minix/kernel/arch/i386/protect.c

/* This file contains code for initialization of protected mode, to initialize
 * code and data segment descriptors, and to initialize global descriptors
 * for local descriptors in the process table.
 */

#include "kernel/kernel.h"
#include "kernel/proc.h"
#include "archconst.h"

#include "arch_proto.h"

#define INT_GATE_TYPE	(INT_286_GATE | DESC_386_BIT)
#define TSS_TYPE	(AVL_286_TSS  | DESC_386_BIT)

struct desctableptr_s {
  char limit[sizeof(u16_t)];
  char base[sizeof(u32_t)];		/* really u24_t + pad for 286 */
};

struct gatedesc_s {
  u16_t offset_low;
  u16_t selector;
  u8_t pad;			/* |000|XXXXX| ig & trpg, |XXXXXXXX| task g */
  u8_t p_dpl_type;		/* |P|DL|0|TYPE| */
  u16_t offset_high;
};


/* used in klib.s and mpx.s */
struct segdesc_s gdt[GDT_SIZE] __aligned(DESC_SIZE) =
{	{0},
	{0,0,0,0}, 				/* GDT descriptor */
	{0,0,0,0}, 				/* IDT descriptor */
	{0xffff,0,0,0x93,0xcf,0}, 	/* kernel DS */
	{0xffff,0,0,0x93,0xcf,0},	/* kernel ES (386: flag 4 Gb at startup) */
	{0xffff,0,0,0x93,0xcf,0},	/* kernel SS (386: monitor SS at startup) */
	{0xffff,0,0,0x9b,0xcf,0},	/* kernel CS */
	{0xffff,0,0,0x9b,0xcf,0},	/* temp for BIOS (386: monitor CS at startup) */
};

/* zero-init so none present */
static struct gatedesc_s idt[IDT_SIZE] __aligned(DESC_SIZE);
struct tss_s tss[CONFIG_MAX_CPUS];			/* zero init */

static void sdesc(struct segdesc_s *segdp, phys_bytes base, vir_bytes
	size);

/*===========================================================================*
 *				enable_iop				     * 
 *===========================================================================*/
void enable_iop(struct proc *pp)
{
/* Allow a user process to use I/O instructions.  Change the I/O Permission
 * Level bits in the psw. These specify least-privileged Current Permission
 * Level allowed to execute I/O instructions. Users and servers have CPL 3. 
 * You can't have less privilege than that. Kernel has CPL 0, tasks CPL 1.
 */
  pp->p_reg.psw |= 0x3000;
}

/*===========================================================================*
 *				seg2phys				     *
 *===========================================================================*/
phys_bytes seg2phys(const u16_t seg)
{
/* Return the base address of a segment, with seg being a 
 * register, or a 286/386 segment selector.
 */
  phys_bytes base;
  struct segdesc_s *segdp;

  segdp = &gdt[seg >> 3];
  base =    ((u32_t) segdp->base_low << 0)
	| ((u32_t) segdp->base_middle << 16)
	| ((u32_t) segdp->base_high << 24);
  return base;
}

/*===========================================================================*
 *				init_dataseg				     *
 *===========================================================================*/
void init_dataseg(register struct segdesc_s *segdp,
	phys_bytes base, vir_bytes size, const int privilege)
{
	/* Build descriptor for a data segment. */
	sdesc(segdp, base, size);
	segdp->access = (privilege << DPL_SHIFT) | (PRESENT | SEGMENT |
		WRITEABLE);
		/* EXECUTABLE = 0, EXPAND_DOWN = 0, ACCESSED = 0 */
}

/*===========================================================================*
 *				init_codeseg				     *
 *===========================================================================*/
static void init_codeseg(register struct segdesc_s *segdp, phys_bytes base,
	vir_bytes size, int privilege)
{
	/* Build descriptor for a code segment. */
	sdesc(segdp, base, size);
	segdp->access = (privilege << DPL_SHIFT)
	        | (PRESENT | SEGMENT | EXECUTABLE | READABLE);
		/* CONFORMING = 0, ACCESSED = 0 */
}

struct gate_table_s gate_table_pic[] = {
	{ hwint00, VECTOR( 0), INTR_PRIVILEGE },
	{ hwint01, VECTOR( 1), INTR_PRIVILEGE },
	{ hwint02, VECTOR( 2), INTR_PRIVILEGE },
	{ hwint03, VECTOR( 3), INTR_PRIVILEGE },
	{ hwint04, VECTOR( 4), INTR_PRIVILEGE },
	{ hwint05, VECTOR( 5), INTR_PRIVILEGE },
	{ hwint06, VECTOR( 6), INTR_PRIVILEGE },
	{ hwint07, VECTOR( 7), INTR_PRIVILEGE },
	{ hwint08, VECTOR( 8), INTR_PRIVILEGE },
	{ hwint09, VECTOR( 9), INTR_PRIVILEGE },
	{ hwint10, VECTOR(10), INTR_PRIVILEGE },
	{ hwint11, VECTOR(11), INTR_PRIVILEGE },
	{ hwint12, VECTOR(12), INTR_PRIVILEGE },
	{ hwint13, VECTOR(13), INTR_PRIVILEGE },
	{ hwint14, VECTOR(14), INTR_PRIVILEGE },
	{ hwint15, VECTOR(15), INTR_PRIVILEGE },
	{ NULL, 0, 0}
};

void tss_init(unsigned cpu, void * kernel_stack)
{
	struct tss_s * t = &tss[cpu];
  
	t->ss0 = DS_SELECTOR;
	init_dataseg(&gdt[TSS_INDEX(cpu)], vir2phys(t),
			sizeof(struct tss_s), INTR_PRIVILEGE);
	gdt[TSS_INDEX(cpu)].access = PRESENT |
		(INTR_PRIVILEGE << DPL_SHIFT) | TSS_TYPE;

	/* Complete building of main TSS. */
	t->iobase = sizeof(struct tss_s);	/* empty i/o permissions map */

	/* 
	 * make space for process pointer and cpu id and point to the first
	 * usable word
	 */
	t->sp0 = ((unsigned) kernel_stack) - X86_STACK_TOP_RESERVED;
	/* 
	 * set the cpu id at the top of the stack so we know on which cpu is
	 * this stak in use when we trap to kernel
	 */
	*((reg_t *)(t->sp0 + 1 * sizeof(reg_t))) = cpu;
}

/*===========================================================================*
 *				prot_init				     *
 *===========================================================================*/
void prot_init(void)
{
/* Set up tables for protected mode.
 * All GDT slots are allocated at compile time.
 */
  struct desctableptr_s *dtp;
  unsigned ldt_index;
  register struct proc *rp;

  /* Click-round kernel. */
  if(kinfo.data_base % CLICK_SIZE)
	panic("kinfo.data_base not aligned");
  kinfo.data_size = (phys_bytes) (CLICK_CEIL(kinfo.data_size));

  /* Build gdt and idt pointers in GDT where the BIOS expects them. */
  dtp= (struct desctableptr_s *) &gdt[GDT_INDEX];
  * (u16_t *) dtp->limit = (sizeof gdt) - 1;
  * (u32_t *) dtp->base = vir2phys(gdt);

  dtp= (struct desctableptr_s *) &gdt[IDT_INDEX];
  * (u16_t *) dtp->limit = (sizeof idt) - 1;
  * (u32_t *) dtp->base = vir2phys(idt);

  /* Build segment descriptors for tasks and interrupt handlers. */
  init_codeseg(&gdt[CS_INDEX],
  	 kinfo.code_base, kinfo.code_size, INTR_PRIVILEGE);
  init_dataseg(&gdt[DS_INDEX],
  	 kinfo.data_base, kinfo.data_size, INTR_PRIVILEGE);
  init_dataseg(&gdt[ES_INDEX], 0L, 0, INTR_PRIVILEGE);

  /* Build local descriptors in GDT for LDT's in process table.
   * The LDT's are allocated at compile time in the process table, and
   * initialized whenever a process' map is initialized or changed.
   */
  for (rp = BEG_PROC_ADDR, ldt_index = FIRST_LDT_INDEX;
       rp < END_PROC_ADDR; ++rp, ldt_index++) {
	init_dataseg(&gdt[ldt_index], vir2phys(rp->p_seg.p_ldt),
				     sizeof(rp->p_seg.p_ldt), INTR_PRIVILEGE);
	gdt[ldt_index].access = PRESENT | LDT;
	rp->p_seg.p_ldt_sel = ldt_index * DESC_SIZE;
  }

  /* Build boot TSS */
  tss_init(0, &k_boot_stktop);
}

void idt_copy_vectors(struct gate_table_s * first)
{
	struct gate_table_s *gtp;
	for (gtp = first; gtp->gate; gtp++) {
		int_gate(gtp->vec_nr, (vir_bytes) gtp->gate,
				PRESENT | INT_GATE_TYPE |
				(gtp->privilege << DPL_SHIFT));
	}
}

/* Build descriptors for interrupt gates in IDT. */
void idt_init(void)
{
	struct gate_table_s gate_table[] = {
		{ divide_error, DIVIDE_VECTOR, INTR_PRIVILEGE },
		{ single_step_exception, DEBUG_VECTOR, INTR_PRIVILEGE },
		{ nmi, NMI_VECTOR, INTR_PRIVILEGE },
		{ breakpoint_exception, BREAKPOINT_VECTOR, USER_PRIVILEGE },
		{ overflow, OVERFLOW_VECTOR, USER_PRIVILEGE },
		{ bounds_check, BOUNDS_VECTOR, INTR_PRIVILEGE },
		{ inval_opcode, INVAL_OP_VECTOR, INTR_PRIVILEGE },
		{ copr_not_available, COPROC_NOT_VECTOR, INTR_PRIVILEGE },
		{ double_fault, DOUBLE_FAULT_VECTOR, INTR_PRIVILEGE },
		{ copr_seg_overrun, COPROC_SEG_VECTOR, INTR_PRIVILEGE },
		{ inval_tss, INVAL_TSS_VECTOR, INTR_PRIVILEGE },
		{ segment_not_present, SEG_NOT_VECTOR, INTR_PRIVILEGE },
		{ stack_exception, STACK_FAULT_VECTOR, INTR_PRIVILEGE },
		{ general_protection, PROTECTION_VECTOR, INTR_PRIVILEGE },
		{ page_fault, PAGE_FAULT_VECTOR, INTR_PRIVILEGE },
		{ copr_error, COPROC_ERR_VECTOR, INTR_PRIVILEGE },
		{ alignment_check, ALIGNMENT_CHECK_VECTOR, INTR_PRIVILEGE },
		{ machine_check, MACHINE_CHECK_VECTOR, INTR_PRIVILEGE },
		{ simd_exception, SIMD_EXCEPTION_VECTOR, INTR_PRIVILEGE },
		{ ipc_entry, IPC_VECTOR, USER_PRIVILEGE },
		{ kernel_call_entry, KERN_CALL_VECTOR, USER_PRIVILEGE },
		{ NULL, 0, 0}
	};

	idt_copy_vectors(gate_table);
	idt_copy_vectors(gate_table_pic);
}


/*===========================================================================*
 *				sdesc					     *
 *===========================================================================*/
static void sdesc(segdp, base, size)
register struct segdesc_s *segdp;
phys_bytes base;
vir_bytes size;
{
/* Fill in the size fields (base, limit and granularity) of a descriptor. */
  segdp->base_low = base;
  segdp->base_middle = base >> BASE_MIDDLE_SHIFT;
  segdp->base_high = base >> BASE_HIGH_SHIFT;

  --size;			/* convert to a limit, 0 size means 4G */
  if (size > BYTE_GRAN_MAX) {
	segdp->limit_low = size >> PAGE_GRAN_SHIFT;
	segdp->granularity = GRANULAR | (size >>
				     (PAGE_GRAN_SHIFT + GRANULARITY_SHIFT));
  } else {
	segdp->limit_low = size;
	segdp->granularity = size >> GRANULARITY_SHIFT;
  }
  segdp->granularity |= DEFAULT;	/* means BIG for data seg */
}

/*===========================================================================*
 *				int_gate				     *
 *===========================================================================*/
void int_gate(unsigned vec_nr, vir_bytes offset, unsigned dpl_type)
{
/* Build descriptor for an interrupt gate. */
  register struct gatedesc_s *idp;

  idp = &idt[vec_nr];
  idp->offset_low = offset;
  idp->selector = CS_SELECTOR;
  idp->p_dpl_type = dpl_type;
  idp->offset_high = offset >> OFFSET_HIGH_SHIFT;
}

/*===========================================================================*
 *				alloc_segments				     *
 *===========================================================================*/
void alloc_segments(register struct proc *rp)
{
/* This is called at system initialization from main() and by do_newmap(). 
 * The code has a separate function because of all hardware-dependencies.
 */
  phys_bytes code_bytes;
  phys_bytes data_bytes;
  phys_bytes text_vaddr, data_vaddr;
  phys_bytes text_segbase, data_segbase;
  int privilege;

      data_bytes = (phys_bytes) (rp->p_memmap[S].mem_vir + 
          rp->p_memmap[S].mem_len) << CLICK_SHIFT;
      if (rp->p_memmap[T].mem_len == 0)
          code_bytes = data_bytes;	/* common I&D, poor protect */
      else
          code_bytes = (phys_bytes) rp->p_memmap[T].mem_len << CLICK_SHIFT;
      privilege = USER_PRIVILEGE;

      text_vaddr = rp->p_memmap[T].mem_vir << CLICK_SHIFT;
      data_vaddr = rp->p_memmap[D].mem_vir << CLICK_SHIFT;
      text_segbase = (rp->p_memmap[T].mem_phys -
		      rp->p_memmap[T].mem_vir) << CLICK_SHIFT;
      data_segbase = (rp->p_memmap[D].mem_phys -
		      rp->p_memmap[D].mem_vir) << CLICK_SHIFT;

      init_codeseg(&rp->p_seg.p_ldt[CS_LDT_INDEX],
		   text_segbase,
		   text_vaddr + code_bytes, privilege);
      init_dataseg(&rp->p_seg.p_ldt[DS_LDT_INDEX],
		   data_segbase,
		   data_vaddr + data_bytes, privilege);
      rp->p_reg.cs = (CS_LDT_INDEX * DESC_SIZE) | TI | privilege;
      rp->p_reg.gs =
      rp->p_reg.fs =
      rp->p_reg.ss =
      rp->p_reg.es =
      rp->p_reg.ds = (DS_LDT_INDEX*DESC_SIZE) | TI | privilege;
}

#if 0
/*===========================================================================*
 *				check_segments				     *
 *===========================================================================*/
static void check_segments(char *File, int line)
{
  int checked = 0;
int fail = 0;
struct proc *rp;
for (rp = BEG_PROC_ADDR; rp < END_PROC_ADDR; ++rp) {

  int privilege;
  int cs, ds;

		if (isemptyp(rp))
			continue;

	privilege = USER_PRIVILEGE;

	cs = (CS_LDT_INDEX*DESC_SIZE) | TI | privilege;
	ds = (DS_LDT_INDEX*DESC_SIZE) | TI | privilege;

#define CHECK(s1, s2) if(s1 != s2) {		\
	printf("%s:%d: " #s1 " != " #s2 " for ep %d\n", \
		File, line, rp->p_endpoint); fail++; } checked++;

	CHECK(rp->p_reg.cs, cs);
	CHECK(rp->p_reg.gs, ds);
	CHECK(rp->p_reg.fs, ds);
	CHECK(rp->p_reg.ss, ds);
	if(rp->p_endpoint != SYSTEM) {
		CHECK(rp->p_reg.es, ds);
	}
	CHECK(rp->p_reg.ds, ds);
     }
     if(fail) {
     	printf("%d/%d checks failed\n", fail, checked);
     	panic("wrong: %d",  fail);
     }
}
#endif

/*===========================================================================*
 *				printseg			     *
 *===========================================================================*/
void printseg(char *banner, const int iscs, struct proc *pr,
  const u32_t selector)
{
#if USE_SYSDEBUG
	u32_t base, limit, index, dpl;
	struct segdesc_s *desc;

	if(banner) { printf("%s", banner); }

	index = selector >> 3;

	printf("RPL %d, ind %d of ",
		(selector & RPL_MASK), index);

	if(selector & TI) {
		printf("LDT");
		if(index >= LDT_SIZE) {
			printf("invalid index in ldt\n");
			return;
		}
		if(!pr) {
			printf("local selector but unknown process\n");
			return;
		}
		desc = &pr->p_seg.p_ldt[index];
	} else {
		printf("GDT");
		if(index >= GDT_SIZE) {
			printf("invalid index in gdt\n");
			return;
		}
		desc = &gdt[index];
	}

	limit = desc->limit_low |
		(((u32_t) desc->granularity & LIMIT_HIGH) << GRANULARITY_SHIFT);

	if(desc->granularity & GRANULAR) {
		limit = (limit << PAGE_GRAN_SHIFT) + 0xfff;
	}

	base = desc->base_low | 
		((u32_t) desc->base_middle << BASE_MIDDLE_SHIFT) |
		((u32_t) desc->base_high << BASE_HIGH_SHIFT);

	printf(" -> base 0x%08lx size 0x%08lx ", base, limit+1);

	if(iscs) {
		if(!(desc->granularity & BIG))
			printf("16bit ");
	} else {
		if(!(desc->granularity & BIG)) 
			printf("not big ");
	}

	if(desc->granularity & 0x20) {	/* reserved */
		panic("granularity reserved field set");
	}

	if(!(desc->access & PRESENT))
		printf("notpresent ");

	if(!(desc->access & SEGMENT))
		printf("system ");

	if(desc->access & EXECUTABLE) {
		printf("   exec ");
		if(desc->access & CONFORMING) printf("conforming ");
		if(!(desc->access & READABLE)) printf("non-readable ");
	} else {
		printf("nonexec ");
		if(desc->access & EXPAND_DOWN) printf("non-expand-down ");
		if(!(desc->access & WRITEABLE)) printf("non-writable ");
	}

	if(!(desc->access & ACCESSED)) {
		printf("nonacc ");
	}

	dpl = ((u32_t) desc->access & DPL) >> DPL_SHIFT;

	printf("DPL %d\n", dpl);

	return;
#endif /* USE_SYSDEBUG */
}

/*===========================================================================*
 *				prot_set_kern_seg_limit			     *
 *===========================================================================*/
int prot_set_kern_seg_limit(const vir_bytes limit)
{
	struct proc *rp;
	int orig_click;
	int incr_clicks;

	if(limit <= kinfo.data_base) {
		printf("prot_set_kern_seg_limit: limit bogus\n");
		return EINVAL;
	}

	/* Do actual increase. */
	orig_click = kinfo.data_size / CLICK_SIZE;
	kinfo.data_size = limit - kinfo.data_base;
	incr_clicks = kinfo.data_size / CLICK_SIZE - orig_click;

	prot_init();

	/* Increase kernel processes too. */
	for (rp = BEG_PROC_ADDR; rp < END_PROC_ADDR; ++rp) {
		if (isemptyp(rp) || !iskernelp(rp))
			continue;
		rp->p_memmap[S].mem_len += incr_clicks;
		alloc_segments(rp);
		rp->p_memmap[S].mem_len -= incr_clicks;
	}

	return OK;
}