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Commit 069f11f9 authored by Vivek Goyal's avatar Vivek Goyal Committed by Linus Torvalds
Browse files

x86_64: display more intuitive error message if kernel is not 2MB aligned 



o x86_64 kernel needs to be compiled for 2MB aligned addresses. Currently
  we are using BUILD_BUG_ON() to warn the user if he has not done so. But
  looks like folks are not finding message very intutive and don't open
  the respective c file to find problem source. (Bug 8439)

arch/x86_64/kernel/head64.c: In function 'x86_64_start_kernel':
arch/x86_64/kernel/head64.c:70: error: size of array 'type name' is negative

o Using preprocessor directive #error to print a better message if
  CONFIG_PHYSICAL_START is not aligned to 2MB boundary.

Signed-off-by: default avatarVivek Goyal <vgoyal@in.ibm.com>
Cc: Andi Kleen <ak@suse.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6041b57c

arch/x86_64/kernel/head64.c

+0 −7
Original line number Diff line number Diff line
@@ -62,13 +62,6 @@ void __init x86_64_start_kernel(char * real_mode_data) 
{

	int i;



	/*

	 * Make sure kernel is aligned to 2MB address. Catching it at compile

	 * time is better. Change your config file and compile the kernel

	 * for a 2MB aligned address (CONFIG_PHYSICAL_START)

	 */

	BUILD_BUG_ON(CONFIG_PHYSICAL_START & (__KERNEL_ALIGN - 1));



	/* clear bss before set_intr_gate with early_idt_handler */

	clear_bss();

include/asm-x86_64/page.h

+9 −0
Original line number Diff line number Diff line
@@ -80,6 +80,15 @@ extern unsigned long phys_base; 
#define __PHYSICAL_START	CONFIG_PHYSICAL_START

#define __KERNEL_ALIGN		0x200000



/*

 * Make sure kernel is aligned to 2MB address. Catching it at compile

 * time is better. Change your config file and compile the kernel

 * for a 2MB aligned address (CONFIG_PHYSICAL_START)

 */

#if (CONFIG_PHYSICAL_START % __KERNEL_ALIGN) != 0

#error "CONFIG_PHYSICAL_START must be a multiple of 2MB"

#endif



#define __START_KERNEL		(__START_KERNEL_map + __PHYSICAL_START)

#define __START_KERNEL_map	_AC(0xffffffff80000000, UL)

#define __PAGE_OFFSET           _AC(0xffff810000000000, UL)