x86/efi/mixed: Set up 1:1 mapping of lower 4GiB in the stub

In preparation for dropping the dependency on startup_32 entirely in the
next patch, add the code that sets up the 1:1 mapping of the lower 4 GiB
of system RAM to the mixed mode stub.

The reload of CR3 after the long mode switch will be removed in a
subsequent patch, when it is no longer needed.

Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/arch/x86/boot/compressed/efi_mixed.S b/arch/x86/boot/compressed/efi_mixed.S
index 0b6b37b08f82fe2f9ad738e0d844507cafa44063..dca916c3e6f0a56b277c79eebdc1ff3ce031cba6 100644 (file)
--- a/arch/x86/boot/compressed/efi_mixed.S
+++ b/arch/x86/boot/compressed/efi_mixed.S
@@ -18,6 +18,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/msr.h>
 #include <asm/page_types.h>
+#include <asm/pgtable_types.h>
 #include <asm/processor-flags.h>
 #include <asm/segment.h>
 #include <asm/setup.h>
@@ -52,6 +53,9 @@ SYM_FUNC_START(startup_64_mixed_mode)
        mov     0(%rdx), %edi
        mov     4(%rdx), %esi
 
+       leaq    (pte + 5 * PAGE_SIZE)(%rip), %rax
+       movq    %rax, %cr3              // reload after startup_32
+
        /* Switch to the firmware's stack */
        movl    efi32_boot_sp(%rip), %esp
        andl    $~7, %esp
@@ -267,11 +271,32 @@ SYM_FUNC_START_LOCAL(efi32_entry)
        movl    $_end - 1b, BP_init_size(%esi)
        subl    $startup_32 - 1b, BP_init_size(%esi)
 
+       call    1f
+1:     pop     %edi
+
        /* Disable paging */
        movl    %cr0, %eax
        btrl    $X86_CR0_PG_BIT, %eax
        movl    %eax, %cr0
 
+       /* Set up 1:1 mapping */
+       leal    (pte - 1b)(%edi), %eax
+       movl    $_PAGE_PRESENT | _PAGE_RW | _PAGE_PSE, %ecx
+       leal    (_PAGE_PRESENT | _PAGE_RW)(%eax), %edx
+2:     movl    %ecx, (%eax)
+       addl    $8, %eax
+       addl    $PMD_SIZE, %ecx
+       jnc     2b
+
+       movl    $PAGE_SIZE, %ecx
+       .irpc   l, 0123
+       movl    %edx, \l * 8(%eax)
+       addl    %ecx, %edx
+       .endr
+       addl    %ecx, %eax
+       movl    %edx, (%eax)
+       movl    %eax, %cr3
+
        jmp     startup_32
 SYM_FUNC_END(efi32_entry)
 
@@ -322,3 +347,7 @@ SYM_DATA_LOCAL(efi32_boot_ds, .word 0)
 SYM_DATA_LOCAL(efi32_boot_sp, .long 0)
 SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0)
 SYM_DATA(efi_is64, .byte 1)
+
+       .bss
+       .balign PAGE_SIZE
+SYM_DATA_LOCAL(pte, .fill 6 * PAGE_SIZE, 1, 0)