x86-64: don't set the early IDT to point directly to 'early_idt_handler'

The code requires the use of the proper per-exception-vector stub
functions (set up as the early_idt_handlers[] array - note the 's') that
make sure to set up the error vector number.  This is true regardless of
whether CONFIG_EARLY_PRINTK is set or not.

Why? The stack offset for the comparison of __KERNEL_CS won't be right
otherwise, nor will the new check (from commit 8170e6bed465: "x86,
64bit: Use a #PF handler to materialize early mappings on demand") for
the page fault exception vector.

Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 3 insertions, 8 deletions

diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h
index 6f414ed88620..6fd3fd769796 100644
--- a/arch/x86/include/asm/proto.h
+++ b/arch/x86/include/asm/proto.h
@@ -5,8 +5,6 @@
 
 /* misc architecture specific prototypes */
 
-void early_idt_handler(void);
-
 void system_call(void);
 void syscall_init(void);
 
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 57334f4cd3af..2590025e52c2 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -159,13 +159,8 @@ void __init x86_64_start_kernel(char * real_mode_data)
         /* clear bss before set_intr_gate with early_idt_handler */
         clear_bss();
 
-        for (i = 0; i < NUM_EXCEPTION_VECTORS; i++) {
-#ifdef CONFIG_EARLY_PRINTK
+        for (i = 0; i < NUM_EXCEPTION_VECTORS; i++)
                 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);
 
         copy_bootdata(__va(real_mode_data));
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index d94f6d68be2a..b7de3b25adb5 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -336,6 +336,7 @@ early_idt_handlers:
         i = i + 1
         .endr
 
+/* This is global to keep gas from relaxing the jumps */
 ENTRY(early_idt_handler)
         cld
 
@@ -404,6 +405,7 @@ ENTRY(early_idt_handler)
         addq $16,%rsp           # drop vector number and error code
         decl early_recursion_flag(%rip)
         INTERRUPT_RETURN
+ENDPROC(early_idt_handler)
 
         __INITDATA