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: 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>
diff --git a/include/asm-x86_64/page.h b/include/asm-x86_64/page.h
index dee632f..e327c83 100644
--- a/include/asm-x86_64/page.h
+++ b/include/asm-x86_64/page.h
@@ -80,6 +80,15 @@
#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)