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 <[email protected]>
---
linux-2.6.21-rc7-mm2-root/arch/x86_64/kernel/head64.c | 7 -------
linux-2.6.21-rc7-mm2-root/include/asm-x86_64/page.h | 9 +++++++++
2 files changed, 9 insertions(+), 7 deletions(-)
diff -puN arch/x86_64/kernel/head64.c~x86_64-warn-if-kernel-is-not-2MB-aligned arch/x86_64/kernel/head64.c
--- linux-2.6.21-rc7-mm2/arch/x86_64/kernel/head64.c~x86_64-warn-if-kernel-is-not-2MB-aligned 2007-05-07 16:17:21.000000000 +0530
+++ linux-2.6.21-rc7-mm2-root/arch/x86_64/kernel/head64.c 2007-05-07 16:25:42.000000000 +0530
@@ -62,13 +62,6 @@ void __init x86_64_start_kernel(char * r
{
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();
diff -puN include/asm-x86_64/page.h~x86_64-warn-if-kernel-is-not-2MB-aligned include/asm-x86_64/page.h
--- linux-2.6.21-rc7-mm2/include/asm-x86_64/page.h~x86_64-warn-if-kernel-is-not-2MB-aligned 2007-05-07 16:24:16.000000000 +0530
+++ linux-2.6.21-rc7-mm2-root/include/asm-x86_64/page.h 2007-05-07 16:25:29.000000000 +0530
@@ -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 0xffffffff80000000
#define __PAGE_OFFSET 0xffff810000000000
_
-
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