* [PATCH v3 2/2] libbpf: kprobe.multi: Filter with available_filter_functions_addrs
2023-07-03 1:36 [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms Jackie Liu
@ 2023-07-03 1:36 ` Jackie Liu
2023-07-03 12:59 ` [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms Jiri Olsa
2023-07-03 19:38 ` John Fastabend
2 siblings, 0 replies; 8+ messages in thread
From: Jackie Liu @ 2023-07-03 1:36 UTC (permalink / raw)
To: olsajiri, andrii; +Cc: martin.lau, song, yhs, bpf, liuyun01, lkp
From: Jackie Liu <liuyun01@kylinos.cn>
Now, we provide a new available_filter_functions_addrs interface, which can
help us not need to cross-validate available_filter_functions and kallsyms,
which can effectively improve efficiency. For example, on my device, the
sample program [1] of start time:
$ sudo ./funccount "tcp_*"
before after
1.2s 1.0s
[1]: https://github.com/JackieLiu1/ketones/tree/master/src/funccount
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
---
v2->v3: fix 'fscanf' may overflow
tools/lib/bpf/libbpf.c | 58 +++++++++++++++++++++++++++++++++++++++++-
1 file changed, 57 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 232268215bb7..afdbd30ac7e0 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10230,6 +10230,12 @@ static const char *tracefs_available_filter_functions(void)
TRACEFS"/available_filter_functions";
}
+static const char *tracefs_available_filter_functions_addrs(void)
+{
+ return use_debugfs() ? DEBUGFS"/available_filter_functions_addrs" :
+ TRACEFS"/available_filter_functions_addrs";
+}
+
static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
const char *kfunc_name, size_t offset)
{
@@ -10654,6 +10660,53 @@ static int libbpf_available_kallsyms_parse(struct kprobe_multi_resolve *res)
return err;
}
+static bool has_available_filter_functions_addrs(void)
+{
+ return access(tracefs_available_filter_functions_addrs(), R_OK) != -1;
+}
+
+static int libbpf_available_kprobes_parse(struct kprobe_multi_resolve *res)
+{
+ char sym_name[500];
+ FILE *f;
+ int ret, err = 0;
+ unsigned long long sym_addr;
+ const char *available_path = tracefs_available_filter_functions_addrs();
+
+ f = fopen(available_path, "r");
+ if (!f) {
+ err = -errno;
+ pr_warn("failed to open %s.\n", available_path);
+ return err;
+ }
+
+ while (true) {
+ ret = fscanf(f, "%llx %499s%*[^\n]\n", &sym_addr, sym_name);
+ if (ret == EOF && feof(f))
+ break;
+
+ if (ret != 2) {
+ pr_warn("failed to read available kprobe entry: %d\n",
+ ret);
+ err = -EINVAL;
+ break;
+ }
+
+ if (!glob_match(sym_name, res->pattern))
+ continue;
+
+ err = libbpf_ensure_mem((void **) &res->addrs, &res->cap,
+ sizeof(unsigned long), res->cnt + 1);
+ if (err)
+ break;
+
+ res->addrs[res->cnt++] = (unsigned long) sym_addr;
+ }
+
+ fclose(f);
+ return err;
+}
+
struct bpf_link *
bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
const char *pattern,
@@ -10690,7 +10743,10 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
return libbpf_err_ptr(-EINVAL);
if (pattern) {
- err = libbpf_available_kallsyms_parse(&res);
+ if (has_available_filter_functions_addrs())
+ err = libbpf_available_kprobes_parse(&res);
+ else
+ err = libbpf_available_kallsyms_parse(&res);
if (err)
goto error;
if (!res.cnt) {
--
2.25.1
^ permalink raw reply related [flat|nested] 8+ messages in thread* Re: [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms
2023-07-03 1:36 [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms Jackie Liu
2023-07-03 1:36 ` [PATCH v3 2/2] libbpf: kprobe.multi: Filter with available_filter_functions_addrs Jackie Liu
@ 2023-07-03 12:59 ` Jiri Olsa
2023-07-04 1:33 ` Jackie Liu
2023-07-03 19:38 ` John Fastabend
2 siblings, 1 reply; 8+ messages in thread
From: Jiri Olsa @ 2023-07-03 12:59 UTC (permalink / raw)
To: Jackie Liu; +Cc: olsajiri, andrii, martin.lau, song, yhs, bpf, liuyun01, lkp
On Mon, Jul 03, 2023 at 09:36:17AM +0800, Jackie Liu wrote:
> From: Jackie Liu <liuyun01@kylinos.cn>
>
> When using regular expression matching with "kprobe multi", it scans all
> the functions under "/proc/kallsyms" that can be matched. However, not all
> of them can be traced by kprobe.multi. If any one of the functions fails
> to be traced, it will result in the failure of all functions. The best
> approach is to filter out the functions that cannot be traced to ensure
> proper tracking of the functions.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202307030355.TdXOHklM-lkp@intel.com/
> Suggested-by: Jiri Olsa <jolsa@kernel.org>
> Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
> ---
> v2->v3: fix 'fscanf' may overflow
>
> tools/lib/bpf/libbpf.c | 122 ++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 109 insertions(+), 13 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 214f828ece6b..232268215bb7 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -10224,6 +10224,12 @@ static const char *tracefs_uprobe_events(void)
> return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events";
> }
>
> +static const char *tracefs_available_filter_functions(void)
> +{
> + return use_debugfs() ? DEBUGFS"/available_filter_functions" :
> + TRACEFS"/available_filter_functions";
> +}
> +
> static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
> const char *kfunc_name, size_t offset)
> {
> @@ -10539,23 +10545,113 @@ struct kprobe_multi_resolve {
> size_t cnt;
> };
>
> -static int
> -resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type,
> - const char *sym_name, void *ctx)
> +static int qsort_compare_function(const void *a, const void *b)
> {
> - struct kprobe_multi_resolve *res = ctx;
> - int err;
> + return strcmp(*(const char **)a, *(const char **)b);
> +}
>
> - if (!glob_match(sym_name, res->pattern))
> - return 0;
> +static int bsearch_compare_function(const void *a, const void *b)
> +{
> + return strcmp((const char *)a, *(const char **)b);
> +}
>
> - err = libbpf_ensure_mem((void **) &res->addrs, &res->cap, sizeof(unsigned long),
> - res->cnt + 1);
> - if (err)
> +static int libbpf_available_kallsyms_parse(struct kprobe_multi_resolve *res)
> +{
> + char sym_name[500];
> + const char *available_functions_file = tracefs_available_filter_functions();
> + FILE *f;
> + int err = 0, ret, i;
> + struct function_info {
> + const char **syms;
> + size_t cap;
> + size_t cnt;
> + } infos = {};
do you need to define new struct for this? there's just on infos
variable of that, you could use just:
const char **syms = NULL;
size_t cap = 0, cnt = 0;
> +
> + f = fopen(available_functions_file, "r");
> + if (!f) {
> + err = -errno;
> + pr_warn("failed to open %s\n", available_functions_file);
> return err;
> + }
>
> - res->addrs[res->cnt++] = (unsigned long) sym_addr;
> - return 0;
> + while (true) {
> + char *name;
> +
> + ret = fscanf(f, "%499s%*[^\n]\n", sym_name);
> + if (ret == EOF && feof(f))
> + break;
> +
> + if (ret != 1) {
> + pr_warn("failed to read available function file entry: %d\n",
> + ret);
> + err = -EINVAL;
> + goto cleanup;
> + }
> +
> + if (!glob_match(sym_name, res->pattern))
> + continue;
> +
> + err = libbpf_ensure_mem((void **)&infos.syms, &infos.cap,
> + sizeof(void *), infos.cnt + 1);
> + if (err)
> + goto cleanup;
> +
> + name = strdup(sym_name);
> + if (!name) {
> + err = -errno;
> + goto cleanup;
> + }
> +
> + infos.syms[infos.cnt++] = name;
> + }
> + fclose(f);
should you check if you found anything (infos.cnt != 0) and return early
if there's nothing found
> +
> + /* sort available functions */
> + qsort(infos.syms, infos.cnt, sizeof(void *), qsort_compare_function);
> +
> + f = fopen("/proc/kallsyms", "r");
why not use libbpf_kallsyms_parse for kallsyms parsing? the call below
would be in its callback
> + if (!f) {
> + err = -errno;
> + pr_warn("failed to open /proc/kallsyms\n");
> + goto free_infos;
> + }
> +
> + while (true) {
> + unsigned long long sym_addr;
> +
> + ret = fscanf(f, "%llx %*c %499s%*[^\n]\n", &sym_addr, sym_name);
> + if (ret == EOF && feof(f))
> + break;
> +
> + if (ret != 2) {
> + pr_warn("failed to read kallsyms entry: %d\n", ret);
> + err = -EINVAL;
> + break;
> + }
> +
> + if (!glob_match(sym_name, res->pattern))
> + continue;
hm, we don't need to call glob_match again, we just want to check
if the kallsyms symbol is in infos.syms
> +
> + if (!bsearch(&sym_name, infos.syms, infos.cnt, sizeof(void *),
> + bsearch_compare_function))
> + continue;
> +
> + err = libbpf_ensure_mem((void **)&res->addrs, &res->cap,
> + sizeof(unsigned long), res->cnt + 1);
> + if (err)
> + break;
> +
> + res->addrs[res->cnt++] = (unsigned long) sym_addr;
> + }
res->cnt is check outside for 0, so we should be find here
jirka
> +
> +cleanup:
> + fclose(f);
> +free_infos:
> + for (i = 0; i < infos.cnt; i++)
> + free((char *)infos.syms[i]);
> + free(infos.syms);
> +
> + return err;
> }
>
> struct bpf_link *
> @@ -10594,7 +10690,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
> return libbpf_err_ptr(-EINVAL);
>
> if (pattern) {
> - err = libbpf_kallsyms_parse(resolve_kprobe_multi_cb, &res);
> + err = libbpf_available_kallsyms_parse(&res);
> if (err)
> goto error;
> if (!res.cnt) {
> --
> 2.25.1
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms
2023-07-03 12:59 ` [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms Jiri Olsa
@ 2023-07-04 1:33 ` Jackie Liu
2023-07-04 14:07 ` Jiri Olsa
0 siblings, 1 reply; 8+ messages in thread
From: Jackie Liu @ 2023-07-04 1:33 UTC (permalink / raw)
To: Jiri Olsa; +Cc: andrii, martin.lau, song, yhs, bpf, liuyun01, lkp
在 2023/7/3 20:59, Jiri Olsa 写道:
> On Mon, Jul 03, 2023 at 09:36:17AM +0800, Jackie Liu wrote:
>> From: Jackie Liu <liuyun01@kylinos.cn>
>>
>> When using regular expression matching with "kprobe multi", it scans all
>> the functions under "/proc/kallsyms" that can be matched. However, not all
>> of them can be traced by kprobe.multi. If any one of the functions fails
>> to be traced, it will result in the failure of all functions. The best
>> approach is to filter out the functions that cannot be traced to ensure
>> proper tracking of the functions.
>>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Closes: https://lore.kernel.org/oe-kbuild-all/202307030355.TdXOHklM-lkp@intel.com/
>> Suggested-by: Jiri Olsa <jolsa@kernel.org>
>> Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
>> Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
>> ---
>> v2->v3: fix 'fscanf' may overflow
>>
>> tools/lib/bpf/libbpf.c | 122 ++++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 109 insertions(+), 13 deletions(-)
>>
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 214f828ece6b..232268215bb7 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -10224,6 +10224,12 @@ static const char *tracefs_uprobe_events(void)
>> return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events";
>> }
>>
>> +static const char *tracefs_available_filter_functions(void)
>> +{
>> + return use_debugfs() ? DEBUGFS"/available_filter_functions" :
>> + TRACEFS"/available_filter_functions";
>> +}
>> +
>> static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
>> const char *kfunc_name, size_t offset)
>> {
>> @@ -10539,23 +10545,113 @@ struct kprobe_multi_resolve {
>> size_t cnt;
>> };
>>
>> -static int
>> -resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type,
>> - const char *sym_name, void *ctx)
>> +static int qsort_compare_function(const void *a, const void *b)
>> {
>> - struct kprobe_multi_resolve *res = ctx;
>> - int err;
>> + return strcmp(*(const char **)a, *(const char **)b);
>> +}
>>
>> - if (!glob_match(sym_name, res->pattern))
>> - return 0;
>> +static int bsearch_compare_function(const void *a, const void *b)
>> +{
>> + return strcmp((const char *)a, *(const char **)b);
>> +}
>>
>> - err = libbpf_ensure_mem((void **) &res->addrs, &res->cap, sizeof(unsigned long),
>> - res->cnt + 1);
>> - if (err)
>> +static int libbpf_available_kallsyms_parse(struct kprobe_multi_resolve *res)
>> +{
>> + char sym_name[500];
>> + const char *available_functions_file = tracefs_available_filter_functions();
>> + FILE *f;
>> + int err = 0, ret, i;
>> + struct function_info {
>> + const char **syms;
>> + size_t cap;
>> + size_t cnt;
>> + } infos = {};
>
> do you need to define new struct for this? there's just on infos
> variable of that, you could use just:
>
> const char **syms = NULL;
> size_t cap = 0, cnt = 0;
>
>> +
>> + f = fopen(available_functions_file, "r");
>> + if (!f) {
>> + err = -errno;
>> + pr_warn("failed to open %s\n", available_functions_file);
>> return err;
>> + }
>>
>> - res->addrs[res->cnt++] = (unsigned long) sym_addr;
>> - return 0;
>> + while (true) {
>> + char *name;
>> +
>> + ret = fscanf(f, "%499s%*[^\n]\n", sym_name);
>> + if (ret == EOF && feof(f))
>> + break;
>> +
>> + if (ret != 1) {
>> + pr_warn("failed to read available function file entry: %d\n",
>> + ret);
>> + err = -EINVAL;
>> + goto cleanup;
>> + }
>> +
>> + if (!glob_match(sym_name, res->pattern))
>> + continue;
>> +
>> + err = libbpf_ensure_mem((void **)&infos.syms, &infos.cap,
>> + sizeof(void *), infos.cnt + 1);
>> + if (err)
>> + goto cleanup;
>> +
>> + name = strdup(sym_name);
>> + if (!name) {
>> + err = -errno;
>> + goto cleanup;
>> + }
>> +
>> + infos.syms[infos.cnt++] = name;
>> + }
>> + fclose(f);
>
> should you check if you found anything (infos.cnt != 0) and return early
> if there's nothing found
>
>> +
>> + /* sort available functions */
>> + qsort(infos.syms, infos.cnt, sizeof(void *), qsort_compare_function);
>> +
>> + f = fopen("/proc/kallsyms", "r");
>
> why not use libbpf_kallsyms_parse for kallsyms parsing? the call below
> would be in its callback
This place cannot directly use libbpf_kallsyms_parse, because we need
info.syms, this value cannot be passed into the parameters of
libbpf_kallsyms_parse, and we cannot turn info.syms into a global
variable, which is unnecessary. The easiest way is to reimplement a A
copy of libbpf_kallsyms_parse.
Modifications to other parts will be carried along with the next
version.
--
Jackie
>
>> + if (!f) {
>> + err = -errno;
>> + pr_warn("failed to open /proc/kallsyms\n");
>> + goto free_infos;
>> + }
>> +
>> + while (true) {
>> + unsigned long long sym_addr;
>> +
>> + ret = fscanf(f, "%llx %*c %499s%*[^\n]\n", &sym_addr, sym_name);
>> + if (ret == EOF && feof(f))
>> + break;
>> +
>> + if (ret != 2) {
>> + pr_warn("failed to read kallsyms entry: %d\n", ret);
>> + err = -EINVAL;
>> + break;
>> + }
>> +
>> + if (!glob_match(sym_name, res->pattern))
>> + continue;
>
> hm, we don't need to call glob_match again, we just want to check
> if the kallsyms symbol is in infos.syms
>
>> +
>> + if (!bsearch(&sym_name, infos.syms, infos.cnt, sizeof(void *),
>> + bsearch_compare_function))
>> + continue;
>> +
>> + err = libbpf_ensure_mem((void **)&res->addrs, &res->cap,
>> + sizeof(unsigned long), res->cnt + 1);
>> + if (err)
>> + break;
>> +
>> + res->addrs[res->cnt++] = (unsigned long) sym_addr;
>> + }
>
> res->cnt is check outside for 0, so we should be find here
>
> jirka
>
>> +
>> +cleanup:
>> + fclose(f);
>> +free_infos:
>> + for (i = 0; i < infos.cnt; i++)
>> + free((char *)infos.syms[i]);
>> + free(infos.syms);
>> +
>> + return err;
>> }
>>
>> struct bpf_link *
>> @@ -10594,7 +10690,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
>> return libbpf_err_ptr(-EINVAL);
>>
>> if (pattern) {
>> - err = libbpf_kallsyms_parse(resolve_kprobe_multi_cb, &res);
>> + err = libbpf_available_kallsyms_parse(&res);
>> if (err)
>> goto error;
>> if (!res.cnt) {
>> --
>> 2.25.1
>>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms
2023-07-04 1:33 ` Jackie Liu
@ 2023-07-04 14:07 ` Jiri Olsa
2023-07-04 14:20 ` Jiri Olsa
0 siblings, 1 reply; 8+ messages in thread
From: Jiri Olsa @ 2023-07-04 14:07 UTC (permalink / raw)
To: Jackie Liu; +Cc: Jiri Olsa, andrii, martin.lau, song, yhs, bpf, liuyun01, lkp
On Tue, Jul 04, 2023 at 09:33:15AM +0800, Jackie Liu wrote:
SNIP
> >
> > should you check if you found anything (infos.cnt != 0) and return early
> > if there's nothing found
> >
> > > +
> > > + /* sort available functions */
> > > + qsort(infos.syms, infos.cnt, sizeof(void *), qsort_compare_function);
> > > +
> > > + f = fopen("/proc/kallsyms", "r");
> >
> > why not use libbpf_kallsyms_parse for kallsyms parsing? the call below
> > would be in its callback
>
> This place cannot directly use libbpf_kallsyms_parse, because we need
> info.syms, this value cannot be passed into the parameters of
> libbpf_kallsyms_parse,
hum, libbpf_kallsyms_parse takes 'void *ctx', so you can pass anything
you want right?
thanks,
jirka
> and we cannot turn info.syms into a global
> variable, which is unnecessary. The easiest way is to reimplement a A
> copy of libbpf_kallsyms_parse.
>
> Modifications to other parts will be carried along with the next
> version.
>
> --
> Jackie
>
> >
> > > + if (!f) {
> > > + err = -errno;
> > > + pr_warn("failed to open /proc/kallsyms\n");
> > > + goto free_infos;
> > > + }
> > > +
> > > + while (true) {
> > > + unsigned long long sym_addr;
> > > +
> > > + ret = fscanf(f, "%llx %*c %499s%*[^\n]\n", &sym_addr, sym_name);
> > > + if (ret == EOF && feof(f))
> > > + break;
> > > +
> > > + if (ret != 2) {
> > > + pr_warn("failed to read kallsyms entry: %d\n", ret);
> > > + err = -EINVAL;
> > > + break;
> > > + }
> > > +
> > > + if (!glob_match(sym_name, res->pattern))
> > > + continue;
> >
> > hm, we don't need to call glob_match again, we just want to check
> > if the kallsyms symbol is in infos.syms
> >
> > > +
> > > + if (!bsearch(&sym_name, infos.syms, infos.cnt, sizeof(void *),
> > > + bsearch_compare_function))
> > > + continue;
> > > +
> > > + err = libbpf_ensure_mem((void **)&res->addrs, &res->cap,
> > > + sizeof(unsigned long), res->cnt + 1);
> > > + if (err)
> > > + break;
> > > +
> > > + res->addrs[res->cnt++] = (unsigned long) sym_addr;
> > > + }
> >
> > res->cnt is check outside for 0, so we should be find here
> >
> > jirka
> >
> > > +
> > > +cleanup:
> > > + fclose(f);
> > > +free_infos:
> > > + for (i = 0; i < infos.cnt; i++)
> > > + free((char *)infos.syms[i]);
> > > + free(infos.syms);
> > > +
> > > + return err;
> > > }
> > > struct bpf_link *
> > > @@ -10594,7 +10690,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
> > > return libbpf_err_ptr(-EINVAL);
> > > if (pattern) {
> > > - err = libbpf_kallsyms_parse(resolve_kprobe_multi_cb, &res);
> > > + err = libbpf_available_kallsyms_parse(&res);
> > > if (err)
> > > goto error;
> > > if (!res.cnt) {
> > > --
> > > 2.25.1
> > >
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms
2023-07-04 14:07 ` Jiri Olsa
@ 2023-07-04 14:20 ` Jiri Olsa
0 siblings, 0 replies; 8+ messages in thread
From: Jiri Olsa @ 2023-07-04 14:20 UTC (permalink / raw)
To: Jackie Liu; +Cc: Jiri Olsa, andrii, martin.lau, song, yhs, bpf, liuyun01, lkp
On Tue, Jul 04, 2023 at 04:07:48PM +0200, Jiri Olsa wrote:
> On Tue, Jul 04, 2023 at 09:33:15AM +0800, Jackie Liu wrote:
>
> SNIP
>
> > >
> > > should you check if you found anything (infos.cnt != 0) and return early
> > > if there's nothing found
> > >
> > > > +
> > > > + /* sort available functions */
> > > > + qsort(infos.syms, infos.cnt, sizeof(void *), qsort_compare_function);
> > > > +
> > > > + f = fopen("/proc/kallsyms", "r");
> > >
> > > why not use libbpf_kallsyms_parse for kallsyms parsing? the call below
> > > would be in its callback
> >
> > This place cannot directly use libbpf_kallsyms_parse, because we need
> > info.syms, this value cannot be passed into the parameters of
> > libbpf_kallsyms_parse,
>
> hum, libbpf_kallsyms_parse takes 'void *ctx', so you can pass anything
> you want right?
somthing like below should save some lines and ease up error handling
I'd add similar parse functions for both available_filter_functions and
available_filter_functions_addrs and add the logic to callbacks
jirka
---
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b9282ef3f8a7..04b980293240 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10559,8 +10559,31 @@ static int bsearch_compare_function(const void *a, const void *b)
return strcmp((const char *)a, *(const char **)b);
}
+struct avail_kallsyms_data {
+ const char **syms;
+ struct kprobe_multi_resolve *res;
+};
+
+static int avail_kallsyms_cb(unsigned long long sym_addr, char sym_type,
+ const char *sym_name, void *ctx)
+{
+ struct avail_kallsyms_data *data = ctx;
+ struct kprobe_multi_resolve *res = data->res;
+
+ if (!bsearch(&sym_name, data->syms, cnt, sizeof(void *), bsearch_compare_function))
+ continue;
+
+ err = libbpf_ensure_mem((void **)&res->addrs, &res->cap,
+ sizeof(unsigned long), res->cnt + 1);
+ if (err)
+ return err;
+ res->addrs[res->cnt++] = (unsigned long) sym_addr;
+ return 0;
+}
+
static int libbpf_available_kallsyms_parse(struct kprobe_multi_resolve *res)
{
+ struct avail_kallsyms_data data;
char sym_name[500];
const char *available_functions_file = tracefs_available_filter_functions();
FILE *f;
@@ -10614,42 +10637,13 @@ static int libbpf_available_kallsyms_parse(struct kprobe_multi_resolve *res)
/* sort available functions */
qsort(syms, cnt, sizeof(void *), qsort_compare_function);
- f = fopen("/proc/kallsyms", "r");
- if (!f) {
- err = -errno;
- pr_warn("failed to open /proc/kallsyms\n");
- goto free_syms;
- }
-
- while (true) {
- unsigned long long sym_addr;
-
- ret = fscanf(f, "%llx %*c %499s%*[^\n]\n", &sym_addr, sym_name);
- if (ret == EOF && feof(f))
- break;
-
- if (ret != 2) {
- pr_warn("failed to read kallsyms entry: %d\n", ret);
- err = -EINVAL;
- goto cleanup;
- }
-
- if (!bsearch(&sym_name, syms, cnt, sizeof(void *), bsearch_compare_function))
- continue;
-
- err = libbpf_ensure_mem((void **)&res->addrs, &res->cap,
- sizeof(unsigned long), res->cnt + 1);
- if (err)
- goto cleanup;
-
- res->addrs[res->cnt++] = (unsigned long) sym_addr;
- }
+ data.syms = syms;
+ data.res = res;
+ libbpf_kallsyms_parse(avail_kallsyms_cb, res);
if (!res->cnt)
err = -ENOENT;
-cleanup:
- fclose(f);
free_syms:
for (i = 0; i < cnt; i++)
free((char *)syms[i]);
^ permalink raw reply related [flat|nested] 8+ messages in thread
* RE: [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms
2023-07-03 1:36 [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms Jackie Liu
2023-07-03 1:36 ` [PATCH v3 2/2] libbpf: kprobe.multi: Filter with available_filter_functions_addrs Jackie Liu
2023-07-03 12:59 ` [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms Jiri Olsa
@ 2023-07-03 19:38 ` John Fastabend
2023-07-04 1:30 ` Jackie Liu
2 siblings, 1 reply; 8+ messages in thread
From: John Fastabend @ 2023-07-03 19:38 UTC (permalink / raw)
To: Jackie Liu, olsajiri, andrii; +Cc: martin.lau, song, yhs, bpf, liuyun01, lkp
Jackie Liu wrote:
> From: Jackie Liu <liuyun01@kylinos.cn>
>
> When using regular expression matching with "kprobe multi", it scans all
> the functions under "/proc/kallsyms" that can be matched. However, not all
> of them can be traced by kprobe.multi. If any one of the functions fails
> to be traced, it will result in the failure of all functions. The best
> approach is to filter out the functions that cannot be traced to ensure
> proper tracking of the functions.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202307030355.TdXOHklM-lkp@intel.com/
> Suggested-by: Jiri Olsa <jolsa@kernel.org>
> Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
> Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
> ---
> v2->v3: fix 'fscanf' may overflow
>
> tools/lib/bpf/libbpf.c | 122 ++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 109 insertions(+), 13 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 214f828ece6b..232268215bb7 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -10224,6 +10224,12 @@ static const char *tracefs_uprobe_events(void)
> return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events";
> }
>
> +static const char *tracefs_available_filter_functions(void)
> +{
> + return use_debugfs() ? DEBUGFS"/available_filter_functions" :
> + TRACEFS"/available_filter_functions";
> +}
> +
> static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
> const char *kfunc_name, size_t offset)
> {
> @@ -10539,23 +10545,113 @@ struct kprobe_multi_resolve {
> size_t cnt;
> };
>
> -static int
> -resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type,
> - const char *sym_name, void *ctx)
> +static int qsort_compare_function(const void *a, const void *b)
> {
> - struct kprobe_multi_resolve *res = ctx;
> - int err;
> + return strcmp(*(const char **)a, *(const char **)b);
> +}
>
> - if (!glob_match(sym_name, res->pattern))
> - return 0;
> +static int bsearch_compare_function(const void *a, const void *b)
> +{
> + return strcmp((const char *)a, *(const char **)b);
> +}
>
> - err = libbpf_ensure_mem((void **) &res->addrs, &res->cap, sizeof(unsigned long),
> - res->cnt + 1);
> - if (err)
> +static int libbpf_available_kallsyms_parse(struct kprobe_multi_resolve *res)
> +{
> + char sym_name[500];
> + const char *available_functions_file = tracefs_available_filter_functions();
> + FILE *f;
> + int err = 0, ret, i;
> + struct function_info {
> + const char **syms;
> + size_t cap;
> + size_t cnt;
> + } infos = {};
> +
> + f = fopen(available_functions_file, "r");
> + if (!f) {
> + err = -errno;
> + pr_warn("failed to open %s\n", available_functions_file);
> return err;
> + }
>
> - res->addrs[res->cnt++] = (unsigned long) sym_addr;
> - return 0;
> + while (true) {
> + char *name;
> +
> + ret = fscanf(f, "%499s%*[^\n]\n", sym_name);
> + if (ret == EOF && feof(f))
> + break;
> +
Looks like you fixed up the fclose() issues, sorry about the noise
reading email backwards.
bit of a nit...
Its probably worth handling the case where ret == EOF and its
not feof(f) that man page claims can happen on read error for
example. Might never happen but would be good to distinguish from
-EINVAL below?
> + if (ret != 1) {
> + pr_warn("failed to read available function file entry: %d\n",
> + ret);
> + err = -EINVAL;
> + goto cleanup;
> + }
> +
> + if (!glob_match(sym_name, res->pattern))
> + continue;
> +
> + err = libbpf_ensure_mem((void **)&infos.syms, &infos.cap,
> + sizeof(void *), infos.cnt + 1);
> + if (err)
> + goto cleanup;
> +
> + name = strdup(sym_name);
> + if (!name) {
> + err = -errno;
> + goto cleanup;
> + }
> +
> + infos.syms[infos.cnt++] = name;
> + }
> + fclose(f);
> +
> + /* sort available functions */
> + qsort(infos.syms, infos.cnt, sizeof(void *), qsort_compare_function);
> +
> + f = fopen("/proc/kallsyms", "r");
> + if (!f) {
> + err = -errno;
> + pr_warn("failed to open /proc/kallsyms\n");
> + goto free_infos;
> + }
> +
> + while (true) {
> + unsigned long long sym_addr;
> +
> + ret = fscanf(f, "%llx %*c %499s%*[^\n]\n", &sym_addr, sym_name);
> + if (ret == EOF && feof(f))
> + break;
Same off chance we get ret == EOF and !feof(f)?
> +
> + if (ret != 2) {
> + pr_warn("failed to read kallsyms entry: %d\n", ret);
> + err = -EINVAL;
> + break;
> + }
> +
> + if (!glob_match(sym_name, res->pattern))
> + continue;
> +
> + if (!bsearch(&sym_name, infos.syms, infos.cnt, sizeof(void *),
> + bsearch_compare_function))
> + continue;
I'm wondering if we could get a debug print if the func was skipped? Its
not always clear when running many kernels what is going to be skipped
and where.
> +
> + err = libbpf_ensure_mem((void **)&res->addrs, &res->cap,
> + sizeof(unsigned long), res->cnt + 1);
> + if (err)
> + break;
> +
> + res->addrs[res->cnt++] = (unsigned long) sym_addr;
> + }
> +
> +cleanup:
> + fclose(f);
> +free_infos:
> + for (i = 0; i < infos.cnt; i++)
> + free((char *)infos.syms[i]);
> + free(infos.syms);
> +
> + return err;
> }
>
> struct bpf_link *
> @@ -10594,7 +10690,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
> return libbpf_err_ptr(-EINVAL);
>
> if (pattern) {
> - err = libbpf_kallsyms_parse(resolve_kprobe_multi_cb, &res);
> + err = libbpf_available_kallsyms_parse(&res);
> if (err)
> goto error;
> if (!res.cnt) {
> --
> 2.25.1
>
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH v3 1/2] libbpf: kprobe.multi: cross filter using available_filter_functions and kallsyms
2023-07-03 19:38 ` John Fastabend
@ 2023-07-04 1:30 ` Jackie Liu
0 siblings, 0 replies; 8+ messages in thread
From: Jackie Liu @ 2023-07-04 1:30 UTC (permalink / raw)
To: John Fastabend, olsajiri, andrii
Cc: martin.lau, song, yhs, bpf, liuyun01, lkp
在 2023/7/4 03:38, John Fastabend 写道:
> Jackie Liu wrote:
>> From: Jackie Liu <liuyun01@kylinos.cn>
>>
>> When using regular expression matching with "kprobe multi", it scans all
>> the functions under "/proc/kallsyms" that can be matched. However, not all
>> of them can be traced by kprobe.multi. If any one of the functions fails
>> to be traced, it will result in the failure of all functions. The best
>> approach is to filter out the functions that cannot be traced to ensure
>> proper tracking of the functions.
>>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Closes: https://lore.kernel.org/oe-kbuild-all/202307030355.TdXOHklM-lkp@intel.com/
>> Suggested-by: Jiri Olsa <jolsa@kernel.org>
>> Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
>> Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
>> ---
>> v2->v3: fix 'fscanf' may overflow
>>
>> tools/lib/bpf/libbpf.c | 122 ++++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 109 insertions(+), 13 deletions(-)
>>
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 214f828ece6b..232268215bb7 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -10224,6 +10224,12 @@ static const char *tracefs_uprobe_events(void)
>> return use_debugfs() ? DEBUGFS"/uprobe_events" : TRACEFS"/uprobe_events";
>> }
>>
>> +static const char *tracefs_available_filter_functions(void)
>> +{
>> + return use_debugfs() ? DEBUGFS"/available_filter_functions" :
>> + TRACEFS"/available_filter_functions";
>> +}
>> +
>> static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
>> const char *kfunc_name, size_t offset)
>> {
>> @@ -10539,23 +10545,113 @@ struct kprobe_multi_resolve {
>> size_t cnt;
>> };
>>
>> -static int
>> -resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type,
>> - const char *sym_name, void *ctx)
>> +static int qsort_compare_function(const void *a, const void *b)
>> {
>> - struct kprobe_multi_resolve *res = ctx;
>> - int err;
>> + return strcmp(*(const char **)a, *(const char **)b);
>> +}
>>
>> - if (!glob_match(sym_name, res->pattern))
>> - return 0;
>> +static int bsearch_compare_function(const void *a, const void *b)
>> +{
>> + return strcmp((const char *)a, *(const char **)b);
>> +}
>>
>> - err = libbpf_ensure_mem((void **) &res->addrs, &res->cap, sizeof(unsigned long),
>> - res->cnt + 1);
>> - if (err)
>> +static int libbpf_available_kallsyms_parse(struct kprobe_multi_resolve *res)
>> +{
>> + char sym_name[500];
>> + const char *available_functions_file = tracefs_available_filter_functions();
>> + FILE *f;
>> + int err = 0, ret, i;
>> + struct function_info {
>> + const char **syms;
>> + size_t cap;
>> + size_t cnt;
>> + } infos = {};
>> +
>> + f = fopen(available_functions_file, "r");
>> + if (!f) {
>> + err = -errno;
>> + pr_warn("failed to open %s\n", available_functions_file);
>> return err;
>> + }
>>
>> - res->addrs[res->cnt++] = (unsigned long) sym_addr;
>> - return 0;
>> + while (true) {
>> + char *name;
>> +
>> + ret = fscanf(f, "%499s%*[^\n]\n", sym_name);
>> + if (ret == EOF && feof(f))
>> + break;
>> +
>
> Looks like you fixed up the fclose() issues, sorry about the noise
> reading email backwards.
>
>
> bit of a nit...
>
> Its probably worth handling the case where ret == EOF and its
> not feof(f) that man page claims can happen on read error for
> example. Might never happen but would be good to distinguish from
> -EINVAL below?
I think it should not be necessary, we only care about whether we have
read the correct data or not, other cases are read failures.
>
>> + if (ret != 1) {
>> + pr_warn("failed to read available function file entry: %d\n",
>> + ret);
>> + err = -EINVAL;
>> + goto cleanup;
>> + }
>> +
>> + if (!glob_match(sym_name, res->pattern))
>> + continue;
>> +
>> + err = libbpf_ensure_mem((void **)&infos.syms, &infos.cap,
>> + sizeof(void *), infos.cnt + 1);
>> + if (err)
>> + goto cleanup;
>> +
>> + name = strdup(sym_name);
>> + if (!name) {
>> + err = -errno;
>> + goto cleanup;
>> + }
>> +
>> + infos.syms[infos.cnt++] = name;
>> + }
>> + fclose(f);
>> +
>> + /* sort available functions */
>> + qsort(infos.syms, infos.cnt, sizeof(void *), qsort_compare_function);
>> +
>> + f = fopen("/proc/kallsyms", "r");
>> + if (!f) {
>> + err = -errno;
>> + pr_warn("failed to open /proc/kallsyms\n");
>> + goto free_infos;
>> + }
>> +
>> + while (true) {
>> + unsigned long long sym_addr;
>> +
>> + ret = fscanf(f, "%llx %*c %499s%*[^\n]\n", &sym_addr, sym_name);
>> + if (ret == EOF && feof(f))
>> + break;
>
> Same off chance we get ret == EOF and !feof(f)?
>
>> +
>> + if (ret != 2) {
>> + pr_warn("failed to read kallsyms entry: %d\n", ret);
>> + err = -EINVAL;
>> + break;
>> + }
>> +
>> + if (!glob_match(sym_name, res->pattern))
>> + continue;
>> +
>> + if (!bsearch(&sym_name, infos.syms, infos.cnt, sizeof(void *),
>> + bsearch_compare_function))
>> + continue;
>
> I'm wondering if we could get a debug print if the func was skipped? Its
> not always clear when running many kernels what is going to be skipped
> and where.
>
If there is no match, it will be skipped, and if you add printing, it
will become particularly noisy. And print here is not more helpful for
debugging, we don't care about skipped functions.
--
Jackie
>> +
>> + err = libbpf_ensure_mem((void **)&res->addrs, &res->cap,
>> + sizeof(unsigned long), res->cnt + 1);
>> + if (err)
>> + break;
>> +
>> + res->addrs[res->cnt++] = (unsigned long) sym_addr;
>> + }
>> +
>> +cleanup:
>> + fclose(f);
>> +free_infos:
>> + for (i = 0; i < infos.cnt; i++)
>> + free((char *)infos.syms[i]);
>> + free(infos.syms);
>> +
>> + return err;
>> }
>>
>> struct bpf_link *
>> @@ -10594,7 +10690,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
>> return libbpf_err_ptr(-EINVAL);
>>
>> if (pattern) {
>> - err = libbpf_kallsyms_parse(resolve_kprobe_multi_cb, &res);
>> + err = libbpf_available_kallsyms_parse(&res);
>> if (err)
>> goto error;
>> if (!res.cnt) {
>> --
>> 2.25.1
>>
>>
^ permalink raw reply [flat|nested] 8+ messages in thread