1 #include "libcflat.h" 2 #include "desc.h" 3 #include "processor.h" 4 5 void set_idt_entry(int vec, void *addr, int dpl) 6 { 7 idt_entry_t *e = &boot_idt[vec]; 8 memset(e, 0, sizeof *e); 9 e->offset0 = (unsigned long)addr; 10 e->selector = read_cs(); 11 e->ist = 0; 12 e->type = 14; 13 e->dpl = dpl; 14 e->p = 1; 15 e->offset1 = (unsigned long)addr >> 16; 16 #ifdef __x86_64__ 17 e->offset2 = (unsigned long)addr >> 32; 18 #endif 19 } 20 21 void set_idt_sel(int vec, u16 sel) 22 { 23 idt_entry_t *e = &boot_idt[vec]; 24 e->selector = sel; 25 } 26 27 struct ex_record { 28 unsigned long rip; 29 unsigned long handler; 30 }; 31 32 extern struct ex_record exception_table_start, exception_table_end; 33 34 static void check_exception_table(struct ex_regs *regs) 35 { 36 struct ex_record *ex; 37 unsigned ex_val; 38 39 ex_val = regs->vector | (regs->error_code << 16) | 40 (((regs->rflags >> 16) & 1) << 8); 41 asm("mov %0, %%gs:4" : : "r"(ex_val)); 42 43 for (ex = &exception_table_start; ex != &exception_table_end; ++ex) { 44 if (ex->rip == regs->rip) { 45 regs->rip = ex->handler; 46 return; 47 } 48 } 49 printf("unhandled excecption %d\n", regs->vector); 50 exit(7); 51 } 52 53 static void (*exception_handlers[32])(struct ex_regs *regs); 54 55 56 void handle_exception(u8 v, void (*func)(struct ex_regs *regs)) 57 { 58 if (v < 32) 59 exception_handlers[v] = func; 60 } 61 62 #ifndef __x86_64__ 63 __attribute__((regparm(1))) 64 #endif 65 void do_handle_exception(struct ex_regs *regs) 66 { 67 if (regs->vector < 32 && exception_handlers[regs->vector]) { 68 exception_handlers[regs->vector](regs); 69 return; 70 } 71 printf("unhandled cpu excecption %d\n", regs->vector); 72 if (regs->vector == 14) 73 printf("PF at %p addr %p\n", regs->rip, read_cr2()); 74 exit(7); 75 } 76 77 #define EX(NAME, N) extern char NAME##_fault; \ 78 asm (".pushsection .text \n\t" \ 79 #NAME"_fault: \n\t" \ 80 "push"W" $0 \n\t" \ 81 "push"W" $"#N" \n\t" \ 82 "jmp __handle_exception \n\t" \ 83 ".popsection") 84 85 #define EX_E(NAME, N) extern char NAME##_fault; \ 86 asm (".pushsection .text \n\t" \ 87 #NAME"_fault: \n\t" \ 88 "push"W" $"#N" \n\t" \ 89 "jmp __handle_exception \n\t" \ 90 ".popsection") 91 92 EX(de, 0); 93 EX(db, 1); 94 EX(nmi, 2); 95 EX(bp, 3); 96 EX(of, 4); 97 EX(br, 5); 98 EX(ud, 6); 99 EX(nm, 7); 100 EX_E(df, 8); 101 EX_E(ts, 10); 102 EX_E(np, 11); 103 EX_E(ss, 12); 104 EX_E(gp, 13); 105 EX_E(pf, 14); 106 EX(mf, 16); 107 EX_E(ac, 17); 108 EX(mc, 18); 109 EX(xm, 19); 110 111 asm (".pushsection .text \n\t" 112 "__handle_exception: \n\t" 113 #ifdef __x86_64__ 114 "push %r15; push %r14; push %r13; push %r12 \n\t" 115 "push %r11; push %r10; push %r9; push %r8 \n\t" 116 #endif 117 "push %"R "di; push %"R "si; push %"R "bp; sub $"S", %"R "sp \n\t" 118 "push %"R "bx; push %"R "dx; push %"R "cx; push %"R "ax \n\t" 119 #ifdef __x86_64__ 120 "mov %"R "sp, %"R "di \n\t" 121 #else 122 "mov %"R "sp, %"R "ax \n\t" 123 #endif 124 "call do_handle_exception \n\t" 125 "pop %"R "ax; pop %"R "cx; pop %"R "dx; pop %"R "bx \n\t" 126 "add $"S", %"R "sp; pop %"R "bp; pop %"R "si; pop %"R "di \n\t" 127 #ifdef __x86_64__ 128 "pop %r8; pop %r9; pop %r10; pop %r11 \n\t" 129 "pop %r12; pop %r13; pop %r14; pop %r15 \n\t" 130 #endif 131 "add $"S", %"R "sp \n\t" 132 "add $"S", %"R "sp \n\t" 133 "iret"W" \n\t" 134 ".popsection"); 135 136 static void *idt_handlers[32] = { 137 [0] = &de_fault, 138 [1] = &db_fault, 139 [2] = &nmi_fault, 140 [3] = &bp_fault, 141 [4] = &of_fault, 142 [5] = &br_fault, 143 [6] = &ud_fault, 144 [7] = &nm_fault, 145 [8] = &df_fault, 146 [10] = &ts_fault, 147 [11] = &np_fault, 148 [12] = &ss_fault, 149 [13] = &gp_fault, 150 [14] = &pf_fault, 151 [16] = &mf_fault, 152 [17] = &ac_fault, 153 [18] = &mc_fault, 154 [19] = &xm_fault, 155 }; 156 157 void setup_idt(void) 158 { 159 int i; 160 static bool idt_initialized = false; 161 162 if (idt_initialized) { 163 return; 164 } 165 idt_initialized = true; 166 for (i = 0; i < 32; i++) 167 if (idt_handlers[i]) 168 set_idt_entry(i, idt_handlers[i], 0); 169 handle_exception(0, check_exception_table); 170 handle_exception(6, check_exception_table); 171 handle_exception(13, check_exception_table); 172 } 173 174 unsigned exception_vector(void) 175 { 176 unsigned char vector; 177 178 asm("movb %%gs:4, %0" : "=q"(vector)); 179 return vector; 180 } 181 182 unsigned exception_error_code(void) 183 { 184 unsigned short error_code; 185 186 asm("mov %%gs:6, %0" : "=rm"(error_code)); 187 return error_code; 188 } 189 190 bool exception_rflags_rf(void) 191 { 192 unsigned char rf_flag; 193 194 asm("movb %%gs:5, %b0" : "=q"(rf_flag)); 195 return rf_flag & 1; 196 } 197 198 static char intr_alt_stack[4096]; 199 200 #ifndef __x86_64__ 201 /* 202 * GDT, with 6 entries: 203 * 0x00 - NULL descriptor 204 * 0x08 - Code segment (ring 0) 205 * 0x10 - Data segment (ring 0) 206 * 0x18 - Not present code segment (ring 0) 207 * 0x20 - Code segment (ring 3) 208 * 0x28 - Data segment (ring 3) 209 * 0x30 - Interrupt task 210 * 0x38 to 0x78 - Free to use for test cases 211 * 0x80 - Primary task (CPU 0) 212 */ 213 214 void set_gdt_entry(int sel, u32 base, u32 limit, u8 access, u8 gran) 215 { 216 int num = sel >> 3; 217 218 /* Setup the descriptor base address */ 219 gdt32[num].base_low = (base & 0xFFFF); 220 gdt32[num].base_middle = (base >> 16) & 0xFF; 221 gdt32[num].base_high = (base >> 24) & 0xFF; 222 223 /* Setup the descriptor limits */ 224 gdt32[num].limit_low = (limit & 0xFFFF); 225 gdt32[num].granularity = ((limit >> 16) & 0x0F); 226 227 /* Finally, set up the granularity and access flags */ 228 gdt32[num].granularity |= (gran & 0xF0); 229 gdt32[num].access = access; 230 } 231 232 void set_gdt_task_gate(u16 sel, u16 tss_sel) 233 { 234 set_gdt_entry(sel, tss_sel, 0, 0x85, 0); // task, present 235 } 236 237 void set_idt_task_gate(int vec, u16 sel) 238 { 239 idt_entry_t *e = &boot_idt[vec]; 240 241 memset(e, 0, sizeof *e); 242 243 e->selector = sel; 244 e->ist = 0; 245 e->type = 5; 246 e->dpl = 0; 247 e->p = 1; 248 } 249 250 /* 251 * 0 - main task 252 * 1 - interrupt task 253 */ 254 255 tss32_t tss_intr; 256 257 void setup_tss32(void) 258 { 259 u16 desc_size = sizeof(tss32_t); 260 261 tss.cr3 = read_cr3(); 262 tss_intr.cr3 = read_cr3(); 263 tss_intr.ss0 = tss_intr.ss1 = tss_intr.ss2 = 0x10; 264 tss_intr.esp = tss_intr.esp0 = tss_intr.esp1 = tss_intr.esp2 = 265 (u32)intr_alt_stack + 4096; 266 tss_intr.cs = 0x08; 267 tss_intr.ds = tss_intr.es = tss_intr.fs = tss_intr.gs = tss_intr.ss = 0x10; 268 tss_intr.iomap_base = (u16)desc_size; 269 set_gdt_entry(TSS_INTR, (u32)&tss_intr, desc_size - 1, 0x89, 0x0f); 270 } 271 272 void set_intr_task_gate(int e, void *fn) 273 { 274 tss_intr.eip = (u32)fn; 275 set_idt_task_gate(e, TSS_INTR); 276 } 277 278 void setup_alt_stack(void) 279 { 280 setup_tss32(); 281 } 282 283 void set_intr_alt_stack(int e, void *fn) 284 { 285 set_intr_task_gate(e, fn); 286 } 287 288 void print_current_tss_info(void) 289 { 290 u16 tr = str(); 291 292 if (tr != TSS_MAIN && tr != TSS_INTR) 293 printf("Unknown TSS %x\n", tr); 294 else 295 printf("TR=%x (%s) Main TSS back link %x. Intr TSS back link %x\n", 296 tr, tr ? "interrupt" : "main", tss.prev, tss_intr.prev); 297 } 298 #else 299 void set_intr_alt_stack(int e, void *addr) 300 { 301 set_idt_entry(e, addr, 0); 302 boot_idt[e].ist = 1; 303 } 304 305 void setup_alt_stack(void) 306 { 307 tss.ist1 = (u64)intr_alt_stack + 4096; 308 } 309 #endif 310 311 static bool exception; 312 static void *exception_return; 313 314 static void exception_handler(struct ex_regs *regs) 315 { 316 exception = true; 317 regs->rip = (unsigned long)exception_return; 318 } 319 320 bool test_for_exception(unsigned int ex, void (*trigger_func)(void *data), 321 void *data) 322 { 323 handle_exception(ex, exception_handler); 324 exception = false; 325 trigger_func(data); 326 handle_exception(ex, NULL); 327 return exception; 328 } 329 330 void set_exception_return(void *addr) 331 { 332 exception_return = addr; 333 } 334