mm: ptdump: fix build failure

READ_ONCE() cannot be used for reading PTEs.  Use ptep_get() instead, to
avoid the following errors:

    CC      mm/ptdump.o
  In file included from <command-line>:
  mm/ptdump.c: In function 'ptdump_pte_entry':
  include/linux/compiler_types.h:320:38: error: call to '__compiletime_assert_207' declared with attribute error: Unsupported access size for {READ,WRITE}_ONCE().
    320 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
        |                                      ^
  include/linux/compiler_types.h:301:4: note: in definition of macro '__compiletime_assert'
    301 |    prefix ## suffix();    \
        |    ^~~~~~
  include/linux/compiler_types.h:320:2: note: in expansion of macro '_compiletime_assert'
    320 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
        |  ^~~~~~~~~~~~~~~~~~~
  include/asm-generic/rwonce.h:36:2: note: in expansion of macro 'compiletime_assert'
     36 |  compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
        |  ^~~~~~~~~~~~~~~~~~
  include/asm-generic/rwonce.h:49:2: note: in expansion of macro 'compiletime_assert_rwonce_type'
     49 |  compiletime_assert_rwonce_type(x);    \
        |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  mm/ptdump.c:114:14: note: in expansion of macro 'READ_ONCE'
    114 |  pte_t val = READ_ONCE(*pte);
        |              ^~~~~~~~~
  make[2]: *** [mm/ptdump.o] Error 1

See commit 481e980a7c19 ("mm: Allow arches to provide ptep_get()") and
commit c0e1c8c22beb ("powerpc/8xx: Provide ptep_get() with 16k pages")
for details.

Link: https://lkml.kernel.org/r/912b349e2bcaa88939904815ca0af945740c6bd4.1618478922.git.christophe.leroy@csgroup.eu
Fixes: 30d621f6723b ("mm: add generic ptdump")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Steven Price <steven.price@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/ptdump.c b/mm/ptdump.c
index 4354c1422d57c962fccfd065910d164d48e93bba..da751448d0e4ef219717294882df9bfb33a66174 100644 (file)
--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -111,7 +111,7 @@ static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
                            unsigned long next, struct mm_walk *walk)
 {
        struct ptdump_state *st = walk->private;
-       pte_t val = READ_ONCE(*pte);
+       pte_t val = ptep_get(pte);
 
        if (st->effective_prot)
                st->effective_prot(st, 4, pte_val(val));