[PATCH] 2.4.25: BUG(): Use guard page instead of page 0

Jason Uhlenkott
2004-02-18T22:13:03Z

The ia64 BUG macro deliberately writes to address 0 in order to
trigger a page fault and an Oops. This won't work if the process has
mapped something into page zero: We'll just print the "kernel BUG"
message and continue (after having stomped on whatever user memory was
at address 0).

A solution is to write to the guard page in region 5, which is
guaranteed to trigger a page fault.

--- linux-2.4.25.orig/include/asm-ia64/page.h Wed Feb 18 05:36:32 2004
+++ linux-2.4.25/include/asm-ia64/page.h Wed Feb 18 13:59:10 2004
@@ -120,7 +120,7 @@
#define is_invalid_hugepage_range(addr, len) 0
#endif

-#define BUG() do { printk("kernel BUG at %s:%d!\n", __FILE__, __LINE__); *(int *)0=0; } while (0)
+#define BUG() do { printk("kernel BUG at %s:%d!\n", __FILE__, __LINE__); *(int *)0xa000000000000000=0; } while (0)
#define PAGE_BUG(page) do { BUG(); } while (0)

static __inline__ int