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Subject[PATCH v2 resend 07/12] mm: factor out main logic of access_process_vm
Date
Introduce an internal helper __access_remote_vm and base access_process_vm on
top of it. This new method may be called with a NULL task_struct if page fault
accounting is not desired. This code will be shared with a new address space
accessor that is independent of task_struct.

Signed-off-by: Stephen Wilson <wilsons@start.ca>
---
mm/memory.c | 35 +++++++++++++++++++++++++----------
1 files changed, 25 insertions(+), 10 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 36445e3..68eec4f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3593,20 +3593,15 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
#endif

/*
- * Access another process' address space.
- * Source/target buffer must be kernel space,
- * Do not walk the page table directly, use get_user_pages
+ * Access another process' address space as given in mm. If non-NULL, use the
+ * given task for page fault accounting.
*/
-int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
+static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
+ unsigned long addr, void *buf, int len, int write)
{
- struct mm_struct *mm;
struct vm_area_struct *vma;
void *old_buf = buf;

- mm = get_task_mm(tsk);
- if (!mm)
- return 0;
-
down_read(&mm->mmap_sem);
/* ignore errors, just check how much was successfully transferred */
while (len) {
@@ -3655,12 +3650,32 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in
addr += bytes;
}
up_read(&mm->mmap_sem);
- mmput(mm);

return buf - old_buf;
}

/*
+ * Access another process' address space.
+ * Source/target buffer must be kernel space,
+ * Do not walk the page table directly, use get_user_pages
+ */
+int access_process_vm(struct task_struct *tsk, unsigned long addr,
+ void *buf, int len, int write)
+{
+ struct mm_struct *mm;
+ int ret;
+
+ mm = get_task_mm(tsk);
+ if (!mm)
+ return 0;
+
+ ret = __access_remote_vm(tsk, mm, addr, buf, len, write);
+ mmput(mm);
+
+ return ret;
+}
+
+/*
* Print the name of a VMA.
*/
void print_vma_addr(char *prefix, unsigned long ip)
--
1.7.3.5


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