tools/testing/selftests/rcutorture/bin/mkinitrd.sh

   1 #!/bin/bash
   2 # SPDX-License-Identifier: GPL-2.0+
   3 #
   4 # Create an initrd directory if one does not already exist.
   5 #
   6 # Copyright (C) IBM Corporation, 2013
   7 #
   8 # Author: Connor Shu <Connor.Shu@ibm.com>
   9
  10 D=tools/testing/selftests/rcutorture
  11
  12 # Prerequisite checks
  13 [ -z "$D" ] && echo >&2 "No argument supplied" && exit 1
  14 if [ ! -d "$D" ]; then
  15     echo >&2 "$D does not exist: Malformed kernel source tree?"
  16     exit 1
  17 fi
  18 if [ -s "$D/initrd/init" ]; then
  19     echo "$D/initrd/init already exists, no need to create it"
  20     exit 0
  21 fi
  22
  23 # Create a C-language initrd/init infinite-loop program and statically
  24 # link it.  This results in a very small initrd.
  25 echo "Creating a statically linked C-language initrd"
  26 cd $D
  27 mkdir -p initrd
  28 cd initrd
  29 cat > init.c << '___EOF___'
  30 #ifndef NOLIBC
  31 #include <unistd.h>
  32 #include <sys/time.h>
  33 #endif
  34
  35 volatile unsigned long delaycount;
  36
  37 int main(int argc, int argv[])
  38 {
  39         int i;
  40         struct timeval tv;
  41         struct timeval tvb;
  42
  43         for (;;) {
  44                 sleep(1);
  45                 /* Need some userspace time. */
  46                 if (gettimeofday(&tvb, NULL))
  47                         continue;
  48                 do {
  49                         for (i = 0; i < 1000 * 100; i++)
  50                                 delaycount = i * i;
  51                         if (gettimeofday(&tv, NULL))
  52                                 break;
  53                         tv.tv_sec -= tvb.tv_sec;
  54                         if (tv.tv_sec > 1)
  55                                 break;
  56                         tv.tv_usec += tv.tv_sec * 1000 * 1000;
  57                         tv.tv_usec -= tvb.tv_usec;
  58                 } while (tv.tv_usec < 1000);
  59         }
  60         return 0;
  61 }
  62 ___EOF___
  63
  64 # build using nolibc on supported archs (smaller executable) and fall
  65 # back to regular glibc on other ones.
  66 if echo -e "#if __x86_64__||__i386__||__i486__||__i586__||__i686__" \
  67            "||__ARM_EABI__||__aarch64__\nyes\n#endif" \
  68    | ${CROSS_COMPILE}gcc -E -nostdlib -xc - \
  69    | grep -q '^yes'; then
  70         # architecture supported by nolibc
  71         ${CROSS_COMPILE}gcc -fno-asynchronous-unwind-tables -fno-ident \
  72                 -nostdlib -include ../../../../include/nolibc/nolibc.h \
  73                 -lgcc -s -static -Os -o init init.c
  74 else
  75         ${CROSS_COMPILE}gcc -s -static -Os -o init init.c
  76 fi
  77
  78 rm init.c
  79 echo "Done creating a statically linked C-language initrd"
  80
  81 exit 0