x86/boot/32: Restructure mk_early_pgtbl_32()

Prepare it for adding a temporary initrd mapping by splitting out the
actual map loop.

No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20231017211722.175910753@linutronix.de

arch/x86/kernel/head32.c

@@ -79,35 +79,40 @@ typedef pgd_t			pl2_t;
 #define SET_PL2(val)		{ .pgd = (val), }
 #endif
 
-void __init __no_stack_protector mk_early_pgtbl_32(void)
+static __init __no_stack_protector pte_t init_map(pte_t pte, pte_t **ptep, pl2_t **pl2p,
+						  const unsigned long limit)
 {
-	/* Enough space to fit pagetables for the low memory linear map */
-	const unsigned long limit = __pa_nodebug(_end) +
-		(PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT);
-	pte_t pte, *ptep = (pte_t *)__pa_nodebug(__brk_base);
-	pl2_t *pl2p = (pl2_t *)__pa_nodebug(pl2_base);
-	unsigned long *ptr;
-	int i;
-
-	pte.pte = PTE_IDENT_ATTR;
-
 	while ((pte.pte & PTE_PFN_MASK) < limit) {
-		pl2_t pl2 = SET_PL2((unsigned long)ptep | PDE_IDENT_ATTR);
-
-		*pl2p = pl2;
+		pl2_t pl2 = SET_PL2((unsigned long)*ptep | PDE_IDENT_ATTR);
+		int i;
 
+		**pl2p = pl2;
 		if (!IS_ENABLED(CONFIG_X86_PAE)) {
 			/* Kernel PDE entry */
-			*(pl2p +  ((PAGE_OFFSET >> PGDIR_SHIFT))) = pl2;
+			*(*pl2p + ((PAGE_OFFSET >> PGDIR_SHIFT))) = pl2;
 		}
 
 		for (i = 0; i < PTRS_PER_PTE; i++) {
-			*ptep = pte;
+			**ptep = pte;
 			pte.pte += PAGE_SIZE;
-			ptep++;
+			(*ptep)++;
 		}
-		pl2p++;
+		(*pl2p)++;
 	}
+	return pte;
+}
+
+void __init __no_stack_protector mk_early_pgtbl_32(void)
+{
+	/* Enough space to fit pagetables for the low memory linear map */
+	const unsigned long limit = __pa_nodebug(_end) +
+		(PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT);
+	pte_t pte, *ptep = (pte_t *)__pa_nodebug(__brk_base);
+	pl2_t *pl2p = (pl2_t *)__pa_nodebug(pl2_base);
+	unsigned long *ptr;
+
+	pte.pte = PTE_IDENT_ATTR;
+	pte = init_map(pte, &ptep, &pl2p, limit);
 
 	ptr = (unsigned long *)__pa_nodebug(&max_pfn_mapped);
 	/* Can't use pte_pfn() since it's a call with CONFIG_PARAVIRT */
@@ -116,4 +121,3 @@ void __init __no_stack_protector mk_early_pgtbl_32(void)
 	ptr = (unsigned long *)__pa_nodebug(&_brk_end);
 	*ptr = (unsigned long)ptep + PAGE_OFFSET;
 }
-