On 15/04/2021 10:31, Christophe Leroy wrote:
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.
It was cargo-culted from the arm64/x86 implementations (where this
happens to be safe).
Fixes: 30d621f6723b ("mm: add generic ptdump")
Cc: Steven Price <steven.price@xxxxxxx>
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Reviewed-by: Steven Price <steven.price@xxxxxxx>
Thanks,
Steve
---
mm/ptdump.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/ptdump.c b/mm/ptdump.c
index 4354c1422d57..da751448d0e4 100644
--- 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));
