1/* 2 * 3 * Copyright 2024 Google Inc. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. The name of the author may not be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 .align 16 30 .global exception_stack_end 31exception_stack_end: 32 .quad 0 33 .global exception_state 34exception_state: 35 .quad 0 36 37/* Some temporary variables which are used while saving exception state. */ 38vector: 39 .quad 0 40error_code: 41 .quad 0 42old_rax: 43 .quad 0 44old_rcx: 45 .quad 0 46 47 .align 16 48 49/* 50 * Each exception vector has a small stub associated with it which sets aside 51 * the error code, if any, records which vector we entered from, and calls 52 * the common exception entry point. Some exceptions have error codes and some 53 * don't, so we have a macro for each type. 54 */ 55 56 .macro stub num 57exception_stub_\num: 58 movq $0, error_code 59 movq $\num, vector 60 jmp exception_common 61 .endm 62 63 .macro stub_err num 64exception_stub_\num: 65 pop error_code 66 movq $\num, vector 67 jmp exception_common 68 .endm 69 70 .altmacro 71 .macro user_defined_stubs from, to 72 stub \from 73 .if \to-\from 74 user_defined_stubs %(from+1),\to 75 .endif 76 .endm 77 78 stub 0 79 stub 1 80 stub 2 81 stub 3 82 stub 4 83 stub 5 84 stub 6 85 stub 7 86 stub_err 8 87 stub 9 88 stub_err 10 89 stub_err 11 90 stub_err 12 91 stub_err 13 92 stub_err 14 93 stub 15 94 stub 16 95 stub_err 17 96 stub 18 97 stub 19 98 stub 20 99 stub 21 100 stub 22 101 stub 23 102 stub 24 103 stub 25 104 stub 26 105 stub 27 106 stub 28 107 stub 29 108 stub_err 30 109 stub 31 110 /* Split the macro so we avoid a stack overflow. */ 111 user_defined_stubs 32, 63 112 user_defined_stubs 64, 127 113 user_defined_stubs 128, 191 114 user_defined_stubs 192, 255 115 116exception_common: 117 /* 118 * At this point, on x86-64, on the stack there is: 119 * 0(%rsp) rip 120 * 8(%rsp) cs 121 * 16(%rsp) rflags 122 * 24(%rsp) rsp 123 * 32(%rsp) ss 124 * 125 * This section sets up the exception stack. 126 * It saves the old stack pointer (rsp) to preserve RIP, CS, RFLAGS and SS. 127 * Then sets up the new stack pointer to point to the exception stack area. 128 */ 129 movq %rax, old_rax 130 movq %rcx, old_rcx 131 132 mov %rsp, %rax 133 movq exception_stack_end, %rsp 134 /* 135 * The `exception_state` struct is not 16-byte aligned. 136 * Push an extra 8 bytes to ensure the stack pointer 137 * is 16-byte aligned before calling exception_dispatch. 138 */ 139 push $0 140 141 /* 142 * Push values onto the top of the exception stack to form an 143 * exception state structure. 144 */ 145 push vector 146 push error_code 147 148 /* push of the gs, fs, es, ds, ss and cs */ 149 mov %gs, %rcx 150 movl %ecx, -4(%rsp) /* gs */ 151 mov %fs, %rcx 152 movl %ecx, -8(%rsp) /* fs */ 153 movl $0, -12(%rsp) /* es */ 154 movl $0, -16(%rsp) /* ds */ 155 movq 32(%rax), %rcx 156 movl %ecx, -20(%rsp) /* ss */ 157 movq 8(%rax), %rcx 158 movl %ecx, -24(%rsp) /* cs */ 159 sub $24, %rsp 160 161 push 16(%rax) /* rflags */ 162 push (%rax) /* rip */ 163 push %r15 164 push %r14 165 push %r13 166 push %r12 167 push %r11 168 push %r10 169 push %r9 170 push %r8 171 push 24(%rax) /* rsp */ 172 push %rbp 173 push %rdi 174 push %rsi 175 push %rdx 176 push old_rcx /* rcx */ 177 push %rbx 178 push old_rax /* rax */ 179 180 /* 181 * Call the C exception handler. It will find the exception state 182 * using the exception_state global pointer. Not 183 * passing parameters means we don't have to worry about what ABI 184 * is being used. 185 */ 186 mov %rsp, exception_state 187 call exception_dispatch 188 189 /* 190 * Restore state from the exception state structure, including any 191 * changes that might have been made. 192 */ 193 pop old_rax 194 pop %rbx 195 pop old_rcx 196 pop %rdx 197 pop %rsi 198 pop %rdi 199 pop %rbp 200 lea exception_stack, %rax 201 pop 24(%rax) /* rsp */ 202 pop %r8 203 pop %r9 204 pop %r10 205 pop %r11 206 pop %r12 207 pop %r13 208 pop %r14 209 pop %r15 210 pop (%rax) /* rip */ 211 pop 16(%rax) /* rflags */ 212 213 /* pop of the gs, fs, es, ds, ss and cs */ 214 movl (%rsp), %ecx 215 movq %rcx, 8(%rax) /* cs */ 216 movl 4(%rsp), %ecx 217 movq %rcx, 32(%rax) /* ss */ 218 movl 16(%rsp), %ecx 219 mov %rcx, %fs /* fs */ 220 movl 20(%rsp), %ecx 221 mov %rcx, %gs /* gs */ 222 223 mov %rax, %rsp 224 movq old_rax, %rax 225 movq old_rcx, %rcx 226 227 iretq 228 229/* 230 * We need segment selectors for the IDT, so we need to know where things are 231 * in the GDT. We set one up here which is pretty standard and largely copied 232 * from coreboot. 233 */ 234 .align 16 235gdt: 236 /* selgdt 0, unused */ 237 .word 0x0000, 0x0000 238 .byte 0x00, 0x00, 0x00, 0x00 239 240 /* selgdt 8, unused */ 241 .word 0x0000, 0x0000 242 .byte 0x00, 0x00, 0x00, 0x00 243 244 /* selgdt 0x10, flat 4GB code segment */ 245 .word 0xffff, 0x0000 246 .byte 0x00, 0x9b, 0xcf, 0x00 247 248 /* selgdt 0x18, flat 4GB data segment */ 249 .word 0xffff, 0x0000 250 .byte 0x00, 0x92, 0xcf, 0x00 251 252 /* selgdt 0x20, flat x64 code segment */ 253 .word 0xffff, 0x0000 254 .byte 0x00, 0x9b, 0xaf, 0x00 255gdt_end: 256 257/* GDT pointer for use with lgdt */ 258.global gdt_ptr 259gdt_ptr: 260 .word gdt_end - gdt - 1 261 .quad gdt 262 263 /* 264 * Record the target and construct the actual entry at init time. This 265 * is necessary because the linker doesn't want to construct the entry 266 * for us. 267 */ 268 .macro interrupt_gate target 269 .word 0 /* patchable */ 270 .word 0x20 /* Target code segment selector */ 271 .word 0xee00 /* Present, Type 64-bit Interrupt Gate */ 272 .word 0 /* patchable */ 273 .quad \target /* patchable */ 274 .endm 275 276 .altmacro 277 .macro user_defined_gates from, to 278 interrupt_gate exception_stub_\from 279 .if \to-\from 280 user_defined_gates %(from+1),\to 281 .endif 282 .endm 283 284 .align 16 285 .global idt 286idt: 287 interrupt_gate exception_stub_0 288 interrupt_gate exception_stub_1 289 interrupt_gate exception_stub_2 290 interrupt_gate exception_stub_3 291 interrupt_gate exception_stub_4 292 interrupt_gate exception_stub_5 293 interrupt_gate exception_stub_6 294 interrupt_gate exception_stub_7 295 interrupt_gate exception_stub_8 296 interrupt_gate exception_stub_9 297 interrupt_gate exception_stub_10 298 interrupt_gate exception_stub_11 299 interrupt_gate exception_stub_12 300 interrupt_gate exception_stub_13 301 interrupt_gate exception_stub_14 302 interrupt_gate exception_stub_15 303 interrupt_gate exception_stub_16 304 interrupt_gate exception_stub_17 305 interrupt_gate exception_stub_18 306 interrupt_gate exception_stub_19 307 interrupt_gate exception_stub_20 308 interrupt_gate exception_stub_21 309 interrupt_gate exception_stub_22 310 interrupt_gate exception_stub_23 311 interrupt_gate exception_stub_24 312 interrupt_gate exception_stub_25 313 interrupt_gate exception_stub_26 314 interrupt_gate exception_stub_27 315 interrupt_gate exception_stub_28 316 interrupt_gate exception_stub_29 317 interrupt_gate exception_stub_30 318 interrupt_gate exception_stub_31 319 user_defined_gates 32, 63 320 user_defined_gates 64, 127 321 user_defined_gates 128, 191 322 user_defined_gates 192, 255 323idt_end: 324 325/* IDT pointer for use with lidt */ 326idt_ptr: 327 .word idt_end - idt - 1 328 .quad idt 329 330.section .text.exception_init_asm 331.globl exception_init_asm 332.type exception_init_asm, @function 333 334exception_init_asm: 335 /* Set up IDT entries */ 336 mov $idt, %rax 3371: 338 movq 8(%rax), %rdi 339 movw %di, (%rax) /* procedure entry point offset bits 0..15 */ 340 shr $16, %rdi 341 movw %di, 6(%rax) /* procedure entry point offset bits 16..31 */ 342 shr $16, %rdi 343 movl %edi, 8(%rax) /* procedure entry point offset bits 32..63 */ 344 movl $0, 12(%rax) /* reserved */ 345 add $16, %rax 346 cmp $idt_end, %rax 347 jne 1b 348 349 /* Load the IDT */ 350 lidt idt_ptr 351 ret 352