By default, sparse assumes a 64bit machine when compiled on x86-64
and 32bit when compiled on anything else.
This can of course create all sort of problems when this doesn't
correspond to the target's machine size, like issuing false
warnings like: 'shift too big (32) for type unsigned long' or
is 64bit while sparse was compiled on a 32bit machine, or worse,
to not emit legitimate warnings.
Fix this by passing the appropriate -m32/-m64 flag to sparse.
Signed-off-by: Luc Van Oostenryck <[email protected]>
---
arch/riscv/Makefile | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 76e958a54..cb2502e4c 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -71,6 +71,8 @@ KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)
# architectures. It's faster to have GCC emit only aligned accesses.
KBUILD_CFLAGS += $(call cc-option,-mstrict-align)
+CHECKFLAGS += -m$(BITS)
+
head-y := arch/riscv/kernel/head.o
core-y += arch/riscv/kernel/ arch/riscv/mm/
--
2.17.0
On Mon, May 28, 2018 at 06:35:05PM +0200, Luc Van Oostenryck wrote:
> By default, sparse assumes a 64bit machine when compiled on x86-64
> and 32bit when compiled on anything else.
>
> This can of course create all sort of problems when this doesn't
> correspond to the target's machine size, like issuing false
> warnings like: 'shift too big (32) for type unsigned long' or
> is 64bit while sparse was compiled on a 32bit machine, or worse,
> to not emit legitimate warnings.
>
> Fix this by passing the appropriate -m32/-m64 flag to sparse.
Can we please move this to the common Kbuild code using the
CONFIG_64BIT syombol? This really should not need boiler plate in
every architecture.
2018-05-29 15:11 GMT+09:00 Christoph Hellwig <[email protected]>:
> On Mon, May 28, 2018 at 06:35:05PM +0200, Luc Van Oostenryck wrote:
>> By default, sparse assumes a 64bit machine when compiled on x86-64
>> and 32bit when compiled on anything else.
>>
>> This can of course create all sort of problems when this doesn't
>> correspond to the target's machine size, like issuing false
>> warnings like: 'shift too big (32) for type unsigned long' or
>> is 64bit while sparse was compiled on a 32bit machine, or worse,
>> to not emit legitimate warnings.
>>
>> Fix this by passing the appropriate -m32/-m64 flag to sparse.
>
> Can we please move this to the common Kbuild code using the
> CONFIG_64BIT syombol? This really should not need boiler plate in
> every architecture.
I agree.
Luc did so for -mbig/little-endian:
https://patchwork.kernel.org/patch/10433957/
We should do likewise for -m32/64.
--
Best Regards
Masahiro Yamada
On Mon, 28 May 2018 23:14:20 PDT (-0700), [email protected] wrote:
> 2018-05-29 15:11 GMT+09:00 Christoph Hellwig <[email protected]>:
>> On Mon, May 28, 2018 at 06:35:05PM +0200, Luc Van Oostenryck wrote:
>>> By default, sparse assumes a 64bit machine when compiled on x86-64
>>> and 32bit when compiled on anything else.
>>>
>>> This can of course create all sort of problems when this doesn't
>>> correspond to the target's machine size, like issuing false
>>> warnings like: 'shift too big (32) for type unsigned long' or
>>> is 64bit while sparse was compiled on a 32bit machine, or worse,
>>> to not emit legitimate warnings.
>>>
>>> Fix this by passing the appropriate -m32/-m64 flag to sparse.
>>
>> Can we please move this to the common Kbuild code using the
>> CONFIG_64BIT syombol? This really should not need boiler plate in
>> every architecture.
>
>
> I agree.
>
> Luc did so for -mbig/little-endian:
> https://patchwork.kernel.org/patch/10433957/
>
> We should do likewise for -m32/64.
Sorry for being a bit slow here, but I like the idea of making the 32/64-bit
issue generic as it seems like it'll be necessary for every port. Looking
through the patch for big/little-endian I did notice:
* RISC-V compilers set "__riscv_xlen" to the length of an X (integer) register
in bits.
* RISC-V compilers define "__riscv", and it doesn't appear we inform sparse
about that.
These two might not be that interesting, but we do already have some cases
where we're checking for __riscv_xlen in Linux. I've yet to successfully use
sparse, but adding at least
CHECKFLAGS += -D__riscv
seems reasonable, and possibly also some sort of
ifeq ($(CONFIG_ARCH_RV64I),y)
CHECKFLAGS += -D__riscv_xlen=64
else
CHECKFLAGS += -D__riscv_xlen=32
fi
might be necessary. We strive to follow the generic rules for ABI-related
stuff like __LP64__ but I don't think there's any generic mapping for XLEN.
Similarly there's "__riscv_flen" and "__riscv_float_abi_*", but those are less
likely to be used by the kernel so they're probably not worth worrying about
for now.
There's also a bunch of other RISC-V macros, the only one of which we're
currently using is "__riscv_muldiv" (and that's in a manner that's unlikely to
trigger any sort of static analysis). Between a lack of Kconfig options and a
glibc port we're essentially mandating IMA right now, so these probably don't
matter.
Thanks!
On Thu, May 31, 2018 at 05:09:21AM -0700, Palmer Dabbelt wrote:
> On Mon, 28 May 2018 23:14:20 PDT (-0700), [email protected] wrote:
> > 2018-05-29 15:11 GMT+09:00 Christoph Hellwig <[email protected]>:
> > > On Mon, May 28, 2018 at 06:35:05PM +0200, Luc Van Oostenryck wrote:
> > > > By default, sparse assumes a 64bit machine when compiled on x86-64
> > > > and 32bit when compiled on anything else.
> > > >
> > > > This can of course create all sort of problems when this doesn't
> > > > correspond to the target's machine size, like issuing false
> > > > warnings like: 'shift too big (32) for type unsigned long' or
> > > > is 64bit while sparse was compiled on a 32bit machine, or worse,
> > > > to not emit legitimate warnings.
> > > >
> > > > Fix this by passing the appropriate -m32/-m64 flag to sparse.
> > >
> > > Can we please move this to the common Kbuild code using the
> > > CONFIG_64BIT syombol? This really should not need boiler plate in
> > > every architecture.
> >
> >
> > I agree.
> >
> > Luc did so for -mbig/little-endian:
> > https://patchwork.kernel.org/patch/10433957/
> >
> > We should do likewise for -m32/64.
>
> Sorry for being a bit slow here, but I like the idea of making the
> 32/64-bit issue generic as it seems like it'll be necessary for
> every port.
Sure, Christophe asked it too.
I've sent a new version doing it once and for all for all archs
but I forgot to CC you:
https://lkml.org/lkml/2018/5/30/948
> Looking through the patch for big/little-endian I did
> notice:
>
> * RISC-V compilers set "__riscv_xlen" to the length of an X
> (integer) register in bits.
> * RISC-V compilers define "__riscv", and it doesn't appear we inform
> sparse about that.
>
> These two might not be that interesting, but we do already have some
> cases where we're checking for __riscv_xlen in Linux. I've yet to
> successfully use sparse, but adding at least
>
> CHECKFLAGS += -D__riscv
>
> seems reasonable,
Sure (but I don't see a dependency in the kernel (yet)).
> and possibly also some sort of
>
> ifeq ($(CONFIG_ARCH_RV64I),y)
> CHECKFLAGS += -D__riscv_xlen=64
> else
> CHECKFLAGS += -D__riscv_xlen=32
> fi
>
> might be necessary.
Yes, this one is really needed.
I'll send a patch for this one and __riscv.
> We strive to follow the generic rules for
> ABI-related stuff like __LP64__ but I don't think there's any
> generic mapping for XLEN. Similarly there's "__riscv_flen" and
> "__riscv_float_abi_*", but those are less likely to be used by the
> kernel so they're probably not worth worrying about for now.
Yes, I agree.
Note that sparse will define __LP64__ (and _LP64) when in -m64 mode.
> There's also a bunch of other RISC-V macros, the only one of which
> we're currently using is "__riscv_muldiv" (and that's in a manner
> that's unlikely to trigger any sort of static analysis). Between a
> lack of Kconfig options and a glibc port we're essentially mandating
> IMA right now, so these probably don't matter.
Yes, I just saw. I think also it's better to leave it so for now.
And if it becomes more used, then better to infer it from the compiler
than harcoding it.
Regards,
-- Luc
On Thu, 31 May 2018 08:35:54 PDT (-0700), [email protected] wrote:
> On Thu, May 31, 2018 at 05:09:21AM -0700, Palmer Dabbelt wrote:
>> On Mon, 28 May 2018 23:14:20 PDT (-0700), [email protected] wrote:
>> > 2018-05-29 15:11 GMT+09:00 Christoph Hellwig <[email protected]>:
>> > > On Mon, May 28, 2018 at 06:35:05PM +0200, Luc Van Oostenryck wrote:
>> > > > By default, sparse assumes a 64bit machine when compiled on x86-64
>> > > > and 32bit when compiled on anything else.
>> > > >
>> > > > This can of course create all sort of problems when this doesn't
>> > > > correspond to the target's machine size, like issuing false
>> > > > warnings like: 'shift too big (32) for type unsigned long' or
>> > > > is 64bit while sparse was compiled on a 32bit machine, or worse,
>> > > > to not emit legitimate warnings.
>> > > >
>> > > > Fix this by passing the appropriate -m32/-m64 flag to sparse.
>> > >
>> > > Can we please move this to the common Kbuild code using the
>> > > CONFIG_64BIT syombol? This really should not need boiler plate in
>> > > every architecture.
>> >
>> >
>> > I agree.
>> >
>> > Luc did so for -mbig/little-endian:
>> > https://patchwork.kernel.org/patch/10433957/
>> >
>> > We should do likewise for -m32/64.
>>
>> Sorry for being a bit slow here, but I like the idea of making the
>> 32/64-bit issue generic as it seems like it'll be necessary for
>> every port.
>
> Sure, Christophe asked it too.
> I've sent a new version doing it once and for all for all archs
> but I forgot to CC you:
> https://lkml.org/lkml/2018/5/30/948
>
>> Looking through the patch for big/little-endian I did
>> notice:
>>
>> * RISC-V compilers set "__riscv_xlen" to the length of an X
>> (integer) register in bits.
>> * RISC-V compilers define "__riscv", and it doesn't appear we inform
>> sparse about that.
>>
>> These two might not be that interesting, but we do already have some
>> cases where we're checking for __riscv_xlen in Linux. I've yet to
>> successfully use sparse, but adding at least
>>
>> CHECKFLAGS += -D__riscv
>>
>> seems reasonable,
>
> Sure (but I don't see a dependency in the kernel (yet)).
>
>> and possibly also some sort of
>>
>> ifeq ($(CONFIG_ARCH_RV64I),y)
>> CHECKFLAGS += -D__riscv_xlen=64
>> else
>> CHECKFLAGS += -D__riscv_xlen=32
>> fi
>>
>> might be necessary.
>
> Yes, this one is really needed.
> I'll send a patch for this one and __riscv.
>
>> We strive to follow the generic rules for
>> ABI-related stuff like __LP64__ but I don't think there's any
>> generic mapping for XLEN. Similarly there's "__riscv_flen" and
>> "__riscv_float_abi_*", but those are less likely to be used by the
>> kernel so they're probably not worth worrying about for now.
>
> Yes, I agree.
> Note that sparse will define __LP64__ (and _LP64) when in -m64 mode.
>
>> There's also a bunch of other RISC-V macros, the only one of which
>> we're currently using is "__riscv_muldiv" (and that's in a manner
>> that's unlikely to trigger any sort of static analysis). Between a
>> lack of Kconfig options and a glibc port we're essentially mandating
>> IMA right now, so these probably don't matter.
>
> Yes, I just saw. I think also it's better to leave it so for now.
> And if it becomes more used, then better to infer it from the compiler
> than harcoding it.
Makes sense. Thanks for the work!