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Date: Tue, 4 Mar 2014 13:14:15 +0000 From: Matt Fleming <matt@...sole-pimps.org> To: linux-efi@...r.kernel.org Cc: "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>, Alan Cox <alan@...rguk.ukuu.org.uk>, Matthew Garrett <mjg59@...f.ucam.org>, linux-kernel@...r.kernel.org, Matt Fleming <matt.fleming@...el.com> Subject: [PATCH 07/13] x86/efi: Add early thunk code to go from 64-bit to 32-bit From: Matt Fleming <matt.fleming@...el.com> Implement the transition code to go from IA32e mode to protected mode in the EFI boot stub. This is required to use 32-bit EFI services from a 64-bit kernel. Since EFI boot stub is executed in an identity-mapped region, there's not much we need to do before invoking the 32-bit EFI boot services. However, we do reload the firmware's global descriptor table (efi32_boot_gdt) in case things like timer events are still running in the firmware. Signed-off-by: Matt Fleming <matt.fleming@...el.com> --- arch/x86/boot/compressed/efi_stub_64.S | 29 +++++++ arch/x86/platform/efi/efi_stub_64.S | 150 +++++++++++++++++++++++++++++++++ 2 files changed, 179 insertions(+) diff --git a/arch/x86/boot/compressed/efi_stub_64.S b/arch/x86/boot/compressed/efi_stub_64.S index cedc60de86eb..7ff3632806b1 100644 --- a/arch/x86/boot/compressed/efi_stub_64.S +++ b/arch/x86/boot/compressed/efi_stub_64.S @@ -1 +1,30 @@ +#include <asm/segment.h> +#include <asm/msr.h> +#include <asm/processor-flags.h> + #include "../../platform/efi/efi_stub_64.S" + +#ifdef CONFIG_EFI_MIXED + .code64 + .text +ENTRY(efi64_thunk) + push %rbp + push %rbx + + subq $16, %rsp + leaq efi_exit32(%rip), %rax + movl %eax, 8(%rsp) + leaq efi_gdt64(%rip), %rax + movl %eax, 4(%rsp) + movl %eax, 2(%rax) /* Fixup the gdt base address */ + leaq efi32_boot_gdt(%rip), %rax + movl %eax, (%rsp) + + call __efi64_thunk + + addq $16, %rsp + pop %rbx + pop %rbp + ret +ENDPROC(efi64_thunk) +#endif /* CONFIG_EFI_MIXED */ diff --git a/arch/x86/platform/efi/efi_stub_64.S b/arch/x86/platform/efi/efi_stub_64.S index 88073b140298..a790d69cc85e 100644 --- a/arch/x86/platform/efi/efi_stub_64.S +++ b/arch/x86/platform/efi/efi_stub_64.S @@ -7,6 +7,10 @@ */ #include <linux/linkage.h> +#include <asm/segment.h> +#include <asm/msr.h> +#include <asm/processor-flags.h> +#include <asm/page_types.h> #define SAVE_XMM \ mov %rsp, %rax; \ @@ -164,6 +168,152 @@ ENTRY(efi_call6) ret ENDPROC(efi_call6) +#ifdef CONFIG_EFI_MIXED + +/* + * We run this function from the 1:1 mapping. + * + * This function must be invoked with a 1:1 mapped stack. + */ +ENTRY(__efi64_thunk) + subq $32, %rsp + movl %esi, 0x0(%rsp) + movl %edx, 0x4(%rsp) + movl %ecx, 0x8(%rsp) + movq %r8, %rsi + movl %esi, 0xc(%rsp) + movq %r9, %rsi + movl %esi, 0x10(%rsp) + + sgdt save_gdt(%rip) + + leaq 1f(%rip), %rbx + movq %rbx, func_rt_ptr(%rip) + + /* Switch to gdt with 32-bit segments */ + movl 40(%rsp), %eax + lgdt (%rax) + + leaq efi_enter32(%rip), %rax + pushq $__KERNEL_CS + pushq %rax + lretq + +1: addq $32, %rsp + + lgdt save_gdt(%rip) + + /* + * Convert 32-bit status code into 64-bit. + */ + test %rax, %rax + jz 1f + movl %eax, %ecx + andl $0x0fffffff, %ecx + andl $0xf0000000, %eax + shl $32, %rax + or %rcx, %rax +1: + ret +ENDPROC(__efi64_thunk) + +ENTRY(efi_exit32) + xorq %rax, %rax + movl %eax, %ds + movl %eax, %es + movl %eax, %ss + + movq func_rt_ptr(%rip), %rax + push %rax + mov %rdi, %rax + ret +ENDPROC(efi_exit32) + + .code32 +/* + * EFI service pointer must be in %edi. + * + * The stack should represent the 32-bit calling convention. + */ +ENTRY(efi_enter32) + movl $__KERNEL_DS, %eax + movl %eax, %ds + movl %eax, %es + movl %eax, %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 + + movl 44(%esp), %eax + movl %eax, 2(%eax) + lgdtl (%eax) + + 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 + + movl 48(%esp), %eax + pushl $__KERNEL_CS + pushl %eax + + /* Enable paging */ + movl %cr0, %eax + btsl $X86_CR0_PG_BIT, %eax + movl %eax, %cr0 + lret +ENDPROC(efi_enter32) + + .data + .balign 8 + .global efi32_boot_gdt +efi32_boot_gdt: .word 0 + .quad 0 + +save_gdt: .word 0 + .quad 0 +func_rt_ptr: .quad 0 + + .global efi_gdt64 +efi_gdt64: + .word efi_gdt64_end - efi_gdt64 + .long 0 /* Filled out by user */ + .word 0 + .quad 0x0000000000000000 /* NULL descriptor */ + .quad 0x00af9a000000ffff /* __KERNEL_CS */ + .quad 0x00cf92000000ffff /* __KERNEL_DS */ + .quad 0x0080890000000000 /* TS descriptor */ + .quad 0x0000000000000000 /* TS continued */ +efi_gdt64_end: +#endif /* CONFIG_EFI_MIXED */ + .data ENTRY(efi_scratch) .fill 3,8,0 -- 1.8.5.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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