Messages in this thread | | | Date | Tue, 14 Jul 2009 18:14:16 +0200 | From | Johannes Weiner <> | Subject | Re: [PATCH] NOMMU: add support for Memory Protection Units (MPU) |
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On Tue, Jul 14, 2009 at 10:22:20AM -0400, Mike Frysinger wrote: > From: Bernd Schmidt <bernds_cb1@t-online.de> > > 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> > CC: David Howells <dhowells@redhat.com> > --- > kernel/module.c | 5 +++++ > mm/nommu.c | 25 +++++++++++++++++++++++++ > 2 files changed, 30 insertions(+), 0 deletions(-) > > diff --git a/kernel/module.c b/kernel/module.c > index 0a04983..e1a3dfc 100644 > --- a/kernel/module.c > +++ b/kernel/module.c > @@ -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> > @@ -1519,6 +1520,10 @@ 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) > diff --git a/mm/nommu.c b/mm/nommu.c > index 53cab10..a0269e5 100644 > --- a/mm/nommu.c > +++ b/mm/nommu.c > @@ -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))) > @@ -640,11 +641,23 @@ static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma) > struct vm_area_struct *pvma, **pp; > struct address_space *mapping; > struct rb_node **p, *parent; > +#ifdef CONFIG_MPU > + long start; > +#endif > > kenter(",%p", vma); > > BUG_ON(!vma->vm_region); > > +#ifdef CONFIG_MPU > + start = vma->vm_start & PAGE_MASK; > + while (start < vma->vm_end) { > + protect_page(mm, start, vma->vm_flags); > + start += PAGE_SIZE; > + } > + update_protections(mm); > +#endif > + > mm->map_count++; > vma->vm_mm = mm; > > @@ -707,9 +720,21 @@ static void delete_vma_from_mm(struct vm_area_struct *vma) > struct vm_area_struct **pp; > struct address_space *mapping; > struct mm_struct *mm = vma->vm_mm; > +#ifdef CONFIG_MPU > + long start; > +#endif > > kenter("%p", vma); > > +#ifdef CONFIG_MPU > + start = vma->vm_start & PAGE_MASK; > + while (start < vma->vm_end) { > + protect_page(mm, start, 0); > + start += PAGE_SIZE; > + } > + update_protections(mm); > +#endif
How about refactoring that into one function? Saves all but one #ifdef.
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