mm: add kernel_move_pages() helper, move compat syscall to mm/migrate.c

Move compat_sys_move_pages() to mm/migrate.c and make it call a newly
introduced helper -- kernel_move_pages() -- instead of the syscall.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

diff --git a/kernel/compat.c b/kernel/compat.c
index 51bdf18..6d21894 100644 (file)
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -488,28 +488,6 @@ get_compat_sigset(sigset_t *set, const compat_sigset_t __user *compat)
 }
 EXPORT_SYMBOL_GPL(get_compat_sigset);
 
-#ifdef CONFIG_NUMA
-COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
-                      compat_uptr_t __user *, pages32,
-                      const int __user *, nodes,
-                      int __user *, status,
-                      int, flags)
-{
-       const void __user * __user *pages;
-       int i;
-
-       pages = compat_alloc_user_space(nr_pages * sizeof(void *));
-       for (i = 0; i < nr_pages; i++) {
-               compat_uptr_t p;
-
-               if (get_user(p, pages32 + i) ||
-                       put_user(compat_ptr(p), pages + i))
-                       return -EFAULT;
-       }
-       return sys_move_pages(pid, nr_pages, pages, nodes, status, flags);
-}
-#endif
-
 /*
  * Allocate user-space memory for the duration of a single system call,
  * in order to marshall parameters inside a compat thunk.

diff --git a/mm/migrate.c b/mm/migrate.c
index 1e5525a..0038866 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -34,6 +34,7 @@
 #include <linux/backing-dev.h>
 #include <linux/compaction.h>
 #include <linux/syscalls.h>
+#include <linux/compat.h>
 #include <linux/hugetlb.h>
 #include <linux/hugetlb_cgroup.h>
 #include <linux/gfp.h>
@@ -1745,10 +1746,10 @@ static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
  * Move a list of pages in the address space of the currently executing
  * process.
  */
-SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
-               const void __user * __user *, pages,
-               const int __user *, nodes,
-               int __user *, status, int, flags)
+static int kernel_move_pages(pid_t pid, unsigned long nr_pages,
+                            const void __user * __user *pages,
+                            const int __user *nodes,
+                            int __user *status, int flags)
 {
        struct task_struct *task;
        struct mm_struct *mm;
@@ -1807,6 +1808,36 @@ out:
        return err;
 }
 
+SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages,
+               const void __user * __user *, pages,
+               const int __user *, nodes,
+               int __user *, status, int, flags)
+{
+       return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
+}
+
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE6(move_pages, pid_t, pid, compat_ulong_t, nr_pages,
+                      compat_uptr_t __user *, pages32,
+                      const int __user *, nodes,
+                      int __user *, status,
+                      int, flags)
+{
+       const void __user * __user *pages;
+       int i;
+
+       pages = compat_alloc_user_space(nr_pages * sizeof(void *));
+       for (i = 0; i < nr_pages; i++) {
+               compat_uptr_t p;
+
+               if (get_user(p, pages32 + i) ||
+                       put_user(compat_ptr(p), pages + i))
+                       return -EFAULT;
+       }
+       return kernel_move_pages(pid, nr_pages, pages, nodes, status, flags);
+}
+#endif /* CONFIG_COMPAT */
+
 #ifdef CONFIG_NUMA_BALANCING
 /*
  * Returns true if this is a safe migration target node for misplaced NUMA