On 14/08/2025 10:42, Changqing Li wrote: > > On 8/14/25 17:20, Changqing Li wrote: >> >> On 8/14/25 07:45, Ihor Solodrai wrote: >>> CAUTION: This email comes from a non Wind River email account! >>> Do not click links or open attachments unless you recognize the >>> sender and know the content is safe. >>> >>> On 8/10/25 6:18 PM, Changqing Li wrote: >>>> Hi, Dear maintainers >>>> >>>> I met a "Segmentation fault" error of pahole. It happened when I >>>> passed an ELF file without .symtab section. >>>> Maybe I passed an unsupport file, but I think it should not segfault, >>>> maybe a warnning or error message is better. >>>> >>>> >>>> Here is the detailed info: >>>> Pahole version: >>>> # pahole --version >>>> v1.29 >>>> >>>> Reproduce Command: >>>> root@intel-x86-64:/~# pahole --btf_features=default -J /boot/ >>>> vmlinux-6.12.40-yocto-standard >>>> pahole[599]: segfault at 8 ip 00007f7c92d819e2 sp 00007f7c799febe0 >>>> error >>>> 6 in libdwarves.so.1.0.0[189e2,7f7c92d72000+1c000] likely on CPU 0 >>>> (core >>>> 0, socket 0) >>>> Code: 74 19 ff ff 48 39 dd 75 ef 4c 89 ef e8 67 19 ff ff 49 8b 7c 24 18 >>>> e8 8d 13 ff ff 49 8b 14 24 49 8b 44 24 08 4c 89 e7 45 31 e4 <48> 89 42 >>>> 08 48 89 10 e8 42 19 ff ff e9 30 ff ff ff e8 58 0a ff ff >>>> Segmentation fault (core dumped) >>>> >>>> root@intel-x86-64:~# file /boot/vmlinux-6.12.40-yocto-standard >>>> /boot/vmlinux-6.12.40-yocto-standard: ELF 64-bit LSB executable, >>>> x86-64, >>>> version 1 (SYSV), statically linked, >>>> BuildID[sha1]=1e73fe48101f07b9d991dc045ab9f9672a0feac0, stripped >>>> >>>> root@intel-x86-64:/usr/bin# readelf -S /boot/vmlinux-6.12.40-yocto- >>>> standard | grep .symtab >>>> [ 4] __ksymtab PROGBITS ffffffff82c11e00 01e11e00 >>>> [ 5] __ksymtab_gpl PROGBITS ffffffff82c24730 01e24730 >>>> [ 6] __ksymtab_strings PROGBITS ffffffff82c397f0 01e397f0 >>>> >>>> >>>> (gdb) bt >>>> #0 elf_functions__new (elf=<optimized out>) at /usr/src/debug/ >>>> pahole/1.29/btf_encoder.c:196 >>>> #1 0x00007ffff7f92a7d in btf_encoder__elf_functions >>>> (encoder=encoder@entry=0x7fffd8008dc0) at /usr/src/debug/pahole/1.29/ >>>> btf_encoder.c:1374 >>>> #2 0x00007ffff7f94489 in btf_encoder__new (cu=cu@entry=0x7fffd8001e50, >>>> detached_filename=<optimized out>, warning: could not convert 'btf' >>>> from >>>> the host encoding (ANSI_X3.4-1968) to UTF-32. >>>> This normally should not happen, please file a bug report. >>>> base_btf=0x0, >>>> verbose=<optimized out>, conf_load=conf_load@entry=0x555555565280 >>>> <conf_load>) at /usr/src/debug/pahole/1.29/btf_encoder.c:2431 >>>> #3 0x000055555555db49 in pahole_stealer__btf_encode >>>> (cu=0x7fffd8001e50, >>>> conf_load=0x555555565280 <conf_load>) >>>> at /usr/src/debug/pahole/1.29/pahole.c:3126 >>>> #4 pahole_stealer (cu=0x7fffd8001e50, conf_load=0x555555565280 >>>> <conf_load>) at /usr/src/debug/pahole/1.29/pahole.c:3187 >>>> #5 0x00007ffff7f9d023 in cus__steal_now (cus=<optimized out>, >>>> cu=<optimized out>, conf=<optimized out>) >>>> at /usr/src/debug/pahole/1.29/dwarf_loader.c:3266 >>>> #6 dwarf_loader__worker_thread (arg=0x7fffffffe700) at /usr/src/debug/ >>>> pahole/1.29/dwarf_loader.c:3672 >>>> #7 0x00007ffff7dbe722 in start_thread (arg=<optimized out>) at >>>> pthread_create.c:448 >>>> #8 0x00007ffff7e314fc in __GI___clone3 () at ../sysdeps/unix/sysv/ >>>> linux/x86_64/clone3.S:78 >>>> (gdb) >>>> >>>> >>>> Command "pahole --btf_features=default -J /boot/.debug/ >>>> vmlinux-6.12.40- >>>> yocto-standard " works well since /boot/.debug/vmlinux-6.12.40-yocto- >>>> standard has .symtab section. >>>> root@intel-x86-64:/usr/bin# file /boot/.debug/vmlinux-6.12.40-yocto- >>>> standard >>>> /boot/.debug/vmlinux-6.12.40-yocto-standard: ELF 64-bit LSB executable, >>>> x86-64, version 1 (SYSV), statically linked, >>>> BuildID[sha1]=1e73fe48101f07b9d991dc045ab9f9672a0feac0, with >>>> debug_info, >>>> not stripped >>>> >>>> root@intel-x86-64:/usr/bin# readelf -S /boot/.debug/vmlinux-6.12.40- >>>> yocto-standard | grep .symtab >>>> [ 4] __ksymtab NOBITS ffffffff82c11e00 00001000 >>>> [ 5] __ksymtab_gpl NOBITS ffffffff82c24730 00001000 >>>> [ 6] __ksymtab_strings NOBITS ffffffff82c397f0 00001000 >>>> [49] .symtab SYMTAB 0000000000000000 154cf200 >>>> >>> >>> Hi Changqing Li, thanks for the bug report. >>> >>> I couldn't reproduce this error with a stripped vmlinux: >>> >>> $ objcopy --strip-all ~/kernels/bpf-next/.tmp_vmlinux1 vmlinux-strip-all >>> >>> v1.29 fails with: >>> $ ./build/pahole --btf_features=default -J $(realpath vmlinux-strip-all) >>> Error creating BTF encoder. >>> >>> v1.30 fails with: >>> $ ./build/pahole --btf_features=default -J $(realpath vmlinux-strip-all) >>> pahole: /home/isolodrai/pahole/vmlinux-strip-all: Invalid argument >>> >>> Different errors are not nice, but at least no segfault. >>> >>> Could you please share the vmlinux binary that causes the error? >>> And also check if you get a segfault on v1.30 too? >>> >>> Thanks. >>> >> Hi, Ihor >> Thanks for checking this. Here is my retest result: >> On version 1.29: >> root@intel-x86-64:~# pahole --btf_features=default -J /boot/ >> vmlinux-6.12.40-yocto-standard >> pahole[333]: segfault at 8 ip 00007fd5025179e2 sp 00007fd4e73febe0 >> error 6 in libdwarves.so.1.0.0[189e2,7fd502508000+1c000] likely on CPU >> 0 (core 0, socket 0) >> Code: 74 19 ff ff 48 39 dd 75 ef 4c 89 ef e8 67 19 ff ff 49 8b 7c 24 >> 18 e8 8d 13 ff ff 49 8b 14 24 49 8b 44 24 08 4c 89 e7 45 31 e4 <48> 89 >> 42 08 48 89 10 e8 42 19 ff ff e9 30 ff ff ff e8 58 0a ff ff >> Segmentation fault (core dumped) >> root@intel-x86-64:~# cp /boot/vmlinux-6.12.40-yocto-standard /root/ >> root@intel-x86-64:~# pahole --btf_features=default -J /root/ >> vmlinux-6.12.40-yocto-standard >> Error creating BTF encoder. >> >> We can see that the same vmlinux-6.12.40-yocto-standard have different >> result. After do some debugging, I found that >> /boot/vmlinux-6.12.40-yocto-standard segfault since it has debuginfo >> file /boot/.debug/vmlinux-6.12.40-yocto-standard. >> after I move .debug to .xxx, it will not segfault. >> root@intel-x86-64:/boot# mv .debug/ .xxx >> root@intel-x86-64:/boot# pahole --btf_features=default -J /boot/ >> vmlinux-6.12.40-yocto-standard >> Error creating BTF encoder. >> >> dwfl_module_getdwarf in cus__process_dwflmod return different when >> with or without debug, without .debug, dw=NULL, >> with .debug, dw will have a value, then causes the different process. >> >> On version 1.30 >> root@intel-x86-64:~# pahole --version >> v1.30 >> root@intel-x86-64:~# pahole --btf_features=default -J /boot/ >> vmlinux-6.12.40-yocto-standard >> pahole[314]: segfault at 8 ip 00007f2b0b6b2bf3 sp 00007f2af05feb20 >> error 6 in libdwarves.so.1.0.0[18bf3,7f2b0b6a3000+1c000] likely on CPU >> 0 (core 0, socket 0) >> Code: 33 17 ff ff 48 39 dd 75 ee 4c 89 ef e8 26 17 ff ff 49 8b 7c 24 >> 18 e8 5c 11 ff ff 49 8b 14 24 49 8b 44 24 08 4c 89 e7 45 31 e4 <48> 89 >> 42 08 48 89 10 e8 01 17 ff ff e9 2d ff ff ff e8 37 08 ff ff >> Segmentation fault (core dumped) >> root@intel-x86-64:~# cp /boot/vmlinux-6.12.40-yocto-standard /root/ >> root@intel-x86-64:~# pahole --btf_features=default -J /root/ >> vmlinux-6.12.40-yocto-standard >> pahole: /root/vmlinux-6.12.40-yocto-standard: Invalid argument >> root@intel-x86-64:~# cd /root >> root@intel-x86-64:~# mkdir .debug >> root@intel-x86-64:~# cp /boot/.debug/vmlinux-6.12.40-yocto- >> standard .debug/ >> root@intel-x86-64:~# pahole --btf_features=default -J /root/ >> vmlinux-6.12.40-yocto-standard >> pahole[441]: segfault at 8 ip 00007f64a9032bf3 sp 00007f648dffeb20 >> error 6 in libdwarves.so.1.0.0[18bf3,7f64a9023000+1c000] likely on CPU >> 0 (core 0, socket 0) >> Code: 33 17 ff ff 48 39 dd 75 ee 4c 89 ef e8 26 17 ff ff 49 8b 7c 24 >> 18 e8 5c 11 ff ff 49 8b 14 24 49 8b 44 24 08 4c 89 e7 45 31 e4 <48> 89 >> 42 08 48 89 10 e8 01 17 ff ff e9 2d ff ff ff e8 37 08 ff ff >> >> Segmentation fault (core dumped) > > I think this " Invalid argument " change is caused by this commit: > > https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/? > id=b4a071d99bb9e7c0d3c6ea7a6835389a4d350ed4 > > encode BTF with DWARF less files is not support for v1.30, so, since / > boot/vmlinux-6.12.40-yocto-standard without debuginfo, it taken as in > invalid argument, > > I think it is ok, but maybe more clear reason is better. > Thanks for the report! With latest pahole (next branch of https://git.kernel.org/pub/scm/devel/pahole/pahole.git/ ) including Arnaldo's change commit 97bf0a0b0572ec023761da9226b068b59b471de0 Author: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Date: Tue Jul 22 11:22:27 2025 -0300 pahole: Don't fail when encoding BTF on an object with no DWARF info I see the following pahole results against a stripped vmlinux: $ pahole --btf_features=default -J vmlinux.stripped $ echo $? 0 Can you reproduce the segmentation fault with the above pahole? If you can provide a way to get a stripped pahole like the above for me to test with, or provide the kernel .config used to build it, that would be great. Thanks! Alan
