From: Christophe Leroy christophe.leroy@csgroup.eu
commit 458376913d86bed2fb781b4952eb6861675ef3be upstream.
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/912b349e2bcaa88939904815ca0af945740c6bd4.161847892... 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/ptdump.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/ptdump.c +++ b/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));