2006-08-17 19:55:04

by Kylene Jo Hall

Subject: [RFC][PATCH 1/8] mprotect patch for use by SLIM

This small patch makes mprotect available for use by SLIM for
write revocation.

Updated to allow the usage locking to work properly.

Signed-off-by: Mimi Zohar <[email protected]>
Signed-off-by: Kylene Hall <[email protected]>
---
include/linux/mm.h | 2 ++
mm/mprotect.c | 23 +++++++++++++++++------
2 files changed, 19 insertions(+), 6 deletions(-)

--- linux-2.6.18-rc3/mm/mprotect.c 2006-07-30 01:15:36.000000000 -0500
+++ linux-2.6.18-rc3-working/mm/mprotect.c 2006-08-07 13:11:07.000000000 -0500
@@ -19,6 +19,7 @@
#include <linux/mempolicy.h>
#include <linux/personality.h>
#include <linux/syscalls.h>
+#include <linux/module.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <asm/uaccess.h>
@@ -202,9 +203,10 @@ fail:
vm_unacct_memory(charged);
return error;
}
-
-asmlinkage long
-sys_mprotect(unsigned long start, size_t len, unsigned long prot)
+/*
+ * Call holding the current->mm->mmap_sem for writing
+ */
+int do_mprotect(unsigned long start, size_t len, unsigned long prot)
{
unsigned long vm_flags, nstart, end, tmp, reqprot;
struct vm_area_struct *vma, *prev;
@@ -234,8 +236,6 @@ sys_mprotect(unsigned long start, size_t

vm_flags = calc_vm_prot_bits(prot);

- down_write(&current->mm->mmap_sem);
-
vma = find_vma_prev(current->mm, start, &prev);
error = -ENOMEM;
if (!vma)
@@ -298,6 +298,17 @@ sys_mprotect(unsigned long start, size_t
}
}
out:
- up_write(&current->mm->mmap_sem);
return error;
}
+EXPORT_SYMBOL_GPL(do_mprotect);
+
+asmlinkage long
+sys_mprotect(unsigned long start, size_t len, unsigned long prot)
+{
+ int ret;
+
+ down_write(&current->mm->mmap_sem);
+ ret = do_mprotect(start, len, prot);
+ up_write(&current->mm->mmap_sem);
+ return ret;
+}
--- linux-2.6.18-rc3/include/linux/mm.h 2006-07-30 01:15:36.000000000 -0500
+++ linux-2.6.18-rc3-working/include/linux/mm.h 2006-08-01 12:18:13.000000000 -0500
@@ -137,6 +137,8 @@ extern unsigned int kobjsize(const void
#define VM_EXEC 0x00000004
#define VM_SHARED 0x00000008

+extern int do_mprotect(unsigned long start, size_t len, unsigned long prot);
+
/* mprotect() hardcodes VM_MAYREAD >> 4 == VM_READ, and so for r/w/x bits. */
#define VM_MAYREAD 0x00000010 /* limits for mprotect() etc */
#define VM_MAYWRITE 0x00000020

2006-08-18 20:52:46

by Randy Dunlap

Subject: Re: [RFC][PATCH 1/8] mprotect patch for use by SLIM

On Thu, 17 Aug 2006 12:53:05 -0700 Kylene Jo Hall wrote:

> This small patch makes mprotect available for use by SLIM for
> write revocation.

A symbol doesn't need to be exported for use by built-in code
(as opposed to loadable modules). Since 'slim' cannot be built
as a loadable module, "do_protect" just needs not to be
static. The EXPORT isn't needed.


> Updated to allow the usage locking to work properly.
>
> Signed-off-by: Mimi Zohar <[email protected]>
> Signed-off-by: Kylene Hall <[email protected]>
> ---
> include/linux/mm.h | 2 ++
> mm/mprotect.c | 23 +++++++++++++++++------
> 2 files changed, 19 insertions(+), 6 deletions(-)
>
> --- linux-2.6.18-rc3/mm/mprotect.c 2006-07-30
> 01:15:36.000000000 -0500 +++
> linux-2.6.18-rc3-working/mm/mprotect.c 2006-08-07
> 13:11:07.000000000 -0500 @@ -19,6 +19,7 @@
> #include <linux/mempolicy.h>
> #include <linux/personality.h>
> #include <linux/syscalls.h>
> +#include <linux/module.h>
> #include <linux/swap.h>
> #include <linux/swapops.h>
> #include <asm/uaccess.h>
> @@ -202,9 +203,10 @@ fail:
> vm_unacct_memory(charged);
> return error;
> }
> -
> -asmlinkage long
> -sys_mprotect(unsigned long start, size_t len, unsigned long prot)
> +/*
> + * Call holding the current->mm->mmap_sem for writing
> + */
> +int do_mprotect(unsigned long start, size_t len, unsigned long
> prot) {
> unsigned long vm_flags, nstart, end, tmp, reqprot;
> struct vm_area_struct *vma, *prev;
> @@ -234,8 +236,6 @@ sys_mprotect(unsigned long start, size_t
>
> vm_flags = calc_vm_prot_bits(prot);
>
> - down_write(&current->mm->mmap_sem);
> -
> vma = find_vma_prev(current->mm, start, &prev);
> error = -ENOMEM;
> if (!vma)
> @@ -298,6 +298,17 @@ sys_mprotect(unsigned long start, size_t
> }
> }
> out:
> - up_write(&current->mm->mmap_sem);
> return error;
> }
> +EXPORT_SYMBOL_GPL(do_mprotect);
> +
> +asmlinkage long
> +sys_mprotect(unsigned long start, size_t len, unsigned long prot)
> +{
> + int ret;
> +
> + down_write(&current->mm->mmap_sem);
> + ret = do_mprotect(start, len, prot);
> + up_write(&current->mm->mmap_sem);
> + return ret;
> +}
> --- linux-2.6.18-rc3/include/linux/mm.h 2006-07-30
> 01:15:36.000000000 -0500 +++
> linux-2.6.18-rc3-working/include/linux/mm.h 2006-08-01
> 12:18:13.000000000 -0500 @@ -137,6 +137,8 @@ extern unsigned int
> kobjsize(const void
> #define VM_EXEC 0x00000004
> #define VM_SHARED 0x00000008
>
> +extern int do_mprotect(unsigned long start, size_t len, unsigned
> long prot); +
> /* mprotect() hardcodes VM_MAYREAD >> 4 == VM_READ, and so for
> r/w/x bits. */
> #define VM_MAYREAD 0x00000010 /* limits for mprotect
> #() etc */ define VM_MAYWRITE 0x00000020
>
>
> -

---
~Randy