LinuxLists.cc - [PATCH v1] powerpc: Make setjmp/longjump signature standard

2020-03-27 10:09:20

Subject: [PATCH v1] powerpc: Make setjmp/longjump signature standard

2020-03-27 17:11:50

Subject: Re: [PATCH v1] powerpc: Make setjmp/longjump signature standard

On Fri, Mar 27, 2020 at 3:08 AM Clement Courbet <[email protected]> wrote:
>
> Declaring setjmp()/longjmp() as taking longs makes the signature
> non-standard, and makes clang complain. In the past, this has been
> worked around by adding -ffreestanding to the compile flags.
>
> The implementation looks like it only ever propagates the value
> (in longjmp) or sets it to 1 (in setjmp), and we only call longjmp
> with integer parameters.
>
> This allows removing -ffreestanding from the compilation flags.
>
> Context:
> https://lore.kernel.org/patchwork/patch/1214060
> https://lore.kernel.org/patchwork/patch/1216174
>
> Signed-off-by: Clement Courbet <[email protected]>

Hi Clement, thanks for the patch! Would you mind sending a V2 that
included a similar fix to arch/powerpc/xmon/Makefile?

For context, this was the original patch:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=aea447141c7e7824b81b49acd1bc78
which was then modified to:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c9029ef9c95765e7b63c4d9aa780674447db1ec0

So on your V2, if you include in the commit message, the line:

Fixes c9029ef9c957 ("powerpc: Avoid clang warnings around setjmp and longjmp")

then that will help our LTS branch maintainers back port it to the
appropriate branches.

>
> ---
> arch/powerpc/include/asm/setjmp.h | 6 ++++--
> arch/powerpc/kexec/Makefile | 3 ---
> 2 files changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/setjmp.h b/arch/powerpc/include/asm/setjmp.h
> index e9f81bb3f83b..84bb0d140d59 100644
> --- a/arch/powerpc/include/asm/setjmp.h
> +++ b/arch/powerpc/include/asm/setjmp.h
> @@ -7,7 +7,9 @@
>
> #define JMP_BUF_LEN 23
>
> -extern long setjmp(long *) __attribute__((returns_twice));
> -extern void longjmp(long *, long) __attribute__((noreturn));
> +typedef long *jmp_buf;
> +
> +extern int setjmp(jmp_buf env) __attribute__((returns_twice));
> +extern void longjmp(jmp_buf env, int val) __attribute__((noreturn));
>
> #endif /* _ASM_POWERPC_SETJMP_H */
> diff --git a/arch/powerpc/kexec/Makefile b/arch/powerpc/kexec/Makefile
> index 378f6108a414..86380c69f5ce 100644
> --- a/arch/powerpc/kexec/Makefile
> +++ b/arch/powerpc/kexec/Makefile
> @@ -3,9 +3,6 @@
> # Makefile for the linux kernel.
> #
>
> -# Avoid clang warnings around longjmp/setjmp declarations
> -CFLAGS_crash.o += -ffreestanding
> -
> obj-y += core.o crash.o core_$(BITS).o
>
> obj-$(CONFIG_PPC32) += relocate_32.o
> --
> 2.25.1.696.g5e7596f4ac-goog
>

--
Thanks,
~Nick Desaulniers

2020-03-27 17:28:00

by Nathan Chancellor

[permalink] [raw]

Subject: Re: [PATCH v1] powerpc: Make setjmp/longjump signature standard

On Fri, Mar 27, 2020 at 10:10:44AM -0700, Nick Desaulniers wrote:
> On Fri, Mar 27, 2020 at 3:08 AM Clement Courbet <[email protected]> wrote:
> >
> > Declaring setjmp()/longjmp() as taking longs makes the signature
> > non-standard, and makes clang complain. In the past, this has been
> > worked around by adding -ffreestanding to the compile flags.
> >
> > The implementation looks like it only ever propagates the value
> > (in longjmp) or sets it to 1 (in setjmp), and we only call longjmp
> > with integer parameters.
> >
> > This allows removing -ffreestanding from the compilation flags.
> >
> > Context:
> > https://lore.kernel.org/patchwork/patch/1214060
> > https://lore.kernel.org/patchwork/patch/1216174
> >
> > Signed-off-by: Clement Courbet <[email protected]>

Thanks for fixing this properly, not really sure why I did not think of
this in the first place. I guess my thought was the warning makes it
seem like clang is going to ignore the kernel's implementation of
setjmp/longjmp but I can't truly remember.

> Hi Clement, thanks for the patch! Would you mind sending a V2 that
> included a similar fix to arch/powerpc/xmon/Makefile?

Agreed.

> For context, this was the original patch:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=aea447141c7e7824b81b49acd1bc78
> which was then modified to:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c9029ef9c95765e7b63c4d9aa780674447db1ec0
>
> So on your V2, if you include in the commit message, the line:
>
> Fixes c9029ef9c957 ("powerpc: Avoid clang warnings around setjmp and longjmp")
>
> then that will help our LTS branch maintainers back port it to the
> appropriate branches.

The tags should be:

Cc: [email protected] # v4.14+
Fixes: c9029ef9c957 ("powerpc: Avoid clang warnings around setjmp and longjmp")

that way it explicitly gets picked up for stable, rather than Sasha's
AUTOSEL process, which could miss it.

With the xmon/Makefile -ffreestanding removed and the tags updated,
consider this:

Reviewed-by: Nathan Chancellor <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>

Cheers,
Nathan

2020-03-27 17:47:33

by Christophe Leroy

[permalink] [raw]

Subject: Re: [PATCH v1] powerpc: Make setjmp/longjump signature standard

Subject line, change longjump to longjmp

Le 27/03/2020 à 11:07, Clement Courbet a écrit :
> Declaring setjmp()/longjmp() as taking longs makes the signature
> non-standard, and makes clang complain. In the past, this has been
> worked around by adding -ffreestanding to the compile flags.
>
> The implementation looks like it only ever propagates the value
> (in longjmp) or sets it to 1 (in setjmp), and we only call longjmp
> with integer parameters.
>
> This allows removing -ffreestanding from the compilation flags.
>
> Context:
> https://lore.kernel.org/patchwork/patch/1214060
> https://lore.kernel.org/patchwork/patch/1216174
>
> Signed-off-by: Clement Courbet <[email protected]>
> ---
> arch/powerpc/include/asm/setjmp.h | 6 ++++--
> arch/powerpc/kexec/Makefile | 3 ---
> 2 files changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/setjmp.h b/arch/powerpc/include/asm/setjmp.h
> index e9f81bb3f83b..84bb0d140d59 100644
> --- a/arch/powerpc/include/asm/setjmp.h
> +++ b/arch/powerpc/include/asm/setjmp.h
> @@ -7,7 +7,9 @@
>
> #define JMP_BUF_LEN 23
>
> -extern long setjmp(long *) __attribute__((returns_twice));
> -extern void longjmp(long *, long) __attribute__((noreturn));
> +typedef long *jmp_buf;

Do we need that new opaque typedef ? Why not just keep long * ?

> +
> +extern int setjmp(jmp_buf env) __attribute__((returns_twice));
> +extern void longjmp(jmp_buf env, int val) __attribute__((noreturn));
>
> #endif /* _ASM_POWERPC_SETJMP_H */
> diff --git a/arch/powerpc/kexec/Makefile b/arch/powerpc/kexec/Makefile
> index 378f6108a414..86380c69f5ce 100644
> --- a/arch/powerpc/kexec/Makefile
> +++ b/arch/powerpc/kexec/Makefile
> @@ -3,9 +3,6 @@
> # Makefile for the linux kernel.
> #
>
> -# Avoid clang warnings around longjmp/setjmp declarations
> -CFLAGS_crash.o += -ffreestanding
> -
> obj-y += core.o crash.o core_$(BITS).o
>
> obj-$(CONFIG_PPC32) += relocate_32.o
>

Christophe

2020-03-27 18:27:57

by Nathan Chancellor

[permalink] [raw]

Subject: Re: [PATCH v1] powerpc: Make setjmp/longjump signature standard

On Fri, Mar 27, 2020 at 06:45:21PM +0100, Christophe Leroy wrote:
> Subject line, change longjump to longjmp
>
> Le 27/03/2020 ? 11:07, Clement Courbet a ?crit?:
> > Declaring setjmp()/longjmp() as taking longs makes the signature
> > non-standard, and makes clang complain. In the past, this has been
> > worked around by adding -ffreestanding to the compile flags.
> >
> > The implementation looks like it only ever propagates the value
> > (in longjmp) or sets it to 1 (in setjmp), and we only call longjmp
> > with integer parameters.
> >
> > This allows removing -ffreestanding from the compilation flags.
> >
> > Context:
> > https://lore.kernel.org/patchwork/patch/1214060
> > https://lore.kernel.org/patchwork/patch/1216174
> >
> > Signed-off-by: Clement Courbet <[email protected]>
> > ---
> > arch/powerpc/include/asm/setjmp.h | 6 ++++--
> > arch/powerpc/kexec/Makefile | 3 ---
> > 2 files changed, 4 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/setjmp.h b/arch/powerpc/include/asm/setjmp.h
> > index e9f81bb3f83b..84bb0d140d59 100644
> > --- a/arch/powerpc/include/asm/setjmp.h
> > +++ b/arch/powerpc/include/asm/setjmp.h
> > @@ -7,7 +7,9 @@
> > #define JMP_BUF_LEN 23
> > -extern long setjmp(long *) __attribute__((returns_twice));
> > -extern void longjmp(long *, long) __attribute__((noreturn));
> > +typedef long *jmp_buf;
>
> Do we need that new opaque typedef ? Why not just keep long * ?

Yes, otherwise the warning comes back:

In file included from arch/powerpc/kexec/crash.c:25:
arch/powerpc/include/asm/setjmp.h:10:12: error: declaration of built-in function 'setjmp' requires the declaration of the 'jmp_buf' type, commonly provided in the header <setjmp.h>. [-Werror,-Wincomplete-setjmp-declaration]
extern int setjmp(long *env) __attribute__((returns_twice));
^
arch/powerpc/include/asm/setjmp.h:11:13: error: declaration of built-in function 'longjmp' requires the declaration of the 'jmp_buf' type, commonly provided in the header <setjmp.h>. [-Werror,-Wincomplete-setjmp-declaration]
extern void longjmp(long *env, int val) __attribute__((noreturn));
^
2 errors generated.

> > +
> > +extern int setjmp(jmp_buf env) __attribute__((returns_twice));
> > +extern void longjmp(jmp_buf env, int val) __attribute__((noreturn));
> > #endif /* _ASM_POWERPC_SETJMP_H */
> > diff --git a/arch/powerpc/kexec/Makefile b/arch/powerpc/kexec/Makefile
> > index 378f6108a414..86380c69f5ce 100644
> > --- a/arch/powerpc/kexec/Makefile
> > +++ b/arch/powerpc/kexec/Makefile
> > @@ -3,9 +3,6 @@
> > # Makefile for the linux kernel.
> > #
> > -# Avoid clang warnings around longjmp/setjmp declarations
> > -CFLAGS_crash.o += -ffreestanding
> > -
> > obj-y += core.o crash.o core_$(BITS).o
> > obj-$(CONFIG_PPC32) += relocate_32.o
> >
>
> Christophe

2020-03-30 06:45:42

by Clement Courbet

[permalink] [raw]

Subject: [PATCH v1] powerpc: Make setjmp/longjump signature standard

Thanks you all for the comments. Everything addressed, plus the array vs
pointer suggestion from Segher Boessenkool on the other thread, which
is only cosmetic and does not change anything wrt behaviour.

2020-03-30 06:46:09

by Clement Courbet

[permalink] [raw]

Subject: [PATCH v2] powerpc: Make setjmp/longjmp signature standard

Declaring setjmp()/longjmp() as taking longs makes the signature
non-standard, and makes clang complain. In the past, this has been
worked around by adding -ffreestanding to the compile flags.

The implementation looks like it only ever propagates the value
(in longjmp) or sets it to 1 (in setjmp), and we only call longjmp
with integer parameters.

This allows removing -ffreestanding from the compilation flags.

Context:
https://lore.kernel.org/patchwork/patch/1214060
https://lore.kernel.org/patchwork/patch/1216174

Signed-off-by: Clement Courbet <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>

---

v2:
Use and array type as suggested by Segher Boessenkool
Cc: [email protected] # v4.14+
Fixes: c9029ef9c957 ("powerpc: Avoid clang warnings around setjmp and longjmp")
---
arch/powerpc/include/asm/setjmp.h | 6 ++++--
arch/powerpc/kexec/Makefile | 3 ---
arch/powerpc/xmon/Makefile | 3 ---
3 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/setjmp.h b/arch/powerpc/include/asm/setjmp.h
index e9f81bb3f83b..f798e80e4106 100644
--- a/arch/powerpc/include/asm/setjmp.h
+++ b/arch/powerpc/include/asm/setjmp.h
@@ -7,7 +7,9 @@

#define JMP_BUF_LEN 23

-extern long setjmp(long *) __attribute__((returns_twice));
-extern void longjmp(long *, long) __attribute__((noreturn));
+typedef long jmp_buf[JMP_BUF_LEN];
+
+extern int setjmp(jmp_buf env) __attribute__((returns_twice));
+extern void longjmp(jmp_buf env, int val) __attribute__((noreturn));

#endif /* _ASM_POWERPC_SETJMP_H */
diff --git a/arch/powerpc/kexec/Makefile b/arch/powerpc/kexec/Makefile
index 378f6108a414..86380c69f5ce 100644
--- a/arch/powerpc/kexec/Makefile
+++ b/arch/powerpc/kexec/Makefile
@@ -3,9 +3,6 @@
# Makefile for the linux kernel.
#

-# Avoid clang warnings around longjmp/setjmp declarations
-CFLAGS_crash.o += -ffreestanding
-
obj-y += core.o crash.o core_$(BITS).o

obj-$(CONFIG_PPC32) += relocate_32.o
diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
index c3842dbeb1b7..6f9cccea54f3 100644
--- a/arch/powerpc/xmon/Makefile
+++ b/arch/powerpc/xmon/Makefile
@@ -1,9 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
# Makefile for xmon

-# Avoid clang warnings around longjmp/setjmp declarations
-subdir-ccflags-y := -ffreestanding
-
GCOV_PROFILE := n
KCOV_INSTRUMENT := n
UBSAN_SANITIZE := n
--
2.26.0.rc2.310.g2932bb562d-goog

2020-03-30 07:58:34

by Nathan Chancellor

[permalink] [raw]

Subject: Re: [PATCH v2] powerpc: Make setjmp/longjmp signature standard

On Mon, Mar 30, 2020 at 08:43:19AM +0200, Clement Courbet wrote:
> Declaring setjmp()/longjmp() as taking longs makes the signature
> non-standard, and makes clang complain. In the past, this has been
> worked around by adding -ffreestanding to the compile flags.
>
> The implementation looks like it only ever propagates the value
> (in longjmp) or sets it to 1 (in setjmp), and we only call longjmp
> with integer parameters.
>
> This allows removing -ffreestanding from the compilation flags.
>
> Context:
> https://lore.kernel.org/patchwork/patch/1214060
> https://lore.kernel.org/patchwork/patch/1216174
>
> Signed-off-by: Clement Courbet <[email protected]>
> Reviewed-by: Nathan Chancellor <[email protected]>
> Tested-by: Nathan Chancellor <[email protected]>
>
> ---
>
> v2:
> Use and array type as suggested by Segher Boessenkool
> Cc: [email protected] # v4.14+
> Fixes: c9029ef9c957 ("powerpc: Avoid clang warnings around setjmp and longjmp")

Actual diff itself looks good but these two tags need to be above your
signoff to be included in the final changelog. Not sure if Michael will
want a v3 with that or if it can manually be done when applying.

Cheers,
Nathan

2020-03-30 08:04:39

by Clement Courbet

[permalink] [raw]

Subject: [PATCH v3] powerpc: Make setjmp/longjmp signature standard

Declaring setjmp()/longjmp() as taking longs makes the signature
non-standard, and makes clang complain. In the past, this has been
worked around by adding -ffreestanding to the compile flags.

The implementation looks like it only ever propagates the value
(in longjmp) or sets it to 1 (in setjmp), and we only call longjmp
with integer parameters.

This allows removing -ffreestanding from the compilation flags.

Context:
https://lore.kernel.org/patchwork/patch/1214060
https://lore.kernel.org/patchwork/patch/1216174

Signed-off-by: Clement Courbet <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Cc: [email protected] # v4.14+
Fixes: c9029ef9c957 ("powerpc: Avoid clang warnings around setjmp and longjmp")

---

v2:
Use and array type as suggested by Segher Boessenkool
Add fix tags.

v3:
Properly place tags.
---
arch/powerpc/include/asm/setjmp.h | 6 ++++--
arch/powerpc/kexec/Makefile | 3 ---
arch/powerpc/xmon/Makefile | 3 ---
3 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/setjmp.h b/arch/powerpc/include/asm/setjmp.h
index e9f81bb3f83b..f798e80e4106 100644
--- a/arch/powerpc/include/asm/setjmp.h
+++ b/arch/powerpc/include/asm/setjmp.h
@@ -7,7 +7,9 @@

#define JMP_BUF_LEN 23

-extern long setjmp(long *) __attribute__((returns_twice));
-extern void longjmp(long *, long) __attribute__((noreturn));
+typedef long jmp_buf[JMP_BUF_LEN];
+
+extern int setjmp(jmp_buf env) __attribute__((returns_twice));
+extern void longjmp(jmp_buf env, int val) __attribute__((noreturn));

#endif /* _ASM_POWERPC_SETJMP_H */
diff --git a/arch/powerpc/kexec/Makefile b/arch/powerpc/kexec/Makefile
index 378f6108a414..86380c69f5ce 100644
--- a/arch/powerpc/kexec/Makefile
+++ b/arch/powerpc/kexec/Makefile
@@ -3,9 +3,6 @@
# Makefile for the linux kernel.
#

-# Avoid clang warnings around longjmp/setjmp declarations
-CFLAGS_crash.o += -ffreestanding
-
obj-y += core.o crash.o core_$(BITS).o

obj-$(CONFIG_PPC32) += relocate_32.o
diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
index c3842dbeb1b7..6f9cccea54f3 100644
--- a/arch/powerpc/xmon/Makefile
+++ b/arch/powerpc/xmon/Makefile
@@ -1,9 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
# Makefile for xmon

-# Avoid clang warnings around longjmp/setjmp declarations
-subdir-ccflags-y := -ffreestanding
-
GCOV_PROFILE := n
KCOV_INSTRUMENT := n
UBSAN_SANITIZE := n
--
2.26.0.rc2.310.g2932bb562d-goog

2020-03-30 16:21:43

by Nick Desaulniers

[permalink] [raw]

Subject: Re: [PATCH v3] powerpc: Make setjmp/longjmp signature standard

On Mon, Mar 30, 2020 at 1:04 AM Clement Courbet <[email protected]> wrote:
>
> Declaring setjmp()/longjmp() as taking longs makes the signature
> non-standard, and makes clang complain. In the past, this has been
> worked around by adding -ffreestanding to the compile flags.
>
> The implementation looks like it only ever propagates the value
> (in longjmp) or sets it to 1 (in setjmp), and we only call longjmp
> with integer parameters.
>
> This allows removing -ffreestanding from the compilation flags.
>
> Context:
> https://lore.kernel.org/patchwork/patch/1214060
> https://lore.kernel.org/patchwork/patch/1216174
>
> Signed-off-by: Clement Courbet <[email protected]>
> Reviewed-by: Nathan Chancellor <[email protected]>
> Tested-by: Nathan Chancellor <[email protected]>
> Cc: [email protected] # v4.14+
> Fixes: c9029ef9c957 ("powerpc: Avoid clang warnings around setjmp and longjmp")

Third time's a charm (for patches that tackle this warning). Thanks
for following up on this cleanup!
Reviewed-by: Nick Desaulniers <[email protected]>
Tested-by: Nick Desaulniers <[email protected]>

The extent of my testing was compile testing with Clang.

>
> ---
>
> v2:
> Use and array type as suggested by Segher Boessenkool
> Add fix tags.
>
> v3:
> Properly place tags.
> ---
> arch/powerpc/include/asm/setjmp.h | 6 ++++--
> arch/powerpc/kexec/Makefile | 3 ---
> arch/powerpc/xmon/Makefile | 3 ---
> 3 files changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/setjmp.h b/arch/powerpc/include/asm/setjmp.h
> index e9f81bb3f83b..f798e80e4106 100644
> --- a/arch/powerpc/include/asm/setjmp.h
> +++ b/arch/powerpc/include/asm/setjmp.h
> @@ -7,7 +7,9 @@
>
> #define JMP_BUF_LEN 23
>
> -extern long setjmp(long *) __attribute__((returns_twice));
> -extern void longjmp(long *, long) __attribute__((noreturn));
> +typedef long jmp_buf[JMP_BUF_LEN];
> +
> +extern int setjmp(jmp_buf env) __attribute__((returns_twice));
> +extern void longjmp(jmp_buf env, int val) __attribute__((noreturn));
>
> #endif /* _ASM_POWERPC_SETJMP_H */
> diff --git a/arch/powerpc/kexec/Makefile b/arch/powerpc/kexec/Makefile
> index 378f6108a414..86380c69f5ce 100644
> --- a/arch/powerpc/kexec/Makefile
> +++ b/arch/powerpc/kexec/Makefile
> @@ -3,9 +3,6 @@
> # Makefile for the linux kernel.
> #
>
> -# Avoid clang warnings around longjmp/setjmp declarations
> -CFLAGS_crash.o += -ffreestanding
> -
> obj-y += core.o crash.o core_$(BITS).o
>
> obj-$(CONFIG_PPC32) += relocate_32.o
> diff --git a/arch/powerpc/xmon/Makefile b/arch/powerpc/xmon/Makefile
> index c3842dbeb1b7..6f9cccea54f3 100644
> --- a/arch/powerpc/xmon/Makefile
> +++ b/arch/powerpc/xmon/Makefile
> @@ -1,9 +1,6 @@
> # SPDX-License-Identifier: GPL-2.0
> # Makefile for xmon
>
> -# Avoid clang warnings around longjmp/setjmp declarations
> -subdir-ccflags-y := -ffreestanding
> -
> GCOV_PROFILE := n
> KCOV_INSTRUMENT := n
> UBSAN_SANITIZE := n
> --
> 2.26.0.rc2.310.g2932bb562d-goog
>

--
Thanks,
~Nick Desaulniers