MIPS: Implement ARCH_HAS_CC_CAN_LINK

The generic CC_CAN_LINK detection does not handle different byte orders
or ABIs. This may lead to userprogs which are not actually runnable on
the target kernel.

Use architecture-specific logic supporting byte orders instead.

Modern 64-bit toolchains default to a n32 libc, which are not
supported by all kernel configurations, as MIPS32_N32 is optional.
On 64-bit, test for a n32 ABI libc first and fall back to o64 and
o32 if necessary.

Link: https://lore.kernel.org/lkml/20260105100507-14db55e3-aa71-48bf-a6ac-33b186bd082f@linutronix.de/
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Author: t-8ch

arch/mips/Kconfig

@@ -4,6 +4,7 @@ config MIPS
 	default y
 	select ARCH_32BIT_OFF_T if !64BIT
 	select ARCH_BINFMT_ELF_STATE if MIPS_FP_SUPPORT
+	select ARCH_HAS_CC_CAN_LINK
 	select ARCH_HAS_CPU_CACHE_ALIASING
 	select ARCH_HAS_CPU_FINALIZE_INIT
 	select ARCH_HAS_CURRENT_STACK_POINTER
@@ -3125,6 +3126,33 @@ config CC_HAS_MNO_BRANCH_LIKELY
 config CC_HAS_BROKEN_INLINE_COMPAT_BRANCH
 	def_bool y if CC_IS_CLANG
 
+config ARCH_CC_CAN_LINK_N32
+	bool
+	default $(cc_can_link_user,-mabi=n32 -EL) if MIPS32_N32 && CPU_LITTLE_ENDIAN
+	default $(cc_can_link_user,-mabi=n32 -EB) if MIPS32_N32 && CPU_BIG_ENDIAN
+
+config ARCH_CC_CAN_LINK_N64
+	bool
+	default $(cc_can_link_user,-mabi=64 -EL) if 64BIT && CPU_LITTLE_ENDIAN
+	default $(cc_can_link_user,-mabi=64 -EB) if 64BIT && CPU_BIG_ENDIAN
+
+config ARCH_CC_CAN_LINK_O32
+	bool
+	default $(cc_can_link_user,-mabi=32 -EL) if (32BIT || MIPS32_O32) && CPU_LITTLE_ENDIAN
+	default $(cc_can_link_user,-mabi=32 -EB) if (32BIT || MIPS32_O32) && CPU_BIG_ENDIAN
+
+config ARCH_CC_CAN_LINK
+	def_bool ARCH_CC_CAN_LINK_N32 || ARCH_CC_CAN_LINK_N64 || ARCH_CC_CAN_LINK_O32
+
+config ARCH_USERFLAGS
+	string
+	default "-mabi=n32 -EL" if ARCH_CC_CAN_LINK_N32 && CPU_LITTLE_ENDIAN
+	default "-mabi=n32 -EB" if ARCH_CC_CAN_LINK_N32 && CPU_BIG_ENDIAN
+	default "-mabi=64 -EL" if ARCH_CC_CAN_LINK_N64 && CPU_LITTLE_ENDIAN
+	default "-mabi=64 -EB" if ARCH_CC_CAN_LINK_N64 && CPU_BIG_ENDIAN
+	default "-mabi=32 -EL" if ARCH_CC_CAN_LINK_O32 && CPU_LITTLE_ENDIAN
+	default "-mabi=32 -EB" if ARCH_CC_CAN_LINK_O32 && CPU_BIG_ENDIAN
+
 menu "Power management options"
 
 config ARCH_HIBERNATION_POSSIBLE