access_process_vm device memory infrastructure

In order to be able to debug things like the X server and programs using
the PPC Cell SPUs, the debugger needs to be able to access device memory
through ptrace and /proc/pid/mem.

This patch:

Add the generic_access_phys access function and put the hooks in place
to allow access_process_vm to access device or PPC Cell SPU memory.

[riel@redhat.com: Add documentation for the vm_ops->access function]
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Benjamin Herrensmidt <benh@kernel.crashing.org>
Cc: Dave Airlie <airlied@linux.ie>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index eb815cfc1b35..5c7f8f64f70e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -170,6 +170,12 @@ struct vm_operations_struct {
         /* notification that a previously read-only page is about to become
          * writable, if an error is returned it will cause a SIGBUS */
         int (*page_mkwrite)(struct vm_area_struct *vma, struct page *page);
+
+        /* called by access_process_vm when get_user_pages() fails, typically
+         * for use by special VMAs that can switch between memory and hardware
+         */
+        int (*access)(struct vm_area_struct *vma, unsigned long addr,
+                      void *buf, int len, int write);
 #ifdef CONFIG_NUMA
         /*
          * set_policy() op must add a reference to any non-NULL @new mempolicy
@@ -771,6 +777,8 @@ int copy_page_range(struct mm_struct *dst, struct mm_struct *src,
                         struct vm_area_struct *vma);
 void unmap_mapping_range(struct address_space *mapping,
                 loff_t const holebegin, loff_t const holelen, int even_cows);
+int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
+                        void *buf, int len, int write);
 
 static inline void unmap_shared_mapping_range(struct address_space *mapping,
                 loff_t const holebegin, loff_t const holelen)