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  ex-
              ported  to  user space via the /proc/iomem file, in an entry la-
              beled "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  execut-
              ing  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_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  ad-
          dress  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 ker-

       The kexec_load() system call is available only if the kernel  was  con-
       figured with CONFIG_KEXEC.

       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 buf-
       fer 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:

              Unload the currently loaded kernel.

              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.

              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 sys-
       tems where "kexec" loading should be restricted to  only  kernels  that
       are  signed.  This system call is available only if the kernel was con-
       figured with CONFIG_KEXEC_FILE.

       On success, these system calls returns 0.  On error, -1 is returned and
       errno is set to indicate the error.

              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.

              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 ex-
              ceeds 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

              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  con-
              tain  an  x86 kernel that is loadable above 4 GiB 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  Documenta-

       This  page  is  part of release 5.05 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

Linux                             2019-03-06                     KEXEC_LOAD(2)
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