1 .\" Copyright (C) 2010 Intel Corporation, Author: Andi Kleen
2 .\" and Copyright 2014, Vivek Goyal <vgoyal@redhat.com>
4 .\" %%%LICENSE_START(VERBATIM)
5 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
26 .TH KEXEC_LOAD 2 2014-08-19 "Linux" "Linux Programmer's Manual"
28 kexec_load, kexec_file_load \- load a new kernel for later execution
31 .B #include <linux/kexec.h>
33 .BI "long kexec_load(unsigned long " entry ", unsigned long " nr_segments ","
34 .BI " struct kexec_segment *" segments \
35 ", unsigned long " flags ");"
37 .BI "long kexec_file_load(int " kernel_fd ", int " initrd_fd ","
39 .BI " unsigned long " cmdline_len \
40 ", const char *" cmdline ","
41 .BI " unsigned long " flags ");"
45 There are no glibc wrappers for these system calls; see NOTES.
49 system call loads a new kernel that can be executed later by
54 argument is a bit mask that controls the operation of the call.
55 The following values can be specified in
58 .BR KEXEC_ON_CRASH " (since Linux 2.6.13)"
59 Execute the new kernel automatically on a system crash.
60 This "crash kernel" is loaded into an area of reserved memory that
61 is determined at boot time using the
63 kernel command-line parameter.
64 The location of this reserved memory is exported to user space via the
66 file, in an entry labeled "Crash kernel".
67 A user-space application can parse this file and prepare a list of
68 segments (see below) that specify this reserved memory as destination.
69 If this flag is specified, the kernel checks that the
70 target segments specified in
72 fall within the reserved region.
74 .BR KEXEC_PRESERVE_CONTEXT " (since Linux 2.6.27)"
75 Preserve the system hardware and
76 software states before executing the new kernel.
77 This could be used for system suspend.
78 This flag is available only if the kernel was configured with
79 .BR CONFIG_KEXEC_JUMP ,
80 and is effective only if
84 The high-order bits (corresponding to the mask 0xffff0000) of
86 contain the architecture of the to-be-executed kernel.
87 Specify (OR) the constant
89 to use the current architecture,
90 or one of the following architecture constants
93 .BR KEXEC_ARCH_X86_64 ,
95 .BR KEXEC_ARCH_PPC64 ,
96 .BR KEXEC_ARCH_IA_64 ,
100 .BR KEXEC_ARCH_MIPS ,
102 .BR KEXEC_ARCH_MIPS_LE .
103 The architecture must be executable on the CPU of the system.
107 argument is the physical entry address in the kernel image.
110 argument is the number of segments pointed to by the
113 the kernel imposes an (arbitrary) limit of 16 on the number of segments.
116 argument is an array of
118 structures which define the kernel layout:
122 struct kexec_segment {
123 void *buf; /* Buffer in user space */
124 size_t bufsz; /* Buffer length in user space */
125 void *mem; /* Physical address of kernel */
126 size_t memsz; /* Physical address length */
131 The kernel image defined by
133 is copied from the calling process into
134 the kernel either in regular
135 memory or in reserved memory (if
138 The kernel first performs various sanity checks on the
139 information passed in
141 If these checks pass, the kernel copies the segment data to kernel memory.
142 Each segment specified in
144 is copied as follows:
149 identify a memory region in the caller's virtual address space
150 that is the source of the copy.
153 may not exceed the value in the
160 specify a physical address range that is the target of the copy.
161 The values specified in both fields must be multiples of
162 the system page size.
165 bytes are copied from the source buffer to the target kernel buffer.
170 then the excess bytes in the kernel buffer are zeroed out.
172 In case of a normal kexec (i.e., the
174 flag is not set), the segment data is loaded in any available memory
175 and is moved to the final destination at kexec reboot time (e.g., when the
177 command is executed with the
181 In case of kexec on panic (i.e., the
183 flag is set), the segment data is
184 loaded to reserved memory at the time of the call, and, after a crash,
185 the kexec mechanism simply passes control to that kernel.
189 system call is available only if the kernel was configured with
191 .SS kexec_file_load()
193 .BR kexec_file_load ()
194 system call is similar to
196 but it takes a different set of arguments.
197 It reads the kernel to be loaded from the file referred to by the descriptor
199 and the initrd (initial RAM disk)
200 to be loaded from file referred to by the descriptor
204 argument is a pointer to a string containing the command line
205 for the new kernel; the
207 argument specifies the length of the string in
212 argument is a bit mask which modifies the behavior of the call.
213 The following values can be specified in
216 .BR KEXEC_FILE_UNLOAD
217 Unload the currently loaded kernel.
219 .BR KEXEC_FILE_ON_CRASH
220 Load the new kernel in the memory region reserved for the crash kernel
223 This kernel is booted if the currently running kernel crashes.
225 .BR KEXEC_FILE_NO_INITRAMFS
226 Loading initrd/initramfs is optional.
227 Specify this flag if no initramfs is being loaded.
228 If this flag is set, the value passed in
233 .BR kexec_file_load ()
234 .\" See also http://lwn.net/Articles/603116/
235 system call was added to provide support for systems
236 where "kexec" loading should be restricted to
237 only kernels that are signed.
238 This system call is available only if the kernel was configured with
239 .BR CONFIG_KEXEC_FILE .
241 On success, these system calls returns 0.
242 On error, \-1 is returned and
244 is set to indicate the error.
248 .\" See kernel/kexec.::sanity_check_segment_list in the 3.19 kernel source
251 flags was specified, but the region specified by the
257 entries lies outside the range of memory reserved for the crash kernel.
266 entries is not a multiple of the system page size.
269 Another crash kernel is already being loaded
270 or a crash kernel is already in use.
281 entries exceeds the value in the corresponding
288 .BR KEXEC_SEGMENT_MAX
292 Two or more of the kernel target buffers overlap.
296 does not refer to an open file, or the kernel can't load this file.
299 The caller does not have the
305 system call first appeared in Linux 2.6.13.
307 .BR kexec_file_load ()
308 system call first appeared in Linux 3.17.
310 These system calls are Linux-specific.
312 Currently, there is no glibc support for these system calls.
320 The kernel source files
321 .IR Documentation/kdump/kdump.txt
323 .IR Documentation/kernel-parameters.txt .