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

From: Wang Nan
Date: Fri Nov 06 2015 - 08:50:49 EST

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@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
---
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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