linux-kernel - [4/6] go BUG on vmallocspace in __pa() (was: Re: [-mm patch] i386: enable 4k stacks by default)

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Date:	Mon, 30 Apr 2007 10:45:10 -0700
From:	William Lee Irwin III <wli@...omorphy.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	David Chinner <dgc@....com>, Zan Lynx <zlynx@....org>,
	Adrian Bunk <bunk@...sta.de>,
	Linux Kernel <linux-kernel@...r.kernel.org>
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@...omorphy.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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