arm64: mm: Fix CFI failure due to kpti_ng_pgd_alloc function signature

Seen during KPTI initialization:

  CFI failure at create_kpti_ng_temp_pgd+0x124/0xce8 (target: kpti_ng_pgd_alloc+0x0/0x14; expected type: 0xd61b88b6)

The call site is alloc_init_pud() at arch/arm64/mm/mmu.c:

  pud_phys = pgtable_alloc(TABLE_PUD);

alloc_init_pud() has the prototype:

  static void alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,
                             phys_addr_t phys, pgprot_t prot,
                             phys_addr_t (*pgtable_alloc)(enum pgtable_type),
                             int flags)

where the pgtable_alloc() prototype is declared.

The target (kpti_ng_pgd_alloc) is used in arch/arm64/kernel/cpufeature.c:

  create_kpti_ng_temp_pgd(kpti_ng_temp_pgd, __pa(alloc), KPTI_NG_TEMP_VA,
                          PAGE_SIZE, PAGE_KERNEL, kpti_ng_pgd_alloc, 0);

which is an alias for __create_pgd_mapping_locked() with prototype:

  extern __alias(__create_pgd_mapping_locked)
  void create_kpti_ng_temp_pgd(pgd_t *pgdir, phys_addr_t phys,
                               unsigned long virt,
                               phys_addr_t size, pgprot_t prot,
                               phys_addr_t (*pgtable_alloc)(enum pgtable_type),
                               int flags);

__create_pgd_mapping_locked() passes the function pointer down:

  __create_pgd_mapping_locked() -> alloc_init_p4d() -> alloc_init_pud()

But the target function (kpti_ng_pgd_alloc) has the wrong signature:

  static phys_addr_t __init kpti_ng_pgd_alloc(int shift);

The "int" should be "enum pgtable_type".

To make "enum pgtable_type" available to cpufeature.c, move
enum pgtable_type definition from arch/arm64/mm/mmu.c to
arch/arm64/include/asm/mmu.h.

Adjust kpti_ng_pgd_alloc to use "enum pgtable_type" instead of "int".
The function behavior remains identical (parameter is unused).

Fixes: c64f46ee13 ("arm64: mm: use enum to identify pgtable level instead of *_SHIFT")
Cc: <stable@vger.kernel.org> # 6.16.x
Signed-off-by: Kees Cook <kees@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250829190721.it.373-kees@kernel.org
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/mmu.h

@@ -17,6 +17,13 @@
 #include <linux/refcount.h>
 #include <asm/cpufeature.h>
 
+enum pgtable_type {
+	TABLE_PTE,
+	TABLE_PMD,
+	TABLE_PUD,
+	TABLE_P4D,
+};
+
 typedef struct {
 	atomic64_t	id;
 #ifdef CONFIG_COMPAT

arch/arm64/kernel/cpufeature.c

@@ -84,6 +84,7 @@
 #include <asm/hwcap.h>
 #include <asm/insn.h>
 #include <asm/kvm_host.h>
+#include <asm/mmu.h>
 #include <asm/mmu_context.h>
 #include <asm/mte.h>
 #include <asm/hypervisor.h>
@@ -1945,11 +1946,11 @@ static bool has_pmuv3(const struct arm64_cpu_capabilities *entry, int scope)
 extern
 void create_kpti_ng_temp_pgd(pgd_t *pgdir, phys_addr_t phys, unsigned long virt,
 			     phys_addr_t size, pgprot_t prot,
-			     phys_addr_t (*pgtable_alloc)(int), int flags);
+			     phys_addr_t (*pgtable_alloc)(enum pgtable_type), int flags);
 
 static phys_addr_t __initdata kpti_ng_temp_alloc;
 
-static phys_addr_t __init kpti_ng_pgd_alloc(int shift)
+static phys_addr_t __init kpti_ng_pgd_alloc(enum pgtable_type type)
 {
 	kpti_ng_temp_alloc -= PAGE_SIZE;
 	return kpti_ng_temp_alloc;

arch/arm64/mm/mmu.c

@@ -47,13 +47,6 @@
 #define NO_CONT_MAPPINGS	BIT(1)
 #define NO_EXEC_MAPPINGS	BIT(2)	/* assumes FEAT_HPDS is not used */
 
-enum pgtable_type {
-	TABLE_PTE,
-	TABLE_PMD,
-	TABLE_PUD,
-	TABLE_P4D,
-};
-
 u64 kimage_voffset __ro_after_init;
 EXPORT_SYMBOL(kimage_voffset);