[bpf-next,5/5] bpftool: Support dumping a map with btf_vmlinux_value_type_id
diff mbox series

Message ID 20200114224426.3028966-1-kafai@fb.com
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series
  • bpftool: Support dumping a map with btf_vmlinux_value_type_id
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Commit Message

Martin KaFai Lau Jan. 14, 2020, 10:44 p.m. UTC
This patch makes bpftool support dumping a map's value properly
when the map's value type is a type of the running kernel's btf.
(i.e. map_info.btf_vmlinux_value_type_id is set instead of
map_info.btf_value_type_id).  The first usecase is for the
BPF_MAP_TYPE_STRUCT_OPS.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
---
 tools/bpf/bpftool/map.c | 43 +++++++++++++++++++++++++++++++----------
 1 file changed, 33 insertions(+), 10 deletions(-)

Comments

Andrii Nakryiko Jan. 15, 2020, 1:49 a.m. UTC | #1
On Tue, Jan 14, 2020 at 2:46 PM Martin KaFai Lau <kafai@fb.com> wrote:
>
> This patch makes bpftool support dumping a map's value properly
> when the map's value type is a type of the running kernel's btf.
> (i.e. map_info.btf_vmlinux_value_type_id is set instead of
> map_info.btf_value_type_id).  The first usecase is for the
> BPF_MAP_TYPE_STRUCT_OPS.
>
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> ---
>  tools/bpf/bpftool/map.c | 43 +++++++++++++++++++++++++++++++----------
>  1 file changed, 33 insertions(+), 10 deletions(-)
>
> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> index 4c5b15d736b6..d25f3b2355ad 100644
> --- a/tools/bpf/bpftool/map.c
> +++ b/tools/bpf/bpftool/map.c
> @@ -20,6 +20,7 @@
>  #include "btf.h"
>  #include "json_writer.h"
>  #include "main.h"
> +#include "libbpf_internal.h"
>
>  const char * const map_type_name[] = {
>         [BPF_MAP_TYPE_UNSPEC]                   = "unspec",
> @@ -252,6 +253,7 @@ static int do_dump_btf(const struct btf_dumper *d,
>                        struct bpf_map_info *map_info, void *key,
>                        void *value)
>  {
> +       __u32 value_id;
>         int ret;
>
>         /* start of key-value pair */
> @@ -265,9 +267,12 @@ static int do_dump_btf(const struct btf_dumper *d,
>                         goto err_end_obj;
>         }
>
> +       value_id = map_info->btf_vmlinux_value_type_id ?
> +               : map_info->btf_value_type_id;
> +
>         if (!map_is_per_cpu(map_info->type)) {
>                 jsonw_name(d->jw, "value");
> -               ret = btf_dumper_type(d, map_info->btf_value_type_id, value);
> +               ret = btf_dumper_type(d, value_id, value);
>         } else {
>                 unsigned int i, n, step;
>
> @@ -279,8 +284,7 @@ static int do_dump_btf(const struct btf_dumper *d,
>                         jsonw_start_object(d->jw);
>                         jsonw_int_field(d->jw, "cpu", i);
>                         jsonw_name(d->jw, "value");
> -                       ret = btf_dumper_type(d, map_info->btf_value_type_id,
> -                                             value + i * step);
> +                       ret = btf_dumper_type(d, value_id, value + i * step);
>                         jsonw_end_object(d->jw);
>                         if (ret)
>                                 break;
> @@ -932,6 +936,27 @@ static int maps_have_btf(int *fds, int nb_fds)
>         return 1;
>  }
>
> +static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
> +{
> +       struct btf *btf = NULL;
> +
> +       if (info->btf_vmlinux_value_type_id) {
> +               btf = bpf_find_kernel_btf();

If there are multiple maps we are dumping, it might become quite
costly to re-read and re-parse kernel BTF all the time. Can we lazily
load it, when required, and cache instead?

> +               if (IS_ERR(btf))
> +                       p_err("failed to get kernel btf");
> +       } else if (info->btf_value_type_id) {
> +               int err;
> +
> +               err = btf__get_from_id(info->btf_id, &btf);
> +               if (err || !btf) {
> +                       p_err("failed to get btf");
> +                       btf = err ? ERR_PTR(err) : ERR_PTR(-ESRCH);
> +               }
> +       }
> +
> +       return btf;
> +}
> +
>  static int
>  map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
>          bool show_header)
> @@ -952,13 +977,11 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
>         prev_key = NULL;
>
>         if (wtr) {
> -               if (info->btf_id) {
> -                       err = btf__get_from_id(info->btf_id, &btf);
> -                       if (err || !btf) {
> -                               err = err ? : -ESRCH;
> -                               p_err("failed to get btf");
> -                               goto exit_free;
> -                       }
> +               btf = get_map_kv_btf(info);
> +               if (IS_ERR(btf)) {
> +                       err = PTR_ERR(btf);
> +                       btf = NULL;
> +                       goto exit_free;
>                 }
>
>                 if (show_header) {
> --
> 2.17.1
>
Martin KaFai Lau Jan. 15, 2020, 6:04 a.m. UTC | #2
On Tue, Jan 14, 2020 at 05:49:00PM -0800, Andrii Nakryiko wrote:
> On Tue, Jan 14, 2020 at 2:46 PM Martin KaFai Lau <kafai@fb.com> wrote:
> >
> > This patch makes bpftool support dumping a map's value properly
> > when the map's value type is a type of the running kernel's btf.
> > (i.e. map_info.btf_vmlinux_value_type_id is set instead of
> > map_info.btf_value_type_id).  The first usecase is for the
> > BPF_MAP_TYPE_STRUCT_OPS.
> >
> > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > ---
> >  tools/bpf/bpftool/map.c | 43 +++++++++++++++++++++++++++++++----------
> >  1 file changed, 33 insertions(+), 10 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> > index 4c5b15d736b6..d25f3b2355ad 100644
> > --- a/tools/bpf/bpftool/map.c
> > +++ b/tools/bpf/bpftool/map.c
> > @@ -20,6 +20,7 @@
> >  #include "btf.h"
> >  #include "json_writer.h"
> >  #include "main.h"
> > +#include "libbpf_internal.h"
> >
> >  const char * const map_type_name[] = {
> >         [BPF_MAP_TYPE_UNSPEC]                   = "unspec",
> > @@ -252,6 +253,7 @@ static int do_dump_btf(const struct btf_dumper *d,
> >                        struct bpf_map_info *map_info, void *key,
> >                        void *value)
> >  {
> > +       __u32 value_id;
> >         int ret;
> >
> >         /* start of key-value pair */
> > @@ -265,9 +267,12 @@ static int do_dump_btf(const struct btf_dumper *d,
> >                         goto err_end_obj;
> >         }
> >
> > +       value_id = map_info->btf_vmlinux_value_type_id ?
> > +               : map_info->btf_value_type_id;
> > +
> >         if (!map_is_per_cpu(map_info->type)) {
> >                 jsonw_name(d->jw, "value");
> > -               ret = btf_dumper_type(d, map_info->btf_value_type_id, value);
> > +               ret = btf_dumper_type(d, value_id, value);
> >         } else {
> >                 unsigned int i, n, step;
> >
> > @@ -279,8 +284,7 @@ static int do_dump_btf(const struct btf_dumper *d,
> >                         jsonw_start_object(d->jw);
> >                         jsonw_int_field(d->jw, "cpu", i);
> >                         jsonw_name(d->jw, "value");
> > -                       ret = btf_dumper_type(d, map_info->btf_value_type_id,
> > -                                             value + i * step);
> > +                       ret = btf_dumper_type(d, value_id, value + i * step);
> >                         jsonw_end_object(d->jw);
> >                         if (ret)
> >                                 break;
> > @@ -932,6 +936,27 @@ static int maps_have_btf(int *fds, int nb_fds)
> >         return 1;
> >  }
> >
> > +static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
> > +{
> > +       struct btf *btf = NULL;
> > +
> > +       if (info->btf_vmlinux_value_type_id) {
> > +               btf = bpf_find_kernel_btf();
> 
> If there are multiple maps we are dumping, it might become quite
> costly to re-read and re-parse kernel BTF all the time. Can we lazily
> load it, when required,
It is loaded lazily.

> and cache instead?
Cache it in bpftool/map.c? Sure.

> 
> > +               if (IS_ERR(btf))
> > +                       p_err("failed to get kernel btf");
> > +       } else if (info->btf_value_type_id) {
> > +               int err;
> > +
> > +               err = btf__get_from_id(info->btf_id, &btf);
> > +               if (err || !btf) {
> > +                       p_err("failed to get btf");
> > +                       btf = err ? ERR_PTR(err) : ERR_PTR(-ESRCH);
> > +               }
> > +       }
> > +
> > +       return btf;
> > +}
> > +
> >  static int
> >  map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
> >          bool show_header)
> > @@ -952,13 +977,11 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
> >         prev_key = NULL;
> >
> >         if (wtr) {
> > -               if (info->btf_id) {
> > -                       err = btf__get_from_id(info->btf_id, &btf);
> > -                       if (err || !btf) {
> > -                               err = err ? : -ESRCH;
> > -                               p_err("failed to get btf");
> > -                               goto exit_free;
> > -                       }
> > +               btf = get_map_kv_btf(info);
> > +               if (IS_ERR(btf)) {
> > +                       err = PTR_ERR(btf);
> > +                       btf = NULL;
> > +                       goto exit_free;
> >                 }
> >
> >                 if (show_header) {
> > --
> > 2.17.1
> >
Andrii Nakryiko Jan. 15, 2020, 6:39 a.m. UTC | #3
On Tue, Jan 14, 2020 at 10:04 PM Martin Lau <kafai@fb.com> wrote:
>
> On Tue, Jan 14, 2020 at 05:49:00PM -0800, Andrii Nakryiko wrote:
> > On Tue, Jan 14, 2020 at 2:46 PM Martin KaFai Lau <kafai@fb.com> wrote:
> > >
> > > This patch makes bpftool support dumping a map's value properly
> > > when the map's value type is a type of the running kernel's btf.
> > > (i.e. map_info.btf_vmlinux_value_type_id is set instead of
> > > map_info.btf_value_type_id).  The first usecase is for the
> > > BPF_MAP_TYPE_STRUCT_OPS.
> > >
> > > Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> > > ---
> > >  tools/bpf/bpftool/map.c | 43 +++++++++++++++++++++++++++++++----------
> > >  1 file changed, 33 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
> > > index 4c5b15d736b6..d25f3b2355ad 100644
> > > --- a/tools/bpf/bpftool/map.c
> > > +++ b/tools/bpf/bpftool/map.c
> > > @@ -20,6 +20,7 @@
> > >  #include "btf.h"
> > >  #include "json_writer.h"
> > >  #include "main.h"
> > > +#include "libbpf_internal.h"
> > >
> > >  const char * const map_type_name[] = {
> > >         [BPF_MAP_TYPE_UNSPEC]                   = "unspec",
> > > @@ -252,6 +253,7 @@ static int do_dump_btf(const struct btf_dumper *d,
> > >                        struct bpf_map_info *map_info, void *key,
> > >                        void *value)
> > >  {
> > > +       __u32 value_id;
> > >         int ret;
> > >
> > >         /* start of key-value pair */
> > > @@ -265,9 +267,12 @@ static int do_dump_btf(const struct btf_dumper *d,
> > >                         goto err_end_obj;
> > >         }
> > >
> > > +       value_id = map_info->btf_vmlinux_value_type_id ?
> > > +               : map_info->btf_value_type_id;
> > > +
> > >         if (!map_is_per_cpu(map_info->type)) {
> > >                 jsonw_name(d->jw, "value");
> > > -               ret = btf_dumper_type(d, map_info->btf_value_type_id, value);
> > > +               ret = btf_dumper_type(d, value_id, value);
> > >         } else {
> > >                 unsigned int i, n, step;
> > >
> > > @@ -279,8 +284,7 @@ static int do_dump_btf(const struct btf_dumper *d,
> > >                         jsonw_start_object(d->jw);
> > >                         jsonw_int_field(d->jw, "cpu", i);
> > >                         jsonw_name(d->jw, "value");
> > > -                       ret = btf_dumper_type(d, map_info->btf_value_type_id,
> > > -                                             value + i * step);
> > > +                       ret = btf_dumper_type(d, value_id, value + i * step);
> > >                         jsonw_end_object(d->jw);
> > >                         if (ret)
> > >                                 break;
> > > @@ -932,6 +936,27 @@ static int maps_have_btf(int *fds, int nb_fds)
> > >         return 1;
> > >  }
> > >
> > > +static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
> > > +{
> > > +       struct btf *btf = NULL;
> > > +
> > > +       if (info->btf_vmlinux_value_type_id) {
> > > +               btf = bpf_find_kernel_btf();
> >
> > If there are multiple maps we are dumping, it might become quite
> > costly to re-read and re-parse kernel BTF all the time. Can we lazily
> > load it, when required,
> It is loaded lazily.
>

yeah, it was meant as "lazy load and cache" vs "pre-load always"
(which makes caching simpler).

> > and cache instead?
> Cache it in bpftool/map.c? Sure.

yeah, for the duration of dumping

>
> >
> > > +               if (IS_ERR(btf))
> > > +                       p_err("failed to get kernel btf");
> > > +       } else if (info->btf_value_type_id) {
> > > +               int err;
> > > +
> > > +               err = btf__get_from_id(info->btf_id, &btf);
> > > +               if (err || !btf) {
> > > +                       p_err("failed to get btf");
> > > +                       btf = err ? ERR_PTR(err) : ERR_PTR(-ESRCH);
> > > +               }
> > > +       }
> > > +
> > > +       return btf;
> > > +}
> > > +
> > >  static int
> > >  map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
> > >          bool show_header)
> > > @@ -952,13 +977,11 @@ map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
> > >         prev_key = NULL;
> > >
> > >         if (wtr) {
> > > -               if (info->btf_id) {
> > > -                       err = btf__get_from_id(info->btf_id, &btf);
> > > -                       if (err || !btf) {
> > > -                               err = err ? : -ESRCH;
> > > -                               p_err("failed to get btf");
> > > -                               goto exit_free;
> > > -                       }
> > > +               btf = get_map_kv_btf(info);
> > > +               if (IS_ERR(btf)) {
> > > +                       err = PTR_ERR(btf);
> > > +                       btf = NULL;
> > > +                       goto exit_free;
> > >                 }
> > >
> > >                 if (show_header) {
> > > --
> > > 2.17.1
> > >

Patch
diff mbox series

diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 4c5b15d736b6..d25f3b2355ad 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -20,6 +20,7 @@ 
 #include "btf.h"
 #include "json_writer.h"
 #include "main.h"
+#include "libbpf_internal.h"
 
 const char * const map_type_name[] = {
 	[BPF_MAP_TYPE_UNSPEC]			= "unspec",
@@ -252,6 +253,7 @@  static int do_dump_btf(const struct btf_dumper *d,
 		       struct bpf_map_info *map_info, void *key,
 		       void *value)
 {
+	__u32 value_id;
 	int ret;
 
 	/* start of key-value pair */
@@ -265,9 +267,12 @@  static int do_dump_btf(const struct btf_dumper *d,
 			goto err_end_obj;
 	}
 
+	value_id = map_info->btf_vmlinux_value_type_id ?
+		: map_info->btf_value_type_id;
+
 	if (!map_is_per_cpu(map_info->type)) {
 		jsonw_name(d->jw, "value");
-		ret = btf_dumper_type(d, map_info->btf_value_type_id, value);
+		ret = btf_dumper_type(d, value_id, value);
 	} else {
 		unsigned int i, n, step;
 
@@ -279,8 +284,7 @@  static int do_dump_btf(const struct btf_dumper *d,
 			jsonw_start_object(d->jw);
 			jsonw_int_field(d->jw, "cpu", i);
 			jsonw_name(d->jw, "value");
-			ret = btf_dumper_type(d, map_info->btf_value_type_id,
-					      value + i * step);
+			ret = btf_dumper_type(d, value_id, value + i * step);
 			jsonw_end_object(d->jw);
 			if (ret)
 				break;
@@ -932,6 +936,27 @@  static int maps_have_btf(int *fds, int nb_fds)
 	return 1;
 }
 
+static struct btf *get_map_kv_btf(const struct bpf_map_info *info)
+{
+	struct btf *btf = NULL;
+
+	if (info->btf_vmlinux_value_type_id) {
+		btf = bpf_find_kernel_btf();
+		if (IS_ERR(btf))
+			p_err("failed to get kernel btf");
+	} else if (info->btf_value_type_id) {
+		int err;
+
+		err = btf__get_from_id(info->btf_id, &btf);
+		if (err || !btf) {
+			p_err("failed to get btf");
+			btf = err ? ERR_PTR(err) : ERR_PTR(-ESRCH);
+		}
+	}
+
+	return btf;
+}
+
 static int
 map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 	 bool show_header)
@@ -952,13 +977,11 @@  map_dump(int fd, struct bpf_map_info *info, json_writer_t *wtr,
 	prev_key = NULL;
 
 	if (wtr) {
-		if (info->btf_id) {
-			err = btf__get_from_id(info->btf_id, &btf);
-			if (err || !btf) {
-				err = err ? : -ESRCH;
-				p_err("failed to get btf");
-				goto exit_free;
-			}
+		btf = get_map_kv_btf(info);
+		if (IS_ERR(btf)) {
+			err = PTR_ERR(btf);
+			btf = NULL;
+			goto exit_free;
 		}
 
 		if (show_header) {