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Message-ID: <65e51538.57aa.1989d162bb8.Coremail.phoenix500526@163.com> Date: Tue, 12 Aug 2025 15:02:12 +0800 (CST) From: 赵佳炜 <phoenix500526@....com> To: "Yonghong Song" <yonghong.song@...ux.dev> Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org, bpf@...r.kernel.org, linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re:Re: [PATCH v7 2/2] selftests/bpf: Force -O2 for USDT selftests to cover SIB handling logic Yes, I've tried that but it didn't help. FYI: $ readelf -nsr usdt_rip Relocation section '.rela.dyn' at offset 0x530 contains 9 entries: Offset Info Type Sym. Value Sym. Name + Addend 000000003df0 000000000008 R_X86_64_RELATIVE 1150 000000003df8 000000000008 R_X86_64_RELATIVE 1110 000000004008 000000000008 R_X86_64_RELATIVE 4008 000000004018 000000000008 R_X86_64_RELATIVE 1160 000000003fd8 000100000006 R_X86_64_GLOB_DAT 0000000000000000 __libc_start_main@...BC_2.34 + 0 000000003fe0 000200000006 R_X86_64_GLOB_DAT 0000000000000000 _ITM_deregisterTM[...] + 0 000000003fe8 000300000006 R_X86_64_GLOB_DAT 0000000000000000 __gmon_start__ + 0 000000003ff0 000400000006 R_X86_64_GLOB_DAT 0000000000000000 _ITM_registerTMCl[...] + 0 000000003ff8 000500000006 R_X86_64_GLOB_DAT 0000000000000000 __cxa_finalize@...BC_2.2.5 + 0 Symbol table '.dynsym' contains 6 entries: Num: Value Size Type Bind Vis Ndx Name 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND 1: 0000000000000000 0 FUNC GLOBAL DEFAULT UND _[...]@GLIBC_2.34 (2) 2: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterT[...] 3: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__ 4: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_registerTMC[...] 5: 0000000000000000 0 FUNC WEAK DEFAULT UND [...]@GLIBC_2.2.5 (3) Symbol table '.symtab' contains 42 entries: Num: Value Size Type Bind Vis Ndx Name 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS Scrt1.o 2: 000000000000038c 32 OBJECT LOCAL DEFAULT 4 __abi_tag 3: 0000000000000000 0 FILE LOCAL DEFAULT ABS usdt_rip.c 4: 0000000000004021 1 OBJECT LOCAL DEFAULT 25 ti 5: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c 6: 00000000000010a0 0 FUNC LOCAL DEFAULT 14 deregister_tm_clones 7: 00000000000010d0 0 FUNC LOCAL DEFAULT 14 register_tm_clones 8: 0000000000001110 0 FUNC LOCAL DEFAULT 14 __do_global_dtors_aux 9: 0000000000004020 1 OBJECT LOCAL DEFAULT 25 completed.0 10: 0000000000003df8 0 OBJECT LOCAL DEFAULT 21 __do_global_dtor[...] 11: 0000000000001150 0 FUNC LOCAL DEFAULT 14 frame_dummy 12: 0000000000003df0 0 OBJECT LOCAL DEFAULT 20 __frame_dummy_in[...] 13: 0000000000000000 0 FILE LOCAL DEFAULT ABS damo.c 14: 0000000000004022 1 OBJECT LOCAL DEFAULT 25 ti 15: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c 16: 00000000000020d8 0 OBJECT LOCAL DEFAULT 19 __FRAME_END__ 17: 0000000000000000 0 FILE LOCAL DEFAULT ABS 18: 0000000000003e00 0 OBJECT LOCAL DEFAULT 22 _DYNAMIC 19: 0000000000002008 0 NOTYPE LOCAL DEFAULT 18 __GNU_EH_FRAME_HDR 20: 0000000000003fc0 0 OBJECT LOCAL DEFAULT 23 _GLOBAL_OFFSET_TABLE_ 21: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __libc_start_mai[...] 22: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterT[...] 23: 0000000000004000 0 NOTYPE WEAK DEFAULT 24 data_start 24: 0000000000001160 8 FUNC GLOBAL DEFAULT 14 add 25: 0000000000004020 0 NOTYPE GLOBAL DEFAULT 24 _edata 26: 0000000000002004 1 NOTYPE WEAK HIDDEN 17 _.stapsdt.base 27: 0000000000004010 8 OBJECT GLOBAL DEFAULT 24 t1 28: 0000000000001168 0 FUNC GLOBAL HIDDEN 15 _fini 29: 0000000000004000 0 NOTYPE GLOBAL DEFAULT 24 __data_start 30: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__ 31: 0000000000004008 0 OBJECT GLOBAL HIDDEN 24 __dso_handle 32: 0000000000002000 4 OBJECT GLOBAL DEFAULT 16 _IO_stdin_used 33: 0000000000004028 0 NOTYPE GLOBAL DEFAULT 25 _end 34: 0000000000001070 38 FUNC GLOBAL DEFAULT 14 _start 35: 0000000000004020 0 NOTYPE GLOBAL DEFAULT 25 __bss_start 36: 0000000000001040 48 FUNC GLOBAL DEFAULT 14 main 37: 0000000000004018 8 OBJECT GLOBAL DEFAULT 24 add_ptr 38: 0000000000004020 0 OBJECT GLOBAL HIDDEN 24 __TMC_END__ 39: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_registerTMC[...] 40: 0000000000000000 0 FUNC WEAK DEFAULT UND __cxa_finalize@G[...] 41: 0000000000001000 0 FUNC GLOBAL HIDDEN 11 _init Displaying notes found in: .note.gnu.property Owner Data size Description GNU 0x00000020 NT_GNU_PROPERTY_TYPE_0 Properties: x86 feature: IBT, SHSTK x86 ISA needed: x86-64-baseline Displaying notes found in: .note.gnu.build-id Owner Data size Description GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring) Build ID: eb615daa575687cc44edc1d339b27890c12c27f1 Displaying notes found in: .note.ABI-tag Owner Data size Description GNU 0x00000010 NT_GNU_ABI_TAG (ABI version tag) OS: Linux, ABI: 3.2.0 Displaying notes found in: .note.stapsdt Owner Data size Description stapsdt 0x00000066 NT_STAPSDT (SystemTap probe descriptors) Provider: usdt_rip Name: rip_global_var Location: 0x0000000000001058, Base: 0x0000000000002004, Semaphore: 0x0000000000000000 Arguments: -1@ti(%rip) 8@..._ptr(%rip) -1@...1(%rip) -1@ti(%rip) At 2025-08-12 13:06:40, "Yonghong Song" <yonghong.song@...ux.dev> wrote: > > >On 8/10/25 1:55 AM, 赵佳炜 wrote: >> >> >> Hi Yonghong, >> >> I found another issue where symbols can be duplicated, and I’m not sure how to tell them apart. >> >> For example, I created two C files named usdt_rip.c and hello.c. Both define their own static ti variables, like:`static volatile char ti = 0;`. >> >> After compiling, I obtained an ELF file usdt_rip whose .symtab contains the following entries: >> >> $ readelf -s usdt_rip >> >> Symbol table '.symtab' contains 42 entries: >> Num: Value Size Type Bind Vis Ndx Name >> 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND >> 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS Scrt1.o >> 2: 000000000000038c 32 OBJECT LOCAL DEFAULT 4 __abi_tag >> 3: 0000000000000000 0 FILE LOCAL DEFAULT ABS usdt_rip.c >> 4: 0000000000004021 1 OBJECT LOCAL DEFAULT 25 ti >> 5: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c >> 6: 00000000000010a0 0 FUNC LOCAL DEFAULT 14 deregister_tm_clones >> 7: 00000000000010d0 0 FUNC LOCAL DEFAULT 14 register_tm_clones >> 8: 0000000000001110 0 FUNC LOCAL DEFAULT 14 __do_global_dtors_aux >> 9: 0000000000004020 1 OBJECT LOCAL DEFAULT 25 completed.0 >> 10: 0000000000003df8 0 OBJECT LOCAL DEFAULT 21 __do_global_dtor[...] >> 11: 0000000000001150 0 FUNC LOCAL DEFAULT 14 frame_dummy >> 12: 0000000000003df0 0 OBJECT LOCAL DEFAULT 20 __frame_dummy_in[...] >> 13: 0000000000000000 0 FILE LOCAL DEFAULT ABS damo.c >> 14: 0000000000004022 1 OBJECT LOCAL DEFAULT 25 ti >> 15: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c >> 16: 00000000000020d8 0 OBJECT LOCAL DEFAULT 19 __FRAME_END__ >> >> >> As you can see, there are two ti variables in the .symtab section. Their values are very close, making them hard to distinguish. >> >> I’m unsure how to handle this situation. Do you have any suggestions? > >Did you check relocations? Relocaitons should be able to point exact which symbol. > >> >> Thanks, >> Jiawei Zhao >[...]
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