diff mbox series

[bpf-next,3/3] libbpf: Check the return value of bpf_iter_<type>_new()

Message ID 20240208090906.56337-4-laoar.shao@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series bpf: Fix an issue in bpf_iter_task | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR success PR summary
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 8 this patch: 8
netdev/build_tools success Errors and warnings before: 1 this patch: 1
netdev/cc_maintainers success CCed 13 of 13 maintainers
netdev/build_clang success Errors and warnings before: 8 this patch: 8
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 8 this patch: 8
netdev/checkpatch warning CHECK: No space is necessary after a cast WARNING: line length of 97 exceeds 80 columns
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-VM_Test-21 success Logs for x86_64-gcc / test (test_maps, false, 360) / test_maps on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-23 success Logs for x86_64-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-24 success Logs for x86_64-gcc / test (test_progs_no_alu32_parallel, true, 30) / test_progs_no_alu32_parallel on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-25 success Logs for x86_64-gcc / test (test_progs_parallel, true, 30) / test_progs_parallel on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-26 success Logs for x86_64-gcc / test (test_verifier, false, 360) / test_verifier on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-27 success Logs for x86_64-gcc / veristat / veristat on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-30 success Logs for x86_64-llvm-17 / test (test_maps, false, 360) / test_maps on x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-31 success Logs for x86_64-llvm-17 / test (test_progs, false, 360) / test_progs on x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-32 success Logs for x86_64-llvm-17 / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-37 success Logs for x86_64-llvm-18 / test (test_maps, false, 360) / test_maps on x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-39 success Logs for x86_64-llvm-18 / test (test_progs_cpuv4, false, 360) / test_progs_cpuv4 on x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-38 success Logs for x86_64-llvm-18 / test (test_progs, false, 360) / test_progs on x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-41 success Logs for x86_64-llvm-18 / test (test_verifier, false, 360) / test_verifier on x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-40 success Logs for x86_64-llvm-18 / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-14 success Logs for s390x-gcc / test (test_progs, false, 360) / test_progs on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-0 success Logs for Lint
bpf/vmtest-bpf-next-VM_Test-1 success Logs for ShellCheck
bpf/vmtest-bpf-next-VM_Test-3 success Logs for Validate matrix.py
bpf/vmtest-bpf-next-VM_Test-2 success Logs for Unittests
bpf/vmtest-bpf-next-VM_Test-5 success Logs for aarch64-gcc / build-release
bpf/vmtest-bpf-next-VM_Test-4 success Logs for aarch64-gcc / build / build for aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-10 success Logs for aarch64-gcc / veristat
bpf/vmtest-bpf-next-VM_Test-12 success Logs for s390x-gcc / build-release
bpf/vmtest-bpf-next-VM_Test-13 success Logs for set-matrix
bpf/vmtest-bpf-next-VM_Test-15 success Logs for x86_64-gcc / build-release
bpf/vmtest-bpf-next-VM_Test-6 success Logs for aarch64-gcc / test (test_maps, false, 360) / test_maps on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-9 success Logs for aarch64-gcc / test (test_verifier, false, 360) / test_verifier on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-8 success Logs for aarch64-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-7 success Logs for aarch64-gcc / test (test_progs, false, 360) / test_progs on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-16 success Logs for x86_64-llvm-17 / build / build for x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-22 success Logs for x86_64-llvm-17 / veristat
bpf/vmtest-bpf-next-VM_Test-11 success Logs for s390x-gcc / build / build for s390x with gcc
bpf/vmtest-bpf-next-VM_Test-17 success Logs for s390x-gcc / veristat
bpf/vmtest-bpf-next-VM_Test-18 success Logs for set-matrix
bpf/vmtest-bpf-next-VM_Test-19 success Logs for x86_64-gcc / build / build for x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-20 success Logs for x86_64-gcc / build-release
bpf/vmtest-bpf-next-VM_Test-28 success Logs for x86_64-llvm-17 / build / build for x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-34 success Logs for x86_64-llvm-17 / veristat
bpf/vmtest-bpf-next-VM_Test-35 success Logs for x86_64-llvm-18 / build / build for x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-42 success Logs for x86_64-llvm-18 / veristat
bpf/vmtest-bpf-next-VM_Test-36 success Logs for x86_64-llvm-18 / build-release / build for x86_64 with llvm-18 and -O2 optimization
bpf/vmtest-bpf-next-VM_Test-29 success Logs for x86_64-llvm-17 / build-release / build for x86_64 with llvm-17 and -O2 optimization
bpf/vmtest-bpf-next-VM_Test-33 success Logs for x86_64-llvm-17 / test (test_verifier, false, 360) / test_verifier on x86_64 with llvm-17

Commit Message

Yafang Shao Feb. 8, 2024, 9:09 a.m. UTC 
On success, bpf_iter_<type>_new() return 0. On failure, it returns ERR.
We'd better check the return value of it.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 tools/lib/bpf/bpf_helpers.h | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

Comments

Yonghong Song Feb. 8, 2024, 5:43 p.m. UTC | #1 
On 2/8/24 1:09 AM, Yafang Shao wrote:
> On success, bpf_iter_<type>_new() return 0. On failure, it returns ERR.
> We'd better check the return value of it.

Not sure whether this patch is necessary or not.

I checked:
   bpf_iter_num_{new,next}
   bpf_iter_task_vma_{new,next}
   bpf_iter_css_task_{new,next}

It looks like the convention is for *_next() return NULL or not
instead of relying on return value of _new() to decide whether to
proceed or not. Maybe Andrii can clarify.

>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
>   tools/lib/bpf/bpf_helpers.h | 16 ++++++++++++----
>   1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> index 79eaa581be98..2cd2428e3bc6 100644
> --- a/tools/lib/bpf/bpf_helpers.h
> +++ b/tools/lib/bpf/bpf_helpers.h
> @@ -133,6 +133,15 @@
>   # define __bpf_unreachable()	__builtin_trap()
>   #endif
>   
> +#ifndef __must_check
> +#define __must_check __attribute__((warn_unused_result))
> +#endif
> +
> +static inline void * __must_check ERR_PTR(long error)
> +{
> +	return (void *) error;
> +}
> +
>   /*
>    * Helper function to perform a tail call with a constant/immediate map slot.
>    */
> @@ -340,14 +349,13 @@ extern void bpf_iter_num_destroy(struct bpf_iter_num *it) __weak __ksym;
>   	/* initialize and define destructor */							\
>   	struct bpf_iter_##type ___it __attribute__((aligned(8), /* enforce, just in case */,	\
>   						    cleanup(bpf_iter_##type##_destroy))),	\
> -	/* ___p pointer is just to call bpf_iter_##type##_new() *once* to init ___it */		\
>   			       *___p __attribute__((unused)) = (				\
> -					bpf_iter_##type##_new(&___it, ##args),			\
>   	/* this is a workaround for Clang bug: it currently doesn't emit BTF */			\
>   	/* for bpf_iter_##type##_destroy() when used from cleanup() attribute */		\
> -					(void)bpf_iter_##type##_destroy, (void *)0);		\
> +					(void)bpf_iter_##type##_destroy,			\
> +					ERR_PTR(bpf_iter_##type##_new(&___it, ##args)));	\
>   	/* iteration and termination check */							\
> -	(((cur) = bpf_iter_##type##_next(&___it)));						\
> +	((!___p) && ((cur) = bpf_iter_##type##_next(&___it)));					\
>   )
>   #endif /* bpf_for_each */
>
Andrii Nakryiko Feb. 8, 2024, 6:56 p.m. UTC | #2 
On Thu, Feb 8, 2024 at 9:43 AM Yonghong Song <yonghong.song@linux.dev> wrote:
>
>
> On 2/8/24 1:09 AM, Yafang Shao wrote:
> > On success, bpf_iter_<type>_new() return 0. On failure, it returns ERR.
> > We'd better check the return value of it.
>
> Not sure whether this patch is necessary or not.
>
> I checked:
>    bpf_iter_num_{new,next}
>    bpf_iter_task_vma_{new,next}
>    bpf_iter_css_task_{new,next}
>
> It looks like the convention is for *_next() return NULL or not
> instead of relying on return value of _new() to decide whether to
> proceed or not. Maybe Andrii can clarify.

Yes, exactly. if bpf_iter_xxx_new() failed, subsequent
bpf_iter_xxx_next() should return NULL and bpf_iter_xxx_destroy() will
be a no-op as well. So yes, there is no need for extra error checking
here.

>
> >
> > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > ---
> >   tools/lib/bpf/bpf_helpers.h | 16 ++++++++++++----
> >   1 file changed, 12 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
> > index 79eaa581be98..2cd2428e3bc6 100644
> > --- a/tools/lib/bpf/bpf_helpers.h
> > +++ b/tools/lib/bpf/bpf_helpers.h
> > @@ -133,6 +133,15 @@
> >   # define __bpf_unreachable()        __builtin_trap()
> >   #endif
> >
> > +#ifndef __must_check
> > +#define __must_check __attribute__((warn_unused_result))
> > +#endif
> > +
> > +static inline void * __must_check ERR_PTR(long error)
> > +{
> > +     return (void *) error;
> > +}
> > +
> >   /*
> >    * Helper function to perform a tail call with a constant/immediate map slot.
> >    */
> > @@ -340,14 +349,13 @@ extern void bpf_iter_num_destroy(struct bpf_iter_num *it) __weak __ksym;
> >       /* initialize and define destructor */                                                  \
> >       struct bpf_iter_##type ___it __attribute__((aligned(8), /* enforce, just in case */,    \
> >                                                   cleanup(bpf_iter_##type##_destroy))),       \
> > -     /* ___p pointer is just to call bpf_iter_##type##_new() *once* to init ___it */         \
> >                              *___p __attribute__((unused)) = (                                \
> > -                                     bpf_iter_##type##_new(&___it, ##args),                  \
> >       /* this is a workaround for Clang bug: it currently doesn't emit BTF */                 \
> >       /* for bpf_iter_##type##_destroy() when used from cleanup() attribute */                \
> > -                                     (void)bpf_iter_##type##_destroy, (void *)0);            \
> > +                                     (void)bpf_iter_##type##_destroy,                        \
> > +                                     ERR_PTR(bpf_iter_##type##_new(&___it, ##args)));        \
> >       /* iteration and termination check */                                                   \
> > -     (((cur) = bpf_iter_##type##_next(&___it)));                                             \
> > +     ((!___p) && ((cur) = bpf_iter_##type##_next(&___it)));                                  \
> >   )
> >   #endif /* bpf_for_each */
> >
diff mbox series

Patch

diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index 79eaa581be98..2cd2428e3bc6 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -133,6 +133,15 @@ 
 # define __bpf_unreachable()	__builtin_trap()
 #endif
 
+#ifndef __must_check
+#define __must_check __attribute__((warn_unused_result))
+#endif
+
+static inline void * __must_check ERR_PTR(long error)
+{
+	return (void *) error;
+}
+
 /*
  * Helper function to perform a tail call with a constant/immediate map slot.
  */
@@ -340,14 +349,13 @@  extern void bpf_iter_num_destroy(struct bpf_iter_num *it) __weak __ksym;
 	/* initialize and define destructor */							\
 	struct bpf_iter_##type ___it __attribute__((aligned(8), /* enforce, just in case */,	\
 						    cleanup(bpf_iter_##type##_destroy))),	\
-	/* ___p pointer is just to call bpf_iter_##type##_new() *once* to init ___it */		\
 			       *___p __attribute__((unused)) = (				\
-					bpf_iter_##type##_new(&___it, ##args),			\
 	/* this is a workaround for Clang bug: it currently doesn't emit BTF */			\
 	/* for bpf_iter_##type##_destroy() when used from cleanup() attribute */		\
-					(void)bpf_iter_##type##_destroy, (void *)0);		\
+					(void)bpf_iter_##type##_destroy,			\
+					ERR_PTR(bpf_iter_##type##_new(&___it, ##args)));	\
 	/* iteration and termination check */							\
-	(((cur) = bpf_iter_##type##_next(&___it)));						\
+	((!___p) && ((cur) = bpf_iter_##type##_next(&___it)));					\
 )
 #endif /* bpf_for_each */