kexec_load

       #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.

DESCRIPTION
       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 craskkernel 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  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_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 */

       *  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 ker-
       nel.

       The kexec_load() system call is available only if the kernel  was  con-
       figured 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 descriptor kernel_fd, and the initrd
       (initial RAM disk) to be loaded from file referred to by the descriptor
       initrd_fd.   The  cmdline  argument is a pointer to a buffer containing
       the command line for the new kernel.  The cmdline_len  argument  speci-
       fies  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 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-
       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).

       ENOMEM Could not allocate memory.

       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  con-
              tain  an  x86  kernel that is loadable above 4GiB in memory (see
              the kernel source file Documentation/x86/boot.txt).

       EPERM  The caller does not have the CAP_SYS_BOOT capability.

VERSIONS
       The kexec_load() system call  first  appeared  in  Linux  2.6.13.   The
       kexec_file_load() system call first appeared in Linux 3.17.

CONFORMING TO
       These system calls are Linux-specific.

NOTES
       Currently, there is no glibc support for these system calls.  Call them
       using syscall(2).

SEE ALSO
       reboot(2), syscall(2), kexec(8)

       The kernel source files  Documentation/kdump/kdump.txt  and  Documenta-
       tion/kernel-parameters.txt.

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