Commit eb8cdec4 authored by Bernd Schmidt's avatar Bernd Schmidt Committed by Linus Torvalds
Browse files

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: default avatarBernd Schmidt <bernds_cb1@t-online.de>
Signed-off-by: default avatarBryan Wu <cooloney@kernel.org>
Signed-off-by: default avatarMike Frysinger <vapier@gentoo.org>
Acked-by: default avatarDavid Howells <dhowells@redhat.com>
Acked-by: default avatarGreg Ungerer <gerg@snapgear.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 02e87d1a

kernel/module.c

+5 −0
Original line number Diff line number Diff line
@@ -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)

mm/nommu.c

+21 −0
Original line number Diff line number Diff line
@@ -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;

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