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-rw-r--r--arch/x86/boot/compressed/efi_mixed.S328
1 files changed, 328 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/efi_mixed.S b/arch/x86/boot/compressed/efi_mixed.S
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+/* 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/msr.h>
+#include <asm/page_types.h>
+#include <asm/processor-flags.h>
+#include <asm/segment.h>
+
+ .code64
+ .text
+/*
+ * When booting in 64-bit mode on 32-bit EFI firmware, startup_64_mixed_mode()
+ * is the first thing that runs after switching to long mode. Depending on
+ * whether the EFI handover protocol or the compat entry point was used to
+ * enter the kernel, it will either branch to the common 64-bit EFI stub
+ * entrypoint efi_stub_entry() directly, or via the 64-bit EFI PE/COFF
+ * entrypoint efi_pe_entry(). In the former case, the bootloader must provide a
+ * struct bootparams pointer as the third argument, so the presence of such a
+ * pointer is used to disambiguate.
+ *
+ * +--------------+
+ * +------------------+ +------------+ +------>| efi_pe_entry |
+ * | efi32_pe_entry |---->| | | +-----------+--+
+ * +------------------+ | | +------+----------------+ |
+ * | startup_32 |---->| startup_64_mixed_mode | |
+ * +------------------+ | | +------+----------------+ |
+ * | efi32_stub_entry |---->| | | |
+ * +------------------+ +------------+ | |
+ * V |
+ * +------------+ +----------------+ |
+ * | startup_64 |<----| efi_stub_entry |<--------+
+ * +------------+ +----------------+
+ */
+SYM_FUNC_START(startup_64_mixed_mode)
+ lea efi32_boot_args(%rip), %rdx
+ mov 0(%rdx), %edi
+ mov 4(%rdx), %esi
+#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
+ mov 8(%rdx), %edx // saved bootparams pointer
+ test %edx, %edx
+ jnz efi_stub_entry
+#endif
+ /*
+ * efi_pe_entry uses MS calling convention, which requires 32 bytes of
+ * shadow space on the stack even if all arguments are passed in
+ * registers. We also need an additional 8 bytes for the space that
+ * would be occupied by the return address, and this also results in
+ * the correct stack alignment for entry.
+ */
+ sub $40, %rsp
+ mov %rdi, %rcx // MS calling convention
+ mov %rsi, %rdx
+ jmp efi_pe_entry
+SYM_FUNC_END(startup_64_mixed_mode)
+
+SYM_FUNC_START(__efi64_thunk)
+ push %rbp
+ push %rbx
+
+ movl %ds, %eax
+ push %rax
+ movl %es, %eax
+ push %rax
+ movl %ss, %eax
+ push %rax
+
+ /* Copy args passed on stack */
+ movq 0x30(%rsp), %rbp
+ movq 0x38(%rsp), %rbx
+ movq 0x40(%rsp), %rax
+
+ /*
+ * Convert x86-64 ABI params to i386 ABI
+ */
+ subq $64, %rsp
+ movl %esi, 0x0(%rsp)
+ movl %edx, 0x4(%rsp)
+ movl %ecx, 0x8(%rsp)
+ movl %r8d, 0xc(%rsp)
+ movl %r9d, 0x10(%rsp)
+ movl %ebp, 0x14(%rsp)
+ movl %ebx, 0x18(%rsp)
+ movl %eax, 0x1c(%rsp)
+
+ leaq 0x20(%rsp), %rbx
+ sgdt (%rbx)
+ sidt 16(%rbx)
+
+ leaq 1f(%rip), %rbp
+
+ /*
+ * Switch to IDT and GDT with 32-bit segments. These are the firmware
+ * GDT and IDT that were installed when the kernel started executing.
+ * The pointers were saved by the efi32_entry() routine below.
+ *
+ * Pass the saved DS selector to the 32-bit code, and use far return to
+ * restore the saved CS selector.
+ */
+ lidt efi32_boot_idt(%rip)
+ lgdt efi32_boot_gdt(%rip)
+
+ movzwl efi32_boot_ds(%rip), %edx
+ movzwq efi32_boot_cs(%rip), %rax
+ pushq %rax
+ leaq efi_enter32(%rip), %rax
+ pushq %rax
+ lretq
+
+1: addq $64, %rsp
+ movq %rdi, %rax
+
+ pop %rbx
+ movl %ebx, %ss
+ pop %rbx
+ movl %ebx, %es
+ pop %rbx
+ movl %ebx, %ds
+ /* Clear out 32-bit selector from FS and GS */
+ xorl %ebx, %ebx
+ movl %ebx, %fs
+ movl %ebx, %gs
+
+ /*
+ * Convert 32-bit status code into 64-bit.
+ */
+ roll $1, %eax
+ rorq $1, %rax
+
+ pop %rbx
+ pop %rbp
+ RET
+SYM_FUNC_END(__efi64_thunk)
+
+ .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 */
+ popl %ecx
+ popl %edx
+ popl %esi
+ jmp efi32_entry
+SYM_FUNC_END(efi32_stub_entry)
+#endif
+
+/*
+ * EFI service pointer must be in %edi.
+ *
+ * The stack should represent the 32-bit calling convention.
+ */
+SYM_FUNC_START_LOCAL(efi_enter32)
+ /* Load firmware selector into data and stack segment registers */
+ movl %edx, %ds
+ movl %edx, %es
+ movl %edx, %fs
+ movl %edx, %gs
+ movl %edx, %ss
+
+ /* Reload pgtables */
+ movl %cr3, %eax
+ movl %eax, %cr3
+
+ /* 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
+
+ /*
+ * Some firmware will return with interrupts enabled. Be sure to
+ * disable them before we switch GDTs and IDTs.
+ */
+ cli
+
+ lidtl 16(%ebx)
+ lgdtl (%ebx)
+
+ movl %cr4, %eax
+ btsl $(X86_CR4_PAE_BIT), %eax
+ movl %eax, %cr4
+
+ movl %cr3, %eax
+ movl %eax, %cr3
+
+ movl $MSR_EFER, %ecx
+ rdmsr
+ btsl $_EFER_LME, %eax
+ wrmsr
+
+ xorl %eax, %eax
+ lldt %ax
+
+ pushl $__KERNEL_CS
+ pushl %ebp
+
+ /* Enable paging */
+ movl %cr0, %eax
+ btsl $X86_CR0_PG_BIT, %eax
+ movl %eax, %cr0
+ lret
+SYM_FUNC_END(efi_enter32)
+
+/*
+ * This is the common EFI stub entry point for mixed mode.
+ *
+ * Arguments: %ecx image handle
+ * %edx EFI system table pointer
+ * %esi struct bootparams pointer (or NULL when not using
+ * the EFI handover protocol)
+ *
+ * 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_entry)
+ call 1f
+1: pop %ebx
+
+ /* Save firmware GDTR and code/data selectors */
+ sgdtl (efi32_boot_gdt - 1b)(%ebx)
+ movw %cs, (efi32_boot_cs - 1b)(%ebx)
+ movw %ds, (efi32_boot_ds - 1b)(%ebx)
+
+ /* Store firmware IDT descriptor */
+ sidtl (efi32_boot_idt - 1b)(%ebx)
+
+ /* Store boot arguments */
+ leal (efi32_boot_args - 1b)(%ebx), %ebx
+ movl %ecx, 0(%ebx)
+ movl %edx, 4(%ebx)
+ movl %esi, 8(%ebx)
+ movb $0x0, 12(%ebx) // efi_is64
+
+ /* Disable paging */
+ movl %cr0, %eax
+ btrl $X86_CR0_PG_BIT, %eax
+ movl %eax, %cr0
+
+ jmp startup_32
+SYM_FUNC_END(efi32_entry)
+
+/*
+ * 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 %ebp
+ movl %esp, %ebp
+ pushl %ebx // save callee-save registers
+ pushl %edi
+
+ call verify_cpu // check for long mode support
+ testl %eax, %eax
+ movl $0x80000003, %eax // EFI_UNSUPPORTED
+ jnz 2f
+
+ movl 8(%ebp), %ecx // image_handle
+ movl 12(%ebp), %edx // sys_table
+ xorl %esi, %esi
+ jmp efi32_entry // pass %ecx, %edx, %esi
+ // no other registers remain live
+
+2: popl %edi // restore callee-save registers
+ popl %ebx
+ leave
+ 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_boot_gdt)
+ .word 0
+ .quad 0
+SYM_DATA_END(efi32_boot_gdt)
+
+SYM_DATA_START_LOCAL(efi32_boot_idt)
+ .word 0
+ .quad 0
+SYM_DATA_END(efi32_boot_idt)
+
+SYM_DATA_LOCAL(efi32_boot_cs, .word 0)
+SYM_DATA_LOCAL(efi32_boot_ds, .word 0)
+SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0)
+SYM_DATA(efi_is64, .byte 1)