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 ? 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? > + > + 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 > + 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 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);
