* [PATCH] kernel/compat.c: mark expected switch fall-throughs
@ 2019-04-16 7:29 Stephen Rothwell
2019-04-16 8:32 ` Arnd Bergmann
0 siblings, 1 reply; 5+ messages in thread
From: Stephen Rothwell @ 2019-04-16 7:29 UTC (permalink / raw)
To: Linux Kernel Mailing List
Cc: Arnd Bergmann, Deepa Dinamani, Gustavo A. R. Silva, Kees Cook, Jann Horn
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In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.
This patch aims to suppress up to 3 missing-break-in-switch false
positives on some architectures.
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: Gustavo A. R. Silva <gustavo@embeddedor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
kernel/compat.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
I know that this makes the lines longer than 80 characters, but I
though that this was better than adding new lines.
Build tested on PowerPC.
diff --git a/kernel/compat.c b/kernel/compat.c
index d8a36c6ad7c9..b61f75df188d 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -345,9 +345,9 @@ get_compat_sigset(sigset_t *set, const compat_sigset_t __user *compat)
if (copy_from_user(&v, compat, sizeof(compat_sigset_t)))
return -EFAULT;
switch (_NSIG_WORDS) {
- case 4: set->sig[3] = v.sig[6] | (((long)v.sig[7]) << 32 );
- case 3: set->sig[2] = v.sig[4] | (((long)v.sig[5]) << 32 );
- case 2: set->sig[1] = v.sig[2] | (((long)v.sig[3]) << 32 );
+ case 4: set->sig[3] = v.sig[6] | (((long)v.sig[7]) << 32 ); /* fall through */
+ case 3: set->sig[2] = v.sig[4] | (((long)v.sig[5]) << 32 ); /* fall through */
+ case 2: set->sig[1] = v.sig[2] | (((long)v.sig[3]) << 32 ); /* fall through */
case 1: set->sig[0] = v.sig[0] | (((long)v.sig[1]) << 32 );
}
#else
--
2.20.1
--
Cheers,
Stephen Rothwell
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] kernel/compat.c: mark expected switch fall-throughs
2019-04-16 7:29 [PATCH] kernel/compat.c: mark expected switch fall-throughs Stephen Rothwell
@ 2019-04-16 8:32 ` Arnd Bergmann
2019-04-16 8:53 ` Stephen Rothwell
0 siblings, 1 reply; 5+ messages in thread
From: Arnd Bergmann @ 2019-04-16 8:32 UTC (permalink / raw)
To: Stephen Rothwell
Cc: Linux Kernel Mailing List, Deepa Dinamani, Gustavo A. R. Silva,
Kees Cook, Jann Horn
On Tue, Apr 16, 2019 at 9:29 AM Stephen Rothwell <sfr@canb.auug.org.au> wrote:
>
> In preparation to enabling -Wimplicit-fallthrough, mark switch cases
> where we are expecting to fall through.
>
> This patch aims to suppress up to 3 missing-break-in-switch false
> positives on some architectures.
>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Deepa Dinamani <deepa.kernel@gmail.com>
> Cc: Gustavo A. R. Silva <gustavo@embeddedor.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Jann Horn <jannh@google.com>
> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Arnd Bergmann <arnd@arndb.de>
> ---
> kernel/compat.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> I know that this makes the lines longer than 80 characters, but I
> though that this was better than adding new lines.
It's a bit inconsistent though since put_compat_sigset() has the
comments in separate lines, as of commit 89976005536c
("include/linux/compat.h: mark expected switch fall-throughs").
I don't care either way, but it might be better to do it the same way
for both.
We could also consider just getting rid of put_compat_sigset() and
get_compat_sigset() but replacing them with a combined
put_sigset()/get_sigset() that does the right thing for both native
and compat tasks. This lets us kill a couple of compat system
calls that only differ in their sigset_t argument. On little-endian
systems (which are the vast majority of the installed base), there
is no difference anyway there is no overhead anyway since
native and compat sigset_t are identical.
Arnd
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] kernel/compat.c: mark expected switch fall-throughs
2019-04-16 8:32 ` Arnd Bergmann
@ 2019-04-16 8:53 ` Stephen Rothwell
2019-04-16 9:14 ` Arnd Bergmann
0 siblings, 1 reply; 5+ messages in thread
From: Stephen Rothwell @ 2019-04-16 8:53 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Linux Kernel Mailing List, Deepa Dinamani, Gustavo A. R. Silva,
Kees Cook, Jann Horn
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Hi Arnd,
On Tue, 16 Apr 2019 10:32:55 +0200 Arnd Bergmann <arnd@arndb.de> wrote:
>
> Acked-by: Arnd Bergmann <arnd@arndb.de>
Thanks
> It's a bit inconsistent though since put_compat_sigset() has the
> comments in separate lines, as of commit 89976005536c
> ("include/linux/compat.h: mark expected switch fall-throughs").
OK, I wasn't aware of that one.
> I don't care either way, but it might be better to do it the same way
> for both.
Indeed, I will redo it that way (with your Acked-by).
> We could also consider just getting rid of put_compat_sigset() and
> get_compat_sigset() but replacing them with a combined
> put_sigset()/get_sigset() that does the right thing for both native
> and compat tasks. This lets us kill a couple of compat system
> calls that only differ in their sigset_t argument. On little-endian
> systems (which are the vast majority of the installed base), there
> is no difference anyway there is no overhead anyway since
> native and compat sigset_t are identical.
That sounds like a bigger patch that would require some real testing :-)
--
Cheers,
Stephen Rothwell
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] kernel/compat.c: mark expected switch fall-throughs
2019-04-16 8:53 ` Stephen Rothwell
@ 2019-04-16 9:14 ` Arnd Bergmann
0 siblings, 0 replies; 5+ messages in thread
From: Arnd Bergmann @ 2019-04-16 9:14 UTC (permalink / raw)
To: Stephen Rothwell
Cc: Linux Kernel Mailing List, Deepa Dinamani, Gustavo A. R. Silva,
Kees Cook, Jann Horn
On Tue, Apr 16, 2019 at 10:54 AM Stephen Rothwell <sfr@canb.auug.org.au> wrote:
> On Tue, 16 Apr 2019 10:32:55 +0200 Arnd Bergmann <arnd@arndb.de> wrote:
> > We could also consider just getting rid of put_compat_sigset() and
> > get_compat_sigset() but replacing them with a combined
> > put_sigset()/get_sigset() that does the right thing for both native
> > and compat tasks. This lets us kill a couple of compat system
> > calls that only differ in their sigset_t argument. On little-endian
> > systems (which are the vast majority of the installed base), there
> > is no difference anyway there is no overhead anyway since
> > native and compat sigset_t are identical.
>
> That sounds like a bigger patch that would require some real testing :-)
Yes, definitely. I mainly mentioned it in case someone wants to
do that work anyway, as it would avoid the need for your patch.
Arnd
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH] kernel/compat.c: mark expected switch fall-throughs
@ 2019-05-15 5:23 Stephen Rothwell
0 siblings, 0 replies; 5+ messages in thread
From: Stephen Rothwell @ 2019-05-15 5:23 UTC (permalink / raw)
To: Linus
Cc: Arnd Bergmann, Deepa Dinamani, Gustavo A. R. Silva, Kees Cook,
Jann Horn, Linux-kernel Mailing List
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In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.
This patch aims to suppress 3 missing-break-in-switch false positives
on some architectures.
Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: Gustavo A. R. Silva <gustavo@embeddedor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
---
kernel/compat.c | 3 +++
1 file changed, 3 insertions(+)
Hi Linus,
This has been sitting in my fixes tree in linux-next for quite some
time. It silences some warnings that irritated me in my builds since I
am building with -Wimplicit-fallthrough to help Gustavo catch new
additions.
diff --git a/kernel/compat.c b/kernel/compat.c
index d8a36c6ad7c9..b5f7063c0db6 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -346,8 +346,11 @@ get_compat_sigset(sigset_t *set, const compat_sigset_t __user *compat)
return -EFAULT;
switch (_NSIG_WORDS) {
case 4: set->sig[3] = v.sig[6] | (((long)v.sig[7]) << 32 );
+ /* fall through */
case 3: set->sig[2] = v.sig[4] | (((long)v.sig[5]) << 32 );
+ /* fall through */
case 2: set->sig[1] = v.sig[2] | (((long)v.sig[3]) << 32 );
+ /* fall through */
case 1: set->sig[0] = v.sig[0] | (((long)v.sig[1]) << 32 );
}
#else
--
2.20.1
--
Cheers,
Stephen Rothwell
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2019-04-16 7:29 [PATCH] kernel/compat.c: mark expected switch fall-throughs Stephen Rothwell
2019-04-16 8:32 ` Arnd Bergmann
2019-04-16 8:53 ` Stephen Rothwell
2019-04-16 9:14 ` Arnd Bergmann
2019-05-15 5:23 Stephen Rothwell
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