man2/kexec_load.2

   1 .\" Copyright (C) 2010 Intel Corporation
   2 .\" Author: Andi Kleen
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  25 .TH KEXEC_LOAD 2 2012-07-13 "Linux" "Linux Programmer's Manual"
  26 .SH NAME
  27 kexec_load \- load a new kernel for later execution
  28 .SH SYNOPSIS
  29 .B #include <linux/kexec.h>
  30 .br
  31 .BI "long kexec_load(unsigned long " entry ", unsigned long " nr_segments ","
  32 .br
  33 .BI "                struct kexec_segment *" segments \
  34 ", unsigned long " flags ");"
  35
  36 .IR Note :
  37 There is no glibc wrapper for this system call; see NOTES.
  38 .SH DESCRIPTION
  39 The
  40 .BR kexec_load ()
  41 system call loads a new kernel that can be executed later by
  42 .BR reboot (2).
  43 .PP
  44 The
  45 .I flags
  46 argument is a mask whose high-order bits control the operation of the call.
  47 The following values can be specified in
  48 .IR flags :
  49 .TP
  50 .BR KEXEC_ON_CRASH " (since Linux 2.6.13)"
  51 Execute the new kernel automatically on a system crash.
  52 .\" FIXME figure out how this is really used
  53 .TP
  54 .BR KEXEC_PRESERVE_CONTEXT " (since Linux 2.6.27)"
  55 Preserve the system hardware and
  56 software states before executing the new kernel.
  57 This could be used for system suspend.
  58 This flag is only available if the kernel was configured with
  59 .BR CONFIG_KEXEC_JUMP ,
  60 and is only effective if
  61 .I nr_segments
  62 is greater than 0.
  63 .PP
  64 The low-order bits of
  65 .I flags
  66 contain the architecture of the to-be-executed kernel.
  67 Specify (OR) the constant
  68 .B KEXEC_ARCH_DEFAULT
  69 to use the current architecture,
  70 or one of the following architecture constants
  71 .BR KEXEC_ARCH_386 ,
  72 .BR KEXEC_ARCH_X86_64 ,
  73 .BR KEXEC_ARCH_PPC ,
  74 .BR KEXEC_ARCH_PPC64 ,
  75 .BR KEXEC_ARCH_IA_64 ,
  76 .BR KEXEC_ARCH_ARM ,
  77 .BR KEXEC_ARCH_S390 ,
  78 .BR KEXEC_ARCH_SH ,
  79 .BR KEXEC_ARCH_MIPS ,
  80 and
  81 .BR KEXEC_ARCH_MIPS_LE .
  82 The architecture must be executable on the CPU of the system.
  83
  84 The
  85 .I entry
  86 argument is the physical entry address in the kernel image.
  87 The
  88 .I nr_segments
  89 argument is the number of segments pointed to by the
  90 .I segments
  91 pointer.
  92 The
  93 .I segments
  94 argument is an array of
  95 .I kexec_segment
  96 structures which define the kernel layout:
  97 .in +4n
  98 .nf
  99
 100 struct kexec_segment {
 101     void   *buf;        /* Buffer in user space */
 102     size_t  bufsz;      /* Buffer length in user space */
 103     void   *mem;        /* Physical address of kernel */
 104     size_t  memsz;      /* Physical address length */
 105 };
 106 .fi
 107 .in
 108 .PP
 109 .\" FIXME elaborate on the following:
 110 The kernel image defined by
 111 .I segments
 112 is copied from the calling process into previously reserved memory.
 113 .SH RETURN VALUE
 114 On success,
 115 .BR kexec_load ()
 116 returns 0.
 117 On error, \-1 is returned and
 118 .I errno
 119 is set to indicate the error.
 120 .SH ERRORS
 121 .TP
 122 .B EBUSY
 123 Another crash kernel is already being loaded
 124 or a crash kernel is already in use.
 125 .TP
 126 .B EINVAL
 127 .I flags
 128 is invalid; or
 129 .IR nr_segments
 130 is too large
 131 .\" KEXEC_SEGMENT_MAX == 16
 132 .TP
 133 .B EPERM
 134 The caller does not have the
 135 .BR CAP_SYS_BOOT
 136 capability.
 137 .SH VERSIONS
 138 The
 139 .BR kexec_load ()
 140 system call first appeared in Linux 2.6.13.
 141 .SH CONFORMING TO
 142 This system call is Linux-specific.
 143 .SH NOTES
 144 Currently, there is no glibc support for
 145 .BR kexec_load ().
 146 Call it using
 147 .BR syscall (2).
 148 .PP
 149 The required constants are in the Linux kernel source file
 150 .IR linux/kexec.h ,
 151 which is not currently exported to glibc.
 152 .\" FIXME Andi submitted a patch for this.
 153 .\" Check if it got accepted later.
 154 Therefore, these constants must be defined manually.
 155
 156 This system call is only available if the kernel was configured with
 157 .BR CONFIG_KEXEC .
 158 .SH SEE ALSO
 159 .BR reboot (2),
 160 .BR syscall (2)