linux-kernel - [PATCH 5.10 072/103] mm: ptdump: fix build failure

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Date:   Mon, 19 Apr 2021 15:06:23 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Steven Price <steven.price@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.10 072/103] mm: ptdump: fix build failure

From: Christophe Leroy <christophe.leroy@...roup.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/912b349e2bcaa88939904815ca0af945740c6bd4.1618478922.git.christophe.leroy@csgroup.eu
Fixes: 30d621f6723b ("mm: add generic ptdump")
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Steven Price <steven.price@....com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 mm/ptdump.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -108,7 +108,7 @@ 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));