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Subject[4/6] go BUG on vmallocspace in __pa() (was: Re: [-mm patch] i386: enable 4k stacks by default)
On Mon, Apr 30, 2007 at 10:38:19AM -0700, William Lee Irwin III wrote:
> Here's what I did for i386 for someone concerned about blowing the stack.

Add checks to __pa() so it goes BUG() on vmallocspace addresses.

Signed-off-by: William Irwin <wli@holomorphy.com>


Index: stack-paranoia/arch/i386/kernel/doublefault.c
===================================================================
--- stack-paranoia.orig/arch/i386/kernel/doublefault.c 2007-04-30 10:26:15.959875324 -0700
+++ stack-paranoia/arch/i386/kernel/doublefault.c 2007-04-30 10:34:55.201465216 -0700
@@ -62,5 +62,5 @@
.ss = __KERNEL_DS,
.ds = __USER_DS,

- .__cr3 = __pa(swapper_pg_dir)
+ .__cr3 = (unsigned long)swapper_pg_dir - PAGE_OFFSET,
};
Index: stack-paranoia/arch/i386/mm/pgtable.c
===================================================================
--- stack-paranoia.orig/arch/i386/mm/pgtable.c 2007-04-30 10:26:16.075881935 -0700
+++ stack-paranoia/arch/i386/mm/pgtable.c 2007-04-30 10:34:55.201465216 -0700
@@ -181,6 +181,15 @@
#endif
}

+unsigned long __kvaddr_to_paddr(unsigned long kvaddr)
+{
+ if (high_memory)
+ BUG_ON(kvaddr >= VMALLOC_START);
+ else
+ BUG_ON(kvaddr >= (unsigned long)__va(MAXMEM));
+ return kvaddr - PAGE_OFFSET;
+}
+
pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
{
return (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO);
Index: stack-paranoia/include/asm-i386/page.h
===================================================================
--- stack-paranoia.orig/include/asm-i386/page.h 2007-04-30 10:26:32.012790127 -0700
+++ stack-paranoia/include/asm-i386/page.h 2007-04-30 10:34:55.197464988 -0700
@@ -118,11 +118,17 @@
#define __PAGE_OFFSET ((unsigned long)CONFIG_PAGE_OFFSET)
#endif

-
#define PAGE_OFFSET ((unsigned long)__PAGE_OFFSET)
+
+#ifdef __ASSEMBLY__
+#define __pa(x) ((unsigned long)(x)-PAGE_OFFSET)
+#else
+extern unsigned long __kvaddr_to_paddr(unsigned long);
+#define __pa(x) __kvaddr_to_paddr((unsigned long)(x))
+#endif
+
#define VMALLOC_RESERVE ((unsigned long)__VMALLOC_RESERVE)
#define MAXMEM (-__PAGE_OFFSET-__VMALLOC_RESERVE)
-#define __pa(x) ((unsigned long)(x)-PAGE_OFFSET)
/* __pa_symbol should be used for C visible symbols.
This seems to be the official gcc blessed way to do such arithmetic. */
#define __pa_symbol(x) __pa(RELOC_HIDE((unsigned long)(x),0))
-
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