[19/19] arm64: vdso32: Enable Clang Compilation
diff mbox series

Message ID 20200213161614.23246-20-vincenzo.frascino@arm.com
State New
Headers show
Series
  • Introduce common headers
Related show

Commit Message

Vincenzo Frascino Feb. 13, 2020, 4:16 p.m. UTC
Enable Clang Compilation for the vdso32 library.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
---
 arch/arm64/kernel/vdso32/Makefile | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Nathan Chancellor Feb. 13, 2020, 6:44 p.m. UTC | #1
On Thu, Feb 13, 2020 at 04:16:14PM +0000, Vincenzo Frascino wrote:
> Enable Clang Compilation for the vdso32 library.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> ---
>  arch/arm64/kernel/vdso32/Makefile | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> index 04df57b43cb1..209639101044 100644
> --- a/arch/arm64/kernel/vdso32/Makefile
> +++ b/arch/arm64/kernel/vdso32/Makefile
> @@ -11,8 +11,10 @@ include $(srctree)/lib/vdso/Makefile
>  # Same as cc-*option, but using CC_COMPAT instead of CC
>  ifeq ($(CONFIG_CC_IS_CLANG), y)
>  CC_COMPAT ?= $(CC)
> +LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc

Well this is unfortunate :/

It looks like adding the --target flag to VDSO_LDFLAGS allows
clang to link the vDSO just fine although it does warn that -nostdinc
is unused:

clang-11: warning: argument unused during compilation: '-nostdinc'
[-Wunused-command-line-argument]

It would be nice if the logic of commit fe00e50b2db8 ("ARM: 8858/1:
vdso: use $(LD) instead of $(CC) to link VDSO") could be adopted here
but I get that this Makefile is its own beast :) at the very least, I
think that the --target flag should be added to VDSO_LDFLAGS so that gcc
is not a requirement for this but I am curious if you tried that already
and noticed any issues with it.

Cheers,
Nathan

>  else
>  CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
> +LD_COMPAT ?= $(CC_COMPAT)
>  endif
>  
>  cc32-option = $(call try-run,\
> @@ -171,7 +173,7 @@ quiet_cmd_vdsold_and_vdso_check = LD32    $@
>        cmd_vdsold_and_vdso_check = $(cmd_vdsold); $(cmd_vdso_check)
>  
>  quiet_cmd_vdsold = LD32    $@
> -      cmd_vdsold = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_LDFLAGS) \
> +      cmd_vdsold = $(LD_COMPAT) -Wp,-MD,$(depfile) $(VDSO_LDFLAGS) \
>                     -Wl,-T $(filter %.lds,$^) $(filter %.o,$^) -o $@
>  quiet_cmd_vdsocc = CC32    $@
>        cmd_vdsocc = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_CFLAGS) -c -o $@ $<
> -- 
> 2.25.0
>
Vincenzo Frascino Feb. 17, 2020, 12:26 p.m. UTC | #2
Hi Nathan,

On 13/02/2020 18:44, Nathan Chancellor wrote:
> On Thu, Feb 13, 2020 at 04:16:14PM +0000, Vincenzo Frascino wrote:
>> Enable Clang Compilation for the vdso32 library.

[...]

>> +LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
> 
> Well this is unfortunate :/
> 
> It looks like adding the --target flag to VDSO_LDFLAGS allows
> clang to link the vDSO just fine although it does warn that -nostdinc
> is unused:
> 
> clang-11: warning: argument unused during compilation: '-nostdinc'
> [-Wunused-command-line-argument]
>

This is why ended up in this "unfortunate" situation :) I wanted to avoid the
warning.

> It would be nice if the logic of commit fe00e50b2db8 ("ARM: 8858/1:
> vdso: use $(LD) instead of $(CC) to link VDSO") could be adopted here
> but I get that this Makefile is its own beast :) at the very least, I
> think that the --target flag should be added to VDSO_LDFLAGS so that gcc
> is not a requirement for this but I am curious if you tried that already
> and noticed any issues with it.
> 

--target is my preferred way as well, I can try to play another little bit with
the flags and see what I can come up with in the next version.

> Cheers,
> Nathan

[...]
Will Deacon Feb. 17, 2020, 4:46 p.m. UTC | #3
On Mon, Feb 17, 2020 at 12:26:16PM +0000, Vincenzo Frascino wrote:
> On 13/02/2020 18:44, Nathan Chancellor wrote:
> > On Thu, Feb 13, 2020 at 04:16:14PM +0000, Vincenzo Frascino wrote:
> >> Enable Clang Compilation for the vdso32 library.
> 
> [...]
> 
> >> +LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
> > 
> > Well this is unfortunate :/
> > 
> > It looks like adding the --target flag to VDSO_LDFLAGS allows
> > clang to link the vDSO just fine although it does warn that -nostdinc
> > is unused:
> > 
> > clang-11: warning: argument unused during compilation: '-nostdinc'
> > [-Wunused-command-line-argument]
> >
> 
> This is why ended up in this "unfortunate" situation :) I wanted to avoid the
> warning.
> 
> > It would be nice if the logic of commit fe00e50b2db8 ("ARM: 8858/1:
> > vdso: use $(LD) instead of $(CC) to link VDSO") could be adopted here
> > but I get that this Makefile is its own beast :) at the very least, I
> > think that the --target flag should be added to VDSO_LDFLAGS so that gcc
> > is not a requirement for this but I am curious if you tried that already
> > and noticed any issues with it.
> > 
> 
> --target is my preferred way as well, I can try to play another little bit with
> the flags and see what I can come up with in the next version.

Yes, please. I'd even prefer the warning rather than silently assuming that
a cross gcc is kicking around on the path.

Will
Ard Biesheuvel Feb. 17, 2020, 10:39 p.m. UTC | #4
On Mon, 17 Feb 2020 at 17:46, Will Deacon <will@kernel.org> wrote:
>
> On Mon, Feb 17, 2020 at 12:26:16PM +0000, Vincenzo Frascino wrote:
> > On 13/02/2020 18:44, Nathan Chancellor wrote:
> > > On Thu, Feb 13, 2020 at 04:16:14PM +0000, Vincenzo Frascino wrote:
> > >> Enable Clang Compilation for the vdso32 library.
> >
> > [...]
> >
> > >> +LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
> > >
> > > Well this is unfortunate :/
> > >
> > > It looks like adding the --target flag to VDSO_LDFLAGS allows
> > > clang to link the vDSO just fine although it does warn that -nostdinc
> > > is unused:
> > >
> > > clang-11: warning: argument unused during compilation: '-nostdinc'
> > > [-Wunused-command-line-argument]
> > >
> >
> > This is why ended up in this "unfortunate" situation :) I wanted to avoid the
> > warning.
> >
> > > It would be nice if the logic of commit fe00e50b2db8 ("ARM: 8858/1:
> > > vdso: use $(LD) instead of $(CC) to link VDSO") could be adopted here
> > > but I get that this Makefile is its own beast :) at the very least, I
> > > think that the --target flag should be added to VDSO_LDFLAGS so that gcc
> > > is not a requirement for this but I am curious if you tried that already
> > > and noticed any issues with it.
> > >
> >
> > --target is my preferred way as well, I can try to play another little bit with
> > the flags and see what I can come up with in the next version.
>
> Yes, please. I'd even prefer the warning rather than silently assuming that
> a cross gcc is kicking around on the path.
>

Doesn't Clang have -Qunused-arguments for that?
Vincenzo Frascino Feb. 18, 2020, 1:03 p.m. UTC | #5
On 17/02/2020 22:39, Ard Biesheuvel wrote:
> On Mon, 17 Feb 2020 at 17:46, Will Deacon <will@kernel.org> wrote:
>>
>> On Mon, Feb 17, 2020 at 12:26:16PM +0000, Vincenzo Frascino wrote:
>>> On 13/02/2020 18:44, Nathan Chancellor wrote:
>>>> On Thu, Feb 13, 2020 at 04:16:14PM +0000, Vincenzo Frascino wrote:
>>>>> Enable Clang Compilation for the vdso32 library.
>>>
>>> [...]
>>>
>>>>> +LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
>>>>
>>>> Well this is unfortunate :/
>>>>
>>>> It looks like adding the --target flag to VDSO_LDFLAGS allows
>>>> clang to link the vDSO just fine although it does warn that -nostdinc
>>>> is unused:
>>>>
>>>> clang-11: warning: argument unused during compilation: '-nostdinc'
>>>> [-Wunused-command-line-argument]
>>>>
>>>
>>> This is why ended up in this "unfortunate" situation :) I wanted to avoid the
>>> warning.
>>>
>>>> It would be nice if the logic of commit fe00e50b2db8 ("ARM: 8858/1:
>>>> vdso: use $(LD) instead of $(CC) to link VDSO") could be adopted here
>>>> but I get that this Makefile is its own beast :) at the very least, I
>>>> think that the --target flag should be added to VDSO_LDFLAGS so that gcc
>>>> is not a requirement for this but I am curious if you tried that already
>>>> and noticed any issues with it.
>>>>
>>>
>>> --target is my preferred way as well, I can try to play another little bit with
>>> the flags and see what I can come up with in the next version.
>>
>> Yes, please. I'd even prefer the warning rather than silently assuming that
>> a cross gcc is kicking around on the path.
>>
> 
> Doesn't Clang have -Qunused-arguments for that?
> 

Yes, this is exactly what I was looking for. Thanks Ard :)

Patch
diff mbox series

diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
index 04df57b43cb1..209639101044 100644
--- a/arch/arm64/kernel/vdso32/Makefile
+++ b/arch/arm64/kernel/vdso32/Makefile
@@ -11,8 +11,10 @@  include $(srctree)/lib/vdso/Makefile
 # Same as cc-*option, but using CC_COMPAT instead of CC
 ifeq ($(CONFIG_CC_IS_CLANG), y)
 CC_COMPAT ?= $(CC)
+LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
 else
 CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc
+LD_COMPAT ?= $(CC_COMPAT)
 endif
 
 cc32-option = $(call try-run,\
@@ -171,7 +173,7 @@  quiet_cmd_vdsold_and_vdso_check = LD32    $@
       cmd_vdsold_and_vdso_check = $(cmd_vdsold); $(cmd_vdso_check)
 
 quiet_cmd_vdsold = LD32    $@
-      cmd_vdsold = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_LDFLAGS) \
+      cmd_vdsold = $(LD_COMPAT) -Wp,-MD,$(depfile) $(VDSO_LDFLAGS) \
                    -Wl,-T $(filter %.lds,$^) $(filter %.o,$^) -o $@
 quiet_cmd_vdsocc = CC32    $@
       cmd_vdsocc = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_CFLAGS) -c -o $@ $<