x86/boot/64: Rewrite startup_64() in C

The patch write most of startup_64 logic in C.

This is preparation for 5-level paging enabling.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20170606113133.22974-8-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/head64.c

@@ -35,9 +35,92 @@
  */
 extern pgd_t early_level4_pgt[PTRS_PER_PGD];
 extern pmd_t early_dynamic_pgts[EARLY_DYNAMIC_PAGE_TABLES][PTRS_PER_PMD];
-static unsigned int __initdata next_early_pgt = 2;
+static unsigned int __initdata next_early_pgt;
 pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
 
+static void __init *fixup_pointer(void *ptr, unsigned long physaddr)
+{
+	return ptr - (void *)_text + (void *)physaddr;
+}
+
+void __init __startup_64(unsigned long physaddr)
+{
+	unsigned long load_delta, *p;
+	pgdval_t *pgd;
+	pudval_t *pud;
+	pmdval_t *pmd, pmd_entry;
+	int i;
+
+	/* Is the address too large? */
+	if (physaddr >> MAX_PHYSMEM_BITS)
+		for (;;);
+
+	/*
+	 * Compute the delta between the address I am compiled to run at
+	 * and the address I am actually running at.
+	 */
+	load_delta = physaddr - (unsigned long)(_text - __START_KERNEL_map);
+
+	/* Is the address not 2M aligned? */
+	if (load_delta & ~PMD_PAGE_MASK)
+		for (;;);
+
+	/* Fixup the physical addresses in the page table */
+
+	pgd = fixup_pointer(&early_level4_pgt, physaddr);
+	pgd[pgd_index(__START_KERNEL_map)] += load_delta;
+
+	pud = fixup_pointer(&level3_kernel_pgt, physaddr);
+	pud[510] += load_delta;
+	pud[511] += load_delta;
+
+	pmd = fixup_pointer(level2_fixmap_pgt, physaddr);
+	pmd[506] += load_delta;
+
+	/*
+	 * Set up the identity mapping for the switchover.  These
+	 * entries should *NOT* have the global bit set!  This also
+	 * creates a bunch of nonsense entries but that is fine --
+	 * it avoids problems around wraparound.
+	 */
+
+	pud = fixup_pointer(early_dynamic_pgts[next_early_pgt++], physaddr);
+	pmd = fixup_pointer(early_dynamic_pgts[next_early_pgt++], physaddr);
+
+	i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD;
+	pgd[i + 0] = (pgdval_t)pud + _KERNPG_TABLE;
+	pgd[i + 1] = (pgdval_t)pud + _KERNPG_TABLE;
+
+	i = (physaddr >> PUD_SHIFT) % PTRS_PER_PUD;
+	pud[i + 0] = (pudval_t)pmd + _KERNPG_TABLE;
+	pud[i + 1] = (pudval_t)pmd + _KERNPG_TABLE;
+
+	pmd_entry = __PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL;
+	pmd_entry +=  physaddr;
+
+	for (i = 0; i < DIV_ROUND_UP(_end - _text, PMD_SIZE); i++) {
+		int idx = i + (physaddr >> PMD_SHIFT) % PTRS_PER_PMD;
+		pmd[idx] = pmd_entry + i * PMD_SIZE;
+	}
+
+	/*
+	 * Fixup the kernel text+data virtual addresses. Note that
+	 * we might write invalid pmds, when the kernel is relocated
+	 * cleanup_highmap() fixes this up along with the mappings
+	 * beyond _end.
+	 */
+
+	pmd = fixup_pointer(level2_kernel_pgt, physaddr);
+	for (i = 0; i < PTRS_PER_PMD; i++) {
+		if (pmd[i] & _PAGE_PRESENT)
+			pmd[i] += load_delta;
+	}
+
+	/* Fixup phys_base */
+	p = fixup_pointer(&phys_base, physaddr);
+	*p += load_delta;
+}
+
 /* Wipe all early page tables except for the kernel symbol map */
 static void __init reset_early_page_tables(void)
 {

arch/x86/kernel/head_64.S

@@ -72,100 +72,11 @@ startup_64:
 	/* Sanitize CPU configuration */
 	call verify_cpu
 
-	/*
-	 * Compute the delta between the address I am compiled to run at and the
-	 * address I am actually running at.
-	 */
-	leaq	_text(%rip), %rbp
-	subq	$_text - __START_KERNEL_map, %rbp
-
-	/* Is the address not 2M aligned? */
-	testl	$~PMD_PAGE_MASK, %ebp
-	jnz	bad_address
-
-	/*
-	 * Is the address too large?
-	 */
-	leaq	_text(%rip), %rax
-	shrq	$MAX_PHYSMEM_BITS, %rax
-	jnz	bad_address
-
-	/*
-	 * Fixup the physical addresses in the page table
-	 */
-	addq	%rbp, early_level4_pgt + (L4_START_KERNEL*8)(%rip)
-
-	addq	%rbp, level3_kernel_pgt + (510*8)(%rip)
-	addq	%rbp, level3_kernel_pgt + (511*8)(%rip)
-
-	addq	%rbp, level2_fixmap_pgt + (506*8)(%rip)
-
-	/*
-	 * Set up the identity mapping for the switchover.  These
-	 * entries should *NOT* have the global bit set!  This also
-	 * creates a bunch of nonsense entries but that is fine --
-	 * it avoids problems around wraparound.
-	 */
 	leaq	_text(%rip), %rdi
-	leaq	early_level4_pgt(%rip), %rbx
+	pushq	%rsi
+	call	__startup_64
+	popq	%rsi
 
-	movq	%rdi, %rax
-	shrq	$PGDIR_SHIFT, %rax
-
-	leaq	(PAGE_SIZE + _KERNPG_TABLE)(%rbx), %rdx
-	movq	%rdx, 0(%rbx,%rax,8)
-	movq	%rdx, 8(%rbx,%rax,8)
-
-	addq	$PAGE_SIZE, %rdx
-	movq	%rdi, %rax
-	shrq	$PUD_SHIFT, %rax
-	andl	$(PTRS_PER_PUD-1), %eax
-	movq	%rdx, PAGE_SIZE(%rbx,%rax,8)
-	incl	%eax
-	andl	$(PTRS_PER_PUD-1), %eax
-	movq	%rdx, PAGE_SIZE(%rbx,%rax,8)
-
-	addq	$PAGE_SIZE * 2, %rbx
-	movq	%rdi, %rax
-	shrq	$PMD_SHIFT, %rdi
-	addq	$(__PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL), %rax
-	leaq	(_end - 1)(%rip), %rcx
-	shrq	$PMD_SHIFT, %rcx
-	subq	%rdi, %rcx
-	incl	%ecx
-
-1:
-	andq	$(PTRS_PER_PMD - 1), %rdi
-	movq	%rax, (%rbx,%rdi,8)
-	incq	%rdi
-	addq	$PMD_SIZE, %rax
-	decl	%ecx
-	jnz	1b
-
-	test %rbp, %rbp
-	jz .Lskip_fixup
-
-	/*
-	 * Fixup the kernel text+data virtual addresses. Note that
-	 * we might write invalid pmds, when the kernel is relocated
-	 * cleanup_highmap() fixes this up along with the mappings
-	 * beyond _end.
-	 */
-	leaq	level2_kernel_pgt(%rip), %rdi
-	leaq	PAGE_SIZE(%rdi), %r8
-	/* See if it is a valid page table entry */
-1:	testb	$_PAGE_PRESENT, 0(%rdi)
-	jz	2f
-	addq	%rbp, 0(%rdi)
-	/* Go to the next page */
-2:	addq	$8, %rdi
-	cmp	%r8, %rdi
-	jne	1b
-
-	/* Fixup phys_base */
-	addq	%rbp, phys_base(%rip)
-
-.Lskip_fixup:
 	movq	$(early_level4_pgt - __START_KERNEL_map), %rax
 	jmp 1f
 ENTRY(secondary_startup_64)