From: Ard Biesheuvel <ardb@xxxxxxxxxx> The EFI mixed mode startup code calls into startup_32 in the legacy decompressor with a mocked up boot_params struct, only to get it to set up the 1:1 mapping of the lower 4 GiB of memory and switch to a GDT that supports 64-bit mode. In order to be able to reuse the EFI mixed mode startup code in EFI zboot images, which do not incorporate the legacy decompressor code, decouple it, by building the 1:1 map and installing the GDT directly. This also removes the need to preserve and restore the stack pointer and the arguments passed to the entrypoint, and instead, the firmware stack can be retained, and the arguments can be loaded from it at the point where they are needed, i.e., before calling into the EFI stub C code. Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> --- arch/x86/boot/compressed/efi_mixed.S | 143 ++++++++++++-------- arch/x86/boot/compressed/head_64.S | 7 - 2 files changed, 86 insertions(+), 64 deletions(-) diff --git a/arch/x86/boot/compressed/efi_mixed.S b/arch/x86/boot/compressed/efi_mixed.S index 067e10eb7897..c010aba7a0d0 100644 --- a/arch/x86/boot/compressed/efi_mixed.S +++ b/arch/x86/boot/compressed/efi_mixed.S @@ -15,15 +15,18 @@ */ #include <linux/linkage.h> -#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> .code64 .text + .balign 8 +SYM_DATA_LOCAL(gdt, .quad 0x0, 0x0, 0xaf9a000000ffff) /* __KERNEL_CS */ + .set gdt_size, . - gdt + /* * 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 @@ -35,30 +38,34 @@ * pointer is used to disambiguate. * * +--------------+ - * +------------------+ +------------+ +------>| efi_pe_entry | - * | efi32_pe_entry |---->| | | +-----------+--+ - * +------------------+ | | +------+----------------+ | - * | startup_32 |---->| startup_64_mixed_mode | | - * +------------------+ | | +------+----------------+ | - * | efi32_stub_entry |---->| | | | - * +------------------+ +------------+ | | + * +------------------+ +-------------+ +------>| efi_pe_entry | + * | efi32_pe_entry |--->| | | +-----------+--+ + * +------------------+ | | +------+----------------+ | + * | efi32_entry |---->| startup_64_mixed_mode | | + * +------------------+ | | +------+----------------+ | + * | efi32_stub_entry |--->| | | | + * +------------------+ +-------------+ | | * V | - * +------------+ +----------------+ | - * | startup_64 |<----| efi_stub_entry |<--------+ - * +------------+ +----------------+ + * +-------------+ +----------------+ | + * | vmlinux |<----| efi_stub_entry |<--------+ + * +-------------+ +----------------+ */ -SYM_FUNC_START(startup_64_mixed_mode) - lea efi32_boot_args(%rip), %rdx - mov 0(%rdx), %edi - mov 4(%rdx), %esi +SYM_FUNC_START_LOCAL_NOALIGN(startup_64_mixed_mode) + xorl %eax, %eax + movl %eax, %ds + movl %eax, %es + movl %eax, %ss + movl %eax, %fs + movl %eax, %gs - /* Switch to the firmware's stack */ - movl efi32_boot_sp(%rip), %esp - andl $~7, %esp + movl 0(%rsp), %ecx // MS calling convention + movl 4(%rsp), %edx #ifdef CONFIG_EFI_HANDOVER_PROTOCOL - mov 8(%rdx), %edx // saved bootparams pointer - test %edx, %edx + test %edi, %edi // struct boot_params provided? + movl %edx, %esi // SysV calling convention + cmovnzl %edi, %edx + movl %ecx, %edi jnz efi_stub_entry #endif /* @@ -69,8 +76,6 @@ SYM_FUNC_START(startup_64_mixed_mode) * 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) @@ -151,7 +156,6 @@ SYM_FUNC_END(__efi64_thunk) SYM_FUNC_START(efi32_stub_entry) call 1f 1: popl %ecx - leal (efi32_boot_args - 1b)(%ecx), %ebx /* Clear BSS */ xorl %eax, %eax @@ -163,10 +167,7 @@ SYM_FUNC_START(efi32_stub_entry) rep stosl add $0x4, %esp /* Discard return address */ - popl %ecx - popl %edx - popl %esi - movl %esi, 8(%ebx) + movl 8(%esp), %edi /* struct boot_params pointer */ jmp efi32_entry SYM_FUNC_END(efi32_stub_entry) #endif @@ -241,8 +242,9 @@ 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 + * Arguments: 0(%esp) image handle + * 4(%esp) EFI system table pointer + * %edi 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 @@ -261,31 +263,58 @@ SYM_FUNC_START_LOCAL(efi32_entry) /* Store firmware IDT descriptor */ sidtl (efi32_boot_idt - 1b)(%ebx) - /* Store firmware stack pointer */ - movl %esp, (efi32_boot_sp - 1b)(%ebx) - - /* Store boot arguments */ - leal (efi32_boot_args - 1b)(%ebx), %ebx - movl %ecx, 0(%ebx) - movl %edx, 4(%ebx) - movb $0x0, 12(%ebx) // efi_is64 - - /* - * Allocate some memory for a temporary struct boot_params, which only - * needs the minimal pieces that startup_32() relies on. - */ - subl $PARAM_SIZE, %esp - movl %esp, %esi - movl $PAGE_SIZE, BP_kernel_alignment(%esi) - movl $_end - 1b, BP_init_size(%esi) - subl $startup_32 - 1b, BP_init_size(%esi) + /* Record mixed mode entry */ + movb $0x0, (efi_is64 - 1b)(%ebx) /* Disable paging */ movl %cr0, %eax btrl $X86_CR0_PG_BIT, %eax movl %eax, %cr0 - jmp startup_32 + /* Set up 1:1 mapping */ + leal (pte - 1b)(%ebx), %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 + + xor %ecx, %ecx + movl $PAGE_SIZE, %esi +3: movl %edx, (%eax,%ecx,8) + addl %esi, %edx + inc %ecx + cmp $4, %ecx + jl 3b + + addl %esi, %eax + movl %edx, (%eax) + movl %eax, %cr3 + + movl %cr4, %eax + orl $X86_CR4_PAE, %eax + movl %eax, %cr4 + + movl $MSR_EFER, %ecx + rdmsr + btsl $_EFER_LME, %eax + wrmsr + + leal (gdt - 1b)(%ebx), %ecx + pushl %ecx + pushw $gdt_size - 1 + lgdtl (%esp) + lea 6(%esp), %esp + + /* Enable paging and jump to long mode */ + leal (startup_64_mixed_mode - 1b)(%ebx), %ecx + pushl $__KERNEL_CS + pushl %ecx + movl %cr0, %eax + btsl $X86_CR0_PG_BIT, %eax + movl %eax, %cr0 + lret SYM_FUNC_END(efi32_entry) /* @@ -301,10 +330,8 @@ SYM_FUNC_START(efi32_pe_entry) btl $29, %edx // check long mode bit jnc 1f leal 8(%esp), %esp // preserve stack alignment - movl (%esp), %ecx // image_handle - movl 4(%esp), %edx // sys_table - jmp efi32_entry // pass %ecx, %edx - // no other registers remain live + xor %edi, %edi // no struct boot_params in EDI + jmp efi32_entry // only ESP and EDI remain live 1: movl $0x80000003, %eax // EFI_UNSUPPORTED popl %ebx RET @@ -318,8 +345,10 @@ SYM_FUNC_START_NOALIGN(efi64_stub_entry) SYM_FUNC_END(efi64_stub_entry) #endif - .data - .balign 8 + .bss + .balign PAGE_SIZE +SYM_DATA_LOCAL(pte, .fill 6 * PAGE_SIZE, 1, 0) + SYM_DATA_START_LOCAL(efi32_boot_gdt) .word 0 .quad 0 @@ -330,8 +359,8 @@ SYM_DATA_START_LOCAL(efi32_boot_idt) .quad 0 SYM_DATA_END(efi32_boot_idt) + .data + .balign 4 SYM_DATA_LOCAL(efi32_boot_cs, .word 0) 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) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 1dcb794c5479..5db6495a3bb9 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -263,13 +263,6 @@ SYM_FUNC_START(startup_32) * used to perform that far jump. */ leal rva(startup_64)(%ebp), %eax -#ifdef CONFIG_EFI_MIXED - cmpb $1, rva(efi_is64)(%ebp) - je 1f - leal rva(startup_64_mixed_mode)(%ebp), %eax -1: -#endif - pushl $__KERNEL_CS pushl %eax -- 2.47.1.613.gc27f4b7a9f-goog
