Messages in this thread Patch in this message | | | From | Adrian Hunter <> | Subject | [PATCH 07/10] perf symbols: Add symbol for .plt header | Date | Fri, 20 Jan 2023 14:34:53 +0200 |
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perf expands the _init symbol over .plt because there are no PLT symbols at that point, but then dso__synthesize_plt_symbols() creates them.
Fix by truncating the previous symbol and inserting a symbol for .plt header.
Example:
Before:
$ perf test --dso `which uname` -v Symbols 74: Symbols : --- start --- test child forked, pid 191028 Problems creating module maps, continuing anyway... Testing /usr/bin/uname Overlapping symbols: 2000-25f0 g _init 2040-2050 g free@plt test child finished with -1 ---- end ---- Symbols: FAILED! $ perf test --dso `which uname` -vv Symbols 2>/tmp/cmp1.txt
After:
$ perf test --dso `which uname` -v Symbols 74: Symbols : --- start --- test child forked, pid 194291 Testing /usr/bin/uname test child finished with 0 ---- end ---- Symbols: Ok $ perf test --dso `which uname` -vv Symbols 2>/tmp/cmp2.txt $ diff /tmp/cmp1.txt /tmp/cmp2.txt 4,5c4 < test child forked, pid 191031 < Problems creating module maps, continuing anyway... --- > test child forked, pid 194296 9c8,9 < 2000-25f0 g _init --- > 2000-2030 g _init > 2030-2040 g .plt 100,103c100 < Overlapping symbols: < 2000-25f0 g _init < 2040-2050 g free@plt < test child finished with -1 --- > test child finished with 0 105c102 < Symbols: FAILED! --- > Symbols: Ok $
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> --- tools/perf/util/symbol-elf.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-)
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c index 87b82507c205..a8b7c3860b2d 100644 --- a/tools/perf/util/symbol-elf.c +++ b/tools/perf/util/symbol-elf.c @@ -389,6 +389,27 @@ int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss) elf = ss->elf; ehdr = ss->ehdr; + if (!elf_section_by_name(elf, &ehdr, &shdr_plt, ".plt", NULL)) + return 0; + + /* + * A symbol from a previous section (e.g. .init) can have been expanded + * by symbols__fixup_end() to overlap .plt. Truncate it before adding + * a symbol for .plt header. + */ + f = dso__find_symbol_nocache(dso, shdr_plt.sh_offset); + if (f && f->start < shdr_plt.sh_offset && f->end > shdr_plt.sh_offset) + f->end = shdr_plt.sh_offset; + + if (!get_plt_sizes(dso, &ehdr, &shdr_plt, &plt_header_size, &plt_entry_size)) + return 0; + + /* Add a symbol for .plt header */ + f = symbol__new(shdr_plt.sh_offset, plt_header_size, STB_GLOBAL, STT_FUNC, ".plt"); + if (!f) + goto out_elf_end; + symbols__insert(&dso->symbols, f); + scn_dynsym = ss->dynsym; shdr_dynsym = ss->dynshdr; dynsym_idx = ss->dynsym_idx; @@ -408,9 +429,6 @@ int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss) if (shdr_rel_plt.sh_link != dynsym_idx) goto out_elf_end; - if (elf_section_by_name(elf, &ehdr, &shdr_plt, ".plt", NULL) == NULL) - goto out_elf_end; - /* * Fetch the relocation section to find the idxes to the GOT * and the symbols in the .dynsym they refer to. @@ -436,8 +454,6 @@ int dso__synthesize_plt_symbols(struct dso *dso, struct symsrc *ss) nr_rel_entries = shdr_rel_plt.sh_size / shdr_rel_plt.sh_entsize; plt_offset = shdr_plt.sh_offset; - if (!get_plt_sizes(dso, &ehdr, &shdr_plt, &plt_header_size, &plt_entry_size)) - return 0; plt_offset += plt_header_size; if (shdr_rel_plt.sh_type == SHT_RELA) { -- 2.34.1
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