| Message ID | 20181029223203.3135200-1-yhs@fb.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | stephen hemminger |
| Headers | show |
| Series | [iproute2] bpf: check map symbol type properly with newer llvm compiler | expand |
On 10/29/2018 11:32 PM, Yonghong Song wrote: > With llvm 7.0 or earlier, the map symbol type is STT_NOTYPE. > -bash-4.4$ cat t.c > __attribute__((section("maps"))) int g; > -bash-4.4$ clang -target bpf -O2 -c t.c > -bash-4.4$ readelf -s t.o > > Symbol table '.symtab' contains 2 entries: > Num: Value Size Type Bind Vis Ndx Name > 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND > 1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 3 g > -bash-4.4$ > > The following llvm commit enables BPF target to generate > proper symbol type and size. > commit bf6ec206615b9718869d48b4e5400d0c6e3638dd > Author: Yonghong Song <yhs@fb.com> > Date: Wed Sep 19 16:04:13 2018 +0000 > > [bpf] Symbol sizes and types in object file > > Clang-compiled object files currently don't include the symbol sizes and > types. Some tools however need that information. For example, ctfconvert > uses that information to generate FreeBSD's CTF representation from ELF > files. > With this patch, symbol sizes and types are included in object files. > > Signed-off-by: Paul Chaignon <paul.chaignon@orange.com> > Reported-by: Yutaro Hayakawa <yhayakawa3720@gmail.com> > > Hence, for llvm 8.0.0 (currently trunk), symbol type will be not NOTYPE, but OBJECT. > -bash-4.4$ clang -target bpf -O2 -c t.c > -bash-4.4$ readelf -s t.o > > Symbol table '.symtab' contains 3 entries: > Num: Value Size Type Bind Vis Ndx Name > 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND > 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS t.c > 2: 0000000000000000 4 OBJECT GLOBAL DEFAULT 3 g > -bash-4.4$ > > This patch makes sure bpf library accepts both NOTYPE and OBJECT types > of global map symbols. > > Signed-off-by: Yonghong Song <yhs@fb.com> Thanks! Acked-by: Daniel Borkmann <daniel@iogearbox.net>
On Mon, 29 Oct 2018 15:32:03 -0700 Yonghong Song <yhs@fb.com> wrote: > With llvm 7.0 or earlier, the map symbol type is STT_NOTYPE. > -bash-4.4$ cat t.c > __attribute__((section("maps"))) int g; > -bash-4.4$ clang -target bpf -O2 -c t.c > -bash-4.4$ readelf -s t.o > > Symbol table '.symtab' contains 2 entries: > Num: Value Size Type Bind Vis Ndx Name > 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND > 1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 3 g > -bash-4.4$ > > The following llvm commit enables BPF target to generate > proper symbol type and size. > commit bf6ec206615b9718869d48b4e5400d0c6e3638dd > Author: Yonghong Song <yhs@fb.com> > Date: Wed Sep 19 16:04:13 2018 +0000 > > [bpf] Symbol sizes and types in object file > > Clang-compiled object files currently don't include the symbol sizes and > types. Some tools however need that information. For example, ctfconvert > uses that information to generate FreeBSD's CTF representation from ELF > files. > With this patch, symbol sizes and types are included in object files. > > Signed-off-by: Paul Chaignon <paul.chaignon@orange.com> > Reported-by: Yutaro Hayakawa <yhayakawa3720@gmail.com> > > Hence, for llvm 8.0.0 (currently trunk), symbol type will be not NOTYPE, but OBJECT. > -bash-4.4$ clang -target bpf -O2 -c t.c > -bash-4.4$ readelf -s t.o > > Symbol table '.symtab' contains 3 entries: > Num: Value Size Type Bind Vis Ndx Name > 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND > 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS t.c > 2: 0000000000000000 4 OBJECT GLOBAL DEFAULT 3 g > -bash-4.4$ > > This patch makes sure bpf library accepts both NOTYPE and OBJECT types > of global map symbols. > > Signed-off-by: Yonghong Song <yhs@fb.com> Looks good, applied.
diff --git a/lib/bpf.c b/lib/bpf.c index d093d0bd..45f279fa 100644 --- a/lib/bpf.c +++ b/lib/bpf.c @@ -1758,11 +1758,13 @@ static const char *bpf_map_fetch_name(struct bpf_elf_ctx *ctx, int which) int i; for (i = 0; i < ctx->sym_num; i++) { + int type = GELF_ST_TYPE(sym.st_info); + if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym) continue; if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL || - GELF_ST_TYPE(sym.st_info) != STT_NOTYPE || + (type != STT_NOTYPE && type != STT_OBJECT) || sym.st_shndx != ctx->sec_maps || sym.st_value / ctx->map_len != which) continue; @@ -1849,11 +1851,13 @@ static int bpf_map_num_sym(struct bpf_elf_ctx *ctx) GElf_Sym sym; for (i = 0; i < ctx->sym_num; i++) { + int type = GELF_ST_TYPE(sym.st_info); + if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym) continue; if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL || - GELF_ST_TYPE(sym.st_info) != STT_NOTYPE || + (type != STT_NOTYPE && type != STT_OBJECT) || sym.st_shndx != ctx->sec_maps) continue; num++; @@ -1927,10 +1931,12 @@ static int bpf_map_verify_all_offs(struct bpf_elf_ctx *ctx, int end) * the table again. */ for (i = 0; i < ctx->sym_num; i++) { + int type = GELF_ST_TYPE(sym.st_info); + if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym) continue; if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL || - GELF_ST_TYPE(sym.st_info) != STT_NOTYPE || + (type != STT_NOTYPE && type != STT_OBJECT) || sym.st_shndx != ctx->sec_maps) continue; if (sym.st_value == off)
With llvm 7.0 or earlier, the map symbol type is STT_NOTYPE. -bash-4.4$ cat t.c __attribute__((section("maps"))) int g; -bash-4.4$ clang -target bpf -O2 -c t.c -bash-4.4$ readelf -s t.o Symbol table '.symtab' contains 2 entries: Num: Value Size Type Bind Vis Ndx Name 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND 1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 3 g -bash-4.4$ The following llvm commit enables BPF target to generate proper symbol type and size. commit bf6ec206615b9718869d48b4e5400d0c6e3638dd Author: Yonghong Song <yhs@fb.com> Date: Wed Sep 19 16:04:13 2018 +0000 [bpf] Symbol sizes and types in object file Clang-compiled object files currently don't include the symbol sizes and types. Some tools however need that information. For example, ctfconvert uses that information to generate FreeBSD's CTF representation from ELF files. With this patch, symbol sizes and types are included in object files. Signed-off-by: Paul Chaignon <paul.chaignon@orange.com> Reported-by: Yutaro Hayakawa <yhayakawa3720@gmail.com> Hence, for llvm 8.0.0 (currently trunk), symbol type will be not NOTYPE, but OBJECT. -bash-4.4$ clang -target bpf -O2 -c t.c -bash-4.4$ readelf -s t.o Symbol table '.symtab' contains 3 entries: Num: Value Size Type Bind Vis Ndx Name 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS t.c 2: 0000000000000000 4 OBJECT GLOBAL DEFAULT 3 g -bash-4.4$ This patch makes sure bpf library accepts both NOTYPE and OBJECT types of global map symbols. Signed-off-by: Yonghong Song <yhs@fb.com> --- lib/bpf.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)