On Wed, 2018-12-19 at 15:34 -0500, Steven Rostedt wrote:
> On Wed, 19 Dec 2018 12:22:38 -0800
> Joe Perches <joe@xxxxxxxxxxx> wrote:
>
> > On Wed, 2018-12-19 at 14:16 -0600, Tom Zanussi wrote:
> > > How's this?
> > >
> > > [PATCH] tracing: Introduce and use strcmp_const() for hist triggers
> > >
> > > Provide a new strcmp_const() macro and make use of it instead of the
> > > longer and more error-prone strncmp(str, "str", sizeof("str") - 1).
> > []
> > > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > []
> > > @@ -22,6 +22,9 @@
> > >
> > > #define STR_VAR_LEN_MAX 32 /* must be multiple of sizeof(u64) */
> > >
> > > +#define strcmp_const(str, str_const) \
> > > + strncmp(str, str_const, sizeof(str_const) - 1)
> >
> > Not good as it's too easy to pass a pointer as str_const
> > and sizeof(pointer) - 1 isn't likely the string length.
>
> Agreed. And I noticed that this is used all over the kernel, so I'm not
> going to add this patch. I'm going to add a:
>
> #define strncmp_prefix(str, prefix) \
> strncmp(str, prefix, strlen(prefix))
>
> in include/linux/string.h
>
> And go around and use that throughout the kernel. By doing a quick
> grep, I already spotted a few bugs.
I hope you also convert the existing uses like
strncmp(str1, "str2", 4)
where the length value is precalculated to the strlen
of the const string
But there seem to be _a lot_ of those...
$ git grep -P "\bstrncmp\s*\([^,]+,[^,]+,\s*\d+\s*\)" | wc -l
1681
