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Date: Fri, 13 Nov 2015 12:39:41 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Wang Nan <wangnan0@...wei.com>
Cc: masami.hiramatsu.pt@...achi.com, ast@...nel.org,
lizefan@...wei.com, pi3orama@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/12] perf tools: Allow BPF program attach to uprobe
events
Em Fri, Nov 13, 2015 at 12:29:12PM +0000, Wang Nan escreveu:
> This patch appends new syntax to BPF object section name to support
> probing at uprobe event. Now we can use BPF program like this:
>
> SEC(
> "exec=/lib64/libc.so.6\n"
> "libcwrite=__write"
> )
> int libcwrite(void *ctx)
> {
> return 1;
> }
>
> Where, in section name of a program, before the main config string,
> we can use 'key=value' style options. Now the only option key "exec"
> is for uprobe probing.
>
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Zefan Li <lizefan@...wei.com>
> Cc: pi3orama@....com
> ---
> tools/perf/util/bpf-loader.c | 122 ++++++++++++++++++++++++++++++++++++++++---
> tools/perf/util/bpf-loader.h | 1 +
> 2 files changed, 117 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
> index 4c50411..5f5505d 100644
> --- a/tools/perf/util/bpf-loader.c
> +++ b/tools/perf/util/bpf-loader.c
> @@ -110,6 +110,115 @@ bpf_prog_priv__clear(struct bpf_program *prog __maybe_unused,
> }
>
> static int
> +config__exec(const char *value, struct perf_probe_event *pev)
> +{
> + pev->uprobes = true;
> + pev->target = strdup(value);
Shouldn't we check if this fails and return some failure error
accordingly?
> + return 0;
> +}
> +
> +static struct {
> + const char *key;
> + const char *usage;
> + const char *desc;
> + int (*func)(const char *, struct perf_probe_event *);
> +} bpf_config_terms[] = {
> + {
> + "exec",
> + "exec=<full path of file>",
> + "Set uprobe target",
> + config__exec,
> + },
Even with the definition of the struct right above it, please use named
initializers, i.e. turn the avove into:
+ {
+ .key = "exec",
+ .usage = "exec=<full path of file>",
+ .desc = "Set uprobe target",
+ .func = config__exec,
+ },
> +};
> +
> +static int
> +do_config(const char *key, const char *value,
> + struct perf_probe_event *pev)
> +{
> + unsigned int i;
> +
> + pr_debug("config bpf program: %s=%s\n", key, value);
> + for (i = 0; i < ARRAY_SIZE(bpf_config_terms); i++)
> + if (strcmp(key, bpf_config_terms[i].key) == 0)
> + return bpf_config_terms[i].func(value, pev);
> +
> + pr_debug("BPF: ERROR: invalid config option in object: %s=%s\n",
> + key, value);
> +
> + pr_debug("\nHint: Currently valid options are:\n");
> + for (i = 0; i < ARRAY_SIZE(bpf_config_terms); i++)
> + pr_debug("\t%s:\t%s\n", bpf_config_terms[i].usage,
> + bpf_config_terms[i].desc);
> + pr_debug("\n");
> +
> + return -BPF_LOADER_ERRNO__CONFIG_TERM;
> +}
> +
> +static const char *
> +parse_config_kvpair(const char *config_str, struct perf_probe_event *pev)
> +{
> + char *text = strdup(config_str);
> + char *sep, *line;
> + const char *main_str = NULL;
> + int err = 0;
> +
> + if (!text) {
See, here you do it correctly, checking the strdup() return, providing
some debugging for -v usage _and_ the right ERR_PTR() return, well done!
> + pr_debug("No enough memory: dup config_str failed\n");
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + line = text;
> + while ((sep = strchr(line, '\n'))) {
> + char *equ;
> +
> + *sep = '\0';
> + equ = strchr(line, '=');
> + if (!equ) {
> + pr_warning("WARNING: invalid config in BPF object: %s\n",
> + line);
> + pr_warning("\tShould be 'key=value'.\n");
> + goto nextline;
> + }
> + *equ = '\0';
> +
> + err = do_config(line, equ + 1, pev);
> + if (err)
> + break;
> +nextline:
> + line = sep + 1;
> + }
> +
> + if (!err)
> + main_str = config_str + (line - text);
> + free(text);
> +
> + if (err)
> + return ERR_PTR(err);
> +
> + return main_str;
No biggie, but doing:
return err ? ERR_PTR(err) : main_str;
Is more compact and clear :-)
> +}
> +
> +static int
> +parse_config(const char *config_str, struct perf_probe_event *pev)
> +{
> + const char *main_str;
> + int err;
> +
> + main_str = parse_config_kvpair(config_str, pev);
Also just for compactness, just a suggestion, doing:
const char *main_str = parse_config_kvpair(config_str, pev);
Saves screen real state :-)
> + if (IS_ERR(main_str))
> + return PTR_ERR(main_str);
> +
> + err = parse_perf_probe_command(main_str, pev);
> + if (err < 0) {
> + pr_debug("bpf: '%s' is not a valid config string\n",
> + config_str);
> + /* parse failed, don't need clear pev. */
> + return -BPF_LOADER_ERRNO__CONFIG;
> + }
> + return 0;
> +}
> +
> +static int
> config_bpf_program(struct bpf_program *prog)
> {
> struct perf_probe_event *pev = NULL;
> @@ -131,13 +240,9 @@ config_bpf_program(struct bpf_program *prog)
> pev = &priv->pev;
>
> pr_debug("bpf: config program '%s'\n", config_str);
> - err = parse_perf_probe_command(config_str, pev);
> - if (err < 0) {
> - pr_debug("bpf: '%s' is not a valid config string\n",
> - config_str);
> - err = -BPF_LOADER_ERRNO__CONFIG;
> + err = parse_config(config_str, pev);
> + if (err)
> goto errout;
> - }
>
> if (pev->group && strcmp(pev->group, PERF_BPF_PROBE_GROUP)) {
> pr_debug("bpf: '%s': group for event is set and not '%s'.\n",
> @@ -340,6 +445,7 @@ static const char *bpf_loader_strerror_table[NR_ERRNO] = {
> [ERRCODE_OFFSET(EVENTNAME)] = "No event name found in config string",
> [ERRCODE_OFFSET(INTERNAL)] = "BPF loader internal error",
> [ERRCODE_OFFSET(COMPILE)] = "Error when compiling BPF scriptlet",
> + [ERRCODE_OFFSET(CONFIG_TERM)] = "Invalid config term in config string",
> };
>
> static int
> @@ -420,6 +526,10 @@ int bpf__strerror_probe(struct bpf_object *obj __maybe_unused,
> int err, char *buf, size_t size)
> {
> bpf__strerror_head(err, buf, size);
> + case BPF_LOADER_ERRNO__CONFIG_TERM: {
> + scnprintf(buf, size, "%s (add -v to see detail)", emsg);
> + break;
> + }
> bpf__strerror_entry(EEXIST, "Probe point exist. Try use 'perf probe -d \"*\"'");
> bpf__strerror_entry(EACCES, "You need to be root");
> bpf__strerror_entry(EPERM, "You need to be root, and /proc/sys/kernel/kptr_restrict should be 0");
> diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
> index 9caf3ae..d19f5c5 100644
> --- a/tools/perf/util/bpf-loader.h
> +++ b/tools/perf/util/bpf-loader.h
> @@ -20,6 +20,7 @@ enum bpf_loader_errno {
> BPF_LOADER_ERRNO__EVENTNAME, /* Event name is missing */
> BPF_LOADER_ERRNO__INTERNAL, /* BPF loader internal error */
> BPF_LOADER_ERRNO__COMPILE, /* Error when compiling BPF scriptlet */
> + BPF_LOADER_ERRNO__CONFIG_TERM, /* Invalid config term in config term */
> __BPF_LOADER_ERRNO__END,
> };
>
> --
> 1.8.3.4
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