Hi, Jiri: On 9/4/23 22:10, Jiri Olsa wrote: > On Mon, Sep 04, 2023 at 02:24:44AM +0000, Hengqi Chen wrote: >> Currently, we allow users to specify symbol name for uprobe in a qualified >> form, i.e. func@@LIB or func@@LIB_VERSION. For dynamic symbols, their version >> info is actually stored in .gnu.version and .gnu.version_d sections of the ELF >> objects. So dynamic symbols and the qualified name won't match. Add support for >> symbol versioning ([0]) so that we can handle the above case. >> >> [0]: https://refspecs.linuxfoundation.org/LSB_3.0.0/LSB-PDA/LSB-PDA.junk/symversion.html >> >> Signed-off-by: Hengqi Chen <hengqi.chen@xxxxxxxxx> >> --- >> tools/lib/bpf/elf.c | 98 +++++++++++++++++++++++++++++++++++++++++---- >> 1 file changed, 90 insertions(+), 8 deletions(-) >> >> diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c >> index 5c9e588b17da..ed3d9880eaa4 100644 >> --- a/tools/lib/bpf/elf.c >> +++ b/tools/lib/bpf/elf.c >> @@ -9,6 +9,7 @@ >> #include "str_error.h" >> >> #define STRERR_BUFSIZE 128 >> +#define HIDDEN_BIT 16 > > hum, the docs says it's bit 15 ? Ahh, right, should be 15. > > SNIP > >> @@ -138,12 +155,57 @@ static struct elf_sym *elf_sym_iter_next(struct elf_sym_iter *iter) >> >> iter->next_sym_idx = idx + 1; >> ret->name = name; >> + ret->ver = 0; >> + ret->hidden = false; >> + >> + if (iter->versyms) { >> + if (!gelf_getversym(iter->versyms, idx, &versym)) >> + continue; >> + ret->ver = versym & ~(1 << HIDDEN_BIT); >> + ret->hidden = versym & (1 << HIDDEN_BIT); >> + } >> return ret; >> } >> >> return NULL; >> } >> >> +static const char *elf_get_vername(Elf *elf, int ver) >> +{ >> + GElf_Verdaux verdaux; >> + GElf_Verdef verdef; >> + Elf_Data *verdefs; >> + size_t strtabidx; >> + GElf_Shdr sh; >> + Elf_Scn *scn; >> + int offset; >> + >> + scn = elf_find_next_scn_by_type(elf, SHT_GNU_verdef, NULL); >> + if (!scn) >> + return NULL; >> + if (!gelf_getshdr(scn, &sh)) >> + return NULL; >> + strtabidx = sh.sh_link; >> + verdefs = elf_getdata(scn, 0); > > should we read verdefs same as you did for versyms in elf_sym_iter_new, > so you don't need to read that every time? > It looks weird to retrieve version from elf_sym_iter, and we should not reach here too many times. >> + >> + offset = 0; >> + while (gelf_getverdef(verdefs, offset, &verdef)) { >> + if (verdef.vd_ndx != ver) { >> + if (!verdef.vd_next) >> + break; >> + >> + offset += verdef.vd_next; >> + continue; >> + } >> + >> + if (!gelf_getverdaux(verdefs, offset + verdef.vd_aux, &verdaux)) >> + break; >> + >> + return elf_strptr(elf, strtabidx, verdaux.vda_name); >> + >> + } >> + return NULL; >> +} >> >> /* Transform symbol's virtual address (absolute for binaries and relative >> * for shared libs) into file offset, which is what kernel is expecting >> @@ -191,6 +253,9 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name) >> for (i = 0; i < ARRAY_SIZE(sh_types); i++) { >> struct elf_sym_iter iter; >> struct elf_sym *sym; >> + size_t sname_len; >> + char sname[256]; > > is this enough? not sure if there's symbol max size, > maybe we could also use asprintf below > OK, will use asprintf instead. >> + const char *ver; >> int last_bind = -1; >> int cur_bind; >> >> @@ -201,14 +266,31 @@ long elf_find_func_offset(Elf *elf, const char *binary_path, const char *name) >> goto out; >> >> while ((sym = elf_sym_iter_next(&iter))) { >> - /* User can specify func, func@@LIB or func@@LIB_VERSION. */ >> - if (strncmp(sym->name, name, name_len) != 0) >> - continue; >> - /* ...but we don't want a search for "foo" to match 'foo2" also, so any >> - * additional characters in sname should be of the form "@@LIB". >> - */ >> - if (!is_name_qualified && sym->name[name_len] != '\0' && sym->name[name_len] != '@') >> - continue; >> + if (sh_types[i] == SHT_DYNSYM && is_name_qualified) { >> + if (sym->hidden) >> + continue; >> + >> + sname_len = strlen(sym->name); >> + if (strncmp(sym->name, name, sname_len) != 0) >> + continue; >> + >> + ver = elf_get_vername(elf, sym->ver); >> + if (!ver) >> + continue; >> + >> + snprintf(sname, sizeof(sname), "%s@@%s", sym->name, ver); >> + if (strncmp(sname, name, name_len) != 0) >> + continue; >> + } else { >> + /* User can specify func, func@@LIB or func@@LIB_VERSION. */ >> + if (strncmp(sym->name, name, name_len) != 0) >> + continue; >> + /* ...but we don't want a search for "foo" to match 'foo2" also, so any >> + * additional characters in sname should be of the form "@@LIB". >> + */ >> + if (!is_name_qualified && sym->name[name_len] != '\0' && sym->name[name_len] != '@') >> + continue; > > hum, I never checked the versioned symbols, but it looks like we > don't get symbols in 'symbol@version' form, so I wonder how that > worked before > > would be great to have a selftest for that > > also I had to add change below to test that through prog's section, > I think we need allow '@' in there > Let me try. > thanks, > jirka > > > --- > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 96ff1aa4bf6a..a30f3c48f891 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -11512,8 +11512,11 @@ static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf > > *link = NULL; > > - n = sscanf(prog->sec_name, "%m[^/]/%m[^:]:%m[a-zA-Z0-9_.]+%li", > + n = sscanf(prog->sec_name, "%m[^/]/%m[^:]:%m[a-zA-Z0-9_.@]+%li", > &probe_type, &binary_path, &func_name, &offset); --- Hengqi
