| Message ID | 20220805154231.31257-4-ojeda@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Rust support | expand |
On Fri, Aug 05, 2022 at 05:41:48PM +0200, Miguel Ojeda wrote: > This adds a static assert to ensure `KSYM_NAME_LEN_BUFFER` > gets updated when `KSYM_NAME_LEN` changes. > > The relationship used is one that keeps the new size (512+1) > close to the original buffer size (500). > > Co-developed-by: Boqun Feng <boqun.feng@gmail.com> > Signed-off-by: Boqun Feng <boqun.feng@gmail.com> > Signed-off-by: Miguel Ojeda <ojeda@kernel.org> > --- > scripts/kallsyms.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c > index f3c5a2623f71..f543b1c4f99f 100644 > --- a/scripts/kallsyms.c > +++ b/scripts/kallsyms.c > @@ -33,7 +33,11 @@ > #define KSYM_NAME_LEN 128 > > /* A substantially bigger size than the current maximum. */ > -#define KSYM_NAME_LEN_BUFFER 499 > +#define KSYM_NAME_LEN_BUFFER 512 > +_Static_assert( > + KSYM_NAME_LEN_BUFFER == KSYM_NAME_LEN * 4, > + "Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN" > +); Why not just make this define: #define KSYM_NAME_LEN_BUFFER (KSYM_NAME_LEN * 4) ? If there's a good reason not it, please put it in the commit log. -Kees
On Wed, Aug 17, 2022 at 12:39:48PM -0700, Kees Cook wrote: > On Fri, Aug 05, 2022 at 05:41:48PM +0200, Miguel Ojeda wrote: > > This adds a static assert to ensure `KSYM_NAME_LEN_BUFFER` > > gets updated when `KSYM_NAME_LEN` changes. > > > > The relationship used is one that keeps the new size (512+1) > > close to the original buffer size (500). > > > > Co-developed-by: Boqun Feng <boqun.feng@gmail.com> > > Signed-off-by: Boqun Feng <boqun.feng@gmail.com> > > Signed-off-by: Miguel Ojeda <ojeda@kernel.org> > > --- > > scripts/kallsyms.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c > > index f3c5a2623f71..f543b1c4f99f 100644 > > --- a/scripts/kallsyms.c > > +++ b/scripts/kallsyms.c > > @@ -33,7 +33,11 @@ > > #define KSYM_NAME_LEN 128 > > > > /* A substantially bigger size than the current maximum. */ > > -#define KSYM_NAME_LEN_BUFFER 499 > > +#define KSYM_NAME_LEN_BUFFER 512 > > +_Static_assert( > > + KSYM_NAME_LEN_BUFFER == KSYM_NAME_LEN * 4, > > + "Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN" > > +); > > Why not just make this define: > > #define KSYM_NAME_LEN_BUFFER (KSYM_NAME_LEN * 4) > > ? If there's a good reason not it, please put it in the commit log. > Because KSYM_NAME_LEN_BUFFER is used as a string by stringify() in fscanf(), defining it as (KSYM_NAME_LEN * 4) will produce a string "128 * 4" after stringify() and that doesn't work with fscanf(). Miguel, maybe we can add something below in the commit log? `KSYM_NAME_LEN_BUFFER` cannot be defined as an expression, because it gets stringified in the fscanf() format. Therefore a _Static_assert() is needed. Thoughts? Regards, Boqun > -Kees > > -- > Kees Cook
On Wed, Aug 17, 2022 at 12:50:50PM -0700, Boqun Feng wrote: > On Wed, Aug 17, 2022 at 12:39:48PM -0700, Kees Cook wrote: > > On Fri, Aug 05, 2022 at 05:41:48PM +0200, Miguel Ojeda wrote: > > > This adds a static assert to ensure `KSYM_NAME_LEN_BUFFER` > > > gets updated when `KSYM_NAME_LEN` changes. > > > > > > The relationship used is one that keeps the new size (512+1) > > > close to the original buffer size (500). > > > > > > Co-developed-by: Boqun Feng <boqun.feng@gmail.com> > > > Signed-off-by: Boqun Feng <boqun.feng@gmail.com> > > > Signed-off-by: Miguel Ojeda <ojeda@kernel.org> > > > --- > > > scripts/kallsyms.c | 6 +++++- > > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > > > diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c > > > index f3c5a2623f71..f543b1c4f99f 100644 > > > --- a/scripts/kallsyms.c > > > +++ b/scripts/kallsyms.c > > > @@ -33,7 +33,11 @@ > > > #define KSYM_NAME_LEN 128 > > > > > > /* A substantially bigger size than the current maximum. */ > > > -#define KSYM_NAME_LEN_BUFFER 499 > > > +#define KSYM_NAME_LEN_BUFFER 512 > > > +_Static_assert( > > > + KSYM_NAME_LEN_BUFFER == KSYM_NAME_LEN * 4, > > > + "Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN" > > > +); > > > > Why not just make this define: > > > > #define KSYM_NAME_LEN_BUFFER (KSYM_NAME_LEN * 4) > > > > ? If there's a good reason not it, please put it in the commit log. > > > > Because KSYM_NAME_LEN_BUFFER is used as a string by stringify() in > fscanf(), defining it as (KSYM_NAME_LEN * 4) will produce a string > > "128 * 4" > > after stringify() and that doesn't work with fscanf(). Ah yeah. Thanks! > Miguel, maybe we can add something below in the commit log? > > `KSYM_NAME_LEN_BUFFER` cannot be defined as an expression, because it > gets stringified in the fscanf() format. Therefore a _Static_assert() is > needed. Yeah, please add a source comment for that. :)
On Wed, Aug 17, 2022 at 10:31 PM Kees Cook <keescook@chromium.org> wrote: > > Yeah, please add a source comment for that. :) I agree, I think this sort of explanation should be in the source vs. the commit message, since it explains something about the code, not the change itself. Cheers, Miguel
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c index f3c5a2623f71..f543b1c4f99f 100644 --- a/scripts/kallsyms.c +++ b/scripts/kallsyms.c @@ -33,7 +33,11 @@ #define KSYM_NAME_LEN 128 /* A substantially bigger size than the current maximum. */ -#define KSYM_NAME_LEN_BUFFER 499 +#define KSYM_NAME_LEN_BUFFER 512 +_Static_assert( + KSYM_NAME_LEN_BUFFER == KSYM_NAME_LEN * 4, + "Please keep KSYM_NAME_LEN_BUFFER in sync with KSYM_NAME_LEN" +); struct sym_entry { unsigned long long addr;