Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH] perf tools: Resolve symbols against debug file first | Date | Thu, 14 Jan 2021 22:17:25 +1100 |
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Namhyung Kim <namhyung@kernel.org> writes: > On Wed, Jan 13, 2021 at 8:43 PM Jiri Slaby <jslaby@suse.cz> wrote: >> >> On 13. 01. 21, 11:46, Jiri Olsa wrote: >> > On Wed, Jan 13, 2021 at 09:01:28AM +0100, Jiri Slaby wrote: >> >> With LTO, there are symbols like these: >> >> /usr/lib/debug/usr/lib64/libantlr4-runtime.so.4.8-4.8-1.4.x86_64.debug >> >> 10305: 0000000000955fa4 0 NOTYPE LOCAL DEFAULT 29 Predicate.cpp.2bc410e7 >> >> >> >> This comes from a runtime/debug split done by the standard way: >> >> objcopy --only-keep-debug $runtime $debug >> >> objcopy --add-gnu-debuglink=$debugfn -R .comment -R .GCC.command.line --strip-all $runtime >> >> ... >> >> diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c >> >> index f3577f7d72fe..a31b716fa61c 100644 >> >> --- a/tools/perf/util/symbol-elf.c >> >> +++ b/tools/perf/util/symbol-elf.c >> >> @@ -1226,12 +1226,20 @@ int dso__load_sym(struct dso *dso, struct map *map, struct symsrc *syms_ss, >> >> if (sym.st_shndx == SHN_ABS) >> >> continue; >> >> >> >> - sec = elf_getscn(runtime_ss->elf, sym.st_shndx); >> >> + sec = elf_getscn(syms_ss->elf, sym.st_shndx); >> >> if (!sec) >> >> goto out_elf_end; >> > >> > we iterate symbols from syms_ss, so the fix seems to be correct >> > to call elf_getscn on syms_ss, not on runtime_ss as we do now >> > >> > I'd think this worked only when runtime_ss == syms_ss >> >> No, because the headers are copied 1:1 from runtime_ss to syms_ss. And >> runtime_ss is then stripped, so only .debug* sections are removed there. >> (And syms_ss's are set as NOBITS.) >> >> We iterated .debug* sections in syms_ss and used runtime_ss section >> _headers_ only to adjust symbols (sometimes). That worked. > > It seems PPC has an opd section only in the runtime_ss and that's why > we use it for section headers.
At least on my system (Ubuntu 20.04.1) I see .opd in the debug file with NOBITS set:
$ readelf -e vmlinux.debug | grep opd [37] .opd NOBITS c000000001c1f548 01202e14
But possibly that's not the case with older toolchains?
cheers
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