arches: lib: add main_decl.h for main() declaration

It is silly to have a single header to declare the main()
symbol, however some of the arches provided it while
lib/bootblock.c relied on the arch headers to declare it. Just
move the declaration into its own header file and utilize it.

Change-Id: I743b4c286956ae047c17fe46241b699feca73628
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/13681
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)

src/arch/arm/include/arch/stages.h

@@ -16,7 +16,7 @@
 #ifndef __ARCH_STAGES_H
 #define __ARCH_STAGES_H
 
-extern void main(void);
+#include <main_decl.h>
 
 void stage_entry(void);
 

src/arch/arm64/include/arch/stages.h

@@ -17,8 +17,7 @@
 #define __ARCH_STAGES_H
 
 #include <stdint.h>
-
-extern void main(void);
+#include <main_decl.h>
 
 void stage_entry(void);
 

src/arch/mips/include/arch/stages.h

@@ -16,7 +16,7 @@
 #ifndef __MIPS_ARCH_STAGES_H
 #define __MIPS_ARCH_STAGES_H
 
-extern void main(void);
+#include <main_decl.h>
 
 void stage_entry(void);
 

src/arch/riscv/include/arch/stages.h

@@ -16,7 +16,7 @@
 #ifndef __ARCH_STAGES_H
 #define __ARCH_STAGES_H
 
-extern void main(void);
+#include <main_decl.h>
 
 void stage_entry(void) __attribute__((section(".text.stage_entry")));
 

src/include/bootblock_common.h

@@ -16,6 +16,8 @@
 #ifndef __BOOTBLOCK_COMMON_H
 #define __BOOTBLOCK_COMMON_H
 
+#include <main_decl.h>
+
 /* These are defined as weak no-ops that can be overridden by mainboard/SoC. */
 void bootblock_mainboard_early_init(void);
 void bootblock_mainboard_init(void);

src/include/bootstate.h

@@ -20,6 +20,10 @@
 #include <stdlib.h>
 #include <stddef.h>
 #include <stdint.h>
+/* Only declare main() when in ramstage. */
+#if ENV_RAMSTAGE
+#include <main_decl.h>
+#endif
 
 /* Control debugging of the boot state machine. */
 #define BOOT_STATE_DEBUG 0
@@ -168,11 +172,6 @@ int boot_state_unblock(boot_state_t state, boot_state_sequence_t seq);
 void boot_state_current_block(void);
 void boot_state_current_unblock(void);
 
-#if ENV_RAMSTAGE
-/* Entry into the boot state machine. */
-void main(void);
-#endif
-
 /* In order to schedule boot state callbacks at compile-time specify the
  * entries in an array using the BOOT_STATE_INIT_ENTRIES and
  * BOOT_STATE_INIT_ENTRY macros below. */

src/include/main_decl.h

@@ -0,0 +1,6 @@
+#ifndef _MAIN_DECL_H_
+#define _MAIN_DECL_H_
+
+void main(void);
+
+#endif

src/soc/intel/apollolake/include/soc/bootblock.h

@@ -3,6 +3,4 @@
 #include <arch/cpu.h>
 
 void asmlinkage bootblock_c_entry(void);
-/* provide prototype for lib/bootblock.c main as workaround */
-void main(void);
 #endif