libbpf: add support for bpf_call

- recognize relocation emitted by llvm
- since all regular function will be kept in .text section and llvm
  takes care of pc-relative offsets in bpf_call instruction
  simply copy all of .text to relevant program section while adjusting
  bpf_call instructions in program section to point to newly copied
  body of instructions from .text
- do so for all programs in the elf file
- set all programs types to the one passed to bpf_prog_load()

Note for elf files with multiple programs that use different
functions in .text section we need to do 'linker' style logic.
This work is still TBD

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index cf446c2..db1b092 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -197,8 +197,14 @@ enum bpf_attach_type {
  */
 #define BPF_F_STRICT_ALIGNMENT (1U << 0)
 
+/* when bpf_ldimm64->src_reg == BPF_PSEUDO_MAP_FD, bpf_ldimm64->imm == fd */
 #define BPF_PSEUDO_MAP_FD      1
 
+/* when bpf_call->src_reg == BPF_PSEUDO_CALL, bpf_call->imm == pc-relative
+ * offset to another bpf function
+ */
+#define BPF_PSEUDO_CALL                1
+
 /* flags for BPF_MAP_UPDATE_ELEM command */
 #define BPF_ANY                0 /* create new element or update existing */
 #define BPF_NOEXIST    1 /* create new element if it didn't exist */

diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 6534889..9f44c19 100644 (file)
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -40,7 +40,7 @@ int bpf_create_map_in_map(enum bpf_map_type map_type, const char *name,
                          __u32 map_flags);
 
 /* Recommend log buffer size */
-#define BPF_LOG_BUF_SIZE 65536
+#define BPF_LOG_BUF_SIZE (256 * 1024)
 int bpf_load_program_name(enum bpf_prog_type type, const char *name,
                          const struct bpf_insn *insns,
                          size_t insns_cnt, const char *license,

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 65d0d0a..5b83875 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -174,12 +174,19 @@ struct bpf_program {
        char *name;
        char *section_name;
        struct bpf_insn *insns;
-       size_t insns_cnt;
+       size_t insns_cnt, main_prog_cnt;
        enum bpf_prog_type type;
 
-       struct {
+       struct reloc_desc {
+               enum {
+                       RELO_LD64,
+                       RELO_CALL,
+               } type;
                int insn_idx;
-               int map_idx;
+               union {
+                       int map_idx;
+                       int text_off;
+               };
        } *reloc_desc;
        int nr_reloc;
 
@@ -234,6 +241,7 @@ struct bpf_object {
                } *reloc;
                int nr_reloc;
                int maps_shndx;
+               int text_shndx;
        } efile;
        /*
         * All loaded bpf_object is linked in a list, which is
@@ -375,9 +383,13 @@ bpf_object__init_prog_names(struct bpf_object *obj)
        size_t pi, si;
 
        for (pi = 0; pi < obj->nr_programs; pi++) {
-               char *name = NULL;
+               const char *name = NULL;
 
                prog = &obj->programs[pi];
+               if (prog->idx == obj->efile.text_shndx) {
+                       name = ".text";
+                       goto skip_search;
+               }
 
                for (si = 0; si < symbols->d_size / sizeof(GElf_Sym) && !name;
                     si++) {
@@ -405,7 +417,7 @@ bpf_object__init_prog_names(struct bpf_object *obj)
                                   prog->section_name);
                        return -EINVAL;
                }
-
+skip_search:
                prog->name = strdup(name);
                if (!prog->name) {
                        pr_warning("failed to allocate memory for prog sym %s\n",
@@ -795,6 +807,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
                } else if ((sh.sh_type == SHT_PROGBITS) &&
                           (sh.sh_flags & SHF_EXECINSTR) &&
                           (data->d_size > 0)) {
+                       if (strcmp(name, ".text") == 0)
+                               obj->efile.text_shndx = idx;
                        err = bpf_object__add_program(obj, data->d_buf,
                                                      data->d_size, name, idx);
                        if (err) {
@@ -856,11 +870,14 @@ bpf_object__find_prog_by_idx(struct bpf_object *obj, int idx)
 }
 
 static int
-bpf_program__collect_reloc(struct bpf_program *prog,
-                          size_t nr_maps, GElf_Shdr *shdr,
-                          Elf_Data *data, Elf_Data *symbols,
-                          int maps_shndx, struct bpf_map *maps)
+bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr,
+                          Elf_Data *data, struct bpf_object *obj)
 {
+       Elf_Data *symbols = obj->efile.symbols;
+       int text_shndx = obj->efile.text_shndx;
+       int maps_shndx = obj->efile.maps_shndx;
+       struct bpf_map *maps = obj->maps;
+       size_t nr_maps = obj->nr_maps;
        int i, nrels;
 
        pr_debug("collecting relocating info for: '%s'\n",
@@ -893,8 +910,10 @@ bpf_program__collect_reloc(struct bpf_program *prog,
                                   GELF_R_SYM(rel.r_info));
                        return -LIBBPF_ERRNO__FORMAT;
                }
+               pr_debug("relo for %ld value %ld name %d\n",
+                        rel.r_info >> 32, sym.st_value, sym.st_name);
 
-               if (sym.st_shndx != maps_shndx) {
+               if (sym.st_shndx != maps_shndx && sym.st_shndx != text_shndx) {
                        pr_warning("Program '%s' contains non-map related relo data pointing to section %u\n",
                                   prog->section_name, sym.st_shndx);
                        return -LIBBPF_ERRNO__RELOC;
@@ -903,6 +922,17 @@ bpf_program__collect_reloc(struct bpf_program *prog,
                insn_idx = rel.r_offset / sizeof(struct bpf_insn);
                pr_debug("relocation: insn_idx=%u\n", insn_idx);
 
+               if (insns[insn_idx].code == (BPF_JMP | BPF_CALL)) {
+                       if (insns[insn_idx].src_reg != BPF_PSEUDO_CALL) {
+                               pr_warning("incorrect bpf_call opcode\n");
+                               return -LIBBPF_ERRNO__RELOC;
+                       }
+                       prog->reloc_desc[i].type = RELO_CALL;
+                       prog->reloc_desc[i].insn_idx = insn_idx;
+                       prog->reloc_desc[i].text_off = sym.st_value;
+                       continue;
+               }
+
                if (insns[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
                        pr_warning("bpf: relocation: invalid relo for insns[%d].code 0x%x\n",
                                   insn_idx, insns[insn_idx].code);
@@ -924,6 +954,7 @@ bpf_program__collect_reloc(struct bpf_program *prog,
                        return -LIBBPF_ERRNO__RELOC;
                }
 
+               prog->reloc_desc[i].type = RELO_LD64;
                prog->reloc_desc[i].insn_idx = insn_idx;
                prog->reloc_desc[i].map_idx = map_idx;
        }
@@ -963,27 +994,76 @@ bpf_object__create_maps(struct bpf_object *obj)
 }
 
 static int
+bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,
+                       struct reloc_desc *relo)
+{
+       struct bpf_insn *insn, *new_insn;
+       struct bpf_program *text;
+       size_t new_cnt;
+
+       if (relo->type != RELO_CALL)
+               return -LIBBPF_ERRNO__RELOC;
+
+       if (prog->idx == obj->efile.text_shndx) {
+               pr_warning("relo in .text insn %d into off %d\n",
+                          relo->insn_idx, relo->text_off);
+               return -LIBBPF_ERRNO__RELOC;
+       }
+
+       if (prog->main_prog_cnt == 0) {
+               text = bpf_object__find_prog_by_idx(obj, obj->efile.text_shndx);
+               if (!text) {
+                       pr_warning("no .text section found yet relo into text exist\n");
+                       return -LIBBPF_ERRNO__RELOC;
+               }
+               new_cnt = prog->insns_cnt + text->insns_cnt;
+               new_insn = realloc(prog->insns, new_cnt * sizeof(*insn));
+               if (!new_insn) {
+                       pr_warning("oom in prog realloc\n");
+                       return -ENOMEM;
+               }
+               memcpy(new_insn + prog->insns_cnt, text->insns,
+                      text->insns_cnt * sizeof(*insn));
+               prog->insns = new_insn;
+               prog->main_prog_cnt = prog->insns_cnt;
+               prog->insns_cnt = new_cnt;
+       }
+       insn = &prog->insns[relo->insn_idx];
+       insn->imm += prog->main_prog_cnt - relo->insn_idx;
+       pr_debug("added %zd insn from %s to prog %s\n",
+                text->insns_cnt, text->section_name, prog->section_name);
+       return 0;
+}
+
+static int
 bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj)
 {
-       int i;
+       int i, err;
 
        if (!prog || !prog->reloc_desc)
                return 0;
 
        for (i = 0; i < prog->nr_reloc; i++) {
-               int insn_idx, map_idx;
-               struct bpf_insn *insns = prog->insns;
+               if (prog->reloc_desc[i].type == RELO_LD64) {
+                       struct bpf_insn *insns = prog->insns;
+                       int insn_idx, map_idx;
 
-               insn_idx = prog->reloc_desc[i].insn_idx;
-               map_idx = prog->reloc_desc[i].map_idx;
+                       insn_idx = prog->reloc_desc[i].insn_idx;
+                       map_idx = prog->reloc_desc[i].map_idx;
 
-               if (insn_idx >= (int)prog->insns_cnt) {
-                       pr_warning("relocation out of range: '%s'\n",
-                                  prog->section_name);
-                       return -LIBBPF_ERRNO__RELOC;
+                       if (insn_idx >= (int)prog->insns_cnt) {
+                               pr_warning("relocation out of range: '%s'\n",
+                                          prog->section_name);
+                               return -LIBBPF_ERRNO__RELOC;
+                       }
+                       insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
+                       insns[insn_idx].imm = obj->maps[map_idx].fd;
+               } else {
+                       err = bpf_program__reloc_text(prog, obj,
+                                                     &prog->reloc_desc[i]);
+                       if (err)
+                               return err;
                }
-               insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
-               insns[insn_idx].imm = obj->maps[map_idx].fd;
        }
 
        zfree(&prog->reloc_desc);
@@ -1026,7 +1106,6 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
                Elf_Data *data = obj->efile.reloc[i].data;
                int idx = shdr->sh_info;
                struct bpf_program *prog;
-               size_t nr_maps = obj->nr_maps;
 
                if (shdr->sh_type != SHT_REL) {
                        pr_warning("internal error at %d\n", __LINE__);
@@ -1040,11 +1119,9 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
                        return -LIBBPF_ERRNO__RELOC;
                }
 
-               err = bpf_program__collect_reloc(prog, nr_maps,
+               err = bpf_program__collect_reloc(prog,
                                                 shdr, data,
-                                                obj->efile.symbols,
-                                                obj->efile.maps_shndx,
-                                                obj->maps);
+                                                obj);
                if (err)
                        return err;
        }
@@ -1197,6 +1274,8 @@ bpf_object__load_progs(struct bpf_object *obj)
        int err;
 
        for (i = 0; i < obj->nr_programs; i++) {
+               if (obj->programs[i].idx == obj->efile.text_shndx)
+                       continue;
                err = bpf_program__load(&obj->programs[i],
                                        obj->license,
                                        obj->kern_version);
@@ -1859,7 +1938,7 @@ long libbpf_get_error(const void *ptr)
 int bpf_prog_load(const char *file, enum bpf_prog_type type,
                  struct bpf_object **pobj, int *prog_fd)
 {
-       struct bpf_program *prog;
+       struct bpf_program *prog, *first_prog = NULL;
        struct bpf_object *obj;
        int err;
 
@@ -1867,25 +1946,30 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type,
        if (IS_ERR(obj))
                return -ENOENT;
 
-       prog = bpf_program__next(NULL, obj);
-       if (!prog) {
-               bpf_object__close(obj);
-               return -ENOENT;
-       }
-
-       /*
-        * If type is not specified, try to guess it based on
-        * section name.
-        */
-       if (type == BPF_PROG_TYPE_UNSPEC) {
-               type = bpf_program__guess_type(prog);
+       bpf_object__for_each_program(prog, obj) {
+               /*
+                * If type is not specified, try to guess it based on
+                * section name.
+                */
                if (type == BPF_PROG_TYPE_UNSPEC) {
-                       bpf_object__close(obj);
-                       return -EINVAL;
+                       type = bpf_program__guess_type(prog);
+                       if (type == BPF_PROG_TYPE_UNSPEC) {
+                               bpf_object__close(obj);
+                               return -EINVAL;
+                       }
                }
+
+               bpf_program__set_type(prog, type);
+               if (prog->idx != obj->efile.text_shndx && !first_prog)
+                       first_prog = prog;
+       }
+
+       if (!first_prog) {
+               pr_warning("object file doesn't contain bpf program\n");
+               bpf_object__close(obj);
+               return -ENOENT;
        }
 
-       bpf_program__set_type(prog, type);
        err = bpf_object__load(obj);
        if (err) {
                bpf_object__close(obj);
@@ -1893,6 +1977,6 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type,
        }
 
        *pobj = obj;
-       *prog_fd = bpf_program__fd(prog);
+       *prog_fd = bpf_program__fd(first_prog);
        return 0;
 }