1 ===================
2 Testing BPF on s390
3 ===================
4
5 1. Introduction
6 ***************
7
8 IBM Z are mainframe computers, which are desce
9 year 1964. They are supported by the Linux ker
10 document describes how to test BPF in an s390
11
12 2. One-time setup
13 *****************
14
15 The following is required to build and run the
16
17 * s390 GCC
18 * s390 development headers and libraries
19 * Clang with BPF support
20 * QEMU with s390 support
21 * Disk image with s390 rootfs
22
23 Debian supports installing compiler and librar
24 Users of other distros may use debootstrap in
25
26 sudo debootstrap \
27 --variant=minbase \
28 --include=sudo \
29 testing \
30 ./s390-toolchain
31 sudo mount --rbind /dev ./s390-toolchain/dev
32 sudo mount --rbind /proc ./s390-toolchain/pr
33 sudo mount --rbind /sys ./s390-toolchain/sys
34 sudo chroot ./s390-toolchain
35
36 Once on Debian, the build prerequisites can be
37
38 sudo dpkg --add-architecture s390x
39 sudo apt-get update
40 sudo apt-get install \
41 bc \
42 bison \
43 cmake \
44 debootstrap \
45 dwarves \
46 flex \
47 g++ \
48 gcc \
49 g++-s390x-linux-gnu \
50 gcc-s390x-linux-gnu \
51 gdb-multiarch \
52 git \
53 make \
54 python3 \
55 qemu-system-misc \
56 qemu-utils \
57 rsync \
58 libcap-dev:s390x \
59 libelf-dev:s390x \
60 libncurses-dev
61
62 Latest Clang targeting BPF can be installed as
63
64 git clone https://github.com/llvm/llvm-proje
65 ln -s ../../clang llvm-project/llvm/tools/
66 mkdir llvm-project-build
67 cd llvm-project-build
68 cmake \
69 -DLLVM_TARGETS_TO_BUILD=BPF \
70 -DCMAKE_BUILD_TYPE=Release \
71 -DCMAKE_INSTALL_PREFIX=/opt/clang-bpf \
72 ../llvm-project/llvm
73 make
74 sudo make install
75 export PATH=/opt/clang-bpf/bin:$PATH
76
77 The disk image can be prepared using a loopbac
78
79 qemu-img create -f raw ./s390.img 1G
80 sudo losetup -f ./s390.img
81 sudo mkfs.ext4 /dev/loopX
82 mkdir ./s390.rootfs
83 sudo mount /dev/loopX ./s390.rootfs
84 sudo debootstrap \
85 --foreign \
86 --arch=s390x \
87 --variant=minbase \
88 --include=" \
89 iproute2, \
90 iputils-ping, \
91 isc-dhcp-client, \
92 kmod, \
93 libcap2, \
94 libelf1, \
95 netcat, \
96 procps" \
97 testing \
98 ./s390.rootfs
99 sudo umount ./s390.rootfs
100 sudo losetup -d /dev/loopX
101
102 3. Compilation
103 **************
104
105 In addition to the usual Kconfig options requi
106 is also helpful to select::
107
108 CONFIG_NET_9P=y
109 CONFIG_9P_FS=y
110 CONFIG_NET_9P_VIRTIO=y
111 CONFIG_VIRTIO_PCI=y
112
113 as that would enable a very easy way to share
114 machine.
115
116 Compiling kernel, modules and testsuite, as we
117 simplify debugging, can be done using the foll
118
119 make ARCH=s390 CROSS_COMPILE=s390x-linux-gnu
120 make ARCH=s390 CROSS_COMPILE=s390x-linux-gnu
121 make ARCH=s390 CROSS_COMPILE=s390x-linux-gnu
122 -C tools/testing/selftests \
123 TARGETS=bpf \
124 INSTALL_PATH=$PWD/tools/testing/selftests/
125 install
126
127 4. Running the test suite
128 *************************
129
130 The virtual machine can be started as follows:
131
132 qemu-system-s390x \
133 -cpu max,zpci=on \
134 -smp 2 \
135 -m 4G \
136 -kernel linux/arch/s390/boot/compressed/vm
137 -drive file=./s390.img,if=virtio,format=ra
138 -nographic \
139 -append 'root=/dev/vda rw console=ttyS1' \
140 -virtfs local,path=./linux,security_model=
141 -object rng-random,filename=/dev/urandom,i
142 -device virtio-rng-ccw,rng=rng0 \
143 -netdev user,id=net0 \
144 -device virtio-net-ccw,netdev=net0
145
146 When using this on a real IBM Z, ``-enable-kvm
147 performance. When starting the virtual machine
148 setup must be finalized using the following co
149
150 /debootstrap/debootstrap --second-stage
151
152 Directory with the code built on the host as w
153 need to be mounted as follows::
154
155 mkdir -p /linux
156 mount -t 9p linux /linux
157 mount -t proc proc /proc
158 mount -t sysfs sys /sys
159
160 After that, the test suite can be run using th
161
162 cd /linux/tools/testing/selftests/kselftest_
163 ./run_kselftest.sh
164
165 As usual, tests can be also run individually::
166
167 cd /linux/tools/testing/selftests/bpf
168 ./test_verifier
169
170 5. Debugging
171 ************
172
173 It is possible to debug the s390 kernel using
174 by passing ``-s`` to QEMU.
175
176 It is preferable to turn KASLR off, so that gd
177 kernel image in memory, by building the kernel
178
179 RANDOMIZE_BASE=n
180
181 GDB can then be attached using the following c
182
183 gdb-multiarch -ex 'target remote localhost:1
184
185 6. Network
186 **********
187
188 In case one needs to use the network in the vi
189 install additional packages, it can be configu
190
191 dhclient eth0
192
193 7. Links
194 ********
195
196 This document is a compilation of techniques,
197 descriptions can be found by following these l
198
199 - `Debootstrap <https://wiki.debian.org/EmDebi
200 - `Multiarch <https://wiki.debian.org/Multiarc
201 - `Building LLVM <https://llvm.org/docs/CMake.
202 - `Cross-compiling the kernel <https://wiki.ge
203 - `QEMU s390x Guest Support <https://wiki.qemu
204 - `Plan 9 folder sharing over Virtio <https://
205 - `Using GDB with QEMU <https://wiki.osdev.org
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.