131 lines
3.2 KiB
Bash
131 lines
3.2 KiB
Bash
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#!/bin/bash
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# SPDX-License-Identifier: GPL-2.0+
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#
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# Create an initrd directory if one does not already exist.
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#
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# Copyright (C) IBM Corporation, 2013
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#
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# Author: Connor Shu <Connor.Shu@ibm.com>
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D=tools/testing/selftests/rcutorture
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# Prerequisite checks
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[ -z "$D" ] && echo >&2 "No argument supplied" && exit 1
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if [ ! -d "$D" ]; then
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echo >&2 "$D does not exist: Malformed kernel source tree?"
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exit 1
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fi
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if [ -s "$D/initrd/init" ]; then
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echo "$D/initrd/init already exists, no need to create it"
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exit 0
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fi
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T=${TMPDIR-/tmp}/mkinitrd.sh.$$
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trap 'rm -rf $T' 0 2
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mkdir $T
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cat > $T/init << '__EOF___'
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#!/bin/sh
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# Run in userspace a few milliseconds every second. This helps to
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# exercise the NO_HZ_FULL portions of RCU. The 192 instances of "a" was
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# empirically shown to give a nice multi-millisecond burst of user-mode
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# execution on a 2GHz CPU, as desired. Modern CPUs will vary from a
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# couple of milliseconds up to perhaps 100 milliseconds, which is an
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# acceptable range.
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#
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# Why not calibrate an exact delay? Because within this initrd, we
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# are restricted to Bourne-shell builtins, which as far as I know do not
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# provide any means of obtaining a fine-grained timestamp.
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a4="a a a a"
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a16="$a4 $a4 $a4 $a4"
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a64="$a16 $a16 $a16 $a16"
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a192="$a64 $a64 $a64"
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while :
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do
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q=
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for i in $a192
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do
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q="$q $i"
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done
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sleep 1
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done
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__EOF___
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# Try using dracut to create initrd
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if command -v dracut >/dev/null 2>&1
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then
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echo Creating $D/initrd using dracut.
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# Filesystem creation
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dracut --force --no-hostonly --no-hostonly-cmdline --module "base" $T/initramfs.img
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cd $D
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mkdir -p initrd
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cd initrd
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zcat $T/initramfs.img | cpio -id
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cp $T/init init
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chmod +x init
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echo Done creating $D/initrd using dracut
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exit 0
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fi
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# No dracut, so create a C-language initrd/init program and statically
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# link it. This results in a very small initrd, but might be a bit less
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# future-proof than dracut.
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echo "Could not find dracut, attempting C initrd"
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cd $D
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mkdir -p initrd
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cd initrd
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cat > init.c << '___EOF___'
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#ifndef NOLIBC
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#include <unistd.h>
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#include <sys/time.h>
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#endif
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volatile unsigned long delaycount;
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int main(int argc, int argv[])
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{
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int i;
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struct timeval tv;
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struct timeval tvb;
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for (;;) {
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sleep(1);
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/* Need some userspace time. */
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if (gettimeofday(&tvb, NULL))
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continue;
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do {
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for (i = 0; i < 1000 * 100; i++)
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delaycount = i * i;
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if (gettimeofday(&tv, NULL))
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break;
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tv.tv_sec -= tvb.tv_sec;
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if (tv.tv_sec > 1)
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break;
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tv.tv_usec += tv.tv_sec * 1000 * 1000;
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tv.tv_usec -= tvb.tv_usec;
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} while (tv.tv_usec < 1000);
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}
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return 0;
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}
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___EOF___
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# build using nolibc on supported archs (smaller executable) and fall
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# back to regular glibc on other ones.
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if echo -e "#if __x86_64__||__i386__||__i486__||__i586__||__i686__" \
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"||__ARM_EABI__||__aarch64__\nyes\n#endif" \
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| ${CROSS_COMPILE}gcc -E -nostdlib -xc - \
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| grep -q '^yes'; then
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# architecture supported by nolibc
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${CROSS_COMPILE}gcc -fno-asynchronous-unwind-tables -fno-ident \
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-nostdlib -include ../../../../include/nolibc/nolibc.h \
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-lgcc -s -static -Os -o init init.c
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else
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${CROSS_COMPILE}gcc -s -static -Os -o init init.c
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fi
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rm init.c
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echo "Done creating a statically linked C-language initrd"
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exit 0
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