1 files changed, 253 insertions, 0 deletions
diff --git a/arch/x86/boot/startup/efi-mixed.S b/arch/x86/boot/startup/efi-mixed.S
new file mode 100644
index 000000000000..e04ed99bc449
--- /dev/null
+++ b/arch/x86/boot/startup/efi-mixed.S
@@ -0,0 +1,253 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2014, 2015 Intel Corporation; author Matt Fleming
+ *
+ * Early support for invoking 32-bit EFI services from a 64-bit kernel.
+ *
+ * Because this thunking occurs before ExitBootServices() we have to
+ * restore the firmware's 32-bit GDT and IDT before we make EFI service
+ * calls.
+ *
+ * On the plus side, we don't have to worry about mangling 64-bit
+ * addresses into 32-bits because we're executing with an identity
+ * mapped pagetable and haven't transitioned to 64-bit virtual addresses
+ * yet.
+ */
+
+#include <linux/linkage.h>
+#include <asm/desc_defs.h>
+#include <asm/msr.h>
+#include <asm/page_types.h>
+#include <asm/pgtable_types.h>
+#include <asm/processor-flags.h>
+#include <asm/segment.h>
+
+	.text
+	.code32
+#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
+SYM_FUNC_START(efi32_stub_entry)
+	call	1f
+1:	popl	%ecx
+
+	/* Clear BSS */
+	xorl	%eax, %eax
+	leal	(_bss - 1b)(%ecx), %edi
+	leal	(_ebss - 1b)(%ecx), %ecx
+	subl	%edi, %ecx
+	shrl	$2, %ecx
+	cld
+	rep	stosl
+
+	add	$0x4, %esp		/* Discard return address */
+	movl	8(%esp), %ebx		/* struct boot_params pointer */
+	jmp	efi32_startup
+SYM_FUNC_END(efi32_stub_entry)
+#endif
+
+/*
+ * Called using a far call from __efi64_thunk() below, using the x86_64 SysV
+ * ABI (except for R8/R9 which are inaccessible to 32-bit code - EAX/EBX are
+ * used instead).  EBP+16 points to the arguments passed via the stack.
+ *
+ * The first argument (EDI) is a pointer to the boot service or protocol, to
+ * which the remaining arguments are passed, each truncated to 32 bits.
+ */
+SYM_FUNC_START_LOCAL(efi_enter32)
+	/*
+	 * Convert x86-64 SysV ABI params to i386 ABI
+	 */
+	pushl	32(%ebp)	/* Up to 3 args passed via the stack */
+	pushl	24(%ebp)
+	pushl	16(%ebp)
+	pushl	%ebx		/* R9 */
+	pushl	%eax		/* R8 */
+	pushl	%ecx
+	pushl	%edx
+	pushl	%esi
+
+	/* Disable paging */
+	movl	%cr0, %eax
+	btrl	$X86_CR0_PG_BIT, %eax
+	movl	%eax, %cr0
+
+	/* Disable long mode via EFER */
+	movl	$MSR_EFER, %ecx
+	rdmsr
+	btrl	$_EFER_LME, %eax
+	wrmsr
+
+	call	*%edi
+
+	/* We must preserve return value */
+	movl	%eax, %edi
+
+	call	efi32_enable_long_mode
+
+	addl	$32, %esp
+	movl	%edi, %eax
+	lret
+SYM_FUNC_END(efi_enter32)
+
+	.code64
+SYM_FUNC_START(__efi64_thunk)
+	push	%rbp
+	movl	%esp, %ebp
+	push	%rbx
+
+	/* Move args #5 and #6 into 32-bit accessible registers */
+	movl	%r8d, %eax
+	movl	%r9d, %ebx
+
+	lcalll	*efi32_call(%rip)
+
+	pop	%rbx
+	pop	%rbp
+	RET
+SYM_FUNC_END(__efi64_thunk)
+
+	.code32
+SYM_FUNC_START_LOCAL(efi32_enable_long_mode)
+	movl	%cr4, %eax
+	btsl	$(X86_CR4_PAE_BIT), %eax
+	movl	%eax, %cr4
+
+	movl	$MSR_EFER, %ecx
+	rdmsr
+	btsl	$_EFER_LME, %eax
+	wrmsr
+
+	/* Disable interrupts - the firmware's IDT does not work in long mode */
+	cli
+
+	/* Enable paging */
+	movl	%cr0, %eax
+	btsl	$X86_CR0_PG_BIT, %eax
+	movl	%eax, %cr0
+	ret
+SYM_FUNC_END(efi32_enable_long_mode)
+
+/*
+ * This is the common EFI stub entry point for mixed mode. It sets up the GDT
+ * and page tables needed for 64-bit execution, after which it calls the
+ * common 64-bit EFI entrypoint efi_stub_entry().
+ *
+ * Arguments:	0(%esp)	image handle
+ * 		4(%esp)	EFI system table pointer
+ *		%ebx	struct boot_params pointer (or NULL)
+ *
+ * Since this is the point of no return for ordinary execution, no registers
+ * are considered live except for the function parameters. [Note that the EFI
+ * stub may still exit and return to the firmware using the Exit() EFI boot
+ * service.]
+ */
+SYM_FUNC_START_LOCAL(efi32_startup)
+	movl	%esp, %ebp
+
+	subl	$8, %esp
+	sgdtl	(%esp)			/* Save GDT descriptor to the stack */
+	movl	2(%esp), %esi		/* Existing GDT pointer */
+	movzwl	(%esp), %ecx		/* Existing GDT limit */
+	inc	%ecx			/* Existing GDT size */
+	andl	$~7, %ecx		/* Ensure size is multiple of 8 */
+
+	subl	%ecx, %esp		/* Allocate new GDT */
+	andl	$~15, %esp		/* Realign the stack */
+	movl	%esp, %edi		/* New GDT address */
+	leal	7(%ecx), %eax		/* New GDT limit */
+	pushw	%cx			/* Push 64-bit CS (for LJMP below) */
+	pushl	%edi			/* Push new GDT address */
+	pushw	%ax			/* Push new GDT limit */
+
+	/* Copy GDT to the stack and add a 64-bit code segment at the end */
+	movl	$GDT_ENTRY(DESC_CODE64, 0, 0xfffff) & 0xffffffff, (%edi,%ecx)
+	movl	$GDT_ENTRY(DESC_CODE64, 0, 0xfffff) >> 32, 4(%edi,%ecx)
+	shrl	$2, %ecx
+	cld
+	rep	movsl			/* Copy the firmware GDT */
+	lgdtl	(%esp)			/* Switch to the new GDT */
+
+	call	1f
+1:	pop	%edi
+
+	/* Record mixed mode entry */
+	movb	$0x0, (efi_is64 - 1b)(%edi)
+
+	/* Set up indirect far call to re-enter 32-bit mode */
+	leal	(efi32_call - 1b)(%edi), %eax
+	addl	%eax, (%eax)
+	movw	%cs, 4(%eax)
+
+	/* 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
+
+	call	efi32_enable_long_mode
+
+	/* Set up far jump to 64-bit mode (CS is already on the stack) */
+	leal	(efi_stub_entry - 1b)(%edi), %eax
+	movl	%eax, 2(%esp)
+
+	movl	0(%ebp), %edi
+	movl	4(%ebp), %esi
+	movl	%ebx, %edx
+	ljmpl	*2(%esp)
+SYM_FUNC_END(efi32_startup)
+
+/*
+ * efi_status_t efi32_pe_entry(efi_handle_t image_handle,
+ *			       efi_system_table_32_t *sys_table)
+ */
+SYM_FUNC_START(efi32_pe_entry)
+	pushl	%ebx				// save callee-save registers
+
+	/* Check whether the CPU supports long mode */
+	movl	$0x80000001, %eax		// assume extended info support
+	cpuid
+	btl	$29, %edx			// check long mode bit
+	jnc	1f
+	leal	8(%esp), %esp			// preserve stack alignment
+	xor	%ebx, %ebx			// no struct boot_params pointer
+	jmp	efi32_startup			// only ESP and EBX remain live
+1:	movl	$0x80000003, %eax		// EFI_UNSUPPORTED
+	popl	%ebx
+	RET
+SYM_FUNC_END(efi32_pe_entry)
+
+#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
+	.org	efi32_stub_entry + 0x200
+	.code64
+SYM_FUNC_START_NOALIGN(efi64_stub_entry)
+	jmp	efi_handover_entry
+SYM_FUNC_END(efi64_stub_entry)
+#endif
+
+	.data
+	.balign	8
+SYM_DATA_START_LOCAL(efi32_call)
+	.long	efi_enter32 - .
+	.word	0x0
+SYM_DATA_END(efi32_call)
+SYM_DATA(efi_is64, .byte 1)
+
+	.bss
+	.balign PAGE_SIZE
+SYM_DATA_LOCAL(pte, .fill 6 * PAGE_SIZE, 1, 0)