man2/kexec_load.2

   1 .\" Copyright (C) 2010 Intel Corporation
   2 .\" Author: Andi Kleen
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  26 .TH KEXEC_LOAD 2 2012-07-13 "Linux" "Linux Programmer's Manual"
  27 .SH NAME
  28 kexec_load \- load a new kernel for later execution
  29 .SH SYNOPSIS
  30 .B #include <linux/kexec.h>
  31 .br
  32 .BI "long kexec_load(unsigned long " entry ", unsigned long " nr_segments ","
  33 .br
  34 .BI "                struct kexec_segment *" segments \
  35 ", unsigned long " flags ");"
  36
  37 .IR Note :
  38 There is no glibc wrapper for this system call; see NOTES.
  39 .SH DESCRIPTION
  40 The
  41 .BR kexec_load ()
  42 system call loads a new kernel that can be executed later by
  43 .BR reboot (2).
  44 .PP
  45 The
  46 .I flags
  47 argument is a bit mask that controls the operation of the call.
  48 The following values can be specified in
  49 .IR flags :
  50 .TP
  51 .BR KEXEC_ON_CRASH " (since Linux 2.6.13)"
  52 Execute the new kernel automatically on a system crash.
  53 .\" FIXME figure out how this is really used
  54 .TP
  55 .BR KEXEC_PRESERVE_CONTEXT " (since Linux 2.6.27)"
  56 Preserve the system hardware and
  57 software states before executing the new kernel.
  58 This could be used for system suspend.
  59 This flag is available only if the kernel was configured with
  60 .BR CONFIG_KEXEC_JUMP ,
  61 and is effective only if
  62 .I nr_segments
  63 is greater than 0.
  64 .PP
  65 The high-order bits (corresponding to the mask 0xffff0000) of
  66 .I flags
  67 contain the architecture of the to-be-executed kernel.
  68 Specify (OR) the constant
  69 .B KEXEC_ARCH_DEFAULT
  70 to use the current architecture,
  71 or one of the following architecture constants
  72 .BR KEXEC_ARCH_386 ,
  73 .BR KEXEC_ARCH_68K ,
  74 .BR KEXEC_ARCH_X86_64 ,
  75 .BR KEXEC_ARCH_PPC ,
  76 .BR KEXEC_ARCH_PPC64 ,
  77 .BR KEXEC_ARCH_IA_64 ,
  78 .BR KEXEC_ARCH_ARM ,
  79 .BR KEXEC_ARCH_S390 ,
  80 .BR KEXEC_ARCH_SH ,
  81 .BR KEXEC_ARCH_MIPS ,
  82 and
  83 .BR KEXEC_ARCH_MIPS_LE .
  84 The architecture must be executable on the CPU of the system.
  85
  86 The
  87 .I entry
  88 argument is the physical entry address in the kernel image.
  89 The
  90 .I nr_segments
  91 argument is the number of segments pointed to by the
  92 .I segments
  93 pointer;
  94 the kernel imposes an (arbitrary) limit of 16 on the number of segments.
  95 The
  96 .I segments
  97 argument is an array of
  98 .I kexec_segment
  99 structures which define the kernel layout:
 100 .in +4n
 101 .nf
 102
 103 struct kexec_segment {
 104     void   *buf;        /* Buffer in user space */
 105     size_t  bufsz;      /* Buffer length in user space */
 106     void   *mem;        /* Physical address of kernel */
 107     size_t  memsz;      /* Physical address length */
 108 };
 109 .fi
 110 .in
 111 .PP
 112 .\" FIXME elaborate on the following:
 113 The kernel image defined by
 114 .I segments
 115 is copied from the calling process into previously reserved memory.
 116 .SH RETURN VALUE
 117 On success,
 118 .BR kexec_load ()
 119 returns 0.
 120 On error, \-1 is returned and
 121 .I errno
 122 is set to indicate the error.
 123 .SH ERRORS
 124 .TP
 125 .B EBUSY
 126 Another crash kernel is already being loaded
 127 or a crash kernel is already in use.
 128 .TP
 129 .B EINVAL
 130 .I flags
 131 is invalid; or
 132 .IR nr_segments
 133 is too large
 134 .\" KEXEC_SEGMENT_MAX == 16
 135 .TP
 136 .B EPERM
 137 The caller does not have the
 138 .BR CAP_SYS_BOOT
 139 capability.
 140 .SH VERSIONS
 141 The
 142 .BR kexec_load ()
 143 system call first appeared in Linux 2.6.13.
 144 .SH CONFORMING TO
 145 This system call is Linux-specific.
 146 .SH NOTES
 147 Currently, there is no glibc support for
 148 .BR kexec_load ().
 149 Call it using
 150 .BR syscall (2).
 151 .PP
 152 The required constants are in the Linux kernel source file
 153 .IR linux/kexec.h ,
 154 which is not currently exported to glibc.
 155 .\" FIXME Andi submitted a patch for this.
 156 .\" Check if it got accepted later.
 157 Therefore, these constants must be defined manually.
 158
 159 This system call is available only if the kernel was configured with
 160 .BR CONFIG_KEXEC .
 161 .SH SEE ALSO
 162 .BR reboot (2),
 163 .BR syscall (2)