[PATCH v2 0/2] bpftool: improve error handing for missing .BTF section

[PATCH v2 0/2] bpftool: improve error handing for missing .BTF section

[Changbin Du]

v2:
 - remove vmlinux specific error info.
 - use builtin target .DELETE_ON_ERROR: to delete empty vmlinux.h

Changbin Du (2):
  libbpf: show error info about missing ".BTF" section
  bpf: makefiles: do not generate empty vmlinux.h

 tools/bpf/bpftool/Makefile           | 3 +++
 tools/lib/bpf/btf.c                  | 1 +
 tools/perf/Makefile.perf             | 2 ++
 tools/testing/selftests/bpf/Makefile | 3 +++
 4 files changed, 9 insertions(+)

-- 
2.37.2

[PATCH v2 1/2] libbpf: show error info about missing ".BTF" section

[Changbin Du]

Show the real problem instead of just saying "No such file or directory".

Now will print below info:
libbpf: can not find '.BTF' section
Error: failed to load BTF from /home/changbin/work/linux/vmlinux: No such file or directory

Signed-off-by: Changbin Du <changbin.du@gmail.com>
---
 tools/lib/bpf/btf.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index d88647da2c7f..1adc0f6019a0 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -990,6 +990,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
 	err = 0;
 
 	if (!btf_data) {
+		pr_warn("can not find '%s' section\n", BTF_ELF_SEC);
 		err = -ENOENT;
 		goto done;
 	}
-- 
2.37.2

Re: [PATCH v2 1/2] libbpf: show error info about missing ".BTF" section

[Andrii Nakryiko]

On Tue, Nov 29, 2022 at 5:42 AM Changbin Du <changbin.du@gmail.com> wrote:
>
> Show the real problem instead of just saying "No such file or directory".
>
> Now will print below info:
> libbpf: can not find '.BTF' section
> Error: failed to load BTF from /home/changbin/work/linux/vmlinux: No such file or directory
>
> Signed-off-by: Changbin Du <changbin.du@gmail.com>
> ---
>  tools/lib/bpf/btf.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index d88647da2c7f..1adc0f6019a0 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -990,6 +990,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
>         err = 0;
>
>         if (!btf_data) {
> +               pr_warn("can not find '%s' section\n", BTF_ELF_SEC);

let's use consistent form of error messages:

pr_warn("failed to find '%s' ELF section in %s\n", BTF_ELF_SEC, path);

>                 err = -ENOENT;
>                 goto done;
>         }
> --
> 2.37.2
>

Re: [PATCH v2 1/2] libbpf: show error info about missing ".BTF" section

[Changbin Du]

On Wed, Nov 30, 2022 at 04:55:13PM -0800, Andrii Nakryiko wrote:
> On Tue, Nov 29, 2022 at 5:42 AM Changbin Du <changbin.du@gmail.com> wrote:
> >
> > Show the real problem instead of just saying "No such file or directory".
> >
> > Now will print below info:
> > libbpf: can not find '.BTF' section
> > Error: failed to load BTF from /home/changbin/work/linux/vmlinux: No such file or directory
> >
> > Signed-off-by: Changbin Du <changbin.du@gmail.com>
> > ---
> >  tools/lib/bpf/btf.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> > index d88647da2c7f..1adc0f6019a0 100644
> > --- a/tools/lib/bpf/btf.c
> > +++ b/tools/lib/bpf/btf.c
> > @@ -990,6 +990,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
> >         err = 0;
> >
> >         if (!btf_data) {
> > +               pr_warn("can not find '%s' section\n", BTF_ELF_SEC);
> 
> let's use consistent form of error messages:
> 
> pr_warn("failed to find '%s' ELF section in %s\n", BTF_ELF_SEC, path);
>
okay.

> >                 err = -ENOENT;
> >                 goto done;
> >         }
> > --
> > 2.37.2
> >

-- 
Cheers,
Changbin Du

[PATCH v2 2/2] bpf: makefiles: do not generate empty vmlinux.h

[Changbin Du]

Remove the empty vmlinux.h if bpftool failed to dump btf info.
The emptry vmlinux.h can hide real error when reading output
of make.

This is done by adding .DELETE_ON_ERROR special target in related
makefiles.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
---
 tools/bpf/bpftool/Makefile           | 3 +++
 tools/perf/Makefile.perf             | 2 ++
 tools/testing/selftests/bpf/Makefile | 3 +++
 3 files changed, 8 insertions(+)

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 4a95c017ad4c..f6b1e65085db 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -265,3 +265,6 @@ FORCE:
 .PHONY: all FORCE bootstrap clean install-bin install uninstall
 .PHONY: doc doc-clean doc-install doc-uninstall
 .DEFAULT_GOAL := all
+
+# Delete partially updated (corrupted) files on error
+.DELETE_ON_ERROR:
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index a432e59afc42..265254fc641a 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -1149,3 +1149,5 @@ FORCE:
 .PHONY: libtraceevent_plugins archheaders
 
 endif # force_fixdep
+
+.DELETE_ON_ERROR:
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index e6cf21fad69f..f41c4b011221 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -617,3 +617,6 @@ EXTRA_CLEAN := $(TEST_CUSTOM_PROGS) $(SCRATCH_DIR) $(HOST_SCRATCH_DIR)	\
 			       liburandom_read.so)
 
 .PHONY: docs docs-clean
+
+# Delete partially updated (corrupted) files on error
+.DELETE_ON_ERROR:
-- 
2.37.2

Re: [PATCH v2 2/2] bpf: makefiles: do not generate empty vmlinux.h

[Andrii Nakryiko]

On Tue, Nov 29, 2022 at 5:42 AM Changbin Du <changbin.du@gmail.com> wrote:
>
> Remove the empty vmlinux.h if bpftool failed to dump btf info.
> The emptry vmlinux.h can hide real error when reading output

typo: empty

> of make.
>
> This is done by adding .DELETE_ON_ERROR special target in related
> makefiles.
>
> Signed-off-by: Changbin Du <changbin.du@gmail.com>
> ---
>  tools/bpf/bpftool/Makefile           | 3 +++
>  tools/perf/Makefile.perf             | 2 ++
>  tools/testing/selftests/bpf/Makefile | 3 +++
>  3 files changed, 8 insertions(+)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index 4a95c017ad4c..f6b1e65085db 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -265,3 +265,6 @@ FORCE:
>  .PHONY: all FORCE bootstrap clean install-bin install uninstall
>  .PHONY: doc doc-clean doc-install doc-uninstall
>  .DEFAULT_GOAL := all
> +
> +# Delete partially updated (corrupted) files on error
> +.DELETE_ON_ERROR:
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index a432e59afc42..265254fc641a 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -1149,3 +1149,5 @@ FORCE:
>  .PHONY: libtraceevent_plugins archheaders
>
>  endif # force_fixdep
> +
> +.DELETE_ON_ERROR:

please split out perf changes, they should go through perf tree

> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index e6cf21fad69f..f41c4b011221 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -617,3 +617,6 @@ EXTRA_CLEAN := $(TEST_CUSTOM_PROGS) $(SCRATCH_DIR) $(HOST_SCRATCH_DIR)      \
>                                liburandom_read.so)
>
>  .PHONY: docs docs-clean
> +
> +# Delete partially updated (corrupted) files on error
> +.DELETE_ON_ERROR:
> --
> 2.37.2
>

Re: [PATCH v2 2/2] bpf: makefiles: do not generate empty vmlinux.h

[Changbin Du]

On Wed, Nov 30, 2022 at 04:52:11PM -0800, Andrii Nakryiko wrote:
> On Tue, Nov 29, 2022 at 5:42 AM Changbin Du <changbin.du@gmail.com> wrote:
> >
> > Remove the empty vmlinux.h if bpftool failed to dump btf info.
> > The emptry vmlinux.h can hide real error when reading output
> 
> typo: empty
>
Will be fixed, thanks.

> > of make.
> >
> > This is done by adding .DELETE_ON_ERROR special target in related
> > makefiles.
> >
> > Signed-off-by: Changbin Du <changbin.du@gmail.com>
> > ---
> >  tools/bpf/bpftool/Makefile           | 3 +++
> >  tools/perf/Makefile.perf             | 2 ++
> >  tools/testing/selftests/bpf/Makefile | 3 +++
> >  3 files changed, 8 insertions(+)
> >
> > diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> > index 4a95c017ad4c..f6b1e65085db 100644
> > --- a/tools/bpf/bpftool/Makefile
> > +++ b/tools/bpf/bpftool/Makefile
> > @@ -265,3 +265,6 @@ FORCE:
> >  .PHONY: all FORCE bootstrap clean install-bin install uninstall
> >  .PHONY: doc doc-clean doc-install doc-uninstall
> >  .DEFAULT_GOAL := all
> > +
> > +# Delete partially updated (corrupted) files on error
> > +.DELETE_ON_ERROR:
> > diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> > index a432e59afc42..265254fc641a 100644
> > --- a/tools/perf/Makefile.perf
> > +++ b/tools/perf/Makefile.perf
> > @@ -1149,3 +1149,5 @@ FORCE:
> >  .PHONY: libtraceevent_plugins archheaders
> >
> >  endif # force_fixdep
> > +
> > +.DELETE_ON_ERROR:
> 
> please split out perf changes, they should go through perf tree
> 
sure, I'll send a standalone patch to perf tree.

> > diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> > index e6cf21fad69f..f41c4b011221 100644
> > --- a/tools/testing/selftests/bpf/Makefile
> > +++ b/tools/testing/selftests/bpf/Makefile
> > @@ -617,3 +617,6 @@ EXTRA_CLEAN := $(TEST_CUSTOM_PROGS) $(SCRATCH_DIR) $(HOST_SCRATCH_DIR)      \
> >                                liburandom_read.so)
> >
> >  .PHONY: docs docs-clean
> > +
> > +# Delete partially updated (corrupted) files on error
> > +.DELETE_ON_ERROR:
> > --
> > 2.37.2
> >

-- 
Cheers,
Changbin Du

Re: [PATCH v2 0/2] bpftool: improve error handing for missing .BTF section

[Andrii Nakryiko]

On Tue, Nov 29, 2022 at 5:42 AM Changbin Du <changbin.du@gmail.com> wrote:
>

please fill out cover letter


> v2:
>  - remove vmlinux specific error info.
>  - use builtin target .DELETE_ON_ERROR: to delete empty vmlinux.h
>
> Changbin Du (2):
>   libbpf: show error info about missing ".BTF" section
>   bpf: makefiles: do not generate empty vmlinux.h
>
>  tools/bpf/bpftool/Makefile           | 3 +++
>  tools/lib/bpf/btf.c                  | 1 +
>  tools/perf/Makefile.perf             | 2 ++
>  tools/testing/selftests/bpf/Makefile | 3 +++
>  4 files changed, 9 insertions(+)
>
> --
> 2.37.2
>