1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * 4 * Trampoline.S Derived from Setup.S by Linus Torvalds 5 * 6 * 4 Jan 1997 Michael Chastain: changed to gnu as. 7 * 15 Sept 2005 Eric Biederman: 64bit PIC support 8 * 9 * Entry: CS:IP point to the start of our code, we are 10 * in real mode with no stack, but the rest of the 11 * trampoline page to make our stack and everything else 12 * is a mystery. 13 * 14 * On entry to trampoline_start, the processor is in real mode 15 * with 16-bit addressing and 16-bit data. CS has some value 16 * and IP is zero. Thus, data addresses need to be absolute 17 * (no relocation) and are taken with regard to r_base. 18 * 19 * With the addition of trampoline_level4_pgt this code can 20 * now enter a 64bit kernel that lives at arbitrary 64bit 21 * physical addresses. 22 * 23 * If you work on this file, check the object module with objdump 24 * --full-contents --reloc to make sure there are no relocation 25 * entries. 26 */ 27 28 #include <linux/linkage.h> 29 #include <asm/pgtable_types.h> 30 #include <asm/page_types.h> 31 #include <asm/msr.h> 32 #include <asm/segment.h> 33 #include <asm/processor-flags.h> 34 #include <asm/realmode.h> 35 #include "realmode.h" 36 37 .text 38 .code16 39 40 .balign PAGE_SIZE 41 SYM_CODE_START(trampoline_start) 42 cli # We should be safe anyway 43 wbinvd 44 45 LJMPW_RM(1f) 46 1: 47 mov %cs, %ax # Code and data in the same place 48 mov %ax, %ds 49 mov %ax, %es 50 mov %ax, %ss 51 52 # Setup stack 53 movl $rm_stack_end, %esp 54 55 call verify_cpu # Verify the cpu supports long mode 56 testl %eax, %eax # Check for return code 57 jnz no_longmode 58 59 .Lswitch_to_protected: 60 /* 61 * GDT tables in non default location kernel can be beyond 16MB and 62 * lgdt will not be able to load the address as in real mode default 63 * operand size is 16bit. Use lgdtl instead to force operand size 64 * to 32 bit. 65 */ 66 67 lidtl tr_idt # load idt with 0, 0 68 lgdtl tr_gdt # load gdt with whatever is appropriate 69 70 movw $__KERNEL_DS, %dx # Data segment descriptor 71 72 # Enable protected mode 73 movl $X86_CR0_PE, %eax # protected mode (PE) bit 74 movl %eax, %cr0 # into protected mode 75 76 # flush prefetch and jump to startup_32 77 ljmpl $__KERNEL32_CS, $pa_startup_32 78 79 no_longmode: 80 hlt 81 jmp no_longmode 82 SYM_CODE_END(trampoline_start) 83 84 #ifdef CONFIG_AMD_MEM_ENCRYPT 85 /* SEV-ES supports non-zero IP for entry points - no alignment needed */ 86 SYM_CODE_START(sev_es_trampoline_start) 87 cli # We should be safe anyway 88 89 LJMPW_RM(1f) 90 1: 91 mov %cs, %ax # Code and data in the same place 92 mov %ax, %ds 93 mov %ax, %es 94 mov %ax, %ss 95 96 # Setup stack 97 movl $rm_stack_end, %esp 98 99 jmp .Lswitch_to_protected 100 SYM_CODE_END(sev_es_trampoline_start) 101 #endif /* CONFIG_AMD_MEM_ENCRYPT */ 102 103 #include "../kernel/verify_cpu.S" 104 105 .section ".text32","ax" 106 .code32 107 .balign 4 108 SYM_CODE_START(startup_32) 109 movl %edx, %ss 110 addl $pa_real_mode_base, %esp 111 movl %edx, %ds 112 movl %edx, %es 113 movl %edx, %fs 114 movl %edx, %gs 115 116 /* 117 * Check for memory encryption support. This is a safety net in 118 * case BIOS hasn't done the necessary step of setting the bit in 119 * the MSR for this AP. If SME is active and we've gotten this far 120 * then it is safe for us to set the MSR bit and continue. If we 121 * don't we'll eventually crash trying to execute encrypted 122 * instructions. 123 */ 124 btl $TH_FLAGS_SME_ACTIVE_BIT, pa_tr_flags 125 jnc .Ldone 126 movl $MSR_K8_SYSCFG, %ecx 127 rdmsr 128 bts $MSR_K8_SYSCFG_MEM_ENCRYPT_BIT, %eax 129 jc .Ldone 130 131 /* 132 * Memory encryption is enabled but the SME enable bit for this 133 * CPU has has not been set. It is safe to set it, so do so. 134 */ 135 wrmsr 136 .Ldone: 137 138 movl pa_tr_cr4, %eax 139 movl %eax, %cr4 # Enable PAE mode 140 141 # Setup trampoline 4 level pagetables 142 movl $pa_trampoline_pgd, %eax 143 movl %eax, %cr3 144 145 # Set up EFER 146 movl pa_tr_efer, %eax 147 movl pa_tr_efer + 4, %edx 148 movl $MSR_EFER, %ecx 149 wrmsr 150 151 # Enable paging and in turn activate Long Mode 152 movl $(X86_CR0_PG | X86_CR0_WP | X86_CR0_PE), %eax 153 movl %eax, %cr0 154 155 /* 156 * At this point we're in long mode but in 32bit compatibility mode 157 * with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn 158 * EFER.LMA = 1). Now we want to jump in 64bit mode, to do that we use 159 * the new gdt/idt that has __KERNEL_CS with CS.L = 1. 160 */ 161 ljmpl $__KERNEL_CS, $pa_startup_64 162 SYM_CODE_END(startup_32) 163 164 .section ".text64","ax" 165 .code64 166 .balign 4 167 SYM_CODE_START(startup_64) 168 # Now jump into the kernel using virtual addresses 169 jmpq *tr_start(%rip) 170 SYM_CODE_END(startup_64) 171 172 .section ".rodata","a" 173 # Duplicate the global descriptor table 174 # so the kernel can live anywhere 175 .balign 16 176 SYM_DATA_START(tr_gdt) 177 .short tr_gdt_end - tr_gdt - 1 # gdt limit 178 .long pa_tr_gdt 179 .short 0 180 .quad 0x00cf9b000000ffff # __KERNEL32_CS 181 .quad 0x00af9b000000ffff # __KERNEL_CS 182 .quad 0x00cf93000000ffff # __KERNEL_DS 183 SYM_DATA_END_LABEL(tr_gdt, SYM_L_LOCAL, tr_gdt_end) 184 185 .bss 186 .balign PAGE_SIZE 187 SYM_DATA(trampoline_pgd, .space PAGE_SIZE) 188 189 .balign 8 190 SYM_DATA_START(trampoline_header) 191 SYM_DATA_LOCAL(tr_start, .space 8) 192 SYM_DATA(tr_efer, .space 8) 193 SYM_DATA(tr_cr4, .space 4) 194 SYM_DATA(tr_flags, .space 4) 195 SYM_DATA_END(trampoline_header) 196 197 #include "trampoline_common.S" 198