> 2023年4月6日 22:19，Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx> 写道：
>
>
>
>> 2023年4月6日 22:09，Nathan Chancellor <nathan@xxxxxxxxxx> 写道：
>>
>> On Thu, Apr 06, 2023 at 09:59:45PM +0100, Jiaxun Yang wrote:
>>>
>>>
>>>> 2023年4月6日 21:09，Nathan Chancellor <nathan@xxxxxxxxxx> 写道：
>>>>
>>>> When building allnoconfig with clang after commit de34007751aa ("MIPS:
>>>> generic: Enable all CPUs supported by virt board in Kconfig"), the
>>>> following error occurs:
>>>>
>>>> error: unknown target CPU 'r4600'
>>>> note: valid target CPU values are: mips1, mips2, mips3, mips4, mips5, mips32, mips32r2, mips32r3, mips32r5, mips32r6, mips64, mips64r2, mips64r3, mips64r5, mips64r6, octeon, octeon+, p5600
>>>>
>>>> Working around that, there are similar errors for 'loongson2e' and
>>>> 'loongson2f'.
>>>>
>>>> These CPUs are not supported in clang/LLVM, so do not select support for
>>>> them in MIPS_GENERIC_KERNEL when building with clang.
>>>>
>>>> Fixes: de34007751aa ("MIPS: generic: Enable all CPUs supported by virt board in Kconfig")
>>>> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
>>>
>>> Thanks for the patch.
>>>
>>> Actually there is no need for any special support for those CPUs.
>>> We should be able to build those kernels with -march=mips3.
>>>
>>> I think something like:
>>>
>>> --- a/arch/mips/Makefile
>>> +++ b/arch/mips/Makefile
>>> @@ -150,7 +150,7 @@ cflags-y += $(call cc-option,-Wa$(comma)-mno-fix-loongson3-llsc,)
>>> #
>>> cflags-$(CONFIG_CPU_R3000) += -march=r3000
>>> cflags-$(CONFIG_CPU_R4300) += -march=r4300 -Wa,--trap
>>> -cflags-$(CONFIG_CPU_R4X00) += -march=r4600 -Wa,--trap
>>> +cflags-$(CONFIG_CPU_R4X00) += $(call cc-option,-march=r4600,-march=mips3) -Wa,--trap
>>> cflags-$(CONFIG_CPU_TX49XX) += -march=r4600 -Wa,--trap
>>> cflags-$(CONFIG_CPU_MIPS32_R1) += -march=mips32 -Wa,--trap
>>> cflags-$(CONFIG_CPU_MIPS32_R2) += -march=mips32r2 -Wa,--trap
>>> @@ -181,8 +181,8 @@ endif
>>> cflags-$(CONFIG_CAVIUM_CN63XXP1) += -Wa,-mfix-cn63xxp1
>>> cflags-$(CONFIG_CPU_BMIPS) += -march=mips32 -Wa,-mips32 -Wa,--trap
>>>
>>> -cflags-$(CONFIG_CPU_LOONGSON2E) += -march=loongson2e -Wa,--trap
>>> -cflags-$(CONFIG_CPU_LOONGSON2F) += -march=loongson2f -Wa,--trap
>>> +cflags-$(CONFIG_CPU_LOONGSON2E) += $(call cc-option,-march=loongson2e,-march=mips3) -Wa,--trap
>>> +cflags-$(CONFIG_CPU_LOONGSON2F) += $(call cc-option,-march=loongson2f,-march=mips3) -Wa,--trap
>>> # Some -march= flags enable MMI instructions, and GCC complains about that
>>> # support being enabled alongside -msoft-float. Thus explicitly disable MMI.
>>> cflags-$(CONFIG_CPU_LOONGSON2EF) += $(call cc-option,-mno-loongson-mmi)
>>>
>>> Will make them build.
>>
>> Thank you for taking a look and the suggestion! I applied it and tried
>> to build allnoconfig but I get
>>
>> error: ABI 'o32' is not supported on CPU 'mips3'
>>
>> immediately, which could certainly be a bug in clang...
>
> There is a clang patch:
> https://reviews.llvm.org/D146269
>
> I’ve seen this warning with CONFIG_MIPS32_O32 enabled, but I think that’s not the case for allnoconfig...
Oh I see, it’s trying to build a o32 kernel.
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1579,7 +1579,7 @@ config CPU_R4300
config CPU_R4X00
bool "R4x00"
depends on SYS_HAS_CPU_R4X00
- select CPU_SUPPORTS_32BIT_KERNEL
+ select CPU_SUPPORTS_32BIT_KERNEL if CC_SUPPORTS_O32_WITH_64BIT_ARCH
select CPU_SUPPORTS_64BIT_KERNEL
select CPU_SUPPORTS_HUGEPAGES
help
@@ -1743,9 +1743,11 @@ config CPU_MIPS32_R5_XPA
if CPU_LOONGSON2F
config CPU_NOP_WORKAROUNDS
bool
+ depends on $(cc-option,-Wa,-mfix-loongson2f-nop)
config CPU_JUMP_WORKAROUNDS
bool
+ depends on $(cc-option,-Wa,-mfix-loongson2f-jump)
config CPU_LOONGSON2F_WORKAROUNDS
bool "Loongson 2F Workarounds"
@@ -2497,6 +2499,7 @@ config CPU_HAS_SYNC
# "MIPS R4400MC Errata, Processor Revision 1.0", erratum #5
config CPU_DADDI_WORKAROUNDS
bool
+ depends on $(cc-option,-mno-daddi)
# Work around certain R4000 CPU errata (as implemented by GCC):
#
@@ -2518,6 +2521,7 @@ config CPU_DADDI_WORKAROUNDS
# erratum #52
config CPU_R4000_WORKAROUNDS
bool
+ depends on $(cc-option,-mfix-r4000)
select CPU_R4400_WORKAROUNDS
# Work around certain R4400 CPU errata (as implemented by GCC):
@@ -2528,6 +2532,7 @@ config CPU_R4000_WORKAROUNDS
# "MIPS R4400MC Errata, Processor Revision 2.0 & 3.0", erratum #4
config CPU_R4400_WORKAROUNDS
bool
+ depends on $(cc-option,-mfix-r4400)
config CPU_R4X00_BUGS64
bool
@@ -3174,6 +3179,7 @@ config COMPAT
config MIPS32_O32
bool "Kernel support for o32 binaries"
depends on 64BIT
+ depends on CC_SUPPORTS_O32_WITH_64BIT_ARCH
select ARCH_WANT_OLD_COMPAT_IPC
select COMPAT
select MIPS32_COMPAT
@@ -3206,6 +3212,9 @@ config CC_HAS_MNO_BRANCH_LIKELY
config CC_HAS_BROKEN_INLINE_COMPAT_BRANCH
def_bool y if CC_IS_CLANG
+config CC_SUPPORTS_O32_WITH_64BIT_ARCH
+ def_bool y if $(cc-option,-march=mips3 -mabi=o32)
+
menu "Power management options"
config ARCH_HIBERNATION_POSSIBLE
This will prevent clang build 32bit kernel in case it doesn’t support o32 ABI with 64bit CPU.
Thanks
Jiaxun
>
> Thanks
> Jiaxun
>
>>
>> Cheers,
>> Nathan
