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 int elf_open(const char *binary_path, struct elf_fd *elf_fd) { @@ -64,11 +65,14 @@ struct elf_sym { const char *name; GElf_Sym sym; GElf_Shdr sh; + int ver; + bool hidden; }; struct elf_sym_iter { Elf *elf; Elf_Data *syms; + Elf_Data *versyms; size_t nr_syms; size_t strtabidx; size_t next_sym_idx; @@ -111,6 +115,18 @@ static int elf_sym_iter_new(struct elf_sym_iter *iter, iter->nr_syms = iter->syms->d_size / sh.sh_entsize; iter->elf = elf; iter->st_type = st_type; + + /* Version symbol table only meaningful to dynsym only */ + if (sh_type != SHT_DYNSYM) + return 0; + + scn = elf_find_next_scn_by_type(elf, SHT_GNU_versym, NULL); + if (!scn) + return 0; + if (!gelf_getshdr(scn, &sh)) + return -EINVAL; + iter->versyms = elf_getdata(scn, 0); + return 0; } @@ -119,6 +135,7 @@ static struct elf_sym *elf_sym_iter_next(struct elf_sym_iter *iter) struct elf_sym *ret = &iter->sym; GElf_Sym *sym = &ret->sym; const char *name = NULL; + GElf_Versym versym; Elf_Scn *sym_scn; size_t idx; @@ -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); + + 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]; + 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; + } cur_bind = GELF_ST_BIND(sym->sym.st_info); -- 2.39.3
