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

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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: Vivek Goyal <vgoyal@in.ibm.com>
Cc: Andi Kleen <ak@suse.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vivek Goyal 2007-05-10 22:22:15 -07:00 committed by Linus Torvalds
parent 6041b57c6c
commit 069f11f9d6
2 changed files with 9 additions and 7 deletions
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7
arch/x86_64/kernel/head64.c
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@ -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();

9
include/asm-x86_64/page.h
View File

@ -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)