RISC-V: Stop emitting attributes

The RISC-V ELF attributes don't contain any useful information.  New
toolchains ignore them, but they frequently trip up various older/mixed
toolchains.  So just turn them off.

Tested-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230223224605.6995-1-palmer@rivosinc.com
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/Makefile

@@ -84,6 +84,13 @@ endif
 # Avoid generating .eh_frame sections.
 KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
 
+# The RISC-V attributes frequently cause compatibility issues and provide no
+# information, so just turn them off.
+KBUILD_CFLAGS += $(call cc-option,-mno-riscv-attribute)
+KBUILD_AFLAGS += $(call cc-option,-mno-riscv-attribute)
+KBUILD_CFLAGS += $(call as-option,-Wa$(comma)-mno-arch-attr)
+KBUILD_AFLAGS += $(call as-option,-Wa$(comma)-mno-arch-attr)
+
 KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)
 KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax)
 

arch/riscv/kernel/compat_vdso/Makefile

@@ -14,6 +14,10 @@ COMPAT_LD := $(LD)
 COMPAT_CC_FLAGS := -march=rv32g -mabi=ilp32
 COMPAT_LD_FLAGS := -melf32lriscv
 
+# Disable attributes, as they're useless and break the build.
+COMPAT_CC_FLAGS += $(call cc-option,-mno-riscv-attribute)
+COMPAT_CC_FLAGS += $(call as-option,-Wa$(comma)-mno-arch-attr)
+
 # Files to link into the compat_vdso
 obj-compat_vdso = $(patsubst %, %.o, $(compat_vdso-syms)) note.o