riscv/purgatory: Omit use of bin2c

The .incbin assembler directive is much faster than bin2c + $(CC).

Do similar refactoring as in commit 4c0f032d49 ("s390/purgatory:
Omit use of bin2c").

Please note the .quad directive matches to size_t in C (both 8 byte)
because the purgatory is compiled only for the 64-bit kernel.
(KEXEC_FILE depends on 64BIT).

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20220625223438.835408-2-masahiroy@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/Kconfig

@@ -494,7 +494,6 @@ config KEXEC_FILE
 
 config ARCH_HAS_KEXEC_PURGATORY
 	def_bool KEXEC_FILE
-	select BUILD_BIN2C
 	depends on CRYPTO=y
 	depends on CRYPTO_SHA256=y
 

arch/riscv/purgatory/.gitignore

@@ -1,4 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
 purgatory.chk
 purgatory.ro
-kexec-purgatory.c

arch/riscv/purgatory/Makefile

@@ -84,12 +84,6 @@ $(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
 $(obj)/purgatory.chk: $(obj)/purgatory.ro FORCE
 		$(call if_changed,ld)
 
-targets += kexec-purgatory.c
-
-quiet_cmd_bin2c = BIN2C   $@
-      cmd_bin2c = $(objtree)/scripts/bin2c kexec_purgatory < $< > $@
-
-$(obj)/kexec-purgatory.c: $(obj)/purgatory.ro $(obj)/purgatory.chk FORCE
-	$(call if_changed,bin2c)
+$(obj)/kexec-purgatory.o: $(obj)/purgatory.ro $(obj)/purgatory.chk
 
 obj-y += kexec-purgatory.o

arch/riscv/purgatory/kexec-purgatory.S

@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+	.section .rodata, "a"
+
+	.align	8
+kexec_purgatory:
+	.globl	kexec_purgatory
+	.incbin	"arch/riscv/purgatory/purgatory.ro"
+.Lkexec_purgatroy_end:
+
+	.align	8
+kexec_purgatory_size:
+	.globl	kexec_purgatory_size
+	.quad	.Lkexec_purgatroy_end - kexec_purgatory

scripts/remove-stale-files

@@ -40,6 +40,8 @@ if [ -n "${building_out_of_srctree}" ]; then
 	done
 fi
 
+rm -f arch/riscv/purgatory/kexec-purgatory.c
+
 rm -f scripts/extract-cert
 
 rm -f arch/x86/purgatory/kexec-purgatory.c