[patch 10/12] mm: ptdump: fix build failure

Andrew Morton
2021-04-16T22:46:23Z

From: Christophe Leroy <christophe.leroy@csgroup.eu>
Subject: mm: ptdump: fix build failure

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

READ_ONCE() cannot be used for reading PTEs. Use ptep_get() instead. 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>
---

mm/ptdump.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/ptdump.c~mm-ptdump-fix-build-failure
+++ a/mm/ptdump.c
@@ -111,7 +111,7 @@ static int ptdump_pte_entry(pte_t *pte,
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));
_