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nommu: add support for Memory Protection Units (MPU) 

Some architectures (like the Blackfin arch) implement some of the
"simpler" features that one would expect out of a MMU such as memory
protection.

In our case, we actually get read/write/exec protection down to the page
boundary so processes can't stomp on each other let alone the kernel.

There is a performance decrease (which depends greatly on the workload)
however as the hardware/software interaction was not optimized at design
time.

Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Greg Ungerer <gerg@snapgear.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Bernd Schmidt 2009-09-21 17:03:57 -07:00 committed by Linus Torvalds
parent 02e87d1a93
commit eb8cdec4a9
2 changed files with 26 additions and 0 deletions
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5
kernel/module.c
View File

@ -47,6 +47,7 @@
#include <linux/rculist.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/mmu_context.h>
#include <linux/license.h>
#include <asm/sections.h>
#include <linux/tracepoint.h>
@ -1535,6 +1536,10 @@ static void free_module(struct module *mod)
/* Finally, free the core (containing the module structure) */
module_free(mod, mod->module_core);
#ifdef CONFIG_MPU
update_protections(current->mm);
#endif
}
void *__symbol_get(const char *symbol)

21
mm/nommu.c
View File

@ -33,6 +33,7 @@
#include <asm/uaccess.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include "internal.h"
static inline __attribute__((format(printf, 1, 2)))
@ -622,6 +623,22 @@ static void put_nommu_region(struct vm_region *region)
__put_nommu_region(region);
}
/*
* update protection on a vma
*/
static void protect_vma(struct vm_area_struct *vma, unsigned long flags)
{
#ifdef CONFIG_MPU
struct mm_struct *mm = vma->vm_mm;
long start = vma->vm_start & PAGE_MASK;
while (start < vma->vm_end) {
protect_page(mm, start, flags);
start += PAGE_SIZE;
}
update_protections(mm);
#endif
}
/*
* add a VMA into a process's mm_struct in the appropriate place in the list
* and tree and add to the address space's page tree also if not an anonymous
@ -641,6 +658,8 @@ static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
mm->map_count++;
vma->vm_mm = mm;
protect_vma(vma, vma->vm_flags);
/* add the VMA to the mapping */
if (vma->vm_file) {
mapping = vma->vm_file->f_mapping;
@ -703,6 +722,8 @@ static void delete_vma_from_mm(struct vm_area_struct *vma)
kenter("%p", vma);
protect_vma(vma, 0);
mm->map_count--;
if (mm->mmap_cache == vma)
mm->mmap_cache = NULL;