* [PATCH] libbpf: Fix build warning on ref_ctr_off
@ 2022-12-05 2:50 Khem Raj
2022-12-07 0:14 ` Andrii Nakryiko
0 siblings, 1 reply; 3+ messages in thread
From: Khem Raj @ 2022-12-05 2:50 UTC (permalink / raw)
To: bpf
Cc: Khem Raj, Alexei Starovoitov, Daniel Borkmann, Song Liu,
Yonghong Song, Jiri Olsa, Paul Walmsley, Palmer Dabbelt,
Nathan Chancellor, Nick Desaulniers
Clang warns on 32-bit ARM on this comparision
libbpf.c:10497:18: error: result of comparison of constant 4294967296 with expression of type 'size_t' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
if (ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Check for platform long int to be larger than 32-bits before enabling
this check, it false on 32bit anyways.
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Song Liu <song@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>
---
tools/lib/bpf/libbpf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 91b7106a4a73..65cb70cdc22b 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9837,7 +9837,7 @@ static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name,
char errmsg[STRERR_BUFSIZE];
int type, pfd;
- if (ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
+ if (BITS_PER_LONG > 32 && ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
return -EINVAL;
memset(&attr, 0, attr_sz);
--
2.38.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] libbpf: Fix build warning on ref_ctr_off
2022-12-05 2:50 [PATCH] libbpf: Fix build warning on ref_ctr_off Khem Raj
@ 2022-12-07 0:14 ` Andrii Nakryiko
2022-12-19 19:17 ` Khem Raj
0 siblings, 1 reply; 3+ messages in thread
From: Andrii Nakryiko @ 2022-12-07 0:14 UTC (permalink / raw)
To: Khem Raj
Cc: bpf, Alexei Starovoitov, Daniel Borkmann, Song Liu,
Yonghong Song, Jiri Olsa, Paul Walmsley, Palmer Dabbelt,
Nathan Chancellor, Nick Desaulniers
On Sun, Dec 4, 2022 at 7:01 PM Khem Raj <raj.khem@gmail.com> wrote:
>
> Clang warns on 32-bit ARM on this comparision
>
> libbpf.c:10497:18: error: result of comparison of constant 4294967296 with expression of type 'size_t' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
> if (ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
> ~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Check for platform long int to be larger than 32-bits before enabling
> this check, it false on 32bit anyways.
>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Cc: Song Liu <song@kernel.org>
> Cc: Yonghong Song <yhs@fb.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Paul Walmsley <paul.walmsley@sifive.com>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: Nick Desaulniers <ndesaulniers@google.com>
>
> Signed-off-by: Khem Raj <raj.khem@gmail.com>
> ---
> tools/lib/bpf/libbpf.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 91b7106a4a73..65cb70cdc22b 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -9837,7 +9837,7 @@ static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name,
> char errmsg[STRERR_BUFSIZE];
> int type, pfd;
>
> - if (ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
> + if (BITS_PER_LONG > 32 && ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
Where is BITS_PER_LONG defined? Is it a compiler-provided macro? A bit
hesitant about taking dependency on such a macro. Also quick googling
suggests user-space programs should use __BITS_PER_LONG?
Can you try if just casting ref_ctr_off to __u64 would make this
warning go away?
> return -EINVAL;
>
> memset(&attr, 0, attr_sz);
> --
> 2.38.1
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] libbpf: Fix build warning on ref_ctr_off
2022-12-07 0:14 ` Andrii Nakryiko
@ 2022-12-19 19:17 ` Khem Raj
0 siblings, 0 replies; 3+ messages in thread
From: Khem Raj @ 2022-12-19 19:17 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: bpf, Alexei Starovoitov, Daniel Borkmann, Song Liu,
Yonghong Song, Jiri Olsa, Paul Walmsley, Palmer Dabbelt,
Nathan Chancellor, Nick Desaulniers
On Tue, Dec 6, 2022 at 4:14 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Sun, Dec 4, 2022 at 7:01 PM Khem Raj <raj.khem@gmail.com> wrote:
> >
> > Clang warns on 32-bit ARM on this comparision
> >
> > libbpf.c:10497:18: error: result of comparison of constant 4294967296 with expression of type 'size_t' (aka 'unsigned int') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
> > if (ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
> > ~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Check for platform long int to be larger than 32-bits before enabling
> > this check, it false on 32bit anyways.
> >
> > Cc: Alexei Starovoitov <ast@kernel.org>
> > Cc: Daniel Borkmann <daniel@iogearbox.net>
> > Cc: Song Liu <song@kernel.org>
> > Cc: Yonghong Song <yhs@fb.com>
> > Cc: Jiri Olsa <jolsa@kernel.org>
> > Cc: Paul Walmsley <paul.walmsley@sifive.com>
> > Cc: Palmer Dabbelt <palmer@dabbelt.com>
> > Cc: Nathan Chancellor <nathan@kernel.org>
> > Cc: Nick Desaulniers <ndesaulniers@google.com>
> >
> > Signed-off-by: Khem Raj <raj.khem@gmail.com>
> > ---
> > tools/lib/bpf/libbpf.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 91b7106a4a73..65cb70cdc22b 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -9837,7 +9837,7 @@ static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name,
> > char errmsg[STRERR_BUFSIZE];
> > int type, pfd;
> >
> > - if (ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
> > + if (BITS_PER_LONG > 32 && ref_ctr_off >= (1ULL << PERF_UPROBE_REF_CTR_OFFSET_BITS))
>
> Where is BITS_PER_LONG defined? Is it a compiler-provided macro? A bit
> hesitant about taking dependency on such a macro. Also quick googling
> suggests user-space programs should use __BITS_PER_LONG?
BITS_PER_LONG is in include/asm-generic/bitsperlong.h, I have sent v2
which implements your suggestion
>
> Can you try if just casting ref_ctr_off to __u64 would make this
> warning go away?
>
> > return -EINVAL;
> >
> > memset(&attr, 0, attr_sz);
> > --
> > 2.38.1
> >
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-12-05 2:50 [PATCH] libbpf: Fix build warning on ref_ctr_off Khem Raj
2022-12-07 0:14 ` Andrii Nakryiko
2022-12-19 19:17 ` Khem Raj
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