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Message-ID: <2559a8cd-b439-43fc-96e4-d5f2941ca4d8@linux.dev> Date: Tue, 12 Aug 2025 09:11:45 -0700 From: Yonghong Song <yonghong.song@...ux.dev> To: 赵佳炜 <phoenix500526@....com> 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: [PATCH v7 2/2] selftests/bpf: Force -O2 for USDT selftests to cover SIB handling logic On 8/12/25 12:02 AM, 赵佳炜 wrote: > 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) Could you share the complete source codes and compiler options which reproduce the above result? > > > > 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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