Changes in V2: - Updated mailing list distribution - Decrease indentation, add null pointer checks per Leo Yan review

Add dso__is_pie global to read the .dynamic section DT_FLAGS_1 entry for the DF_1_PIE flag. This identifies position executable code.

Signed-off-by: Steve Clevenger scclevenger@os.amperecomputing.com --- tools/perf/util/symbol-elf.c | 60 ++++++++++++++++++++++++++++++++++++ 1 file changed, 60 insertions(+)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c index e398abfd13a0..0e49c1345a67 100644 --- a/tools/perf/util/symbol-elf.c +++ b/tools/perf/util/symbol-elf.c @@ -662,6 +662,66 @@ static int dso__synthesize_plt_got_symbols(struct dso *dso, Elf *elf, return err; }

+/* + * Check dynamic section DT_FLAGS_1 for a Position Independent + * Executable (PIE). + */ +bool dso__is_pie(struct dso *dso) +{ + Elf *elf = NULL; + Elf_Scn *scn = NULL; + GElf_Ehdr ehdr; + GElf_Shdr shdr; + bool is_pie = false; + char dso_path[PATH_MAX]; + int fd = -1; + + if (!dso || (elf_version(EV_CURRENT) == EV_NONE)) + goto exit; // false + + dso__build_id_filename(dso, dso_path, sizeof(dso_path), false); + + fd = open(dso_path, O_RDONLY); + + if (fd < 0) { + pr_debug("%s: cannot read cached %s.\n", __func__, dso_path); + goto exit; // false + } + + elf = elf_begin(fd, ELF_C_READ, NULL); + gelf_getehdr(elf, &ehdr); + + if (ehdr.e_type == ET_DYN) { + Elf_Data *data; + GElf_Dyn *entry; + int n_entries = shdr.sh_size / sizeof(GElf_Dyn); + + scn = elf_section_by_name(elf, &ehdr, &shdr, ".dynamic", NULL); + if (!scn) + goto exit; // false + + data = (Elf_Data *) elf_getdata(scn, NULL); + if (!data || !data->d_buf) + goto exit; // false + + // check DT_FLAGS_1 + for (int i = 0; i < n_entries; i++) { + entry = ((GElf_Dyn *) data->d_buf) + i; + if (entry->d_tag == DT_FLAGS_1) { + if ((entry->d_un.d_val & DF_1_PIE) != 0) { + is_pie = true; + break; + } + } + } // end for + } + + elf_end(elf); + close(fd); +exit: + return is_pie; +} + /* * We need to check if we have a .dynsym, so that we can handle the * .plt, synthesizing its symbols, that aren't on the symtabs (be it