x86: make early printk selectable on 64-bit as well

Enable CONFIG_EMBEDDED to select CONFIG_EARLY_PRINTK on 64-bit as well.

saves ~2K:

   text    data     bss     dec     hex filename
   7290283 3672091 1907848 12870222         c4624e vmlinux.before
   7288373 3671795 1907848 12868016         c459b0 vmlinux.after

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/Kconfig.debug

@@ -6,7 +6,7 @@ config TRACE_IRQFLAGS_SUPPORT
 source "lib/Kconfig.debug"
 
 config EARLY_PRINTK
-	bool "Early printk" if EMBEDDED && DEBUG_KERNEL && X86_32
+	bool "Early printk" if EMBEDDED
 	default y
 	help
 	  Write kernel log output directly into the VGA buffer or to a serial

arch/x86/kernel/head64.c

@@ -58,8 +58,13 @@ void __init x86_64_start_kernel(char * real_mode_data)
 	/* Make NULL pointers segfault */
 	zap_identity_mappings();
 
-	for (i = 0; i < IDT_ENTRIES; i++)
+	for (i = 0; i < IDT_ENTRIES; i++) {
+#ifdef CONFIG_EARLY_PRINTK
 		set_intr_gate(i, &early_idt_handlers[i]);
+#else
+		set_intr_gate(i, early_idt_handler);
+#endif
+	}
 	load_idt((const struct desc_ptr *)&idt_descr);
 
 	early_printk("Kernel alive\n");

arch/x86/kernel/head_64.S

@@ -267,6 +267,7 @@ init_rsp:
 bad_address:
 	jmp bad_address
 
+#ifdef CONFIG_EARLY_PRINTK
 .macro early_idt_tramp first, last
 	.ifgt \last-\first
 	early_idt_tramp \first, \last-1
@@ -281,8 +282,10 @@ early_idt_handlers:
 	early_idt_tramp 64, 127
 	early_idt_tramp 128, 191
 	early_idt_tramp 192, 255
+#endif
 
 ENTRY(early_idt_handler)
+#ifdef CONFIG_EARLY_PRINTK
 	cmpl $2,early_recursion_flag(%rip)
 	jz  1f
 	incl early_recursion_flag(%rip)
@@ -311,8 +314,11 @@ ENTRY(early_idt_handler)
 	movq 8(%rsp),%rsi	# get rip again
 	call __print_symbol
 #endif
+#endif /* EARLY_PRINTK */
 1:	hlt
 	jmp 1b
+
+#ifdef CONFIG_EARLY_PRINTK
 early_recursion_flag:
 	.long 0
 
@@ -320,6 +326,7 @@ early_idt_msg:
 	.asciz "PANIC: early exception %02lx rip %lx:%lx error %lx cr2 %lx\n"
 early_idt_ripmsg:
 	.asciz "RIP %s\n"
+#endif /* CONFIG_EARLY_PRINTK */
 
 .balign PAGE_SIZE
 

include/asm-x86/kdebug.h

@@ -22,7 +22,6 @@ enum die_val {
 	DIE_PAGE_FAULT,
 };
 
-extern void early_printk(const char *fmt, ...) __attribute__((format(printf,1,2)));
 extern void printk_address(unsigned long address);
 extern void die(const char *,struct pt_regs *,long);
 extern int __must_check __die(const char *, struct pt_regs *, long);

include/linux/kernel.h

@@ -194,6 +194,9 @@ static inline int log_buf_read(int idx) { return 0; }
 static inline int log_buf_copy(char *dest, int idx, int len) { return 0; }
 #endif
 
+extern void __attribute__((format(printf, 1, 2)))
+	early_printk(const char *fmt, ...);
+
 unsigned long int_sqrt(unsigned long);
 
 extern int printk_ratelimit(void);

kernel/printk.c

@@ -36,6 +36,13 @@
 
 #include <asm/uaccess.h>
 
+/*
+ * Architectures can override it:
+ */
+void __attribute__((weak)) early_printk(const char *fmt, ...)
+{
+}
+
 #define __LOG_BUF_LEN	(1 << CONFIG_LOG_BUF_SHIFT)
 
 /* printk's without a loglevel use this.. */