| Message ID | 20180508113211.7026-1-stefan@agner.ch (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 08/05/18 12:32, Stefan Agner wrote: > Mixing asm and C code is not recommended in a naked function by > gcc and leads to an error when using clang: > drivers/bus/arm-cci.c:2107:2: error: non-ASM statement in naked > function is not supported > unreachable(); > ^ > > While the function is marked __naked it actually properly return > in asm. There is no need for the unreachable() call. The commit title is a bit out-of-date now (I guess it could just be something like "remove unnecessary unreachable()" now), but the rest looks OK to me - even GCC clearly doesn't expect anything beyond the asm to be reachable anyway since the lack of epilogue includes the lack of any compiler-generated return. I've checked that GCC 7.2 generates identical object files before and after, other than (for obvious reasons) the line numbers generated by WANT_WARN_ON_SLOWPATH for all the WARN()s appearing later in the file. Reviewed-by: Robin Murphy <robin.murphy@arm.com> > Suggested-by: Russell King <linux@arm.linux.org.uk> > Signed-off-by: Stefan Agner <stefan@agner.ch> > Acked-by: Nicolas Pitre <nico@linaro.org> > --- > drivers/bus/arm-cci.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c > index 443e4c3fd357..b8184a903583 100644 > --- a/drivers/bus/arm-cci.c > +++ b/drivers/bus/arm-cci.c > @@ -371,8 +371,6 @@ asmlinkage void __naked cci_enable_port_for_self(void) > [sizeof_struct_cpu_port] "i" (sizeof(struct cpu_port)), > [sizeof_struct_ace_port] "i" (sizeof(struct cci_ace_port)), > [offsetof_port_phys] "i" (offsetof(struct cci_ace_port, phys)) ); > - > - unreachable(); > } > > /** >
On 08.05.2018 14:19, Robin Murphy wrote: > On 08/05/18 12:32, Stefan Agner wrote: >> Mixing asm and C code is not recommended in a naked function by >> gcc and leads to an error when using clang: >> drivers/bus/arm-cci.c:2107:2: error: non-ASM statement in naked >> function is not supported >> unreachable(); >> ^ >> >> While the function is marked __naked it actually properly return >> in asm. There is no need for the unreachable() call. > > The commit title is a bit out-of-date now (I guess it could just be > something like "remove unnecessary unreachable()" now), but the rest > looks OK to me - even GCC clearly doesn't expect anything beyond the > asm to be reachable anyway since the lack of epilogue includes the > lack of any compiler-generated return. I've checked that GCC 7.2 > generates identical object files before and after, other than (for > obvious reasons) the line numbers generated by WANT_WARN_ON_SLOWPATH > for all the WARN()s appearing later in the file. Title: Oops, good catch! Will send a v3. Thanks for checking gcc. -- Stefan > > Reviewed-by: Robin Murphy <robin.murphy@arm.com> > >> Suggested-by: Russell King <linux@arm.linux.org.uk> >> Signed-off-by: Stefan Agner <stefan@agner.ch> >> Acked-by: Nicolas Pitre <nico@linaro.org> >> --- >> drivers/bus/arm-cci.c | 2 -- >> 1 file changed, 2 deletions(-) >> >> diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c >> index 443e4c3fd357..b8184a903583 100644 >> --- a/drivers/bus/arm-cci.c >> +++ b/drivers/bus/arm-cci.c >> @@ -371,8 +371,6 @@ asmlinkage void __naked cci_enable_port_for_self(void) >> [sizeof_struct_cpu_port] "i" (sizeof(struct cpu_port)), >> [sizeof_struct_ace_port] "i" (sizeof(struct cci_ace_port)), >> [offsetof_port_phys] "i" (offsetof(struct cci_ace_port, phys)) ); >> - >> - unreachable(); >> } >> /** >>
diff --git a/drivers/bus/arm-cci.c b/drivers/bus/arm-cci.c index 443e4c3fd357..b8184a903583 100644 --- a/drivers/bus/arm-cci.c +++ b/drivers/bus/arm-cci.c @@ -371,8 +371,6 @@ asmlinkage void __naked cci_enable_port_for_self(void) [sizeof_struct_cpu_port] "i" (sizeof(struct cpu_port)), [sizeof_struct_ace_port] "i" (sizeof(struct cci_ace_port)), [offsetof_port_phys] "i" (offsetof(struct cci_ace_port, phys)) ); - - unreachable(); } /**
Mixing asm and C code is not recommended in a naked function by gcc and leads to an error when using clang: drivers/bus/arm-cci.c:2107:2: error: non-ASM statement in naked function is not supported unreachable(); ^ While the function is marked __naked it actually properly return in asm. There is no need for the unreachable() call. Suggested-by: Russell King <linux@arm.linux.org.uk> Signed-off-by: Stefan Agner <stefan@agner.ch> Acked-by: Nicolas Pitre <nico@linaro.org> --- drivers/bus/arm-cci.c | 2 -- 1 file changed, 2 deletions(-)