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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
KEXEC_LOAD(2) Linux Programmer's Manual KEXEC_LOAD(2)
kexec_load, kexec_file_load - load a new kernel for later execution
#include <linux/kexec.h>
long kexec_load(unsigned long entry, unsigned long nr_segments,
struct kexec_segment *segments, unsigned long flags);
long kexec_file_load(int kernel_fd, int initrd_fd,
unsigned long cmdline_len, const char *cmdline,
unsigned long flags);
Note: There are no glibc wrappers for these system calls; see NOTES.
The kexec_load() system call loads a new kernel that can be executed
later by reboot(2).
The flags argument is a bit mask that controls the operation of the
call. The following values can be specified in flags:
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 crashkernel kernel
command-line parameter. The location of this reserved memory
is exported to user space via the /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 segments fall within the reserved region.
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 CONFIG_KEXEC_JUMP, and is effective only if
nr_segments is greater than 0.
The high-order bits (corresponding to the mask 0xffff0000) of flags
contain the architecture of the to-be-executed kernel. Specify (OR)
the constant KEXEC_ARCH_DEFAULT to use the current architecture, or
one of the following architecture constants KEXEC_ARCH_386,
KEXEC_ARCH_68K, KEXEC_ARCH_X86_64, KEXEC_ARCH_PPC, KEXEC_ARCH_PPC64,
KEXEC_ARCH_IA_64, KEXEC_ARCH_ARM, KEXEC_ARCH_S390, KEXEC_ARCH_SH,
KEXEC_ARCH_MIPS, and KEXEC_ARCH_MIPS_LE. The architecture must be
executable on the CPU of the system.
The entry argument is the physical entry address in the kernel image.
The nr_segments argument is the number of segments pointed to by the
segments pointer; the kernel imposes an (arbitrary) limit of 16 on
the number of segments. The segments argument is an array of
kexec_segment structures which define the kernel layout:
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 */
};
The kernel image defined by segments is copied from the calling
process into the kernel either in regular memory or in reserved
memory (if KEXEC_ON_CRASH is set). The kernel first performs various
sanity checks on the information passed in segments. If these checks
pass, the kernel copies the segment data to kernel memory. Each
segment specified in segments is copied as follows:
* buf and bufsz identify a memory region in the caller's virtual
address space that is the source of the copy. The value in bufsz
may not exceed the value in the memsz field.
* mem and 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.
* bufsz bytes are copied from the source buffer to the target kernel
buffer. If bufsz is less than memsz, then the excess bytes in the
kernel buffer are zeroed out.
In case of a normal kexec (i.e., the 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 kexec(8)
command is executed with the -e option).
In case of kexec on panic (i.e., the 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 kexec_load() system call is available only if the kernel was
configured with CONFIG_KEXEC.
kexec_file_load()
The kexec_file_load() system call is similar to 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 kernel_fd, and the
initrd (initial RAM disk) to be loaded from file referred to by the
file descriptor initrd_fd. The cmdline argument is a pointer to a
buffer containing the command line for the new kernel. The
cmdline_len argument specifies size of the buffer. The last byte in
the buffer must be a null byte ('\0').
The flags argument is a bit mask which modifies the behavior of the
call. The following values can be specified in flags:
KEXEC_FILE_UNLOAD
Unload the currently loaded kernel.
KEXEC_FILE_ON_CRASH
Load the new kernel in the memory region reserved for the
crash kernel (as for KEXEC_ON_CRASH). This kernel is booted
if the currently running kernel crashes.
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 initrd_fd is ignored.
The kexec_file_load() 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 CONFIG_KEXEC_FILE.
On success, these system calls returns 0. On error, -1 is returned
and errno is set to indicate the error.
EADDRNOTAVAIL
The KEXEC_ON_CRASH flags was specified, but the region
specified by the mem and memsz fields of one of the segments
entries lies outside the range of memory reserved for the
crash kernel.
EADDRNOTAVAIL
The value in a mem or memsz field in one of the segments
entries is not a multiple of the system page size.
EBADF kernel_fd or initrd_fd is not a valid file descriptor.
EBUSY Another crash kernel is already being loaded or a crash kernel
is already in use.
EINVAL flags is invalid.
EINVAL The value of a bufsz field in one of the segments entries
exceeds the value in the corresponding memsz field.
EINVAL nr_segments exceeds KEXEC_SEGMENT_MAX (16).
EINVAL Two or more of the kernel target buffers overlap.
EINVAL The value in cmdline[cmdline_len-1] is not '\0'.
EINVAL The file referred to by kernel_fd or initrd_fd is empty
(length zero).
ENOEXEC
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 Documentation/x86/boot.txt).
ENOMEM Could not allocate memory.
EPERM The caller does not have the CAP_SYS_BOOT capability.
The kexec_load() system call first appeared in Linux 2.6.13. The
kexec_file_load() system call first appeared in Linux 3.17.
These system calls are Linux-specific.
Currently, there is no glibc support for these system calls. Call
them using syscall(2).
reboot(2), syscall(2), kexec(8)
The kernel source files Documentation/kdump/kdump.txt and
Documentation/admin-guide/kernel-parameters.txt
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2017-05-03 KEXEC_LOAD(2)
Pages that refer to this page: reboot(2), syscalls(2), capabilities(7)