From: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Subject: mm/debug_vm_pgtable: fix build failure with powerpc 8xx
Since commit 9e343b467c70 ("READ_ONCE: Enforce atomicity for
{READ,WRITE}_ONCE() memory accesses"), READ_ONCE() cannot be used anymore
to read complex page table entries. This leads to:
CC mm/debug_vm_pgtable.o
In file included from ./include/asm-generic/bug.h:5,
from ./arch/powerpc/include/asm/bug.h:109,
from ./include/linux/bug.h:5,
from ./include/linux/mmdebug.h:5,
from ./include/linux/gfp.h:5,
from mm/debug_vm_pgtable.c:13:
In function 'pte_clear_tests',
inlined from 'debug_vm_pgtable' at mm/debug_vm_pgtable.c:363:2:
./include/linux/compiler.h:392:38: error: call to '__compiletime_assert_210' declared with attribute error: Unsupported access size for {READ,WRITE}_ONCE().
392 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^
./include/linux/compiler.h:373:4: note: in definition of macro '__compiletime_assert'
373 | prefix ## suffix(); \
| ^~~~~~
./include/linux/compiler.h:392:2: note: in expansion of macro '_compiletime_assert'
392 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
./include/linux/compiler.h:405:2: note: in expansion of macro 'compiletime_assert'
405 | compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
| ^~~~~~~~~~~~~~~~~~
./include/linux/compiler.h:291:2: note: in expansion of macro 'compiletime_assert_rwonce_type'
291 | compiletime_assert_rwonce_type(x); \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mm/debug_vm_pgtable.c:249:14: note: in expansion of macro 'READ_ONCE'
249 | pte_t pte = READ_ONCE(*ptep);
| ^~~~~~~~~
make[2]: *** [mm/debug_vm_pgtable.o] Error 1
Fix it by using the recently added ptep_get() helper.
Link: http://lkml.kernel.org/r/6ca8c972e6c920dc4ae0d4affbed9703afa4d010.1592490570.git.christophe.leroy@xxxxxxxxxx
Fixes: 9e343b467c70 ("READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses")
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Acked-by: Will Deacon <will@xxxxxxxxxx>
Reviewed-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/debug_vm_pgtable.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/debug_vm_pgtable.c~mm-debug_vm_pgtable-fix-build-failure-with-powerpc-8xx
+++ a/mm/debug_vm_pgtable.c
@@ -246,13 +246,13 @@ static void __init pgd_populate_tests(st
static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep,
unsigned long vaddr)
{
- pte_t pte = READ_ONCE(*ptep);
+ pte_t pte = ptep_get(ptep);
pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
set_pte_at(mm, vaddr, ptep, pte);
barrier();
pte_clear(mm, vaddr, ptep);
- pte = READ_ONCE(*ptep);
+ pte = ptep_get(ptep);
WARN_ON(!pte_none(pte));
}
_
