kernel/arch/i386/protect.c

   1 /* This file contains code for initialization of protected mode, to initialize
   2  * code and data segment descriptors, and to initialize global descriptors
   3  * for local descriptors in the process table.
   4  */
   5
   6 #include <string.h>
   7 #include <assert.h>
   8 #include <machine/multiboot.h>
   9
  10 #include "kernel/kernel.h"
  11 #include "archconst.h"
  12
  13 #include "arch_proto.h"
  14
  15 #include <libexec.h>
  16
  17 #define INT_GATE_TYPE   (INT_286_GATE | DESC_386_BIT)
  18 #define TSS_TYPE        (AVL_286_TSS  | DESC_386_BIT)
  19
  20 /* This is OK initially, when the 1:1 mapping is still there. */
  21 char *video_mem = (char *) MULTIBOOT_VIDEO_BUFFER;
  22
  23 /* Storage for gdt, idt and tss. */
  24 struct segdesc_s gdt[GDT_SIZE] __aligned(DESC_SIZE);
  25 struct gatedesc_s idt[IDT_SIZE] __aligned(DESC_SIZE);
  26 struct tss_s tss[CONFIG_MAX_CPUS];
  27
  28 int prot_init_done = 0;
  29
  30 phys_bytes vir2phys(void *vir)
  31 {
  32         extern char _kern_vir_base, _kern_phys_base;    /* in kernel.lds */
  33         u32_t offset = (vir_bytes) &_kern_vir_base -
  34                 (vir_bytes) &_kern_phys_base;
  35         return (phys_bytes)vir - offset;
  36 }
  37
  38 /*===========================================================================*
  39  *                              enable_iop                                   *
  40  *===========================================================================*/
  41 void enable_iop(struct proc *pp)
  42 {
  43 /* Allow a user process to use I/O instructions.  Change the I/O Permission
  44  * Level bits in the psw. These specify least-privileged Current Permission
  45  * Level allowed to execute I/O instructions. Users and servers have CPL 3.
  46  * You can't have less privilege than that. Kernel has CPL 0, tasks CPL 1.
  47  */
  48   pp->p_reg.psw |= 0x3000;
  49 }
  50
  51
  52 /*===========================================================================*
  53  *                              sdesc                                        *
  54  *===========================================================================*/
  55  void sdesc(struct segdesc_s *segdp, phys_bytes base, vir_bytes size)
  56 {
  57 /* Fill in the size fields (base, limit and granularity) of a descriptor. */
  58   segdp->base_low = base;
  59   segdp->base_middle = base >> BASE_MIDDLE_SHIFT;
  60   segdp->base_high = base >> BASE_HIGH_SHIFT;
  61
  62   --size;                       /* convert to a limit, 0 size means 4G */
  63   if (size > BYTE_GRAN_MAX) {
  64         segdp->limit_low = size >> PAGE_GRAN_SHIFT;
  65         segdp->granularity = GRANULAR | (size >>
  66                              (PAGE_GRAN_SHIFT + GRANULARITY_SHIFT));
  67   } else {
  68         segdp->limit_low = size;
  69         segdp->granularity = size >> GRANULARITY_SHIFT;
  70   }
  71   segdp->granularity |= DEFAULT;        /* means BIG for data seg */
  72 }
  73
  74 /*===========================================================================*
  75  *                              init_dataseg                                 *
  76  *===========================================================================*/
  77 void init_param_dataseg(register struct segdesc_s *segdp,
  78         phys_bytes base, vir_bytes size, const int privilege)
  79 {
  80         /* Build descriptor for a data segment. */
  81         sdesc(segdp, base, size);
  82         segdp->access = (privilege << DPL_SHIFT) | (PRESENT | SEGMENT |
  83                 WRITEABLE | ACCESSED);
  84                 /* EXECUTABLE = 0, EXPAND_DOWN = 0, ACCESSED = 0 */
  85 }
  86
  87 void init_dataseg(int index, const int privilege)
  88 {
  89         init_param_dataseg(&gdt[index], 0, 0xFFFFFFFF, privilege);
  90 }
  91
  92 /*===========================================================================*
  93  *                              init_codeseg                                 *
  94  *===========================================================================*/
  95 static void init_codeseg(int index, int privilege)
  96 {
  97         /* Build descriptor for a code segment. */
  98         sdesc(&gdt[index], 0, 0xFFFFFFFF);
  99         gdt[index].access = (privilege << DPL_SHIFT)
 100                 | (PRESENT | SEGMENT | EXECUTABLE | READABLE);
 101                 /* CONFORMING = 0, ACCESSED = 0 */
 102 }
 103
 104 static struct gate_table_s gate_table_pic[] = {
 105         { hwint00, VECTOR( 0), INTR_PRIVILEGE },
 106         { hwint01, VECTOR( 1), INTR_PRIVILEGE },
 107         { hwint02, VECTOR( 2), INTR_PRIVILEGE },
 108         { hwint03, VECTOR( 3), INTR_PRIVILEGE },
 109         { hwint04, VECTOR( 4), INTR_PRIVILEGE },
 110         { hwint05, VECTOR( 5), INTR_PRIVILEGE },
 111         { hwint06, VECTOR( 6), INTR_PRIVILEGE },
 112         { hwint07, VECTOR( 7), INTR_PRIVILEGE },
 113         { hwint08, VECTOR( 8), INTR_PRIVILEGE },
 114         { hwint09, VECTOR( 9), INTR_PRIVILEGE },
 115         { hwint10, VECTOR(10), INTR_PRIVILEGE },
 116         { hwint11, VECTOR(11), INTR_PRIVILEGE },
 117         { hwint12, VECTOR(12), INTR_PRIVILEGE },
 118         { hwint13, VECTOR(13), INTR_PRIVILEGE },
 119         { hwint14, VECTOR(14), INTR_PRIVILEGE },
 120         { hwint15, VECTOR(15), INTR_PRIVILEGE },
 121         { NULL, 0, 0}
 122 };
 123
 124 static struct gate_table_s gate_table_exceptions[] = {
 125         { divide_error, DIVIDE_VECTOR, INTR_PRIVILEGE },
 126         { single_step_exception, DEBUG_VECTOR, INTR_PRIVILEGE },
 127         { nmi, NMI_VECTOR, INTR_PRIVILEGE },
 128         { breakpoint_exception, BREAKPOINT_VECTOR, USER_PRIVILEGE },
 129         { overflow, OVERFLOW_VECTOR, USER_PRIVILEGE },
 130         { bounds_check, BOUNDS_VECTOR, INTR_PRIVILEGE },
 131         { inval_opcode, INVAL_OP_VECTOR, INTR_PRIVILEGE },
 132         { copr_not_available, COPROC_NOT_VECTOR, INTR_PRIVILEGE },
 133         { double_fault, DOUBLE_FAULT_VECTOR, INTR_PRIVILEGE },
 134         { copr_seg_overrun, COPROC_SEG_VECTOR, INTR_PRIVILEGE },
 135         { inval_tss, INVAL_TSS_VECTOR, INTR_PRIVILEGE },
 136         { segment_not_present, SEG_NOT_VECTOR, INTR_PRIVILEGE },
 137         { stack_exception, STACK_FAULT_VECTOR, INTR_PRIVILEGE },
 138         { general_protection, PROTECTION_VECTOR, INTR_PRIVILEGE },
 139         { page_fault, PAGE_FAULT_VECTOR, INTR_PRIVILEGE },
 140         { copr_error, COPROC_ERR_VECTOR, INTR_PRIVILEGE },
 141         { alignment_check, ALIGNMENT_CHECK_VECTOR, INTR_PRIVILEGE },
 142         { machine_check, MACHINE_CHECK_VECTOR, INTR_PRIVILEGE },
 143         { simd_exception, SIMD_EXCEPTION_VECTOR, INTR_PRIVILEGE },
 144         { ipc_entry, IPC_VECTOR, USER_PRIVILEGE },
 145         { kernel_call_entry, KERN_CALL_VECTOR, USER_PRIVILEGE },
 146         { NULL, 0, 0}
 147 };
 148
 149 int tss_init(unsigned cpu, void * kernel_stack)
 150 {
 151         struct tss_s * t = &tss[cpu];
 152         int index = TSS_INDEX(cpu);
 153         struct segdesc_s *tssgdt;
 154
 155         tssgdt = &gdt[index];
 156
 157         init_param_dataseg(tssgdt, (phys_bytes) t,
 158                         sizeof(struct tss_s), INTR_PRIVILEGE);
 159         tssgdt->access = PRESENT | (INTR_PRIVILEGE << DPL_SHIFT) | TSS_TYPE;
 160
 161         /* Build TSS. */
 162         memset(t, 0, sizeof(*t));
 163         t->ds = t->es = t->fs = t->gs = t->ss0 = KERN_DS_SELECTOR;
 164         t->cs = KERN_CS_SELECTOR;
 165         t->iobase = sizeof(struct tss_s);       /* empty i/o permissions map */
 166
 167         /*
 168          * make space for process pointer and cpu id and point to the first
 169          * usable word
 170          */
 171         t->sp0 = ((unsigned) kernel_stack) - X86_STACK_TOP_RESERVED;
 172         /*
 173          * set the cpu id at the top of the stack so we know on which cpu is
 174          * this stak in use when we trap to kernel
 175          */
 176         *((reg_t *)(t->sp0 + 1 * sizeof(reg_t))) = cpu;
 177
 178         return SEG_SELECTOR(index);
 179 }
 180
 181 phys_bytes init_segdesc(int gdt_index, void *base, int size)
 182 {
 183         struct desctableptr_s *dtp = (struct desctableptr_s *) &gdt[gdt_index];
 184         dtp->limit = size - 1;
 185         dtp->base = (phys_bytes) base;
 186
 187         return (phys_bytes) dtp;
 188 }
 189
 190 void int_gate(struct gatedesc_s *tab,
 191         unsigned vec_nr, vir_bytes offset, unsigned dpl_type)
 192 {
 193 /* Build descriptor for an interrupt gate. */
 194   register struct gatedesc_s *idp;
 195
 196   idp = &tab[vec_nr];
 197   idp->offset_low = offset;
 198   idp->selector = KERN_CS_SELECTOR;
 199   idp->p_dpl_type = dpl_type;
 200   idp->offset_high = offset >> OFFSET_HIGH_SHIFT;
 201 }
 202
 203 void int_gate_idt(unsigned vec_nr, vir_bytes offset, unsigned dpl_type)
 204 {
 205         int_gate(idt, vec_nr, offset, dpl_type);
 206 }
 207
 208 void idt_copy_vectors(struct gate_table_s * first)
 209 {
 210         struct gate_table_s *gtp;
 211         for (gtp = first; gtp->gate; gtp++) {
 212                 int_gate(idt, gtp->vec_nr, (vir_bytes) gtp->gate,
 213                                 PRESENT | INT_GATE_TYPE |
 214                                 (gtp->privilege << DPL_SHIFT));
 215         }
 216 }
 217
 218 void idt_copy_vectors_pic(void)
 219 {
 220         idt_copy_vectors(gate_table_pic);
 221 }
 222
 223 void idt_init(void)
 224 {
 225         idt_copy_vectors_pic();
 226         idt_copy_vectors(gate_table_exceptions);
 227 }
 228
 229 struct desctableptr_s gdt_desc, idt_desc;
 230
 231 void idt_reload(void)
 232 {
 233         x86_lidt(&idt_desc);
 234 }
 235
 236 multiboot_module_t *bootmod(int pnr)
 237 {
 238         int i;
 239
 240         assert(pnr >= 0);
 241
 242         /* Search for desired process in boot process
 243          * list. The first NR_TASKS ones do not correspond
 244          * to a module, however, so we don't search those.
 245          */
 246         for(i = NR_TASKS; i < NR_BOOT_PROCS; i++) {
 247                 int p;
 248                 p = i - NR_TASKS;
 249                 if(image[i].proc_nr == pnr) {
 250                         assert(p < MULTIBOOT_MAX_MODS);
 251                         assert(p < kinfo.mbi.mods_count);
 252                         return &kinfo.module_list[p];
 253                 }
 254         }
 255
 256         panic("boot module %d not found", pnr);
 257 }
 258
 259 int booting_cpu = 0;
 260
 261 void prot_load_selectors(void)
 262 {
 263   /* this function is called by both prot_init by the BSP and
 264    * the early AP booting code in mpx.S by secondary CPU's.
 265    * everything is set up the same except for the TSS that is per-CPU.
 266    */
 267   x86_lgdt(&gdt_desc);  /* Load gdt */
 268   idt_init();
 269   idt_reload();
 270   x86_lldt(LDT_SELECTOR);       /* Load bogus ldt */
 271   x86_ltr(TSS_SELECTOR(booting_cpu));
 272
 273   x86_load_kerncs();
 274   x86_load_ds(KERN_DS_SELECTOR);
 275   x86_load_es(KERN_DS_SELECTOR);
 276   x86_load_fs(KERN_DS_SELECTOR);
 277   x86_load_gs(KERN_DS_SELECTOR);
 278   x86_load_ss(KERN_DS_SELECTOR);
 279 }
 280
 281 /*===========================================================================*
 282  *                              prot_init                                    *
 283  *===========================================================================*/
 284 void prot_init()
 285 {
 286   extern char k_boot_stktop;
 287
 288   memset(gdt, 0, sizeof(gdt));
 289   memset(idt, 0, sizeof(idt));
 290
 291   /* Build GDT, IDT, IDT descriptors. */
 292   gdt_desc.base = (u32_t) gdt;
 293   gdt_desc.limit = sizeof(gdt)-1;
 294   idt_desc.base = (u32_t) idt;
 295   idt_desc.limit = sizeof(idt)-1;
 296   tss_init(0, &k_boot_stktop);
 297
 298   /* Build GDT */
 299   init_param_dataseg(&gdt[LDT_INDEX],
 300     (phys_bytes) 0, 0, INTR_PRIVILEGE); /* unusable LDT */
 301   gdt[LDT_INDEX].access = PRESENT | LDT;
 302   init_codeseg(KERN_CS_INDEX, INTR_PRIVILEGE);
 303   init_dataseg(KERN_DS_INDEX, INTR_PRIVILEGE);
 304   init_codeseg(USER_CS_INDEX, USER_PRIVILEGE);
 305   init_dataseg(USER_DS_INDEX, USER_PRIVILEGE);
 306
 307   /* Currently the multiboot segments are loaded; which is fine, but
 308    * let's replace them with the ones from our own GDT so we test
 309    * right away whether they work as expected.
 310    */
 311   prot_load_selectors();
 312
 313   /* Set up a new post-relocate bootstrap pagetable so that
 314    * we can map in VM, and we no longer rely on pre-relocated
 315    * data.
 316    */
 317
 318   pg_clear();
 319   pg_identity(&kinfo); /* Still need 1:1 for lapic and video mem and such. */
 320   pg_mapkernel();
 321   pg_load();
 322
 323   prot_init_done = 1;
 324 }
 325
 326 void arch_post_init(void)
 327 {
 328   /* Let memory mapping code know what's going on at bootstrap time */
 329   struct proc *vm;
 330   vm = proc_addr(VM_PROC_NR);
 331   get_cpulocal_var(ptproc) = vm;
 332   pg_info(&vm->p_seg.p_cr3, &vm->p_seg.p_cr3_v);
 333 }
 334
 335 int libexec_pg_alloc(struct exec_info *execi, off_t vaddr, size_t len)
 336 {
 337         pg_map(PG_ALLOCATEME, vaddr, vaddr+len, &kinfo);
 338         pg_load();
 339         memset((char *) vaddr, 0, len);
 340         return OK;
 341 }
 342
 343 void arch_boot_proc(struct boot_image *ip, struct proc *rp)
 344 {
 345         multiboot_module_t *mod;
 346
 347         if(rp->p_nr < 0) return;
 348
 349         mod = bootmod(rp->p_nr);
 350
 351         /* Important special case: we put VM in the bootstrap pagetable
 352          * so it can run.
 353          */
 354
 355         if(rp->p_nr == VM_PROC_NR) {
 356                 struct exec_info execi;
 357
 358                 memset(&execi, 0, sizeof(execi));
 359
 360                 /* exec parameters */
 361                 execi.stack_high = kinfo.user_sp;
 362                 execi.stack_size = 16 * 1024;   /* not too crazy as it must be preallocated */
 363                 execi.proc_e = ip->endpoint;
 364                 execi.hdr = (char *) mod->mod_start; /* phys mem direct */
 365                 execi.hdr_len = mod->mod_end - mod->mod_start;
 366                 strlcpy(execi.progname, ip->proc_name, sizeof(execi.progname));
 367                 execi.frame_len = 0;
 368
 369                 /* callbacks for use in the kernel */
 370                 execi.copymem = libexec_copy_memcpy;
 371                 execi.clearmem = libexec_clear_memset;
 372                 execi.allocmem_prealloc = libexec_pg_alloc;
 373                 execi.allocmem_ondemand = libexec_pg_alloc;
 374                 execi.clearproc = NULL;
 375
 376                 /* parse VM ELF binary and alloc/map it into bootstrap pagetable */
 377                 libexec_load_elf(&execi);
 378
 379                 /* Initialize the server stack pointer. Take it down three words
 380                  * to give startup code something to use as "argc", "argv" and "envp".
 381                  */
 382                 arch_proc_init(rp, execi.pc, kinfo.user_sp - 3*4, ip->proc_name);
 383
 384                 /* Free VM blob that was just copied into existence. */
 385                 cut_memmap(&kinfo, mod->mod_start, mod->mod_end);
 386         }
 387 }