Hi,
After updating Dwarves to v1.25 we are getting SIGSEGV while building
kernel on 32-bit x86 architecture. It looks like this:
BTF .btf.vmlinux.bin.o
scripts/link-vmlinux.sh: line 111: 395728 Segmentation fault LLVM_OBJCOPY="${OBJCOPY}" ${PAHOLE} -J ${PAHOLE_FLAGS} ${1}
LD .tmp_vmlinux.kallsyms1
NM .tmp_vmlinux.kallsyms1.syms
KSYMS .tmp_vmlinux.kallsyms1.S
AS .tmp_vmlinux.kallsyms1.S
LD .tmp_vmlinux.kallsyms2
NM .tmp_vmlinux.kallsyms2.syms
KSYMS .tmp_vmlinux.kallsyms2.S
AS .tmp_vmlinux.kallsyms2.S
LD vmlinux
BTFIDS vmlinux
libbpf: failed to find '.BTF' ELF section in vmlinux
FAILED: load BTF from vmlinux: No data available
What crashes is this command:
pahole -J --btf_gen_floats -j --lang_exclude=rust .tmp_vmlinux.btf
I found that cause of the crash is that build box having 128 cores. By
experiment I found that with -j81 pahole works OK, but with -j82 or
greater it crashes.
$ gdb -q --args pahole -J --btf_gen_floats -j111 --lang_exclude=rust .tmp_vmlinux.btf
Thread 15 "pahole" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0xda5ffb40 (LWP 3102466)]
0xf7f3c944 in btf_encoder__btf (encoder=0x0) at /usr/src/debug/dwarves-1.25/btf_encoder.c:1890
1890 return encoder->btf;
(gdb) bt
#0 0xf7f3c944 in btf_encoder__btf (encoder=0x0) at /usr/src/debug/dwarves-1.25/btf_encoder.c:1890
#1 0x5655c25d in pahole_stealer (cu=0xd9a01f80, conf_load=0x565640c0 <conf_load>, thr_data=0x56567c18) at /usr/src/debug/dwarves-1.25/pahole.c:3100
#2 0xf7f452d7 in cu__finalize (cu=cu@entry=0xd9a01f80, conf=0x565640c0 <conf_load>, thr_data=thr_data@entry=0x56567c18)
at /usr/src/debug/dwarves-1.25/dwarf_loader.c:3001
#3 0xf7f4541d in cus__finalize (thr_data=0x56567c18, conf=<optimized out>, cu=0xd9a01f80, cus=0x565651c0) at /usr/src/debug/dwarves-1.25/dwarf_loader.c:3008
#4 dwarf_cus__create_and_process_cu (dcus=dcus@entry=0xffffd19c, cu_die=cu_die@entry=0xda5ff38c, pointer_size=<optimized out>, thr_data=0x56567c18)
at /usr/src/debug/dwarves-1.25/dwarf_loader.c:3207
#5 0xf7f461af in dwarf_cus__process_cu_thread (arg=0xffffcbf8) at /usr/src/debug/dwarves-1.25/dwarf_loader.c:3250
#6 0xf7db4258 in start_thread (arg=<optimized out>) at pthread_create.c:444
#7 0xf7e3a878 in clone3 () from /lib/libc.so.6
(gdb) p encoder
$1 = (struct btf_encoder *) 0x0
(gdb) f 1
#1 0x5655c25d in pahole_stealer (cu=0xd9a01f80, conf_load=0x565640c0 <conf_load>, thr_data=0x56567c18) at /usr/src/debug/dwarves-1.25/pahole.c:3100
3100 thread->btf = btf_encoder__btf(thread->encoder);
(gdb) list -2
3093 thread->encoder =
3094 btf_encoder__new(cu, detached_btf_filename,
3095 NULL,
3096 skip_encoding_btf_vars,
3097 btf_encode_force,
3098 btf_gen_floats,
3099 global_verbose);
3100 thread->btf = btf_encoder__btf(thread->encoder);
3101 }
3102 encoder = thread->encoder;
I think that return value of btf_encoder__new is not checked. But did
not investigate further why is this happening. It would be great to have
this fixed.
Thanks,
