| Message ID | 20220517173534.10878-1-alok08jha@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Makefile: Globally enable fall-through warning | expand |
On Tue, 17 May 2022 23:05:34 +0530 ALOK JHA <alok08jha@gmail.com> wrote: > From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> > > Now that all the fall-through warnings have been addressed in the > kernel, enable the fall-through warning globally. > > Also, update the deprecated.rst file to include implicit fall-through > as 'deprecated' so people can be pointed to a single location for > justification. > > Cc: Masahiro Yamada <yamada.masahiro@socionext.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Michal Marek <michal.lkml@markovi.net> > Cc: Kees Cook <keescook@chromium.org> > Cc: linux-kbuild@vger.kernel.org > Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> Since you sent the patch, it should have your signoff as well as Gustavo's. Please resend?
On Tue, 17 May 2022 23:05:34 +0530 ALOK JHA <alok08jha@gmail.com> wrote: > From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> > > Now that all the fall-through warnings have been addressed in the > kernel, enable the fall-through warning globally. > > Also, update the deprecated.rst file to include implicit fall-through > as 'deprecated' so people can be pointed to a single location for > justification. > > ... > > --- a/Documentation/process/deprecated.rst > +++ b/Documentation/process/deprecated.rst > @@ -119,3 +119,17 @@ array may exceed the remaining memory in the stack segment. This could > lead to a crash, possible overwriting sensitive contents at the end of the > stack (when built without `CONFIG_THREAD_INFO_IN_TASK=y`), or overwriting > memory adjacent to the stack (when built without `CONFIG_VMAP_STACK=y`) > + > +Implicit switch case fall-through > +--------------------------------- > > ... > Documentation/process/deprecated.rst already has a section "Implicit switch case fall-through". Maybe you're working against an old kernel. Please update when resending.
On 5/17/2022 11:46 AM, Andrew Morton wrote: > On Tue, 17 May 2022 23:05:34 +0530 ALOK JHA <alok08jha@gmail.com> wrote: > >> From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> >> >> Now that all the fall-through warnings have been addressed in the >> kernel, enable the fall-through warning globally. >> >> Also, update the deprecated.rst file to include implicit fall-through >> as 'deprecated' so people can be pointed to a single location for >> justification. >> >> ... >> >> --- a/Documentation/process/deprecated.rst >> +++ b/Documentation/process/deprecated.rst >> @@ -119,3 +119,17 @@ array may exceed the remaining memory in the stack segment. This could >> lead to a crash, possible overwriting sensitive contents at the end of the >> stack (when built without `CONFIG_THREAD_INFO_IN_TASK=y`), or overwriting >> memory adjacent to the stack (when built without `CONFIG_VMAP_STACK=y`) >> + >> +Implicit switch case fall-through >> +--------------------------------- >> >> ... >> > > Documentation/process/deprecated.rst already has a section "Implicit > switch case fall-through". Maybe you're working against an old kernel. > Please update when resending. > shouldn't we now just be referencing the fallthrough() macro?
On Tue, May 17, 2022 at 11:46:01AM -0700, Andrew Morton wrote: > On Tue, 17 May 2022 23:05:34 +0530 ALOK JHA <alok08jha@gmail.com> wrote: > > > From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> > > > > Now that all the fall-through warnings have been addressed in the > > kernel, enable the fall-through warning globally. > > > > Also, update the deprecated.rst file to include implicit fall-through > > as 'deprecated' so people can be pointed to a single location for > > justification. > > > > ... > > > > --- a/Documentation/process/deprecated.rst > > +++ b/Documentation/process/deprecated.rst > > @@ -119,3 +119,17 @@ array may exceed the remaining memory in the stack segment. This could > > lead to a crash, possible overwriting sensitive contents at the end of the > > stack (when built without `CONFIG_THREAD_INFO_IN_TASK=y`), or overwriting > > memory adjacent to the stack (when built without `CONFIG_VMAP_STACK=y`) > > + > > +Implicit switch case fall-through > > +--------------------------------- > > > > ... > > > > Documentation/process/deprecated.rst already has a section "Implicit > switch case fall-through". Maybe you're working against an old kernel. > Please update when resending. This looks like spam to me. Let's just ignore this. -- Gustavo
diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst index 49e0f64a3427..053b24a6dd38 100644 --- a/Documentation/process/deprecated.rst +++ b/Documentation/process/deprecated.rst @@ -119,3 +119,17 @@ array may exceed the remaining memory in the stack segment. This could lead to a crash, possible overwriting sensitive contents at the end of the stack (when built without `CONFIG_THREAD_INFO_IN_TASK=y`), or overwriting memory adjacent to the stack (when built without `CONFIG_VMAP_STACK=y`) + +Implicit switch case fall-through +--------------------------------- +The C language allows switch cases to "fall through" when +a "break" statement is missing at the end of a case. This, +however, introduces ambiguity in the code, as it's not always +clear if the missing break is intentional or a bug. As there +have been a long list of flaws `due to missing "break" statements +<https://cwe.mitre.org/data/definitions/484.html>`_, we no longer allow +"implicit fall-through". In order to identify an intentional fall-through +case, we have adopted the marking used by static analyzers: a comment +saying `/* Fall through */`. Once the C++17 `__attribute__((fallthrough))` +is more widely handled by C compilers, static analyzers, and IDEs, we can +switch to using that instead. diff --git a/Makefile b/Makefile index 9be5834073f8..bdf8eac51b07 100644 --- a/Makefile +++ b/Makefile @@ -843,6 +843,9 @@ NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) # warn about C99 declaration after statement KBUILD_CFLAGS += -Wdeclaration-after-statement +# Warn about unmarked fall-throughs in switch statement. +KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough=3,) + # Variable Length Arrays (VLAs) should not be used anywhere in the kernel KBUILD_CFLAGS += -Wvla