+.P
+.BI "long syscall(SYS_kexec_load, unsigned long " entry ,
+.BI "             unsigned long " nr_segments \
+", struct kexec_segment *" segments ,
+.BI "             unsigned long " flags );
+.BI "long syscall(SYS_kexec_file_load, int " kernel_fd ", int " initrd_fd ,
+.BI "             unsigned long " cmdline_len ", const char *" cmdline ,
+.BI "             unsigned long " flags );
+.fi
+.P
+.IR Note :
+glibc provides no wrappers for these system calls,
+necessitating the use of
+.BR syscall (2).
+.SH DESCRIPTION
+The
+.BR kexec_load ()
+system call loads a new kernel that can be executed later by
+.BR reboot (2).
+.P
+The
+.I flags
+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.
+This "crash kernel" is loaded into an area of reserved memory that
+is determined at boot time using the
+.I crashkernel
+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
+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
+.BR CONFIG_KEXEC_JUMP ,
+and is effective only if
+.I nr_segments
+is greater than 0.
+.P
+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
+.B KEXEC_ARCH_DEFAULT
+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 ,
+.BR KEXEC_ARCH_IA_64 ,
+.BR KEXEC_ARCH_ARM ,
+.BR KEXEC_ARCH_S390 ,
+.BR KEXEC_ARCH_SH ,
+.BR KEXEC_ARCH_MIPS ,
+and
+.BR KEXEC_ARCH_MIPS_LE .
+The architecture must be executable on the CPU of the system.
+.P
+The
+.I entry
+argument is the physical entry address in the kernel image.
+The
+.I nr_segments
+argument is the number of segments pointed to by the
+.I segments
+pointer;
+the kernel imposes an (arbitrary) limit of 16 on the number of segments.
+The
+.I segments
+argument is an array of
+.I kexec_segment
+structures which define the kernel layout:
+.P
+.in +4n
+.EX
+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 */
+};
+.EE
+.in
+.P
+The kernel image defined by
+.I segments
+is copied from the calling process into
+the kernel either in regular
+memory or in reserved memory (if
+.B 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 \[bu] 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 \[bu]
+.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 \[bu]
+.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.
+.P
+In case of a normal kexec (i.e., the
+.B 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).
+.P
+In case of kexec on panic (i.e., the
+.B 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.
+.P
+The
+.BR kexec_load ()
+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 file descriptor
+.IR kernel_fd ,
+and the initrd (initial RAM disk)
+to be loaded from file referred to by the file descriptor
+.IR initrd_fd .
+The
+.I cmdline
+argument is a pointer to a buffer containing the command line
+for the new kernel.
+The
+.I cmdline_len
+argument specifies size of the buffer.
+The last byte in the buffer must be a null byte (\[aq]\e0\[aq]).
+.P
+The
+.I flags
+argument is a bit mask which modifies the behavior of the call.
+The following values can be specified in
+.IR flags :
+.TP
+.B KEXEC_FILE_UNLOAD
+Unload the currently loaded kernel.
+.TP
+.B 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
+.B 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
+.I initrd_fd
+is ignored.
+.P
+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.
+.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
+.I nr_segments
+exceeds
+.B 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]\e0\[aq].
+.TP
+.B EINVAL
+The file referred to by
+.I kernel_fd
+or
+.I initrd_fd
+is empty (length zero).
+.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 4\ GiB in memory (see the kernel source file
+.IR Documentation/x86/boot.txt ).
+.TP
+.B ENOMEM
+Could not allocate memory.
+.TP
+.B EPERM
+The caller does not have the
+.B CAP_SYS_BOOT
+capability.
+.SH STANDARDS
+Linux.
+.SH HISTORY
+.TP
+.BR kexec_load ()
+Linux 2.6.13.
+.TP
+.BR kexec_file_load ()
+Linux 3.17.
+.SH SEE ALSO
+.BR reboot (2),
+.BR syscall (2),
+.BR kexec (8)
+.P
+The kernel source files
+.I Documentation/kdump/kdump.txt
+and
+.I Documentation/admin\-guide/kernel\-parameters.txt