[PATCHv7 07/14] x86/boot/64: Rewrite startup_64 in C

Kirill A. Shutemov
2017-06-06T11:32:04Z

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>
---
arch/x86/kernel/head64.c | 85 +++++++++++++++++++++++++++++++++++++++++-
arch/x86/kernel/head_64.S | 95 ++---------------------------------------------
2 files changed, 87 insertions(+), 93 deletions(-)

diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 43b7002f44fb..b59c550b1d3a 100644
--- a/arch/x86/kernel/head64.c
+++ b/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)
{
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index ac9d327d2e42..1432d530fa35 100644
--- a/arch/x86/kernel/head_64.S
+++ b/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
-
- 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
+ pushq %rsi
+ call __startup_64
+ popq %rsi

-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)
--
2.11.0