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* [PATCH bpf-next] bpftool: fix bpftool build by switching to bpf_object__open_file()
@ 2019-10-07 21:22 Andrii Nakryiko
  2019-10-07 21:46 ` Stanislav Fomichev
  0 siblings, 1 reply; 5+ messages in thread
From: Andrii Nakryiko @ 2019-10-07 21:22 UTC (permalink / raw)
  To: bpf, netdev, ast, daniel, sdf
  Cc: andrii.nakryiko, kernel-team, Andrii Nakryiko

As part of libbpf in 5e61f2707029 ("libbpf: stop enforcing kern_version,
populate it for users") non-LIBBPF_API __bpf_object__open_xattr() API
was removed from libbpf.h header. This broke bpftool, which relied on
that function. This patch fixes the build by switching to newly added
bpf_object__open_file() which provides the same capabilities, but is
official and future-proof API.

Fixes: 5e61f2707029 ("libbpf: stop enforcing kern_version, populate it for users")
Reported-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 tools/bpf/bpftool/main.c |  4 ++--
 tools/bpf/bpftool/main.h |  2 +-
 tools/bpf/bpftool/prog.c | 22 ++++++++++++----------
 3 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 93d008687020..4764581ff9ea 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -27,7 +27,7 @@ bool json_output;
 bool show_pinned;
 bool block_mount;
 bool verifier_logs;
-int bpf_flags;
+bool relaxed_maps;
 struct pinned_obj_table prog_table;
 struct pinned_obj_table map_table;
 
@@ -396,7 +396,7 @@ int main(int argc, char **argv)
 			show_pinned = true;
 			break;
 		case 'm':
-			bpf_flags = MAPS_RELAX_COMPAT;
+			relaxed_maps = true;
 			break;
 		case 'n':
 			block_mount = true;
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index af9ad56c303a..2899095f8254 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -94,7 +94,7 @@ extern bool json_output;
 extern bool show_pinned;
 extern bool block_mount;
 extern bool verifier_logs;
-extern int bpf_flags;
+extern bool relaxed_maps;
 extern struct pinned_obj_table prog_table;
 extern struct pinned_obj_table map_table;
 
diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 43fdbbfe41bb..8191cd595963 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -1092,9 +1092,7 @@ static int do_run(int argc, char **argv)
 static int load_with_options(int argc, char **argv, bool first_prog_only)
 {
 	struct bpf_object_load_attr load_attr = { 0 };
-	struct bpf_object_open_attr open_attr = {
-		.prog_type = BPF_PROG_TYPE_UNSPEC,
-	};
+	enum bpf_prog_type prog_type = BPF_PROG_TYPE_UNSPEC;
 	enum bpf_attach_type expected_attach_type;
 	struct map_replace *map_replace = NULL;
 	struct bpf_program *prog = NULL, *pos;
@@ -1105,11 +1103,16 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 	const char *pinfile;
 	unsigned int i, j;
 	__u32 ifindex = 0;
+	const char *file;
 	int idx, err;
 
+	LIBBPF_OPTS(bpf_object_open_opts, open_opts,
+		.relaxed_maps = relaxed_maps,
+	);
+
 	if (!REQ_ARGS(2))
 		return -1;
-	open_attr.file = GET_ARG();
+	file = GET_ARG();
 	pinfile = GET_ARG();
 
 	while (argc) {
@@ -1118,7 +1121,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 
 			NEXT_ARG();
 
-			if (open_attr.prog_type != BPF_PROG_TYPE_UNSPEC) {
+			if (prog_type != BPF_PROG_TYPE_UNSPEC) {
 				p_err("program type already specified");
 				goto err_free_reuse_maps;
 			}
@@ -1135,8 +1138,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 			strcat(type, *argv);
 			strcat(type, "/");
 
-			err = libbpf_prog_type_by_name(type,
-						       &open_attr.prog_type,
+			err = libbpf_prog_type_by_name(type, &prog_type,
 						       &expected_attach_type);
 			free(type);
 			if (err < 0)
@@ -1224,16 +1226,16 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
 
 	set_max_rlimit();
 
-	obj = __bpf_object__open_xattr(&open_attr, bpf_flags);
+	obj = bpf_object__open_file(file, &open_opts);
 	if (IS_ERR_OR_NULL(obj)) {
 		p_err("failed to open object file");
 		goto err_free_reuse_maps;
 	}
 
 	bpf_object__for_each_program(pos, obj) {
-		enum bpf_prog_type prog_type = open_attr.prog_type;
+		enum bpf_prog_type prog_type = prog_type;
 
-		if (open_attr.prog_type == BPF_PROG_TYPE_UNSPEC) {
+		if (prog_type == BPF_PROG_TYPE_UNSPEC) {
 			const char *sec_name = bpf_program__title(pos, false);
 
 			err = libbpf_prog_type_by_name(sec_name, &prog_type,
-- 
2.17.1


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH bpf-next] bpftool: fix bpftool build by switching to bpf_object__open_file()
  2019-10-07 21:22 [PATCH bpf-next] bpftool: fix bpftool build by switching to bpf_object__open_file() Andrii Nakryiko
@ 2019-10-07 21:46 ` Stanislav Fomichev
  2019-10-07 21:50   ` Andrii Nakryiko
  0 siblings, 1 reply; 5+ messages in thread
From: Stanislav Fomichev @ 2019-10-07 21:46 UTC (permalink / raw)
  To: Andrii Nakryiko
  Cc: bpf, netdev, ast, daniel, sdf, andrii.nakryiko, kernel-team

On 10/07, Andrii Nakryiko wrote:
> As part of libbpf in 5e61f2707029 ("libbpf: stop enforcing kern_version,
> populate it for users") non-LIBBPF_API __bpf_object__open_xattr() API
> was removed from libbpf.h header. This broke bpftool, which relied on
> that function. This patch fixes the build by switching to newly added
> bpf_object__open_file() which provides the same capabilities, but is
> official and future-proof API.
> 
> Fixes: 5e61f2707029 ("libbpf: stop enforcing kern_version, populate it for users")
> Reported-by: Stanislav Fomichev <sdf@google.com>
> Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> ---
>  tools/bpf/bpftool/main.c |  4 ++--
>  tools/bpf/bpftool/main.h |  2 +-
>  tools/bpf/bpftool/prog.c | 22 ++++++++++++----------
>  3 files changed, 15 insertions(+), 13 deletions(-)
> 
> diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
> index 93d008687020..4764581ff9ea 100644
> --- a/tools/bpf/bpftool/main.c
> +++ b/tools/bpf/bpftool/main.c
> @@ -27,7 +27,7 @@ bool json_output;
>  bool show_pinned;
>  bool block_mount;
>  bool verifier_logs;
> -int bpf_flags;
> +bool relaxed_maps;
>  struct pinned_obj_table prog_table;
>  struct pinned_obj_table map_table;
>  
> @@ -396,7 +396,7 @@ int main(int argc, char **argv)
>  			show_pinned = true;
>  			break;
>  		case 'm':
> -			bpf_flags = MAPS_RELAX_COMPAT;
> +			relaxed_maps = true;
>  			break;
>  		case 'n':
>  			block_mount = true;
> diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
> index af9ad56c303a..2899095f8254 100644
> --- a/tools/bpf/bpftool/main.h
> +++ b/tools/bpf/bpftool/main.h
> @@ -94,7 +94,7 @@ extern bool json_output;
>  extern bool show_pinned;
>  extern bool block_mount;
>  extern bool verifier_logs;
> -extern int bpf_flags;
> +extern bool relaxed_maps;
>  extern struct pinned_obj_table prog_table;
>  extern struct pinned_obj_table map_table;
>  
> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index 43fdbbfe41bb..8191cd595963 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c
> @@ -1092,9 +1092,7 @@ static int do_run(int argc, char **argv)
>  static int load_with_options(int argc, char **argv, bool first_prog_only)
>  {
>  	struct bpf_object_load_attr load_attr = { 0 };
> -	struct bpf_object_open_attr open_attr = {
> -		.prog_type = BPF_PROG_TYPE_UNSPEC,
> -	};
> +	enum bpf_prog_type prog_type = BPF_PROG_TYPE_UNSPEC;
>  	enum bpf_attach_type expected_attach_type;
>  	struct map_replace *map_replace = NULL;
>  	struct bpf_program *prog = NULL, *pos;
> @@ -1105,11 +1103,16 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
>  	const char *pinfile;
>  	unsigned int i, j;
>  	__u32 ifindex = 0;
> +	const char *file;
>  	int idx, err;
>  
> +	LIBBPF_OPTS(bpf_object_open_opts, open_opts,
> +		.relaxed_maps = relaxed_maps,
> +	);
> +
>  	if (!REQ_ARGS(2))
>  		return -1;
> -	open_attr.file = GET_ARG();
> +	file = GET_ARG();
>  	pinfile = GET_ARG();
>  
>  	while (argc) {
> @@ -1118,7 +1121,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
>  
>  			NEXT_ARG();
>  
> -			if (open_attr.prog_type != BPF_PROG_TYPE_UNSPEC) {
> +			if (prog_type != BPF_PROG_TYPE_UNSPEC) {
>  				p_err("program type already specified");
>  				goto err_free_reuse_maps;
>  			}
> @@ -1135,8 +1138,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
>  			strcat(type, *argv);
>  			strcat(type, "/");
>  
> -			err = libbpf_prog_type_by_name(type,
> -						       &open_attr.prog_type,
> +			err = libbpf_prog_type_by_name(type, &prog_type,
>  						       &expected_attach_type);
>  			free(type);
>  			if (err < 0)
> @@ -1224,16 +1226,16 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
>  
>  	set_max_rlimit();
>  
> -	obj = __bpf_object__open_xattr(&open_attr, bpf_flags);
> +	obj = bpf_object__open_file(file, &open_opts);
>  	if (IS_ERR_OR_NULL(obj)) {
>  		p_err("failed to open object file");
>  		goto err_free_reuse_maps;
>  	}
>  
>  	bpf_object__for_each_program(pos, obj) {
> -		enum bpf_prog_type prog_type = open_attr.prog_type;
> +		enum bpf_prog_type prog_type = prog_type;
Are you sure it works that way?

$ cat tmp.c
#include <stdio.h>

int main()
{
	int x = 1;
	printf("outer x=%d\n", x);

	{
		int x = x;
		printf("inner x=%d\n", x);
	}

	return 0;
}

$ gcc tmp.c && ./a.out
outer x=1
inner x=0

Other than that:
Reviewed-by: Stanislav Fomichev <sdf@google.com>

>  
> -		if (open_attr.prog_type == BPF_PROG_TYPE_UNSPEC) {
> +		if (prog_type == BPF_PROG_TYPE_UNSPEC) {
>  			const char *sec_name = bpf_program__title(pos, false);
>  
>  			err = libbpf_prog_type_by_name(sec_name, &prog_type,
> -- 
> 2.17.1
> 

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH bpf-next] bpftool: fix bpftool build by switching to bpf_object__open_file()
  2019-10-07 21:46 ` Stanislav Fomichev
@ 2019-10-07 21:50   ` Andrii Nakryiko
  2019-10-07 23:00     ` Andrii Nakryiko
  0 siblings, 1 reply; 5+ messages in thread
From: Andrii Nakryiko @ 2019-10-07 21:50 UTC (permalink / raw)
  To: Stanislav Fomichev
  Cc: Andrii Nakryiko, bpf, Networking, Alexei Starovoitov,
	Daniel Borkmann, Stanislav Fomichev, Kernel Team

On Mon, Oct 7, 2019 at 2:46 PM Stanislav Fomichev <sdf@fomichev.me> wrote:
>
> On 10/07, Andrii Nakryiko wrote:
> > As part of libbpf in 5e61f2707029 ("libbpf: stop enforcing kern_version,
> > populate it for users") non-LIBBPF_API __bpf_object__open_xattr() API
> > was removed from libbpf.h header. This broke bpftool, which relied on
> > that function. This patch fixes the build by switching to newly added
> > bpf_object__open_file() which provides the same capabilities, but is
> > official and future-proof API.
> >
> > Fixes: 5e61f2707029 ("libbpf: stop enforcing kern_version, populate it for users")
> > Reported-by: Stanislav Fomichev <sdf@google.com>
> > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > ---
> >  tools/bpf/bpftool/main.c |  4 ++--
> >  tools/bpf/bpftool/main.h |  2 +-
> >  tools/bpf/bpftool/prog.c | 22 ++++++++++++----------
> >  3 files changed, 15 insertions(+), 13 deletions(-)
> >
> > diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
> > index 93d008687020..4764581ff9ea 100644
> > --- a/tools/bpf/bpftool/main.c
> > +++ b/tools/bpf/bpftool/main.c
> > @@ -27,7 +27,7 @@ bool json_output;
> >  bool show_pinned;
> >  bool block_mount;
> >  bool verifier_logs;
> > -int bpf_flags;
> > +bool relaxed_maps;
> >  struct pinned_obj_table prog_table;
> >  struct pinned_obj_table map_table;
> >
> > @@ -396,7 +396,7 @@ int main(int argc, char **argv)
> >                       show_pinned = true;
> >                       break;
> >               case 'm':
> > -                     bpf_flags = MAPS_RELAX_COMPAT;
> > +                     relaxed_maps = true;
> >                       break;
> >               case 'n':
> >                       block_mount = true;
> > diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
> > index af9ad56c303a..2899095f8254 100644
> > --- a/tools/bpf/bpftool/main.h
> > +++ b/tools/bpf/bpftool/main.h
> > @@ -94,7 +94,7 @@ extern bool json_output;
> >  extern bool show_pinned;
> >  extern bool block_mount;
> >  extern bool verifier_logs;
> > -extern int bpf_flags;
> > +extern bool relaxed_maps;
> >  extern struct pinned_obj_table prog_table;
> >  extern struct pinned_obj_table map_table;
> >
> > diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> > index 43fdbbfe41bb..8191cd595963 100644
> > --- a/tools/bpf/bpftool/prog.c
> > +++ b/tools/bpf/bpftool/prog.c
> > @@ -1092,9 +1092,7 @@ static int do_run(int argc, char **argv)
> >  static int load_with_options(int argc, char **argv, bool first_prog_only)
> >  {
> >       struct bpf_object_load_attr load_attr = { 0 };
> > -     struct bpf_object_open_attr open_attr = {
> > -             .prog_type = BPF_PROG_TYPE_UNSPEC,
> > -     };
> > +     enum bpf_prog_type prog_type = BPF_PROG_TYPE_UNSPEC;
> >       enum bpf_attach_type expected_attach_type;
> >       struct map_replace *map_replace = NULL;
> >       struct bpf_program *prog = NULL, *pos;
> > @@ -1105,11 +1103,16 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >       const char *pinfile;
> >       unsigned int i, j;
> >       __u32 ifindex = 0;
> > +     const char *file;
> >       int idx, err;
> >
> > +     LIBBPF_OPTS(bpf_object_open_opts, open_opts,
> > +             .relaxed_maps = relaxed_maps,
> > +     );
> > +
> >       if (!REQ_ARGS(2))
> >               return -1;
> > -     open_attr.file = GET_ARG();
> > +     file = GET_ARG();
> >       pinfile = GET_ARG();
> >
> >       while (argc) {
> > @@ -1118,7 +1121,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >
> >                       NEXT_ARG();
> >
> > -                     if (open_attr.prog_type != BPF_PROG_TYPE_UNSPEC) {
> > +                     if (prog_type != BPF_PROG_TYPE_UNSPEC) {
> >                               p_err("program type already specified");
> >                               goto err_free_reuse_maps;
> >                       }
> > @@ -1135,8 +1138,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >                       strcat(type, *argv);
> >                       strcat(type, "/");
> >
> > -                     err = libbpf_prog_type_by_name(type,
> > -                                                    &open_attr.prog_type,
> > +                     err = libbpf_prog_type_by_name(type, &prog_type,
> >                                                      &expected_attach_type);
> >                       free(type);
> >                       if (err < 0)
> > @@ -1224,16 +1226,16 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >
> >       set_max_rlimit();
> >
> > -     obj = __bpf_object__open_xattr(&open_attr, bpf_flags);
> > +     obj = bpf_object__open_file(file, &open_opts);
> >       if (IS_ERR_OR_NULL(obj)) {
> >               p_err("failed to open object file");
> >               goto err_free_reuse_maps;
> >       }
> >
> >       bpf_object__for_each_program(pos, obj) {
> > -             enum bpf_prog_type prog_type = open_attr.prog_type;
> > +             enum bpf_prog_type prog_type = prog_type;
> Are you sure it works that way?

Oh, I did this pretty mechanically, didn't notice I'm shadowing. In
either case I'd like to avoid shadowing, so I'll rename one of them,
good catch!

>
> $ cat tmp.c
> #include <stdio.h>
>
> int main()
> {
>         int x = 1;
>         printf("outer x=%d\n", x);
>
>         {
>                 int x = x;
>                 printf("inner x=%d\n", x);
>         }
>
>         return 0;
> }
>
> $ gcc tmp.c && ./a.out
> outer x=1
> inner x=0
>
> Other than that:
> Reviewed-by: Stanislav Fomichev <sdf@google.com>
>
> >
> > -             if (open_attr.prog_type == BPF_PROG_TYPE_UNSPEC) {
> > +             if (prog_type == BPF_PROG_TYPE_UNSPEC) {
> >                       const char *sec_name = bpf_program__title(pos, false);
> >
> >                       err = libbpf_prog_type_by_name(sec_name, &prog_type,
> > --
> > 2.17.1
> >

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH bpf-next] bpftool: fix bpftool build by switching to bpf_object__open_file()
  2019-10-07 21:50   ` Andrii Nakryiko
@ 2019-10-07 23:00     ` Andrii Nakryiko
  2019-10-08 15:26       ` Stanislav Fomichev
  0 siblings, 1 reply; 5+ messages in thread
From: Andrii Nakryiko @ 2019-10-07 23:00 UTC (permalink / raw)
  To: Stanislav Fomichev
  Cc: Andrii Nakryiko, bpf, Networking, Alexei Starovoitov,
	Daniel Borkmann, Stanislav Fomichev, Kernel Team

-- Andrii

On Mon, Oct 7, 2019 at 2:50 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Mon, Oct 7, 2019 at 2:46 PM Stanislav Fomichev <sdf@fomichev.me> wrote:
> >
> > On 10/07, Andrii Nakryiko wrote:
> > > As part of libbpf in 5e61f2707029 ("libbpf: stop enforcing kern_version,
> > > populate it for users") non-LIBBPF_API __bpf_object__open_xattr() API
> > > was removed from libbpf.h header. This broke bpftool, which relied on
> > > that function. This patch fixes the build by switching to newly added
> > > bpf_object__open_file() which provides the same capabilities, but is
> > > official and future-proof API.
> > >
> > > Fixes: 5e61f2707029 ("libbpf: stop enforcing kern_version, populate it for users")
> > > Reported-by: Stanislav Fomichev <sdf@google.com>
> > > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > > ---
> > >  tools/bpf/bpftool/main.c |  4 ++--
> > >  tools/bpf/bpftool/main.h |  2 +-
> > >  tools/bpf/bpftool/prog.c | 22 ++++++++++++----------
> > >  3 files changed, 15 insertions(+), 13 deletions(-)
> > >

[...]

> > > --- a/tools/bpf/bpftool/prog.c
> > > +++ b/tools/bpf/bpftool/prog.c
> > > @@ -1092,9 +1092,7 @@ static int do_run(int argc, char **argv)
> > >  static int load_with_options(int argc, char **argv, bool first_prog_only)
> > >  {
> > >       struct bpf_object_load_attr load_attr = { 0 };
> > > -     struct bpf_object_open_attr open_attr = {
> > > -             .prog_type = BPF_PROG_TYPE_UNSPEC,
> > > -     };
> > > +     enum bpf_prog_type prog_type = BPF_PROG_TYPE_UNSPEC;
> > >       enum bpf_attach_type expected_attach_type;
> > >       struct map_replace *map_replace = NULL;

[...]

> > >
> > >       bpf_object__for_each_program(pos, obj) {
> > > -             enum bpf_prog_type prog_type = open_attr.prog_type;
> > > +             enum bpf_prog_type prog_type = prog_type;
> > Are you sure it works that way?
>
> Oh, I did this pretty mechanically, didn't notice I'm shadowing. In
> either case I'd like to avoid shadowing, so I'll rename one of them,
> good catch!
>
> >
> > $ cat tmp.c
> > #include <stdio.h>
> >
> > int main()
> > {
> >         int x = 1;
> >         printf("outer x=%d\n", x);
> >
> >         {
> >                 int x = x;

It's amazing `int x = x;` is compiled successfully when there is no x
in outer scope. And it's also amazing that it's doing the wrong thing
when there is a shadowed variable in outer scope. I can't imagine the
case where this will be a meaningful behavior...

> >                 printf("inner x=%d\n", x);
> >         }
> >
> >         return 0;
> > }
> >
> > $ gcc tmp.c && ./a.out
> > outer x=1
> > inner x=0
> >
> > Other than that:
> > Reviewed-by: Stanislav Fomichev <sdf@google.com>
> >
> > >
> > > -             if (open_attr.prog_type == BPF_PROG_TYPE_UNSPEC) {
> > > +             if (prog_type == BPF_PROG_TYPE_UNSPEC) {
> > >                       const char *sec_name = bpf_program__title(pos, false);
> > >
> > >                       err = libbpf_prog_type_by_name(sec_name, &prog_type,
> > > --
> > > 2.17.1
> > >

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH bpf-next] bpftool: fix bpftool build by switching to bpf_object__open_file()
  2019-10-07 23:00     ` Andrii Nakryiko
@ 2019-10-08 15:26       ` Stanislav Fomichev
  0 siblings, 0 replies; 5+ messages in thread
From: Stanislav Fomichev @ 2019-10-08 15:26 UTC (permalink / raw)
  To: Andrii Nakryiko
  Cc: Andrii Nakryiko, bpf, Networking, Alexei Starovoitov,
	Daniel Borkmann, Stanislav Fomichev, Kernel Team

On 10/07, Andrii Nakryiko wrote:
> -- Andrii
> 
> On Mon, Oct 7, 2019 at 2:50 PM Andrii Nakryiko
> <andrii.nakryiko@gmail.com> wrote:
> >
> > On Mon, Oct 7, 2019 at 2:46 PM Stanislav Fomichev <sdf@fomichev.me> wrote:
> > >
> > > On 10/07, Andrii Nakryiko wrote:
> > > > As part of libbpf in 5e61f2707029 ("libbpf: stop enforcing kern_version,
> > > > populate it for users") non-LIBBPF_API __bpf_object__open_xattr() API
> > > > was removed from libbpf.h header. This broke bpftool, which relied on
> > > > that function. This patch fixes the build by switching to newly added
> > > > bpf_object__open_file() which provides the same capabilities, but is
> > > > official and future-proof API.
> > > >
> > > > Fixes: 5e61f2707029 ("libbpf: stop enforcing kern_version, populate it for users")
> > > > Reported-by: Stanislav Fomichev <sdf@google.com>
> > > > Signed-off-by: Andrii Nakryiko <andriin@fb.com>
> > > > ---
> > > >  tools/bpf/bpftool/main.c |  4 ++--
> > > >  tools/bpf/bpftool/main.h |  2 +-
> > > >  tools/bpf/bpftool/prog.c | 22 ++++++++++++----------
> > > >  3 files changed, 15 insertions(+), 13 deletions(-)
> > > >
> 
> [...]
> 
> > > > --- a/tools/bpf/bpftool/prog.c
> > > > +++ b/tools/bpf/bpftool/prog.c
> > > > @@ -1092,9 +1092,7 @@ static int do_run(int argc, char **argv)
> > > >  static int load_with_options(int argc, char **argv, bool first_prog_only)
> > > >  {
> > > >       struct bpf_object_load_attr load_attr = { 0 };
> > > > -     struct bpf_object_open_attr open_attr = {
> > > > -             .prog_type = BPF_PROG_TYPE_UNSPEC,
> > > > -     };
> > > > +     enum bpf_prog_type prog_type = BPF_PROG_TYPE_UNSPEC;
> > > >       enum bpf_attach_type expected_attach_type;
> > > >       struct map_replace *map_replace = NULL;
> 
> [...]
> 
> > > >
> > > >       bpf_object__for_each_program(pos, obj) {
> > > > -             enum bpf_prog_type prog_type = open_attr.prog_type;
> > > > +             enum bpf_prog_type prog_type = prog_type;
> > > Are you sure it works that way?
> >
> > Oh, I did this pretty mechanically, didn't notice I'm shadowing. In
> > either case I'd like to avoid shadowing, so I'll rename one of them,
> > good catch!
> >
> > >
> > > $ cat tmp.c
> > > #include <stdio.h>
> > >
> > > int main()
> > > {
> > >         int x = 1;
> > >         printf("outer x=%d\n", x);
> > >
> > >         {
> > >                 int x = x;
> 
> It's amazing `int x = x;` is compiled successfully when there is no x
> in outer scope. And it's also amazing that it's doing the wrong thing
> when there is a shadowed variable in outer scope. I can't imagine the
> case where this will be a meaningful behavior...
Enjoy your daily dose of undefined behavior :-D

> > >                 printf("inner x=%d\n", x);
> > >         }
> > >
> > >         return 0;
> > > }
> > >
> > > $ gcc tmp.c && ./a.out
> > > outer x=1
> > > inner x=0
> > >
> > > Other than that:
> > > Reviewed-by: Stanislav Fomichev <sdf@google.com>
> > >
> > > >
> > > > -             if (open_attr.prog_type == BPF_PROG_TYPE_UNSPEC) {
> > > > +             if (prog_type == BPF_PROG_TYPE_UNSPEC) {
> > > >                       const char *sec_name = bpf_program__title(pos, false);
> > > >
> > > >                       err = libbpf_prog_type_by_name(sec_name, &prog_type,
> > > > --
> > > > 2.17.1
> > > >

^ permalink raw reply	[flat|nested] 5+ messages in thread

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Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-10-07 21:22 [PATCH bpf-next] bpftool: fix bpftool build by switching to bpf_object__open_file() Andrii Nakryiko
2019-10-07 21:46 ` Stanislav Fomichev
2019-10-07 21:50   ` Andrii Nakryiko
2019-10-07 23:00     ` Andrii Nakryiko
2019-10-08 15:26       ` Stanislav Fomichev

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