diff mbox series

[1/4] kbuild: remove cc-option test of -fno-strict-overflow

Message ID 20200910135120.3527468-1-masahiroy@kernel.org
State New
Headers show
Series [1/4] kbuild: remove cc-option test of -fno-strict-overflow | expand

Commit Message

Masahiro Yamada Sept. 10, 2020, 1:51 p.m. UTC
The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.

Here is the godbolt:
https://godbolt.org/z/odq8h9

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 Makefile                          | 2 +-
 arch/arm64/kernel/vdso32/Makefile | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

Comments

Nathan Chancellor Sept. 10, 2020, 4:26 p.m. UTC | #1
On Thu, Sep 10, 2020 at 10:51:17PM +0900, Masahiro Yamada wrote:
> The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.
> 
> Here is the godbolt:
> https://godbolt.org/z/odq8h9
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Appeared in clang 3.0.0 in commit 6e50103acda2b918545f30141edeb991d766f2a4.

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> ---
> 
>  Makefile                          | 2 +-
>  arch/arm64/kernel/vdso32/Makefile | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 4b5a305e30d2..059b36f2ea53 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -922,7 +922,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
>  KBUILD_CFLAGS += $(call cc-disable-warning, maybe-uninitialized)
>  
>  # disable invalid "can't wrap" optimizations for signed / pointers
> -KBUILD_CFLAGS	+= $(call cc-option,-fno-strict-overflow)
> +KBUILD_CFLAGS	+= -fno-strict-overflow
>  
>  # clang sets -fmerge-all-constants by default as optimization, but this
>  # is non-conforming behavior for C and in fact breaks the kernel, so we
> diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> index d6adb4677c25..dfffd55175a3 100644
> --- a/arch/arm64/kernel/vdso32/Makefile
> +++ b/arch/arm64/kernel/vdso32/Makefile
> @@ -90,7 +90,7 @@ VDSO_CFLAGS  += -O2
>  # Some useful compiler-dependent flags from top-level Makefile
>  VDSO_CFLAGS += $(call cc32-option,-Wdeclaration-after-statement,)
>  VDSO_CFLAGS += $(call cc32-option,-Wno-pointer-sign)
> -VDSO_CFLAGS += $(call cc32-option,-fno-strict-overflow)
> +VDSO_CFLAGS += -fno-strict-overflow
>  VDSO_CFLAGS += $(call cc32-option,-Werror=strict-prototypes)
>  VDSO_CFLAGS += $(call cc32-option,-Werror=date-time)
>  VDSO_CFLAGS += $(call cc32-option,-Werror=incompatible-pointer-types)
> -- 
> 2.25.1
>
Nathan Chancellor Sept. 10, 2020, 4:33 p.m. UTC | #2
On Thu, Sep 10, 2020 at 10:51:18PM +0900, Masahiro Yamada wrote:
> The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.
> 
> Here is the godbolt:
> https://godbolt.org/z/8T4177
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

For what it's worth, the commit that introduced this block is going to
be reverted:

https://lore.kernel.org/mm-commits/20200903201518.JKrRS%25akpm@linux-foundation.org/

Regardless, it was introduced in LLVM 2.7.0 in commit
f9d41df0930986c52e198292cf875eb5d1761ece.

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> ---
> 
>  Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 059b36f2ea53..1b6abecc5cab 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -927,7 +927,7 @@ KBUILD_CFLAGS	+= -fno-strict-overflow
>  # clang sets -fmerge-all-constants by default as optimization, but this
>  # is non-conforming behavior for C and in fact breaks the kernel, so we
>  # need to disable it here generally.
> -KBUILD_CFLAGS	+= $(call cc-option,-fno-merge-all-constants)
> +KBUILD_CFLAGS	+= -fno-merge-all-constants
>  
>  # for gcc -fno-merge-all-constants disables everything, but it is fine
>  # to have actual conforming behavior enabled.
> -- 
> 2.25.1
>
Nathan Chancellor Sept. 10, 2020, 4:37 p.m. UTC | #3
On Thu, Sep 10, 2020 at 10:51:19PM +0900, Masahiro Yamada wrote:
> The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.
> 
> Here is the godbolt:
> https://godbolt.org/z/59cK6o
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

This flag is technically ignored by clang (see commit
05b0798916f01690b5903302e51f3136274e291f) but that obviously does not
matter for the sake of this.

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> ---
> 
>  Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 1b6abecc5cab..5102c89d3167 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -934,7 +934,7 @@ KBUILD_CFLAGS	+= -fno-merge-all-constants
>  KBUILD_CFLAGS	+= $(call cc-option,-fmerge-constants)
>  
>  # Make sure -fstack-check isn't enabled (like gentoo apparently did)
> -KBUILD_CFLAGS  += $(call cc-option,-fno-stack-check,)
> +KBUILD_CFLAGS  += -fno-stack-check
>  
>  # conserve stack if available
>  KBUILD_CFLAGS   += $(call cc-option,-fconserve-stack)
> -- 
> 2.25.1
>
Masahiro Yamada Sept. 10, 2020, 4:41 p.m. UTC | #4
On Fri, Sep 11, 2020 at 1:33 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Thu, Sep 10, 2020 at 10:51:18PM +0900, Masahiro Yamada wrote:
> > The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.
> >
> > Here is the godbolt:
> > https://godbolt.org/z/8T4177
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
>
> For what it's worth, the commit that introduced this block is going to
> be reverted:
>
> https://lore.kernel.org/mm-commits/20200903201518.JKrRS%25akpm@linux-foundation.org/


My bad - you are right.
This hunk has already gone by Nick's patch.

Thanks.



> Regardless, it was introduced in LLVM 2.7.0 in commit
> f9d41df0930986c52e198292cf875eb5d1761ece.
>
> Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
>
> > ---
> >
> >  Makefile | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/Makefile b/Makefile
> > index 059b36f2ea53..1b6abecc5cab 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -927,7 +927,7 @@ KBUILD_CFLAGS     += -fno-strict-overflow
> >  # clang sets -fmerge-all-constants by default as optimization, but this
> >  # is non-conforming behavior for C and in fact breaks the kernel, so we
> >  # need to disable it here generally.
> > -KBUILD_CFLAGS        += $(call cc-option,-fno-merge-all-constants)
> > +KBUILD_CFLAGS        += -fno-merge-all-constants
> >
> >  # for gcc -fno-merge-all-constants disables everything, but it is fine
> >  # to have actual conforming behavior enabled.
> > --
> > 2.25.1
> >
>
> --
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Nathan Chancellor Sept. 10, 2020, 4:43 p.m. UTC | #5
On Thu, Sep 10, 2020 at 10:51:20PM +0900, Masahiro Yamada wrote:
> The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.
> 
> Here is the godbolt:
> https://godbolt.org/z/xvjcMa
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Introduced in clang 3.5.0, see commit
4f43e554081ecac149fe360bee6eef2ed7dab8ea in LLVM.

Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>

> ---
> 
>  Makefile                          | 2 +-
>  arch/arm64/kernel/vdso32/Makefile | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 5102c89d3167..1d7c58684fda 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -940,7 +940,7 @@ KBUILD_CFLAGS  += -fno-stack-check
>  KBUILD_CFLAGS   += $(call cc-option,-fconserve-stack)
>  
>  # Prohibit date/time macros, which would make the build non-deterministic
> -KBUILD_CFLAGS   += $(call cc-option,-Werror=date-time)
> +KBUILD_CFLAGS   += -Werror=date-time
>  
>  # enforce correct pointer usage
>  KBUILD_CFLAGS   += $(call cc-option,-Werror=incompatible-pointer-types)
> diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> index dfffd55175a3..1feb4f8e556e 100644
> --- a/arch/arm64/kernel/vdso32/Makefile
> +++ b/arch/arm64/kernel/vdso32/Makefile
> @@ -92,7 +92,7 @@ VDSO_CFLAGS += $(call cc32-option,-Wdeclaration-after-statement,)
>  VDSO_CFLAGS += $(call cc32-option,-Wno-pointer-sign)
>  VDSO_CFLAGS += -fno-strict-overflow
>  VDSO_CFLAGS += $(call cc32-option,-Werror=strict-prototypes)
> -VDSO_CFLAGS += $(call cc32-option,-Werror=date-time)
> +VDSO_CFLAGS += -Werror=date-time
>  VDSO_CFLAGS += $(call cc32-option,-Werror=incompatible-pointer-types)
>  
>  # The 32-bit compiler does not provide 128-bit integers, which are used in
> -- 
> 2.25.1
>
Will Deacon Sept. 11, 2020, 3:22 p.m. UTC | #6
On Thu, Sep 10, 2020 at 10:51:17PM +0900, Masahiro Yamada wrote:
> The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.
> 
> Here is the godbolt:
> https://godbolt.org/z/odq8h9
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
>  Makefile                          | 2 +-
>  arch/arm64/kernel/vdso32/Makefile | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)

This, and the other patch (4/4 -- I didn't see 2 or 3), look good to me.
Are you taking them via the kbuild tree, or shall I queue them in the arm64
tree? Please just let me know what you prefer.

Will
Masahiro Yamada Sept. 14, 2020, 12:51 p.m. UTC | #7
Hi Will,

On Sat, Sep 12, 2020 at 12:22 AM Will Deacon <will@kernel.org> wrote:
>
> On Thu, Sep 10, 2020 at 10:51:17PM +0900, Masahiro Yamada wrote:
> > The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.
> >
> > Here is the godbolt:
> > https://godbolt.org/z/odq8h9
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > ---
> >
> >  Makefile                          | 2 +-
> >  arch/arm64/kernel/vdso32/Makefile | 2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
>
> This, and the other patch (4/4 -- I didn't see 2 or 3), look good to me.
> Are you taking them via the kbuild tree, or shall I queue them in the arm64
> tree? Please just let me know what you prefer.
>
> Will


I will apply all to the kbuild tree.
Your Ack is appreciated.

Thanks.
Will Deacon Sept. 14, 2020, 1:20 p.m. UTC | #8
On Mon, Sep 14, 2020 at 09:51:31PM +0900, Masahiro Yamada wrote:
> On Sat, Sep 12, 2020 at 12:22 AM Will Deacon <will@kernel.org> wrote:
> > On Thu, Sep 10, 2020 at 10:51:17PM +0900, Masahiro Yamada wrote:
> > > The minimal compiler versions, GCC 4.9 and Clang 10 support this flag.
> > >
> > > Here is the godbolt:
> > > https://godbolt.org/z/odq8h9
> > >
> > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > ---
> > >
> > >  Makefile                          | 2 +-
> > >  arch/arm64/kernel/vdso32/Makefile | 2 +-
> > >  2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > This, and the other patch (4/4 -- I didn't see 2 or 3), look good to me.
> > Are you taking them via the kbuild tree, or shall I queue them in the arm64
> > tree? Please just let me know what you prefer.
> 
> I will apply all to the kbuild tree.
> Your Ack is appreciated.

For both:

Acked-by: Will Deacon <will@kernel.org>

Will
diff mbox series

Patch

diff --git a/Makefile b/Makefile
index 4b5a305e30d2..059b36f2ea53 100644
--- a/Makefile
+++ b/Makefile
@@ -922,7 +922,7 @@  KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
 KBUILD_CFLAGS += $(call cc-disable-warning, maybe-uninitialized)
 
 # disable invalid "can't wrap" optimizations for signed / pointers
-KBUILD_CFLAGS	+= $(call cc-option,-fno-strict-overflow)
+KBUILD_CFLAGS	+= -fno-strict-overflow
 
 # clang sets -fmerge-all-constants by default as optimization, but this
 # is non-conforming behavior for C and in fact breaks the kernel, so we
diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
index d6adb4677c25..dfffd55175a3 100644
--- a/arch/arm64/kernel/vdso32/Makefile
+++ b/arch/arm64/kernel/vdso32/Makefile
@@ -90,7 +90,7 @@  VDSO_CFLAGS  += -O2
 # Some useful compiler-dependent flags from top-level Makefile
 VDSO_CFLAGS += $(call cc32-option,-Wdeclaration-after-statement,)
 VDSO_CFLAGS += $(call cc32-option,-Wno-pointer-sign)
-VDSO_CFLAGS += $(call cc32-option,-fno-strict-overflow)
+VDSO_CFLAGS += -fno-strict-overflow
 VDSO_CFLAGS += $(call cc32-option,-Werror=strict-prototypes)
 VDSO_CFLAGS += $(call cc32-option,-Werror=date-time)
 VDSO_CFLAGS += $(call cc32-option,-Werror=incompatible-pointer-types)