[RFC PATCH v2 10/20] powerpc/mm: Fix __find_linux_pte() on 32 bits with PMD leaf entries

Christophe Leroy
2024-05-17T19:01:06Z

Building on 32 bits with pmd_leaf() not returning always false leads
to the following error:

CC arch/powerpc/mm/pgtable.o
arch/powerpc/mm/pgtable.c: In function '__find_linux_pte':
arch/powerpc/mm/pgtable.c:506:1: error: function may return address of local variable [-Werror=return-local-addr]
506 | }
| ^
arch/powerpc/mm/pgtable.c:394:15: note: declared here
394 | pud_t pud, *pudp;
| ^~~
arch/powerpc/mm/pgtable.c:394:15: note: declared here

This is due to pmd_offset() being a no-op in that case.

So rework it for powerpc/32 so that pXd_offset() are used on real
pointers and not on on-stack copies.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
arch/powerpc/mm/pgtable.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index 59f0d7706d2f..51ee508eeb5b 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -390,8 +390,12 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea,
bool *is_thp, unsigned *hpage_shift)
{
pgd_t *pgdp;
- p4d_t p4d, *p4dp;
- pud_t pud, *pudp;
+ p4d_t *p4dp;
+ pud_t *pudp;
+#ifdef CONFIG_PPC64
+ p4d_t p4d;
+ pud_t pud;
+#endif
pmd_t pmd, *pmdp;
pte_t *ret_pte;
hugepd_t *hpdp = NULL;
@@ -412,6 +416,7 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea,
*/
pgdp = pgdir + pgd_index(ea);
p4dp = p4d_offset(pgdp, ea);
+#ifdef CONFIG_PPC64
p4d = READ_ONCE(*p4dp);
pdshift = P4D_SHIFT;

@@ -452,6 +457,11 @@ pte_t *__find_linux_pte(pgd_t *pgdir, unsigned long ea,

pdshift = PMD_SHIFT;
pmdp = pmd_offset(&pud, ea);
+#else
+ p4dp = p4d_offset(pgdp, ea);
+ pudp = pud_offset(p4dp, ea);
+ pmdp = pmd_offset(pudp, ea);
+#endif
pmd = READ_ONCE(*pmdp);

/*
--
2.44.0