riscv: fix detection of toolchain Zihintpause support

It is not sufficient to check if a toolchain supports a particular
extension without checking if the linker supports that extension
too. For example, Clang 15 supports Zihintpause but GNU bintutils
2.35.2 does not, leading build errors like so:

riscv64-linux-gnu-ld: -march=rv64i2p0_m2p0_a2p0_c2p0_zihintpause2p0: Invalid or unknown z ISA extension: 'zihintpause'

Add a TOOLCHAIN_HAS_ZIHINTPAUSE which checks if each of the compiler,
assembler and linker support the extension. Replace the ifdef in the
vdso with one depending on this new symbol.

Fixes: 8eb060e101 ("arch/riscv: add Zihintpause support")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20221006173520.1785507-3-conor@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/Kconfig

@@ -425,6 +425,13 @@ config RISCV_ISA_ZICBOM
 
 	   If you don't know what to do here, say Y.
 
+config TOOLCHAIN_HAS_ZIHINTPAUSE
+	bool
+	default y
+	depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zihintpause)
+	depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zihintpause)
+	depends on LLD_VERSION >= 150000 || LD_VERSION >= 23600
+
 config FPU
 	bool "FPU support"
 	default y

arch/riscv/Makefile

@@ -60,8 +60,7 @@ riscv-march-$(toolchain-need-zicsr-zifencei) := $(riscv-march-y)_zicsr_zifencei
 riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZICBOM) := $(riscv-march-y)_zicbom
 
 # Check if the toolchain supports Zihintpause extension
-toolchain-supports-zihintpause := $(call cc-option-yn, -march=$(riscv-march-y)_zihintpause)
-riscv-march-$(toolchain-supports-zihintpause) := $(riscv-march-y)_zihintpause
+riscv-march-$(CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE) := $(riscv-march-y)_zihintpause
 
 KBUILD_CFLAGS += -march=$(subst fd,,$(riscv-march-y))
 KBUILD_AFLAGS += -march=$(riscv-march-y)

arch/riscv/include/asm/vdso/processor.h

@@ -21,7 +21,7 @@ static inline void cpu_relax(void)
 		 * Reduce instruction retirement.
 		 * This assumes the PC changes.
 		 */
-#ifdef __riscv_zihintpause
+#ifdef CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE
 		__asm__ __volatile__ ("pause");
 #else
 		/* Encoding of the pause instruction */