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Re: [git pull] x86 PAT changes

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To: Linus Torvalds <torvalds@...>
Cc: Pallipadi, Venkatesh <venkatesh.pallipadi@...>, Ingo Molnar <mingo@...>, H. Peter Anvin <hpa@...>, <linux-kernel@...>, Andrew Morton <akpm@...>, Thomas Gleixner <tglx@...>
Date: Saturday, April 26, 2008 - 2:32 pm

On Sat, Apr 26, 2008 at 10:15:33AM -0700, Linus Torvalds wrote:

OK. Below is the quick to disable /dev/mem mmap of RAM with PAT.
This should go along with Ingo's patch that removes PAT dependency on
NONPROMISC_DEVMEM.  It makes things safer and eliminates aliasing.
Still somewhat unclean as the range_is_allowed is duplicated.
And also, just compile tested right now.


Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>

---
 arch/x86/mm/pat.c |   31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

Index: linux-2.6/arch/x86/mm/pat.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/pat.c	2008-04-26 09:34:31.000000000 -0700
+++ linux-2.6/arch/x86/mm/pat.c	2008-04-26 11:25:57.000000000 -0700
@@ -16,6 +16,7 @@
 #include <asm/msr.h>
 #include <asm/tlbflush.h>
 #include <asm/processor.h>
+#include <asm/page.h>
 #include <asm/pgtable.h>
 #include <asm/pat.h>
 #include <asm/e820.h>
@@ -477,6 +478,33 @@ pgprot_t phys_mem_access_prot(struct fil
 	return vma_prot;
 }
 
+#ifdef CONFIG_NONPROMISC_DEVMEM
+/* This check is done in drivers/char/mem.c in case of NONPROMISC_DEVMEM*/
+static inline int range_is_allowed(unsigned long pfn, unsigned long size)
+{
+	return 1;
+}
+#else
+static inline int range_is_allowed(unsigned long pfn, unsigned long size)
+{
+	u64 from = ((u64)pfn) << PAGE_SHIFT;
+	u64 to = from + size;
+	u64 cursor = from;
+
+	while (cursor < to) {
+		if (!devmem_is_allowed(pfn)) {
+			printk(KERN_INFO
+		"Program %s tried to access /dev/mem between %Lx->%Lx.\n",
+				current->comm, from, to);
+			return 0;
+		}
+		cursor += PAGE_SIZE;
+		pfn++;
+	}
+	return 1;
+}
+#endif /* CONFIG_NONPROMISC_DEVMEM */
+
 int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
 				unsigned long size, pgprot_t *vma_prot)
 {
@@ -485,6 +513,9 @@ int phys_mem_access_prot_allowed(struct 
 	unsigned long ret_flags;
 	int retval;
 
+	if (!range_is_allowed(pfn, size))
+		return 0;
+
 	if (file->f_flags & O_SYNC) {
 		flags = _PAGE_CACHE_UC;
 	}

--
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Messages in current thread:
[git pull] x86 PAT changes, Ingo Molnar, (Thu Apr 24, 6:56 pm)
Re: [git pull] x86 PAT changes, Gabriel C, (Sat Apr 26, 9:40 am)
Re: [git pull] x86 PAT changes, Ingo Molnar, (Sat Apr 26, 10:42 am)
Re: [git pull] x86 PAT changes, Gabriel C, (Sat Apr 26, 11:37 am)
Re: [git pull] x86 PAT changes, Ingo Molnar, (Sat Apr 26, 11:41 am)
Re: [git pull] x86 PAT changes, Linus Torvalds, (Sat Apr 26, 12:43 pm)
Re: [git pull] x86 PAT changes, Linus Torvalds, (Fri Apr 25, 7:43 pm)
Re: [git pull] x86 PAT changes, Ingo Molnar, (Sat Apr 26, 5:57 am)
Re: [git pull] x86 PAT changes, H. Peter Anvin, (Fri Apr 25, 8:06 pm)
Re: [git pull] x86 PAT changes, Linus Torvalds, (Fri Apr 25, 9:12 pm)
Re: [git pull] x86 PAT changes, Ingo Molnar, (Sat Apr 26, 4:56 am)
RE: [git pull] x86 PAT changes, Pallipadi, Venkatesh, (Sat Apr 26, 12:54 pm)
RE: [git pull] x86 PAT changes, Linus Torvalds, (Sat Apr 26, 1:15 pm)
Re: [git pull] x86 PAT changes, Venki Pallipadi, (Sat Apr 26, 2:32 pm)
[patch] x86, PAT: disable /dev/mem mmap RAM with PAT, Ingo Molnar, (Sat Apr 26, 3:07 pm)
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