Am 24.10.2019 um 19:49 schrieb Yonghong Song yhs@fb.com:
On 10/24/19 9:04 AM, Ilya Leoshkevich wrote:
Am 23.10.2019 um 03:35 schrieb Prabhakar Kushwaha prabhakar.pkin@gmail.com:
Adding other mailing list, folks...
Hi All,
I am trying to build kselftest on Linux-5.4 on ubuntu 18.04. I installed LLVM-9.0.0 and Clang-9.0.0 from below links after following steps from [1] because of discussion [2]
https://urldefense.proofpoint.com/v2/url?u=https-3A__releases.llvm.org_9.0.0... https://urldefense.proofpoint.com/v2/url?u=https-3A__releases.llvm.org_9.0.0... https://urldefense.proofpoint.com/v2/url?u=https-3A__releases.llvm.org_9.0.0...
Now, i am trying with llc -march=bpf, with this segmentation fault is coming as below:
gcc -g -Wall -O2 -I../../../include/uapi -I../../../lib -I../../../lib/bpf -I../../../../include/generated -DHAVE_GENHDR -I../../../include -Dbpf_prog_load=bpf_prog_test_load -Dbpf_load_program=bpf_test_load_program test_flow_dissector.c /usr/src/tovards/linux/tools/testing/selftests/bpf/test_stub.o /usr/src/tovards/linux/tools/testing/selftests/bpf/libbpf.a -lcap -lelf -lrt -lpthread -o /usr/src/tovards/linux/tools/testing/selftests/bpf/test_flow_dissector gcc -g -Wall -O2 -I../../../include/uapi -I../../../lib -I../../../lib/bpf -I../../../../include/generated -DHAVE_GENHDR -I../../../include -Dbpf_prog_load=bpf_prog_test_load -Dbpf_load_program=bpf_test_load_program test_tcp_check_syncookie_user.c /usr/src/tovards/linux/tools/testing/selftests/bpf/test_stub.o /usr/src/tovards/linux/tools/testing/selftests/bpf/libbpf.a -lcap -lelf -lrt -lpthread -o /usr/src/tovards/linux/tools/testing/selftests/bpf/test_tcp_check_syncookie_user gcc -g -Wall -O2 -I../../../include/uapi -I../../../lib -I../../../lib/bpf -I../../../../include/generated -DHAVE_GENHDR -I../../../include -Dbpf_prog_load=bpf_prog_test_load -Dbpf_load_program=bpf_test_load_program test_lirc_mode2_user.c /usr/src/tovards/linux/tools/testing/selftests/bpf/test_stub.o /usr/src/tovards/linux/tools/testing/selftests/bpf/libbpf.a -lcap -lelf -lrt -lpthread -o /usr/src/tovards/linux/tools/testing/selftests/bpf/test_lirc_mode2_user (clang -I. -I./include/uapi -I../../../include/uapi -I/usr/src/tovards/linux/tools/testing/selftests/bpf/../usr/include -D__TARGET_ARCH_arm64 -g -idirafter /usr/local/include -idirafter /usr/local/lib/clang/9.0.0/include -idirafter /usr/include/aarch64-linux-gnu -idirafter /usr/include -Wno-compare-distinct-pointer-types -O2 -target bpf -emit-llvm \ -c progs/test_core_reloc_arrays.c -o - || echo "clang failed") | \ llc -march=bpf -mcpu=probe -filetype=obj -o /usr/src/tovards/linux/tools/testing/selftests/bpf/test_core_reloc_arrays.o Stack dump: 0. Program arguments: llc -march=bpf -mcpu=probe -filetype=obj -o /usr/src/tovards/linux/tools/testing/selftests/bpf/test_core_reloc_arrays.o
- Running pass 'Function Pass Manager' on module '<stdin>'.
- Running pass 'BPF Assembly Printer' on function '@test_core_arrays'
#0 0x0000aaaac618db08 llvm::sys::PrintStackTrace(llvm::raw_ostream&) (/usr/local/bin/llc+0x152eb08) Segmentation fault
Hi,
FWIW I can confirm that this is happening on s390 too with llvm-project commit 950b800c451f.
Here is the reduced sample that triggers this (with -march=bpf -mattr=+alu32):
struct b { int e; } c; int f() { return __builtin_preserve_field_info(c.e, 0); }
This is compiled into:
0B bb.0 (%ir-block.0): 16B %0:gpr = LD_imm64 @"b:0:0$0:0" 32B $w0 = COPY %0:gpr, debug-location !17; 1-E.c:5:3 48B RET implicit killed $w0, debug-location !17; 1-E.c:5:3
and then BPFInstrInfo::copyPhysReg chokes on COPY, since $w0 and %0 are in different register classes.
Ilya,
Thanks for reporting. I can reproduce the issue with latest trunk. I will investigate and fix the problem soon.
Yonghong
Thanks for taking care of this! Just FYI, bisect pointed to 05e46979d2f4 ("[BPF] do compile-once run-everywhere relocation for bitfields").
Could you please add me to Phabricator review? I'm curious what the proper solution is going to be, as I'm still not sure whether handling asymmetric copies is the right approach, or whether they should rather be prevented from occuring in the first place.
Best regards, Ilya