sparc32: srmmu: improve type safety of __nocache_fix()

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/r/CAHk-=wisORTa7QVPnFqNw9pFs62UiwgsD4C4d=MtYy1o4JPyGQ@mail.gmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/arch/sparc/include/asm/pgtsrmmu.h b/arch/sparc/include/asm/pgtsrmmu.h
index 7708d01..6067925 100644 (file)
--- a/arch/sparc/include/asm/pgtsrmmu.h
+++ b/arch/sparc/include/asm/pgtsrmmu.h
@@ -113,7 +113,7 @@ 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 f5fa079..da4e10b 100644 (file)
--- a/arch/sparc/mm/srmmu.c
+++ b/arch/sparc/mm/srmmu.c
@@ -689,7 +689,7 @@ static void __init srmmu_early_allocate_ptable_skeleton(unsigned long start,
                pgdp = pgd_offset_k(start);
                p4dp = p4d_offset(pgdp, start);
                pudp = pud_offset(p4dp, start);
-               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)
@@ -698,7 +698,7 @@ 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");
@@ -810,11 +810,11 @@ 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 += 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)
@@ -828,7 +828,7 @@ static void __init srmmu_inherit_prom_mappings(unsigned long start,
                        start += PMD_SIZE;
                        continue;
                }
-               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");
@@ -836,7 +836,7 @@ static void __init srmmu_inherit_prom_mappings(unsigned long start,
                        pmd_set(__nocache_fix(pmdp), ptep);
                }
                ptep = pte_offset_kernel(__nocache_fix(pmdp), start);
-               *(pte_t *)__nocache_fix(ptep) = __pte(probed);
+               *__nocache_fix(ptep) = __pte(probed);
                start += PAGE_SIZE;
        }
 }
@@ -850,7 +850,7 @@ 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. */
@@ -940,7 +940,7 @@ 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);