Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses

2017-04-13 Thread H. Peter Anvin 
On 04/13/17 16:14, Matthias Kaehlcke wrote:
> El Mon, Apr 03, 2017 at 04:01:58PM -0700 Matthias Kaehlcke ha dit:
> 
>> El Fri, Mar 17, 2017 at 04:50:19PM -0700 h...@zytor.com ha dit:
>>
>>> On March 16, 2017 5:15:16 PM PDT, Michael Davidson  wrote:
 Suppress clang warnings about potential unaliged accesses
 to members in packed structs. This gets rid of almost 10,000
 warnings about accesses to the ring 0 stack pointer in the TSS.

 Signed-off-by: Michael Davidson 
 ---
 arch/x86/Makefile | 5 +
 1 file changed, 5 insertions(+)

 diff --git a/arch/x86/Makefile b/arch/x86/Makefile
 index 894a8d18bf97..7f21703c475d 100644
 --- a/arch/x86/Makefile
 +++ b/arch/x86/Makefile
 @@ -128,6 +128,11 @@ endif
 KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args)
 endif

 +ifeq ($(cc-name),clang)
 +# Suppress clang warnings about potential unaligned accesses.
 +KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
 +endif
 +
 ifdef CONFIG_X86_X32
x32_ld_ok := $(call try-run,\
/bin/echo -e '1: .quad 1b' | \
>>>
>>> Why conditional on clang?
>>
>> My understanding is that this warning is clang specific, it is not
>> listed on https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
> 
> Actually this warning affects other platforms besides x86
> (e.g. arm64), I'll submit a patch that disables the warning on all
> platforms.
> 

Drop the ifeq ($(cc-name),clang).

You should assume that if you have to add one of those ifeq's then you
are doing something fundamentally wrong.

-hpa

Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses

2017-04-13 Thread Matthias Kaehlcke 
El Mon, Apr 03, 2017 at 04:01:58PM -0700 Matthias Kaehlcke ha dit:

> El Fri, Mar 17, 2017 at 04:50:19PM -0700 h...@zytor.com ha dit:
> 
> > On March 16, 2017 5:15:16 PM PDT, Michael Davidson  wrote:
> > >Suppress clang warnings about potential unaliged accesses
> > >to members in packed structs. This gets rid of almost 10,000
> > >warnings about accesses to the ring 0 stack pointer in the TSS.
> > >
> > >Signed-off-by: Michael Davidson 
> > >---
> > > arch/x86/Makefile | 5 +
> > > 1 file changed, 5 insertions(+)
> > >
> > >diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> > >index 894a8d18bf97..7f21703c475d 100644
> > >--- a/arch/x86/Makefile
> > >+++ b/arch/x86/Makefile
> > >@@ -128,6 +128,11 @@ endif
> > > KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args)
> > > endif
> > > 
> > >+ifeq ($(cc-name),clang)
> > >+# Suppress clang warnings about potential unaligned accesses.
> > >+KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
> > >+endif
> > >+
> > > ifdef CONFIG_X86_X32
> > >   x32_ld_ok := $(call try-run,\
> > >   /bin/echo -e '1: .quad 1b' | \
> > 
> > Why conditional on clang?
> 
> My understanding is that this warning is clang specific, it is not
> listed on https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html

Actually this warning affects other platforms besides x86
(e.g. arm64), I'll submit a patch that disables the warning on all
platforms.

Cheers

Matthias

Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses

2017-04-03 Thread Matthias Kaehlcke 
El Fri, Mar 17, 2017 at 04:50:19PM -0700 h...@zytor.com ha dit:

> On March 16, 2017 5:15:16 PM PDT, Michael Davidson  wrote:
> >Suppress clang warnings about potential unaliged accesses
> >to members in packed structs. This gets rid of almost 10,000
> >warnings about accesses to the ring 0 stack pointer in the TSS.
> >
> >Signed-off-by: Michael Davidson 
> >---
> > arch/x86/Makefile | 5 +
> > 1 file changed, 5 insertions(+)
> >
> >diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> >index 894a8d18bf97..7f21703c475d 100644
> >--- a/arch/x86/Makefile
> >+++ b/arch/x86/Makefile
> >@@ -128,6 +128,11 @@ endif
> > KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args)
> > endif
> > 
> >+ifeq ($(cc-name),clang)
> >+# Suppress clang warnings about potential unaligned accesses.
> >+KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
> >+endif
> >+
> > ifdef CONFIG_X86_X32
> > x32_ld_ok := $(call try-run,\
> > /bin/echo -e '1: .quad 1b' | \
> 
> Why conditional on clang?

My understanding is that this warning is clang specific, it is not
listed on https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html

Cheers

Matthias

Re: [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses

2017-03-17 Thread hpa 
On March 16, 2017 5:15:16 PM PDT, Michael Davidson  wrote:
>Suppress clang warnings about potential unaliged accesses
>to members in packed structs. This gets rid of almost 10,000
>warnings about accesses to the ring 0 stack pointer in the TSS.
>
>Signed-off-by: Michael Davidson 
>---
> arch/x86/Makefile | 5 +
> 1 file changed, 5 insertions(+)
>
>diff --git a/arch/x86/Makefile b/arch/x86/Makefile
>index 894a8d18bf97..7f21703c475d 100644
>--- a/arch/x86/Makefile
>+++ b/arch/x86/Makefile
>@@ -128,6 +128,11 @@ endif
> KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args)
> endif
> 
>+ifeq ($(cc-name),clang)
>+# Suppress clang warnings about potential unaligned accesses.
>+KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
>+endif
>+
> ifdef CONFIG_X86_X32
>   x32_ld_ok := $(call try-run,\
>   /bin/echo -e '1: .quad 1b' | \

Why conditional on clang?
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

[PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses

2017-03-16 Thread Michael Davidson 
Suppress clang warnings about potential unaliged accesses
to members in packed structs. This gets rid of almost 10,000
warnings about accesses to the ring 0 stack pointer in the TSS.

Signed-off-by: Michael Davidson 
---
 arch/x86/Makefile | 5 +
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 894a8d18bf97..7f21703c475d 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -128,6 +128,11 @@ endif
 KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args)
 endif
 
+ifeq ($(cc-name),clang)
+# Suppress clang warnings about potential unaligned accesses.
+KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
+endif
+
 ifdef CONFIG_X86_X32
x32_ld_ok := $(call try-run,\
/bin/echo -e '1: .quad 1b' | \
-- 
2.12.0.367.g23dc2f6d3c-goog