[PATCH 2/2] sparc32: srmmu: improve type safety of __nocache_fix()

Mike Rapoport
2020-05-24T16:22:06Z

The __nocache_fix(VADDR) macro is used to add an offset for pointers and
its "return type" is 'void *'.

We can do better and keep the type information with simply by casting the
return value to (__typeof__(VADDR)).

This will ".. show when those pgd/p4d/pud pointers get mis-used because
they don't end up dropping the type info.."

The addition of the casting to __nocache_fix() also allows to remove
explicit casts at its call sites.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Link: https://lkml.kernel.org/stablestablestablestablestabler/CAHk-=wisORTa7QVPnFqNw9pFs62UiwgsD4C4d=MtYy1o4JPyGQ@mail.gmail.com
---
arch/sparc/include/asm/pgtsrmmu.h | 2 +-
arch/sparc/mm/srmmu.c | 16 ++++++++--------
2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/arch/sparc/include/asm/pgtsrmmu.h b/arch/sparc/include/asm/pgtsrmmu.h
index 32a508897501..941d42a59b81 100644
--- a/arch/sparc/include/asm/pgtsrmmu.h
+++ b/arch/sparc/include/asm/pgtsrmmu.h
@@ -143,7 +143,7 @@ extern unsigned long last_valid_pfn;
extern void *srmmu_nocache_pool;
#define __nocache_pa(VADDR) (((unsigned long)VADDR) - SRMMU_NOCACHE_VADDR + __pa((unsigned long)srmmu_nocache_pool))
#define __nocache_va(PADDR) (__va((unsigned long)PADDR) - (unsigned long)srmmu_nocache_pool + SRMMU_NOCACHE_VADDR)
-#define __nocache_fix(VADDR) __va(__nocache_pa(VADDR))
+#define __nocache_fix(VADDR) ((__typeof__(VADDR))__va(__nocache_pa(VADDR)))

/* Accessing the MMU control register. */
unsigned int srmmu_get_mmureg(void);
diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c
index dbf5334dd084..d86e6c657922 100644
--- a/arch/sparc/mm/srmmu.c
+++ b/arch/sparc/mm/srmmu.c
@@ -724,7 +724,7 @@ static void __init srmmu_early_allocate_ptable_skeleton(unsigned long start,
pud_set(__nocache_fix(pudp), pmdp);
}
pmdp = pmd_offset(__nocache_fix(pudp), start);
- if (srmmu_pmd_none(*(pmd_t *)__nocache_fix(pmdp))) {
+ if (srmmu_pmd_none(*__nocache_fix(pmdp))) {
ptep = __srmmu_get_nocache(PTE_SIZE, PTE_SIZE);
if (ptep == NULL)
early_pgtable_allocfail("pte");
@@ -836,11 +836,11 @@ static void __init srmmu_inherit_prom_mappings(unsigned long start,
p4dp = p4d_offset(pgdp, start);
pudp = pud_offset(p4dp, start);
if (what == 2) {
- *(pgd_t *)__nocache_fix(pgdp) = __pgd(probed);
+ *__nocache_fix(pgdp) = __pgd(probed);
start += SRMMU_PGDIR_SIZE;
continue;
}
- if (pud_none(*(pud_t *)__nocache_fix(pudp))) {
+ if (pud_none(*__nocache_fix(pudp))) {
pmdp = __srmmu_get_nocache(SRMMU_PMD_TABLE_SIZE,
SRMMU_PMD_TABLE_SIZE);
if (pmdp == NULL)
@@ -849,7 +849,7 @@ static void __init srmmu_inherit_prom_mappings(unsigned long start,
pud_set(__nocache_fix(pudp), pmdp);
}
pmdp = pmd_offset(__nocache_fix(pudp), start);
- if (srmmu_pmd_none(*(pmd_t *)__nocache_fix(pmdp))) {
+ if (srmmu_pmd_none(*__nocache_fix(pmdp))) {
ptep = __srmmu_get_nocache(PTE_SIZE, PTE_SIZE);
if (ptep == NULL)
early_pgtable_allocfail("pte");
@@ -865,12 +865,12 @@ static void __init srmmu_inherit_prom_mappings(unsigned long start,
unsigned long *val;
x = (start >> PMD_SHIFT) & 15;
val = &pmdp->pmdv[x];
- *(unsigned long *)__nocache_fix(val) = probed;
+ *__nocache_fix(val) = probed;
start += SRMMU_REAL_PMD_SIZE;
continue;
}
ptep = pte_offset_kernel(__nocache_fix(pmdp), start);
- *(pte_t *)__nocache_fix(ptep) = __pte(probed);
+ *__nocache_fix(ptep) = __pte(probed);
start += PAGE_SIZE;
}
}
@@ -884,7 +884,7 @@ static void __init do_large_mapping(unsigned long vaddr, unsigned long phys_base
unsigned long big_pte;

big_pte = KERNEL_PTE(phys_base >> 4);
- *(pgd_t *)__nocache_fix(pgdp) = __pgd(big_pte);
+ *__nocache_fix(pgdp) = __pgd(big_pte);
}

/* Map sp_bank entry SP_ENTRY, starting at virtual address VBASE. */
@@ -974,7 +974,7 @@ void __init srmmu_paging_init(void)
srmmu_ctx_table_phys = (ctxd_t *)__nocache_pa(srmmu_context_table);

for (i = 0; i < num_contexts; i++)
- srmmu_ctxd_set((ctxd_t *)__nocache_fix(&srmmu_context_table[i]), srmmu_swapper_pg_dir);
+ srmmu_ctxd_set(__nocache_fix(&srmmu_context_table[i]), srmmu_swapper_pg_dir);

flush_cache_all();
srmmu_set_ctable_ptr((unsigned long)srmmu_ctx_table_phys);
--
2.26.2