Based on the last recent conversation (and comment #9) I am closing this ticket
for now as Invalid.
If the upstream work succeeded and BPF got stabilized and tested again and
further issues occur, a new LP bug can be opened any time.
** Changed in: linux (Ubuntu Focal)
Status: In Progress => Invalid
** Changed in: linux (Ubuntu Bionic)
Status: Triaged => Invalid
** Changed in: linux (Ubuntu)
Status: New => Invalid
** Changed in: ubuntu-z-systems
Status: In Progress => Invalid
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https://bugs.launchpad.net/bugs/1888507
Title:
[UBUNTU 18.04] BPF programs fail on Ubuntu s390x
Status in Ubuntu on IBM z Systems:
Invalid
Status in linux package in Ubuntu:
Invalid
Status in linux source package in Bionic:
Invalid
Status in linux source package in Focal:
Invalid
Bug description:
[Impact]
Some bpf programs will fail to execute on s390x, returning EFAULT when they
should be able to read user memory.
[Test case]
apt-get source linux
mkdir -p /usr/lib/perf/
cp -a linux-5.4.0/tools/perf/include /usr/lib/perf/
probe_read=$(grep -w probe_read /usr/lib/perf/include/bpf/bpf.h)
probe_read_user=${probe_read//read/read_user}
sed -i "/probe_read)/i$probe_read_user" /usr/lib/perf/include/bpf/bpf.h
probe_read_user_str=${probe_read//read/read_user_str}
sed -i "/probe_read)/i$probe_read_user_str" /usr/lib/perf/include/bpf/bpf.h
ed - linux-5.4.0/tools/perf/examples/bpf/augmented_raw_syscalls.c << EOF
100c
int string_len = probe_read_user_str(&augmented_arg->value, arg_len, arg);
.
w
EOF
perf trace -eopenat,augmented_raw_syscalls.c cat /etc/passwd > /dev/null
You should see:
0.332 ( 0.002 ms): cat/3223 openat(dfd: CWD, filename: "/etc/passwd")
= 3
instead of
0.334 ( 0.003 ms): cat/3739 openat(dfd: CWD, filename: "")
= 3
[Potential regressions]
One potential regression is that unprivileged code can be able to exploit the
changes to read or write kernel memory.
--------------------------------------------------------------------------
We need to run BPF filters to analyse and monitor network traffic. The BPF
filters are created by skydive (http://skydive.network). Currently skydive
fails to install BPF filters on s390x (using Ubuntu 18.04 currently, soon
moving to Ubuntu 20.04).
Because of these failures, we decided to try the BPF samples that come
with the kernel first. These samples also fail on s390x while they
work fine on Intel.
shense@boe-build:~/bionic/samples/bpf$ uname -a
Linux boe-build 4.15.0-112-generic #113-Ubuntu SMP Thu Jul 9 23:40:36 UTC
2020 s390x s390x s390x GNU/Linux
Example instructions:
sudo apt install -y dpkg-dev clang llvm libelf-dev
sudo apt-get source linux-image-unsigned-$(uname -r)
cd linux-4.15.0/
make headers_install
make samples/bpf/
Errors:
shense@boe-build:~/bionic/samples/bpf$ sudo ./test_map_in_map
[sudo] password for shense:
invalid relo for insn[4].code 0x85
bpf_load_program() err=22
0: (bf) r7 = r1
1: (b7) r1 = 0
2: (63) *(u32 *)(r10 -32) = r1
3: (bf) r1 = r7
4: (85) call unknown#-1
BPF_CALL uses reserved fields
0: (bf) r7 = r1
1: (b7) r1 = 0
2: (63) *(u32 *)(r10 -32) = r1
3: (bf) r1 = r7
4: (85) call unknown#-1
BPF_CALL uses reserved fields
shense@boe-build:~/bionic/samples/bpf$ sudo ./map_perf_test
invalid relo for insn[22].code 0x85
bpf_load_program() err=22
0: (bf) r7 = r1
1: (18) r1 = 0x207265743a25646e
3: (7b) *(u64 *)(r10 -16) = r1
4: (18) r1 = 0x705f616c6c6f632e
6: (7b) *(u64 *)(r10 -24) = r1
7: (18) r1 = 0x5f6c72755f686d61
9: (7b) *(u64 *)(r10 -32) = r1
10: (18) r1 = 0x7420737472657373
12: (7b) *(u64 *)(r10 -40) = r1
13: (18) r1 = 0x4661696c65642061
15: (7b) *(u64 *)(r10 -48) = r1
16: (b7) r1 = 0
17: (73) *(u8 *)(r10 -8) = r1
18: (b7) r2 = 1
19: (7b) *(u64 *)(r10 -72) = r2
20: (63) *(u32 *)(r10 -76) = r1
21: (bf) r1 = r7
22: (85) call unknown#-1
BPF_CALL uses reserved fields
0: (bf) r7 = r1
1: (18) r1 = 0x207265743a25646e
3: (7b) *(u64 *)(r10 -16) = r1
4: (18) r1 = 0x705f616c6c6f632e
6: (7b) *(u64 *)(r10 -24) = r1
7: (18) r1 = 0x5f6c72755f686d61
9: (7b) *(u64 *)(r10 -32) = r1
10: (18) r1 = 0x7420737472657373
12: (7b) *(u64 *)(r10 -40) = r1
13: (18) r1 = 0x4661696c65642061
15: (7b) *(u64 *)(r10 -48) = r1
16: (b7) r1 = 0
17: (73) *(u8 *)(r10 -8) = r1
18: (b7) r2 = 1
19: (7b) *(u64 *)(r10 -72) = r2
20: (63) *(u32 *)(r10 -76) = r1
21: (bf) r1 = r7
22: (85) call unknown#-1
BPF_CALL uses reserved fields
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