Merge branch 'btf-func-info'

Martin KaFai Lau says:

====================
The BTF support was added to kernel by Commit 69b693f0aefa
("bpf: btf: Introduce BPF Type Format (BTF)"), which introduced
.BTF section into ELF file and is primarily
used for map pretty print.
pahole is used to convert dwarf to BTF for ELF files.

This patch added func info support to the kernel so we can
get better ksym's for bpf function calls. Basically,
function call types are passed to kernel and the kernel
extract function names from these types in order to contruct ksym
for these functions.

The llvm patch at https://reviews.llvm.org/D53736
will generate .BTF section and one more section .BTF.ext.
The .BTF.ext section encodes function type
information. The following is a sample output for selftests
test_btf with file test_btf_haskv.o for translated insns
and jited insns respectively.

  $ bpftool prog dump xlated id 1
  int _dummy_tracepoint(struct dummy_tracepoint_args * arg):
     0: (85) call pc+2#bpf_prog_2dcecc18072623fc_test_long_fname_1
     1: (b7) r0 = 0
     2: (95) exit
  int test_long_fname_1(struct dummy_tracepoint_args * arg):
     3: (85) call pc+1#bpf_prog_89d64e4abf0f0126_test_long_fname_2
     4: (95) exit
  int test_long_fname_2(struct dummy_tracepoint_args * arg):
     5: (b7) r2 = 0
     6: (63) *(u32 *)(r10 -4) = r2
     7: (79) r1 = *(u64 *)(r1 +8)
     ...
     22: (07) r1 += 1
     23: (63) *(u32 *)(r0 +4) = r1
     24: (95) exit

  $ bpftool prog dump jited id 1
  int _dummy_tracepoint(struct dummy_tracepoint_args * arg):
  bpf_prog_b07ccb89267cf242__dummy_tracepoint:
     0:   push   %rbp
     1:   mov    %rsp,%rbp
    ......
    3c:   add    $0x28,%rbp
    40:   leaveq
    41:   retq

  int test_long_fname_1(struct dummy_tracepoint_args * arg):
  bpf_prog_2dcecc18072623fc_test_long_fname_1:
     0:   push   %rbp
     1:   mov    %rsp,%rbp
    ......
    3a:   add    $0x28,%rbp
    3e:   leaveq
    3f:   retq

  int test_long_fname_2(struct dummy_tracepoint_args * arg):
  bpf_prog_89d64e4abf0f0126_test_long_fname_2:
     0:   push   %rbp
     1:   mov    %rsp,%rbp
    ......
    80:   add    $0x28,%rbp
    84:   leaveq
    85:   retq

Changelogs:
  v4 -> v5:
    . Add back BTF_KIND_FUNC_PROTO as v1 did.  The difference
      is BTF_KIND_FUNC_PROTO cannot have t->name_off now.
      All param metadata is defined in BTF_KIND_FUNC_PROTO.
      BTF_KIND_FUNC must have t->name_off != 0 and t->type
      refers to a BTF_KIND_FUNC_PROTO.

      The above is the conclusion after the discussion between
      Edward Cree, Alexei, Daniel, Yonghong and Martin.
  v3 -> v4:
    . Remove BTF_KIND_FUNC_PROTO. BTF_KIND_FUNC is used for
      both function pointer and subprogram. The name_off field
      is used to distinguish both.
    . The record size is added to the func_info subsection
      in .BTF.ext to enable future extension.
    . The bpf_prog_info interface change to make it similar
      bpf_prog_load.
    . Related kernel and libbpf changes to accommodate the
      new .BTF.ext and kernel interface changes.
  v2 -> v3:
    . Removed kernel btf extern functions btf_type_id_func()
      and btf_get_name_by_id(). Instead, exposing existing
      functions btf_type_by_id() and btf_name_by_offset().
    . Added comments about ELF section .BTF.ext layout.
    . Better codes in btftool as suggested by Edward Cree.
  v1 -> v2:
    . Added missing sign-off.
    . Limited the func_name/struct_member_name length for validity test.
    . Removed/changed several verifier messages.
    . Modified several commit messages to remove line_off reference.
====================

Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 73 insertions, 14 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a01eb9584e52..cb6565d79603 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -156,6 +156,10 @@ struct bpf_program {
 	bpf_program_clear_priv_t clear_priv;
 
 	enum bpf_attach_type expected_attach_type;
+	int btf_fd;
+	void *func_info;
+	__u32 func_info_rec_size;
+	__u32 func_info_len;
 };
 
 struct bpf_map {
@@ -212,6 +216,7 @@ struct bpf_object {
 	struct list_head list;
 
 	struct btf *btf;
+	struct btf_ext *btf_ext;
 
 	void *priv;
 	bpf_object_clear_priv_t clear_priv;
@@ -241,6 +246,9 @@ void bpf_program__unload(struct bpf_program *prog)
 
 	prog->instances.nr = -1;
 	zfree(&prog->instances.fds);
+
+	zclose(prog->btf_fd);
+	zfree(&prog->func_info);
 }
 
 static void bpf_program__exit(struct bpf_program *prog)
@@ -315,6 +323,7 @@ bpf_program__init(void *data, size_t size, char *section_name, int idx,
 	prog->instances.fds = NULL;
 	prog->instances.nr = -1;
 	prog->type = BPF_PROG_TYPE_KPROBE;
+	prog->btf_fd = -1;
 
 	return 0;
 errout:
@@ -807,6 +816,15 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 					   BTF_ELF_SEC, PTR_ERR(obj->btf));
 				obj->btf = NULL;
 			}
+		} else if (strcmp(name, BTF_EXT_ELF_SEC) == 0) {
+			obj->btf_ext = btf_ext__new(data->d_buf, data->d_size,
+						    __pr_debug);
+			if (IS_ERR(obj->btf_ext)) {
+				pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n",
+					   BTF_EXT_ELF_SEC,
+					   PTR_ERR(obj->btf_ext));
+				obj->btf_ext = NULL;
+			}
 		} else if (sh.sh_type == SHT_SYMTAB) {
 			if (obj->efile.symbols) {
 				pr_warning("bpf: multiple SYMTAB in %s\n",
@@ -1190,6 +1208,7 @@ bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,
 	struct bpf_insn *insn, *new_insn;
 	struct bpf_program *text;
 	size_t new_cnt;
+	int err;
 
 	if (relo->type != RELO_CALL)
 		return -LIBBPF_ERRNO__RELOC;
@@ -1212,6 +1231,20 @@ bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,
 			pr_warning("oom in prog realloc\n");
 			return -ENOMEM;
 		}
+
+		if (obj->btf && obj->btf_ext) {
+			err = btf_ext__reloc(obj->btf, obj->btf_ext,
+					     text->section_name,
+					     prog->insns_cnt,
+					     &prog->func_info,
+					     &prog->func_info_len);
+			if (err) {
+				pr_warning("error in btf_ext__reloc for sec %s\n",
+					   text->section_name);
+				return err;
+			}
+		}
+
 		memcpy(new_insn + prog->insns_cnt, text->insns,
 		       text->insns_cnt * sizeof(*insn));
 		prog->insns = new_insn;
@@ -1231,7 +1264,24 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj)
 {
 	int i, err;
 
-	if (!prog || !prog->reloc_desc)
+	if (!prog)
+		return 0;
+
+	if (obj->btf && obj->btf_ext) {
+		err = btf_ext__reloc_init(obj->btf, obj->btf_ext,
+					  prog->section_name,
+					  &prog->func_info,
+					  &prog->func_info_rec_size,
+					  &prog->func_info_len);
+		if (err) {
+			pr_warning("err in btf_ext__reloc_init for sec %s\n",
+				   prog->section_name);
+			return err;
+		}
+		prog->btf_fd = btf__fd(obj->btf);
+	}
+
+	if (!prog->reloc_desc)
 		return 0;
 
 	for (i = 0; i < prog->nr_reloc; i++) {
@@ -1319,9 +1369,9 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
 }
 
 static int
-load_program(enum bpf_prog_type type, enum bpf_attach_type expected_attach_type,
-	     const char *name, struct bpf_insn *insns, int insns_cnt,
-	     char *license, __u32 kern_version, int *pfd, int prog_ifindex)
+load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
+	     char *license, __u32 kern_version, int *pfd,
+	     __u32 func_info_cnt)
 {
 	struct bpf_load_program_attr load_attr;
 	char *cp, errmsg[STRERR_BUFSIZE];
@@ -1329,14 +1379,18 @@ load_program(enum bpf_prog_type type, enum bpf_attach_type expected_attach_type,
 	int ret;
 
 	memset(&load_attr, 0, sizeof(struct bpf_load_program_attr));
-	load_attr.prog_type = type;
-	load_attr.expected_attach_type = expected_attach_type;
-	load_attr.name = name;
+	load_attr.prog_type = prog->type;
+	load_attr.expected_attach_type = prog->expected_attach_type;
+	load_attr.name = prog->name;
 	load_attr.insns = insns;
 	load_attr.insns_cnt = insns_cnt;
 	load_attr.license = license;
 	load_attr.kern_version = kern_version;
-	load_attr.prog_ifindex = prog_ifindex;
+	load_attr.prog_ifindex = prog->prog_ifindex;
+	load_attr.prog_btf_fd = prog->btf_fd;
+	load_attr.func_info = prog->func_info;
+	load_attr.func_info_rec_size = prog->func_info_rec_size;
+	load_attr.func_info_cnt = func_info_cnt;
 
 	if (!load_attr.insns || !load_attr.insns_cnt)
 		return -EINVAL;
@@ -1394,8 +1448,14 @@ int
 bpf_program__load(struct bpf_program *prog,
 		  char *license, __u32 kern_version)
 {
+	__u32 func_info_cnt;
 	int err = 0, fd, i;
 
+	if (prog->func_info_len == 0)
+		func_info_cnt = 0;
+	else
+		func_info_cnt = prog->func_info_len / prog->func_info_rec_size;
+
 	if (prog->instances.nr < 0 || !prog->instances.fds) {
 		if (prog->preprocessor) {
 			pr_warning("Internal error: can't load program '%s'\n",
@@ -1417,10 +1477,9 @@ bpf_program__load(struct bpf_program *prog,
 			pr_warning("Program '%s' is inconsistent: nr(%d) != 1\n",
 				   prog->section_name, prog->instances.nr);
 		}
-		err = load_program(prog->type, prog->expected_attach_type,
-				   prog->name, prog->insns, prog->insns_cnt,
+		err = load_program(prog, prog->insns, prog->insns_cnt,
 				   license, kern_version, &fd,
-				   prog->prog_ifindex);
+				   func_info_cnt);
 		if (!err)
 			prog->instances.fds[0] = fd;
 		goto out;
@@ -1448,11 +1507,10 @@ bpf_program__load(struct bpf_program *prog,
 			continue;
 		}
 
-		err = load_program(prog->type, prog->expected_attach_type,
-				   prog->name, result.new_insn_ptr,
+		err = load_program(prog, result.new_insn_ptr,
 				   result.new_insn_cnt,
 				   license, kern_version, &fd,
-				   prog->prog_ifindex);
+				   func_info_cnt);
 
 		if (err) {
 			pr_warning("Loading the %dth instance of program '%s' failed\n",
@@ -2120,6 +2178,7 @@ void bpf_object__close(struct bpf_object *obj)
 	bpf_object__elf_finish(obj);
 	bpf_object__unload(obj);
 	btf__free(obj->btf);
+	btf_ext__free(obj->btf_ext);
 
 	for (i = 0; i < obj->nr_maps; i++) {
 		zfree(&obj->maps[i].name);