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[PATCH v2 1/7] bpf tools: Improve libbpf error reporting

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  [PATCH v2 1/7] bpf tools: Improve libbpf error reporting Wang Nan <wangnan0@huawei.com> - 2015-11-06 15:00 +0100
    Re: [PATCH v2 1/7] bpf tools: Improve libbpf error reporting Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-11-06 15:10 +0100
    [tip:perf/urgent] bpf tools: Improve libbpf error reporting tip-bot for Wang Nan <tipbot@zytor.com> - 2015-11-08 08:40 +0100

#1264035 — [PATCH v2 1/7] 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.

load_program() is improved not to dump log buffer if it is empty. log
buffer is also used to deduce whether the error is caused by invalid
program or other problem.

v1 -> v2:

 - Using macro for error code.

 - Fetch error message based on array index, eliminate for-loop.

 - Use log buffer to detect the reason of failure. 3 new error code
   are introduced to replace LIBBPF_ERRNO__LOAD.

In v1:

# perf record -e ./test_ill_program.o ls
event syntax error: './test_ill_program.o'
                     \___ Failed to load program: Validate your program and check 'license'/'version' sections in your object
[SKIP]

# perf record -e ./test_kversion_nomatch_program.o ls
event syntax error: './test_kversion_nomatch_program.o'
                     \___ Failed to load program: Validate your program and check 'license'/'version' sections in your object
[SKIP]

# perf record -e ./test_big_program.o ls
event syntax error: './test_big_program.o'
                     \___ Failed to load program: Validate your program and check 'license'/'version' sections in your object
[SKIP]

In v2:

# perf record -e ./test_ill_program.o ls
event syntax error: './test_ill_program.o'
                     \___ Kernel verifier blocks program loading
[SKIP]

# perf record -e ./test_kversion_nomatch_program.o
event syntax error: './test_kversion_nomatch_program.o'
                     \___ Incorrect kernel version
[SKIP]
(Will be further improved by following patches)

# perf record -e ./test_big_program.o
event syntax error: './test_big_program.o'
                     \___ Program too big
[SKIP]

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
---
 tools/lib/bpf/libbpf.c         | 159 ++++++++++++++++++++++++++++-------------
 tools/lib/bpf/libbpf.h         |  20 ++++++
 tools/perf/tests/llvm.c        |   2 +-
 tools/perf/util/bpf-loader.c   |  33 +++++++--
 tools/perf/util/parse-events.c |   4 +-
 5 files changed, 159 insertions(+), 59 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 9f3c8cf..07b492d 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -61,6 +61,60 @@ void libbpf_set_print(libbpf_print_fn_t warn,
 	__pr_debug = debug;
 }
 
+#define STRERR_BUFSIZE  128
+
+#define ERRNO_OFFSET(e)		((e) - __LIBBPF_ERRNO__START)
+#define ERRCODE_OFFSET(c)	ERRNO_OFFSET(LIBBPF_ERRNO__##c)
+#define NR_ERRNO	(__LIBBPF_ERRNO__END - __LIBBPF_ERRNO__START)
+
+static const char *libbpf_strerror_table[NR_ERRNO] = {
+	[ERRCODE_OFFSET(LIBELF)]	= "Something wrong in libelf",
+	[ERRCODE_OFFSET(FORMAT)]	= "BPF object format invalid",
+	[ERRCODE_OFFSET(KVERSION)]	= "'version' section incorrect or lost",
+	[ERRCODE_OFFSET(ENDIAN)]	= "Endian missmatch",
+	[ERRCODE_OFFSET(INTERNAL)]	= "Internal error in libbpf",
+	[ERRCODE_OFFSET(RELOC)]		= "Relocation failed",
+	[ERRCODE_OFFSET(VERIFY)]	= "Kernel verifier blocks program loading",
+	[ERRCODE_OFFSET(PROG2BIG)]	= "Program too big",
+	[ERRCODE_OFFSET(KVER)]		= "Incorrect kernel version",
+};
+
+int libbpf_strerror(int err, char *buf, size_t size)
+{
+	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;
+	}
+
+	if (err < __LIBBPF_ERRNO__END) {
+		const char *msg;
+
+		msg = libbpf_strerror_table[ERRNO_OFFSET(err)];
+		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 +312,7 @@ 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 +359,7 @@ 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__LIBELF;
 	}
 
 	if (obj->efile.obj_buf_sz > 0) {
@@ -331,14 +385,14 @@ 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__LIBELF;
 		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__FORMAT;
 		goto errout;
 	}
 	ep = &obj->efile.ehdr;
@@ -346,7 +400,7 @@ 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__FORMAT;
 		goto errout;
 	}
 
@@ -374,14 +428,14 @@ bpf_object__check_endianness(struct bpf_object *obj)
 			goto mismatch;
 		break;
 	default:
-		return -EINVAL;
+		return -LIBBPF_ERRNO__ENDIAN;
 	}
 
 	return 0;
 
 mismatch:
 	pr_warning("Error: endianness mismatch.\n");
-	return -EINVAL;
+	return -LIBBPF_ERRNO__ENDIAN;
 }
 
 static int
@@ -402,7 +456,7 @@ 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__FORMAT;
 	}
 	memcpy(&kver, data, sizeof(kver));
 	obj->kern_version = kver;
@@ -444,7 +498,7 @@ 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__FORMAT;
 	}
 
 	while ((scn = elf_nextscn(elf, scn)) != NULL) {
@@ -456,7 +510,7 @@ 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__FORMAT;
 			goto out;
 		}
 
@@ -464,7 +518,7 @@ 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__FORMAT;
 			goto out;
 		}
 
@@ -472,7 +526,7 @@ 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__FORMAT;
 			goto out;
 		}
 		pr_debug("section %s, size %ld, link %d, flags %lx, type=%d\n",
@@ -495,7 +549,7 @@ 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__FORMAT;
 			} else
 				obj->efile.symbols = data;
 		} else if ((sh.sh_type == SHT_PROGBITS) &&
@@ -504,7 +558,8 @@ 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 +631,7 @@ 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__FORMAT;
 		}
 
 		insn_idx = rel.r_offset / sizeof(struct bpf_insn);
@@ -587,20 +642,20 @@ 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__FORMAT;
 		}
 
 		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__RELOC;
 		}
 
 		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__RELOC;
 		}
 
 		prog->reloc_desc[i].insn_idx = insn_idx;
@@ -683,7 +738,7 @@ 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__RELOC;
 		}
 		insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
 		insns[insn_idx].imm = map_fds[map_idx];
@@ -721,7 +776,7 @@ 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__INTERNAL;
 	}
 
 	for (i = 0; i < obj->efile.nr_reloc; i++) {
@@ -734,21 +789,21 @@ 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__INTERNAL;
 		}
 
 		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__RELOC;
 		}
 
 		err = bpf_program__collect_reloc(prog, nr_maps,
 						 shdr, data,
 						 obj->efile.symbols);
 		if (err)
-			return -EINVAL;
+			return err;
 	}
 	return 0;
 }
@@ -777,13 +832,23 @@ load_program(struct bpf_insn *insns, int insns_cnt,
 		goto out;
 	}
 
-	ret = -EINVAL;
+	ret = -LIBBPF_ERRNO__LOAD;
 	pr_warning("load bpf program failed: %s\n", strerror(errno));
 
-	if (log_buf) {
+	if (log_buf && log_buf[0] != '\0') {
+		ret = -LIBBPF_ERRNO__VERIFY;
 		pr_warning("-- BEGIN DUMP LOG ---\n");
 		pr_warning("\n%s\n", log_buf);
 		pr_warning("-- END LOG --\n");
+	} else {
+		if (insns_cnt >= BPF_MAXINSNS) {
+			pr_warning("Program too large (%d insns), at most %d insns\n",
+				   insns_cnt, BPF_MAXINSNS);
+			ret = -LIBBPF_ERRNO__PROG2BIG;
+		} else if (log_buf) {
+			pr_warning("log buffer is empty\n");
+			ret = -LIBBPF_ERRNO__KVER;
+		}
 	}
 
 out:
@@ -831,7 +896,7 @@ 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__KVERSION;
 	}
 	return 0;
 }
@@ -840,32 +905,28 @@ 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__LIBELF);
 	}
 
 	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 +983,8 @@ int bpf_object__unload(struct bpf_object *obj)
 
 int bpf_object__load(struct bpf_object *obj)
 {
+	int err;
+
 	if (!obj)
 		return -EINVAL;
 
@@ -931,18 +994,16 @@ 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 +1051,7 @@ const char *
 bpf_object__get_name(struct bpf_object *obj)
 {
 	if (!obj)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	return obj->path;
 }
 
@@ -1043,7 +1104,7 @@ 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..30a40e9 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -10,6 +10,26 @@
 
 #include <stdio.h>
 #include <stdbool.h>
+#include <linux/err.h>
+
+enum libbpf_errno {
+	__LIBBPF_ERRNO__START = 4000,
+
+	/* Something wrong in libelf */
+	LIBBPF_ERRNO__LIBELF = __LIBBPF_ERRNO__START,
+	LIBBPF_ERRNO__FORMAT,	/* BPF object format invalid */
+	LIBBPF_ERRNO__KVERSION,	/* Incorrect or no 'version' section */
+	LIBBPF_ERRNO__ENDIAN,	/* Endian missmatch */
+	LIBBPF_ERRNO__INTERNAL,	/* Internal error in libbpf */
+	LIBBPF_ERRNO__RELOC,	/* Relocation failed */
+	LIBBPF_ERRNO__LOAD,	/* Load program failure for unknown reason */
+	LIBBPF_ERRNO__VERIFY,	/* Kernel verifier blocks program loading */
+	LIBBPF_ERRNO__PROG2BIG,	/* Program too big */
+	LIBBPF_ERRNO__KVER,	/* Incorrect kernel version */
+	__LIBBPF_ERRNO__END,
+};
+
+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..c46256b 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 +366,6 @@ 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_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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#1264044

Em Fri, Nov 06, 2015 at 01:49:37PM +0000, Wang Nan escreveu:
> 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.
> 
> load_program() is improved not to dump log buffer if it is empty. log
> buffer is also used to deduce whether the error is caused by invalid
> program or other problem.
> 
> v1 -> v2:
> 
>  - Using macro for error code.
> 
>  - Fetch error message based on array index, eliminate for-loop.
> 
>  - Use log buffer to detect the reason of failure. 3 new error code
>    are introduced to replace LIBBPF_ERRNO__LOAD.

Thanks a lot for taking into account, from what I quickly skimmed, all
the review comments, really appreciated!

Applying and retesting!

- Arnaldo

> In v1:
> 
> # perf record -e ./test_ill_program.o ls
> event syntax error: './test_ill_program.o'
>                      \___ Failed to load program: Validate your program and check 'license'/'version' sections in your object
> [SKIP]
> 
> # perf record -e ./test_kversion_nomatch_program.o ls
> event syntax error: './test_kversion_nomatch_program.o'
>                      \___ Failed to load program: Validate your program and check 'license'/'version' sections in your object
> [SKIP]
> 
> # perf record -e ./test_big_program.o ls
> event syntax error: './test_big_program.o'
>                      \___ Failed to load program: Validate your program and check 'license'/'version' sections in your object
> [SKIP]
> 
> In v2:
> 
> # perf record -e ./test_ill_program.o ls
> event syntax error: './test_ill_program.o'
>                      \___ Kernel verifier blocks program loading
> [SKIP]
> 
> # perf record -e ./test_kversion_nomatch_program.o
> event syntax error: './test_kversion_nomatch_program.o'
>                      \___ Incorrect kernel version
> [SKIP]
> (Will be further improved by following patches)
> 
> # perf record -e ./test_big_program.o
> event syntax error: './test_big_program.o'
>                      \___ Program too big
> [SKIP]
> 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> ---
>  tools/lib/bpf/libbpf.c         | 159 ++++++++++++++++++++++++++++-------------
>  tools/lib/bpf/libbpf.h         |  20 ++++++
>  tools/perf/tests/llvm.c        |   2 +-
>  tools/perf/util/bpf-loader.c   |  33 +++++++--
>  tools/perf/util/parse-events.c |   4 +-
>  5 files changed, 159 insertions(+), 59 deletions(-)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 9f3c8cf..07b492d 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -61,6 +61,60 @@ void libbpf_set_print(libbpf_print_fn_t warn,
>  	__pr_debug = debug;
>  }
>  
> +#define STRERR_BUFSIZE  128
> +
> +#define ERRNO_OFFSET(e)		((e) - __LIBBPF_ERRNO__START)
> +#define ERRCODE_OFFSET(c)	ERRNO_OFFSET(LIBBPF_ERRNO__##c)
> +#define NR_ERRNO	(__LIBBPF_ERRNO__END - __LIBBPF_ERRNO__START)
> +
> +static const char *libbpf_strerror_table[NR_ERRNO] = {
> +	[ERRCODE_OFFSET(LIBELF)]	= "Something wrong in libelf",
> +	[ERRCODE_OFFSET(FORMAT)]	= "BPF object format invalid",
> +	[ERRCODE_OFFSET(KVERSION)]	= "'version' section incorrect or lost",
> +	[ERRCODE_OFFSET(ENDIAN)]	= "Endian missmatch",
> +	[ERRCODE_OFFSET(INTERNAL)]	= "Internal error in libbpf",
> +	[ERRCODE_OFFSET(RELOC)]		= "Relocation failed",
> +	[ERRCODE_OFFSET(VERIFY)]	= "Kernel verifier blocks program loading",
> +	[ERRCODE_OFFSET(PROG2BIG)]	= "Program too big",
> +	[ERRCODE_OFFSET(KVER)]		= "Incorrect kernel version",
> +};
> +
> +int libbpf_strerror(int err, char *buf, size_t size)
> +{
> +	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;
> +	}
> +
> +	if (err < __LIBBPF_ERRNO__END) {
> +		const char *msg;
> +
> +		msg = libbpf_strerror_table[ERRNO_OFFSET(err)];
> +		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 +312,7 @@ 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 +359,7 @@ 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__LIBELF;
>  	}
>  
>  	if (obj->efile.obj_buf_sz > 0) {
> @@ -331,14 +385,14 @@ 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__LIBELF;
>  		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__FORMAT;
>  		goto errout;
>  	}
>  	ep = &obj->efile.ehdr;
> @@ -346,7 +400,7 @@ 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__FORMAT;
>  		goto errout;
>  	}
>  
> @@ -374,14 +428,14 @@ bpf_object__check_endianness(struct bpf_object *obj)
>  			goto mismatch;
>  		break;
>  	default:
> -		return -EINVAL;
> +		return -LIBBPF_ERRNO__ENDIAN;
>  	}
>  
>  	return 0;
>  
>  mismatch:
>  	pr_warning("Error: endianness mismatch.\n");
> -	return -EINVAL;
> +	return -LIBBPF_ERRNO__ENDIAN;
>  }
>  
>  static int
> @@ -402,7 +456,7 @@ 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__FORMAT;
>  	}
>  	memcpy(&kver, data, sizeof(kver));
>  	obj->kern_version = kver;
> @@ -444,7 +498,7 @@ 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__FORMAT;
>  	}
>  
>  	while ((scn = elf_nextscn(elf, scn)) != NULL) {
> @@ -456,7 +510,7 @@ 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__FORMAT;
>  			goto out;
>  		}
>  
> @@ -464,7 +518,7 @@ 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__FORMAT;
>  			goto out;
>  		}
>  
> @@ -472,7 +526,7 @@ 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__FORMAT;
>  			goto out;
>  		}
>  		pr_debug("section %s, size %ld, link %d, flags %lx, type=%d\n",
> @@ -495,7 +549,7 @@ 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__FORMAT;
>  			} else
>  				obj->efile.symbols = data;
>  		} else if ((sh.sh_type == SHT_PROGBITS) &&
> @@ -504,7 +558,8 @@ 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 +631,7 @@ 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__FORMAT;
>  		}
>  
>  		insn_idx = rel.r_offset / sizeof(struct bpf_insn);
> @@ -587,20 +642,20 @@ 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__FORMAT;
>  		}
>  
>  		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__RELOC;
>  		}
>  
>  		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__RELOC;
>  		}
>  
>  		prog->reloc_desc[i].insn_idx = insn_idx;
> @@ -683,7 +738,7 @@ 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__RELOC;
>  		}
>  		insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
>  		insns[insn_idx].imm = map_fds[map_idx];
> @@ -721,7 +776,7 @@ 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__INTERNAL;
>  	}
>  
>  	for (i = 0; i < obj->efile.nr_reloc; i++) {
> @@ -734,21 +789,21 @@ 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__INTERNAL;
>  		}
>  
>  		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__RELOC;
>  		}
>  
>  		err = bpf_program__collect_reloc(prog, nr_maps,
>  						 shdr, data,
>  						 obj->efile.symbols);
>  		if (err)
> -			return -EINVAL;
> +			return err;
>  	}
>  	return 0;
>  }
> @@ -777,13 +832,23 @@ load_program(struct bpf_insn *insns, int insns_cnt,
>  		goto out;
>  	}
>  
> -	ret = -EINVAL;
> +	ret = -LIBBPF_ERRNO__LOAD;
>  	pr_warning("load bpf program failed: %s\n", strerror(errno));
>  
> -	if (log_buf) {
> +	if (log_buf && log_buf[0] != '\0') {
> +		ret = -LIBBPF_ERRNO__VERIFY;
>  		pr_warning("-- BEGIN DUMP LOG ---\n");
>  		pr_warning("\n%s\n", log_buf);
>  		pr_warning("-- END LOG --\n");
> +	} else {
> +		if (insns_cnt >= BPF_MAXINSNS) {
> +			pr_warning("Program too large (%d insns), at most %d insns\n",
> +				   insns_cnt, BPF_MAXINSNS);
> +			ret = -LIBBPF_ERRNO__PROG2BIG;
> +		} else if (log_buf) {
> +			pr_warning("log buffer is empty\n");
> +			ret = -LIBBPF_ERRNO__KVER;
> +		}
>  	}
>  
>  out:
> @@ -831,7 +896,7 @@ 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__KVERSION;
>  	}
>  	return 0;
>  }
> @@ -840,32 +905,28 @@ 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__LIBELF);
>  	}
>  
>  	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 +983,8 @@ int bpf_object__unload(struct bpf_object *obj)
>  
>  int bpf_object__load(struct bpf_object *obj)
>  {
> +	int err;
> +
>  	if (!obj)
>  		return -EINVAL;
>  
> @@ -931,18 +994,16 @@ 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 +1051,7 @@ const char *
>  bpf_object__get_name(struct bpf_object *obj)
>  {
>  	if (!obj)
> -		return NULL;
> +		return ERR_PTR(-EINVAL);
>  	return obj->path;
>  }
>  
> @@ -1043,7 +1104,7 @@ 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..30a40e9 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -10,6 +10,26 @@
>  
>  #include <stdio.h>
>  #include <stdbool.h>
> +#include <linux/err.h>
> +
> +enum libbpf_errno {
> +	__LIBBPF_ERRNO__START = 4000,
> +
> +	/* Something wrong in libelf */
> +	LIBBPF_ERRNO__LIBELF = __LIBBPF_ERRNO__START,
> +	LIBBPF_ERRNO__FORMAT,	/* BPF object format invalid */
> +	LIBBPF_ERRNO__KVERSION,	/* Incorrect or no 'version' section */
> +	LIBBPF_ERRNO__ENDIAN,	/* Endian missmatch */
> +	LIBBPF_ERRNO__INTERNAL,	/* Internal error in libbpf */
> +	LIBBPF_ERRNO__RELOC,	/* Relocation failed */
> +	LIBBPF_ERRNO__LOAD,	/* Load program failure for unknown reason */
> +	LIBBPF_ERRNO__VERIFY,	/* Kernel verifier blocks program loading */
> +	LIBBPF_ERRNO__PROG2BIG,	/* Program too big */
> +	LIBBPF_ERRNO__KVER,	/* Incorrect kernel version */
> +	__LIBBPF_ERRNO__END,
> +};
> +
> +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..c46256b 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 +366,6 @@ 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_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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#1265022 — [tip:perf/urgent] bpf tools: Improve libbpf error reporting

Commit-ID:  6371ca3b541c82d8aa6a9002bd52d92bcdda5944
Gitweb:     http://git.kernel.org/tip/6371ca3b541c82d8aa6a9002bd52d92bcdda5944
Author:     Wang Nan <wangnan0@huawei.com>
AuthorDate: Fri, 6 Nov 2015 13:49:37 +0000
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 6 Nov 2015 15:52:41 -0300

bpf tools: Improve libbpf error reporting

In this patch, a series of libbpf specific error numbers and
libbpf_strerror() are introduced to help reporting errors.

Functions are updated to pass correct the error number through the
CHECK_ERR() macro.

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

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

load_program() is improved not to dump log buffer if it is empty. log
buffer is also used to deduce whether the error was caused by an invalid
program or other problem.

v1 -> v2:

 - Using macro for error code.

 - Fetch error message based on array index, eliminate for-loop.

 - Use log buffer to detect the reason of failure. 3 new error code
   are introduced to replace LIBBPF_ERRNO__LOAD.

In v1:

  # perf record -e ./test_ill_program.o ls
  event syntax error: './test_ill_program.o'
                       \___ Failed to load program: Validate your program and check 'license'/'version' sections in your object
  SKIP

  # perf record -e ./test_kversion_nomatch_program.o ls
  event syntax error: './test_kversion_nomatch_program.o'
                       \___ Failed to load program: Validate your program and check 'license'/'version' sections in your object
  SKIP

  # perf record -e ./test_big_program.o ls
  event syntax error: './test_big_program.o'
                       \___ Failed to load program: Validate your program and check 'license'/'version' sections in your object
  SKIP

  In v2:

  # perf record -e ./test_ill_program.o ls
  event syntax error: './test_ill_program.o'
                       \___ Kernel verifier blocks program loading
  SKIP

  # perf record -e ./test_kversion_nomatch_program.o
  event syntax error: './test_kversion_nomatch_program.o'
                       \___ Incorrect kernel version
  SKIP
  (Will be further improved by following patches)

  # perf record -e ./test_big_program.o
  event syntax error: './test_big_program.o'
                       \___ Program too big
  SKIP

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1446817783-86722-2-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/lib/bpf/libbpf.c         | 159 ++++++++++++++++++++++++++++-------------
 tools/lib/bpf/libbpf.h         |  20 ++++++
 tools/perf/tests/llvm.c        |   2 +-
 tools/perf/util/bpf-loader.c   |  33 +++++++--
 tools/perf/util/parse-events.c |   4 +-
 5 files changed, 159 insertions(+), 59 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 9f3c8cf..07b492d 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -61,6 +61,60 @@ void libbpf_set_print(libbpf_print_fn_t warn,
 	__pr_debug = debug;
 }
 
+#define STRERR_BUFSIZE  128
+
+#define ERRNO_OFFSET(e)		((e) - __LIBBPF_ERRNO__START)
+#define ERRCODE_OFFSET(c)	ERRNO_OFFSET(LIBBPF_ERRNO__##c)
+#define NR_ERRNO	(__LIBBPF_ERRNO__END - __LIBBPF_ERRNO__START)
+
+static const char *libbpf_strerror_table[NR_ERRNO] = {
+	[ERRCODE_OFFSET(LIBELF)]	= "Something wrong in libelf",
+	[ERRCODE_OFFSET(FORMAT)]	= "BPF object format invalid",
+	[ERRCODE_OFFSET(KVERSION)]	= "'version' section incorrect or lost",
+	[ERRCODE_OFFSET(ENDIAN)]	= "Endian missmatch",
+	[ERRCODE_OFFSET(INTERNAL)]	= "Internal error in libbpf",
+	[ERRCODE_OFFSET(RELOC)]		= "Relocation failed",
+	[ERRCODE_OFFSET(VERIFY)]	= "Kernel verifier blocks program loading",
+	[ERRCODE_OFFSET(PROG2BIG)]	= "Program too big",
+	[ERRCODE_OFFSET(KVER)]		= "Incorrect kernel version",
+};
+
+int libbpf_strerror(int err, char *buf, size_t size)
+{
+	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;
+	}
+
+	if (err < __LIBBPF_ERRNO__END) {
+		const char *msg;
+
+		msg = libbpf_strerror_table[ERRNO_OFFSET(err)];
+		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 +312,7 @@ 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 +359,7 @@ 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__LIBELF;
 	}
 
 	if (obj->efile.obj_buf_sz > 0) {
@@ -331,14 +385,14 @@ 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__LIBELF;
 		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__FORMAT;
 		goto errout;
 	}
 	ep = &obj->efile.ehdr;
@@ -346,7 +400,7 @@ 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__FORMAT;
 		goto errout;
 	}
 
@@ -374,14 +428,14 @@ bpf_object__check_endianness(struct bpf_object *obj)
 			goto mismatch;
 		break;
 	default:
-		return -EINVAL;
+		return -LIBBPF_ERRNO__ENDIAN;
 	}
 
 	return 0;
 
 mismatch:
 	pr_warning("Error: endianness mismatch.\n");
-	return -EINVAL;
+	return -LIBBPF_ERRNO__ENDIAN;
 }
 
 static int
@@ -402,7 +456,7 @@ 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__FORMAT;
 	}
 	memcpy(&kver, data, sizeof(kver));
 	obj->kern_version = kver;
@@ -444,7 +498,7 @@ 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__FORMAT;
 	}
 
 	while ((scn = elf_nextscn(elf, scn)) != NULL) {
@@ -456,7 +510,7 @@ 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__FORMAT;
 			goto out;
 		}
 
@@ -464,7 +518,7 @@ 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__FORMAT;
 			goto out;
 		}
 
@@ -472,7 +526,7 @@ 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__FORMAT;
 			goto out;
 		}
 		pr_debug("section %s, size %ld, link %d, flags %lx, type=%d\n",
@@ -495,7 +549,7 @@ 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__FORMAT;
 			} else
 				obj->efile.symbols = data;
 		} else if ((sh.sh_type == SHT_PROGBITS) &&
@@ -504,7 +558,8 @@ 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 +631,7 @@ 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__FORMAT;
 		}
 
 		insn_idx = rel.r_offset / sizeof(struct bpf_insn);
@@ -587,20 +642,20 @@ 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__FORMAT;
 		}
 
 		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__RELOC;
 		}
 
 		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__RELOC;
 		}
 
 		prog->reloc_desc[i].insn_idx = insn_idx;
@@ -683,7 +738,7 @@ 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__RELOC;
 		}
 		insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
 		insns[insn_idx].imm = map_fds[map_idx];
@@ -721,7 +776,7 @@ 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__INTERNAL;
 	}
 
 	for (i = 0; i < obj->efile.nr_reloc; i++) {
@@ -734,21 +789,21 @@ 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__INTERNAL;
 		}
 
 		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__RELOC;
 		}
 
 		err = bpf_program__collect_reloc(prog, nr_maps,
 						 shdr, data,
 						 obj->efile.symbols);
 		if (err)
-			return -EINVAL;
+			return err;
 	}
 	return 0;
 }
@@ -777,13 +832,23 @@ load_program(struct bpf_insn *insns, int insns_cnt,
 		goto out;
 	}
 
-	ret = -EINVAL;
+	ret = -LIBBPF_ERRNO__LOAD;
 	pr_warning("load bpf program failed: %s\n", strerror(errno));
 
-	if (log_buf) {
+	if (log_buf && log_buf[0] != '\0') {
+		ret = -LIBBPF_ERRNO__VERIFY;
 		pr_warning("-- BEGIN DUMP LOG ---\n");
 		pr_warning("\n%s\n", log_buf);
 		pr_warning("-- END LOG --\n");
+	} else {
+		if (insns_cnt >= BPF_MAXINSNS) {
+			pr_warning("Program too large (%d insns), at most %d insns\n",
+				   insns_cnt, BPF_MAXINSNS);
+			ret = -LIBBPF_ERRNO__PROG2BIG;
+		} else if (log_buf) {
+			pr_warning("log buffer is empty\n");
+			ret = -LIBBPF_ERRNO__KVER;
+		}
 	}
 
 out:
@@ -831,7 +896,7 @@ 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__KVERSION;
 	}
 	return 0;
 }
@@ -840,32 +905,28 @@ 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__LIBELF);
 	}
 
 	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 +983,8 @@ int bpf_object__unload(struct bpf_object *obj)
 
 int bpf_object__load(struct bpf_object *obj)
 {
+	int err;
+
 	if (!obj)
 		return -EINVAL;
 
@@ -931,18 +994,16 @@ 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 +1051,7 @@ const char *
 bpf_object__get_name(struct bpf_object *obj)
 {
 	if (!obj)
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	return obj->path;
 }
 
@@ -1043,7 +1104,7 @@ 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..30a40e9 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -10,6 +10,26 @@
 
 #include <stdio.h>
 #include <stdbool.h>
+#include <linux/err.h>
+
+enum libbpf_errno {
+	__LIBBPF_ERRNO__START = 4000,
+
+	/* Something wrong in libelf */
+	LIBBPF_ERRNO__LIBELF = __LIBBPF_ERRNO__START,
+	LIBBPF_ERRNO__FORMAT,	/* BPF object format invalid */
+	LIBBPF_ERRNO__KVERSION,	/* Incorrect or no 'version' section */
+	LIBBPF_ERRNO__ENDIAN,	/* Endian missmatch */
+	LIBBPF_ERRNO__INTERNAL,	/* Internal error in libbpf */
+	LIBBPF_ERRNO__RELOC,	/* Relocation failed */
+	LIBBPF_ERRNO__LOAD,	/* Load program failure for unknown reason */
+	LIBBPF_ERRNO__VERIFY,	/* Kernel verifier blocks program loading */
+	LIBBPF_ERRNO__PROG2BIG,	/* Program too big */
+	LIBBPF_ERRNO__KVER,	/* Incorrect kernel version */
+	__LIBBPF_ERRNO__END,
+};
+
+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..c46256b 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 +366,6 @@ 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_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),
--
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