Message-ID: <1446697622-4072-2-git-send-email-wangnan0@huawei.com>
Date:	Thu, 5 Nov 2015 04:26:58 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<acme@...nel.org>, <namhyung@...nel.org>
CC:	<lizefan@...wei.com>, <pi3orama@....com>,
	<linux-kernel@...r.kernel.org>, Wang Nan <wangnan0@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 1/5] bpf tools: Improve libbpf error reporting

In this patch, a series libbpf specific error numbers and
libbpf_strerror() are created to help reporting error to caller.
Functions are updated to pass correct error number through macro
CHECK_ERR().

All users of bpf_object__open{_buffer}() and bpf_program__title()
in perf are modified accordingly. In addition, due to error code
changing, bpf__strerror_load() also modified to use new error code.

bpf__strerror_head() is also changed accordingly so it can parse
libbpf error. bpf_loader_strerror() is introduced for it, and will
be improved by following patch.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
---
 tools/lib/bpf/libbpf.c         | 149 ++++++++++++++++++++++++++++-------------
 tools/lib/bpf/libbpf.h         |  12 ++++
 tools/perf/tests/llvm.c        |   2 +-
 tools/perf/util/bpf-loader.c   |  36 ++++++++--
 tools/perf/util/parse-events.c |   4 +-
 5 files changed, 145 insertions(+), 58 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 9f3c8cf..c4dcee0 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -61,6 +61,62 @@ void libbpf_set_print(libbpf_print_fn_t warn,
 	__pr_debug = debug;
 }
 
+#define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
+#define STRERR_BUFSIZE  128
+
+struct {
+	int code;
+	const char *msg;
+} libbpf_strerror_table[] = {
+	{LIBBPF_ERRNO__ELIBELF, "Something wrong in libelf"},
+	{LIBBPF_ERRNO__EFORMAT, "BPF object format invalid"},
+	{LIBBPF_ERRNO__EKVERSION, "'version' section incorrect or lost"},
+	{LIBBPF_ERRNO__EENDIAN, "Endian missmatch"},
+	{LIBBPF_ERRNO__EINTERNAL, "Internal error in libbpf"},
+	{LIBBPF_ERRNO__ERELOC, "Relocation failed"},
+	{LIBBPF_ERRNO__ELOAD, "Failed to load program"},
+};
+
+int libbpf_strerror(int err, char *buf, size_t size)
+{
+	unsigned int i;
+
+	if (!buf || !size)
+		return -1;
+
+	err = err > 0 ? err : -err;
+
+	if (err < LIBBPF_ERRNO__START) {
+		int ret;
+
+		ret = strerror_r(err, buf, size);
+		buf[size - 1] = '\0';
+		return ret;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(libbpf_strerror_table); i++) {
+		if (libbpf_strerror_table[i].code == err) {
+			const char *msg;
+
+			msg = libbpf_strerror_table[i].msg;
+			snprintf(buf, size, "%s", msg);
+			buf[size - 1] = '\0';
+			return 0;
+		}
+	}
+
+	snprintf(buf, size, "Unknown libbpf error %d", err);
+	buf[size - 1] = '\0';
+	return -1;
+}
+
+#define CHECK_ERR(action, err, out) do {	\
+	err = action;			\
+	if (err)			\
+		goto out;		\
+} while(0)
+
+
 /* Copied from tools/perf/util/util.h */
 #ifndef zfree
 # define zfree(ptr) ({ free(*ptr); *ptr = NULL; })
@@ -258,7 +314,7 @@ static struct bpf_object *bpf_object__new(const char *path,
 	obj = calloc(1, sizeof(struct bpf_object) + strlen(path) + 1);
 	if (!obj) {
 		pr_warning("alloc memory failed for %s\n", path);
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 	}
 
 	strcpy(obj->path, path);
@@ -305,7 +361,7 @@ static int bpf_object__elf_init(struct bpf_object *obj)
 
 	if (obj_elf_valid(obj)) {
 		pr_warning("elf init: internal error\n");
-		return -EEXIST;
+		return -LIBBPF_ERRNO__ELIBELF;
 	}
 
 	if (obj->efile.obj_buf_sz > 0) {
@@ -331,14 +387,14 @@ static int bpf_object__elf_init(struct bpf_object *obj)
 	if (!obj->efile.elf) {
 		pr_warning("failed to open %s as ELF file\n",
 				obj->path);
-		err = -EINVAL;
+		err = -LIBBPF_ERRNO__ELIBELF;
 		goto errout;
 	}
 
 	if (!gelf_getehdr(obj->efile.elf, &obj->efile.ehdr)) {
 		pr_warning("failed to get EHDR from %s\n",
 				obj->path);
-		err = -EINVAL;
+		err = -LIBBPF_ERRNO__EFORMAT;
 		goto errout;
 	}
 	ep = &obj->efile.ehdr;
@@ -346,7 +402,7 @@ static int bpf_object__elf_init(struct bpf_object *obj)
 	if ((ep->e_type != ET_REL) || (ep->e_machine != 0)) {
 		pr_warning("%s is not an eBPF object file\n",
 			obj->path);
-		err = -EINVAL;
+		err = -LIBBPF_ERRNO__EFORMAT;
 		goto errout;
 	}
 
@@ -374,14 +430,14 @@ bpf_object__check_endianness(struct bpf_object *obj)
 			goto mismatch;
 		break;
 	default:
-		return -EINVAL;
+		return -LIBBPF_ERRNO__EENDIAN;
 	}
 
 	return 0;
 
 mismatch:
 	pr_warning("Error: endianness mismatch.\n");
-	return -EINVAL;
+	return -LIBBPF_ERRNO__EENDIAN;
 }
 
 static int
@@ -402,7 +458,7 @@ bpf_object__init_kversion(struct bpf_object *obj,
 
 	if (size != sizeof(kver)) {
 		pr_warning("invalid kver section in %s\n", obj->path);
-		return -EINVAL;
+		return -LIBBPF_ERRNO__EFORMAT;
 	}
 	memcpy(&kver, data, sizeof(kver));
 	obj->kern_version = kver;
@@ -444,7 +500,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 	if (!elf_rawdata(elf_getscn(elf, ep->e_shstrndx), NULL)) {
 		pr_warning("failed to get e_shstrndx from %s\n",
 			   obj->path);
-		return -EINVAL;
+		return -LIBBPF_ERRNO__EFORMAT;
 	}
 
 	while ((scn = elf_nextscn(elf, scn)) != NULL) {
@@ -456,7 +512,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 		if (gelf_getshdr(scn, &sh) != &sh) {
 			pr_warning("failed to get section header from %s\n",
 				   obj->path);
-			err = -EINVAL;
+			err = -LIBBPF_ERRNO__EFORMAT;
 			goto out;
 		}
 
@@ -464,7 +520,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 		if (!name) {
 			pr_warning("failed to get section name from %s\n",
 				   obj->path);
-			err = -EINVAL;
+			err = -LIBBPF_ERRNO__EFORMAT;
 			goto out;
 		}
 
@@ -472,7 +528,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 		if (!data) {
 			pr_warning("failed to get section data from %s(%s)\n",
 				   name, obj->path);
-			err = -EINVAL;
+			err = -LIBBPF_ERRNO__EFORMAT;
 			goto out;
 		}
 		pr_debug("section %s, size %ld, link %d, flags %lx, type=%d\n",
@@ -495,7 +551,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 			if (obj->efile.symbols) {
 				pr_warning("bpf: multiple SYMTAB in %s\n",
 					   obj->path);
-				err = -EEXIST;
+				err = -LIBBPF_ERRNO__EFORMAT;
 			} else
 				obj->efile.symbols = data;
 		} else if ((sh.sh_type == SHT_PROGBITS) &&
@@ -504,7 +560,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
 			err = bpf_object__add_program(obj, data->d_buf,
 						      data->d_size, name, idx);
 			if (err) {
-				char errmsg[128];
+				char errmsg[STRERR_BUFSIZE];
+
 				strerror_r(-err, errmsg, sizeof(errmsg));
 				pr_warning("failed to alloc program %s (%s): %s",
 					   name, obj->path, errmsg);
@@ -576,7 +633,7 @@ bpf_program__collect_reloc(struct bpf_program *prog,
 
 		if (!gelf_getrel(data, i, &rel)) {
 			pr_warning("relocation: failed to get %d reloc\n", i);
-			return -EINVAL;
+			return -LIBBPF_ERRNO__EFORMAT;
 		}
 
 		insn_idx = rel.r_offset / sizeof(struct bpf_insn);
@@ -587,20 +644,20 @@ bpf_program__collect_reloc(struct bpf_program *prog,
 				 &sym)) {
 			pr_warning("relocation: symbol %"PRIx64" not found\n",
 				   GELF_R_SYM(rel.r_info));
-			return -EINVAL;
+			return -LIBBPF_ERRNO__EFORMAT;
 		}
 
 		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);
-			return -EINVAL;
+			return -LIBBPF_ERRNO__ERELOC;
 		}
 
 		map_idx = sym.st_value / sizeof(struct bpf_map_def);
 		if (map_idx >= nr_maps) {
 			pr_warning("bpf relocation: map_idx %d large than %d\n",
 				   (int)map_idx, (int)nr_maps - 1);
-			return -EINVAL;
+			return -LIBBPF_ERRNO__ERELOC;
 		}
 
 		prog->reloc_desc[i].insn_idx = insn_idx;
@@ -683,7 +740,7 @@ bpf_program__relocate(struct bpf_program *prog, int *map_fds)
 		if (insn_idx >= (int)prog->insns_cnt) {
 			pr_warning("relocation out of range: '%s'\n",
 				   prog->section_name);
-			return -ERANGE;
+			return -LIBBPF_ERRNO__ERELOC;
 		}
 		insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
 		insns[insn_idx].imm = map_fds[map_idx];
@@ -721,7 +778,7 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
 
 	if (!obj_elf_valid(obj)) {
 		pr_warning("Internal error: elf object is closed\n");
-		return -EINVAL;
+		return -LIBBPF_ERRNO__EINTERNAL;
 	}
 
 	for (i = 0; i < obj->efile.nr_reloc; i++) {
@@ -734,21 +791,21 @@ static int bpf_object__collect_reloc(struct bpf_object *obj)
 
 		if (shdr->sh_type != SHT_REL) {
 			pr_warning("internal error at %d\n", __LINE__);
-			return -EINVAL;
+			return -LIBBPF_ERRNO__EINTERNAL;
 		}
 
 		prog = bpf_object__find_prog_by_idx(obj, idx);
 		if (!prog) {
 			pr_warning("relocation failed: no %d section\n",
 				   idx);
-			return -ENOENT;
+			return -LIBBPF_ERRNO__ERELOC;
 		}
 
 		err = bpf_program__collect_reloc(prog, nr_maps,
 						 shdr, data,
 						 obj->efile.symbols);
 		if (err)
-			return -EINVAL;
+			return err;
 	}
 	return 0;
 }
@@ -777,7 +834,7 @@ load_program(struct bpf_insn *insns, int insns_cnt,
 		goto out;
 	}
 
-	ret = -EINVAL;
+	ret = -LIBBPF_ERRNO__ELOAD;
 	pr_warning("load bpf program failed: %s\n", strerror(errno));
 
 	if (log_buf) {
@@ -831,7 +888,7 @@ static int bpf_object__validate(struct bpf_object *obj)
 	if (obj->kern_version == 0) {
 		pr_warning("%s doesn't provide kernel version\n",
 			   obj->path);
-		return -EINVAL;
+		return -LIBBPF_ERRNO__EKVERSION;
 	}
 	return 0;
 }
@@ -840,32 +897,28 @@ static struct bpf_object *
 __bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz)
 {
 	struct bpf_object *obj;
+	int err;
 
 	if (elf_version(EV_CURRENT) == EV_NONE) {
 		pr_warning("failed to init libelf for %s\n", path);
-		return NULL;
+		return ERR_PTR(-LIBBPF_ERRNO__ELIBELF);
 	}
 
 	obj = bpf_object__new(path, obj_buf, obj_buf_sz);
-	if (!obj)
-		return NULL;
+	if (IS_ERR(obj))
+		return obj;
 
-	if (bpf_object__elf_init(obj))
-		goto out;
-	if (bpf_object__check_endianness(obj))
-		goto out;
-	if (bpf_object__elf_collect(obj))
-		goto out;
-	if (bpf_object__collect_reloc(obj))
-		goto out;
-	if (bpf_object__validate(obj))
-		goto out;
+	CHECK_ERR(bpf_object__elf_init(obj), err, out);
+	CHECK_ERR(bpf_object__check_endianness(obj), err, out);
+	CHECK_ERR(bpf_object__elf_collect(obj), err, out);
+	CHECK_ERR(bpf_object__collect_reloc(obj), err, out);
+	CHECK_ERR(bpf_object__validate(obj), err, out);
 
 	bpf_object__elf_finish(obj);
 	return obj;
 out:
 	bpf_object__close(obj);
-	return NULL;
+	return ERR_PTR(err);
 }
 
 struct bpf_object *bpf_object__open(const char *path)
@@ -922,6 +975,8 @@ int bpf_object__unload(struct bpf_object *obj)
 
 int bpf_object__load(struct bpf_object *obj)
 {
+	int err;
+
 	if (!obj)
 		return -EINVAL;
 
@@ -931,18 +986,16 @@ int bpf_object__load(struct bpf_object *obj)
 	}
 
 	obj->loaded = true;
-	if (bpf_object__create_maps(obj))
-		goto out;
-	if (bpf_object__relocate(obj))
-		goto out;
-	if (bpf_object__load_progs(obj))
-		goto out;
+
+	CHECK_ERR(bpf_object__create_maps(obj), err, out);
+	CHECK_ERR(bpf_object__relocate(obj), err, out);
+	CHECK_ERR(bpf_object__load_progs(obj), err, out);
 
 	return 0;
 out:
 	bpf_object__unload(obj);
 	pr_warning("failed to load object '%s'\n", obj->path);
-	return -EINVAL;
+	return err;
 }
 
 void bpf_object__close(struct bpf_object *obj)
@@ -990,7 +1043,7 @@ const char *
 bpf_object__get_name(struct bpf_object *obj)
 {
 	if (!obj)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	return obj->path;
 }
 
@@ -1043,7 +1096,7 @@ const char *bpf_program__title(struct bpf_program *prog, bool needs_copy)
 		title = strdup(title);
 		if (!title) {
 			pr_warning("failed to strdup program title\n");
-			return NULL;
+			return ERR_PTR(-ENOMEM);
 		}
 	}
 
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index bc80af0..6491be6 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -10,6 +10,18 @@
 
 #include <stdio.h>
 #include <stdbool.h>
+#include <linux/err.h>
+
+#define LIBBPF_ERRNO__START	4000
+#define LIBBPF_ERRNO__ELIBELF	4000	/* Something wrong in libelf */
+#define LIBBPF_ERRNO__EFORMAT	4001	/* BPF object format invalid */
+#define LIBBPF_ERRNO__EKVERSION	4002	/* Incorrect or no 'version' section */
+#define LIBBPF_ERRNO__EENDIAN	4003	/* Endian missmatch */
+#define LIBBPF_ERRNO__EINTERNAL	4004	/* Internal error in libbpf */
+#define LIBBPF_ERRNO__ERELOC	4005	/* Relocation failed */
+#define LIBBPF_ERRNO__ELOAD	4006	/* Failed to load program */
+
+int libbpf_strerror(int err, char *buf, size_t size);
 
 /*
  * In include/linux/compiler-gcc.h, __printf is defined. However
diff --git a/tools/perf/tests/llvm.c b/tools/perf/tests/llvm.c
index 512d362..8f713f6 100644
--- a/tools/perf/tests/llvm.c
+++ b/tools/perf/tests/llvm.c
@@ -27,7 +27,7 @@ static int test__bpf_parsing(void *obj_buf, size_t obj_buf_sz)
 	struct bpf_object *obj;
 
 	obj = bpf_object__open_buffer(obj_buf, obj_buf_sz, NULL);
-	if (!obj)
+	if (IS_ERR(obj))
 		return -1;
 	bpf_object__close(obj);
 	return 0;
diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 0c5d174..72ad3dc 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -59,9 +59,9 @@ struct bpf_object *bpf__prepare_load(const char *filename, bool source)
 	} else
 		obj = bpf_object__open(filename);
 
-	if (!obj) {
+	if (IS_ERR(obj)) {
 		pr_debug("bpf: failed to load %s\n", filename);
-		return ERR_PTR(-EINVAL);
+		return obj;
 	}
 
 	return obj;
@@ -96,9 +96,9 @@ config_bpf_program(struct bpf_program *prog)
 	int err;
 
 	config_str = bpf_program__title(prog, false);
-	if (!config_str) {
+	if (IS_ERR(config_str)) {
 		pr_debug("bpf: unable to get title for program\n");
-		return -EINVAL;
+		return PTR_ERR(config_str);
 	}
 
 	priv = calloc(sizeof(*priv), 1);
@@ -308,13 +308,34 @@ int bpf__foreach_tev(struct bpf_object *obj,
 	return 0;
 }
 
+static int
+bpf_loader_strerror(int err, char *buf, size_t size)
+{
+	char sbuf[STRERR_BUFSIZE];
+	const char *msg;
+
+	if (!buf || !size)
+		return -1;
+
+	err = err > 0 ? err : -err;
+
+	if (err >= LIBBPF_ERRNO__START)
+		return libbpf_strerror(err, buf, size);
+
+	msg = strerror_r(err, sbuf, sizeof(sbuf));
+	snprintf(buf, size, "%s", msg);
+	buf[size - 1] = '\0';
+	return 0;
+}
+
 #define bpf__strerror_head(err, buf, size) \
 	char sbuf[STRERR_BUFSIZE], *emsg;\
 	if (!size)\
 		return 0;\
 	if (err < 0)\
 		err = -err;\
-	emsg = strerror_r(err, sbuf, sizeof(sbuf));\
+	bpf_loader_strerror(err, sbuf, sizeof(sbuf));\
+	emsg = sbuf;\
 	switch (err) {\
 	default:\
 		scnprintf(buf, size, "%s", emsg);\
@@ -345,8 +366,9 @@ int bpf__strerror_load(struct bpf_object *obj __maybe_unused,
 		       int err, char *buf, size_t size)
 {
 	bpf__strerror_head(err, buf, size);
-	bpf__strerror_entry(EINVAL, "%s: Are you root and runing a CONFIG_BPF_SYSCALL kernel?",
-			    emsg)
+	bpf__strerror_entry(LIBBPF_ERRNO__ELOAD,
+			    "%s: Validate your program and check 'license'/'version' sections in your object",
+			    emsg);
 	bpf__strerror_end(buf, size);
 	return 0;
 }
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index bee6058..c75b25d 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -632,11 +632,11 @@ int parse_events_load_bpf(struct parse_events_evlist *data,
 	struct bpf_object *obj;
 
 	obj = bpf__prepare_load(bpf_file_name, source);
-	if (IS_ERR(obj) || !obj) {
+	if (IS_ERR(obj)) {
 		char errbuf[BUFSIZ];
 		int err;
 
-		err = obj ? PTR_ERR(obj) : -EINVAL;
+		err = PTR_ERR(obj);
 
 		if (err == -ENOTSUP)
 			snprintf(errbuf, sizeof(errbuf),
-- 
1.8.3.4

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