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minix/kernel/arch/i386/protect.c
Tomas Hruby ebbce7507b Complete ovehaul of mode switching code 
- after a trap to kernel, the code automatically switches to kernel
  stack, in the future local to the CPU

- k_reenter variable replaced by a test whether the CS is kernel cs or
  not. The information is passed further if needed. Removes a global
  variable which would need to be cpu local

- no need for global variables describing the exception or trap
  context. This information is kept on stack and a pointer to this
  structure is passed to the C code as a single structure

- removed loadedcr3 variable and its use replaced by reading the %cr3
  register

- no need to redisable interrupts in restart() as they are already
  disabled.

- unified handling of traps that push and don't push errorcode

- removed save() function as the process context is not saved directly
  to process table but saved as required by the trap code. Essentially
  it means that save() code is inlined everywhere not only in the
  exception handling routine

- returning from syscall is more arch independent - it sets the retger
  in C

- top of the x86 stack contains the current CPU id and pointer to the
  currently scheduled process (the one right interrupted) so the mode
  switch code can find where to save the context without need to use
  proc_ptr which will be cpu local in the future and therefore
  difficult to access in assembler and expensive to access in general

- some more clean up of level0 code. No need to read-back the argument
  passed in
  %eax from the proc structure. The mode switch code does not clobber
  %the general registers and hence we can just call what is in %eax

- many assebly macros in sconst.h as they will be reused by the apic
  assembly
2009-11-06 09:08:26 +00:00

467 lines
15 KiB
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/* 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.h"
#include "../../proc.h"
#include <archconst.h>
#include "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;
};
PUBLIC struct segdesc_s gdt[GDT_SIZE]; /* used in klib.s and mpx.s */
PRIVATE struct gatedesc_s idt[IDT_SIZE]; /* zero-init so none present */
PUBLIC struct tss_s tss; /* zero init */
FORWARD _PROTOTYPE( void int_gate, (unsigned vec_nr, vir_bytes offset,
unsigned dpl_type) );
FORWARD _PROTOTYPE( void sdesc, (struct segdesc_s *segdp, phys_bytes base,
vir_bytes size) );
/*===========================================================================*
* enable_iop *
*===========================================================================*/
PUBLIC 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 *
*===========================================================================*/
PUBLIC phys_bytes seg2phys(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;
}
/*===========================================================================*
* phys2seg *
*===========================================================================*/
PUBLIC void phys2seg(u16_t *seg, vir_bytes *off, phys_bytes phys)
{
/* Return a segment selector and offset that can be used to reach a physical
* address, for use by a driver doing memory I/O in the A0000 - DFFFF range.
*/
*seg = FLAT_DS_SELECTOR;
*off = phys;
}
/*===========================================================================*
* init_dataseg *
*===========================================================================*/
PUBLIC void init_dataseg(register struct segdesc_s *segdp,
phys_bytes base, vir_bytes size, 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 *
*===========================================================================*/
PUBLIC 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 */
}
PUBLIC 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}
};
/*===========================================================================*
* prot_init *
*===========================================================================*/
PUBLIC void prot_init(void)
{
/* Set up tables for protected mode.
* All GDT slots are allocated at compile time.
*/
struct gate_table_s *gtp;
struct desctableptr_s *dtp;
unsigned ldt_index;
register struct proc *rp;
/* Click-round kernel. */
if(kinfo.data_base % CLICK_SIZE)
minix_panic("kinfo.data_base not aligned", NO_NUM);
kinfo.data_size = ((kinfo.data_size+CLICK_SIZE-1)/CLICK_SIZE) * CLICK_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, TASK_PRIVILEGE);
/* Build scratch descriptors for functions in klib88. */
init_dataseg(&gdt[DS_286_INDEX], 0L, 0, TASK_PRIVILEGE);
init_dataseg(&gdt[ES_286_INDEX], 0L, 0, TASK_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 main TSS */
tss.ss0 = DS_SELECTOR;
init_dataseg(&gdt[TSS_INDEX], vir2phys(&tss), sizeof(tss), INTR_PRIVILEGE);
gdt[TSS_INDEX].access = PRESENT | (INTR_PRIVILEGE << DPL_SHIFT) | TSS_TYPE;
/* Complete building of main TSS. */
tss.iobase = sizeof tss; /* empty i/o permissions map */
}
PUBLIC 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. */
PUBLIC 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 },
{ syscall_entry, SYS386_VECTOR, USER_PRIVILEGE },/* 386 system call */
{ level0_call, LEVEL0_VECTOR, TASK_PRIVILEGE },
{ NULL, 0, 0}
};
idt_copy_vectors(gate_table);
idt_copy_vectors(gate_table_pic);
}
/*===========================================================================*
* sdesc *
*===========================================================================*/
PRIVATE 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 *
*===========================================================================*/
PRIVATE void int_gate(vec_nr, offset, dpl_type)
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 *
*===========================================================================*/
PUBLIC 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.
* Note that IDLE is part of the kernel and gets TASK_PRIVILEGE here.
*/
phys_bytes code_bytes;
phys_bytes data_bytes;
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;
if( (iskernelp(rp)))
privilege = TASK_PRIVILEGE;
else
privilege = USER_PRIVILEGE;
init_codeseg(&rp->p_seg.p_ldt[CS_LDT_INDEX],
(phys_bytes) rp->p_memmap[T].mem_phys << CLICK_SHIFT,
code_bytes, privilege);
init_dataseg(&rp->p_seg.p_ldt[DS_LDT_INDEX],
(phys_bytes) rp->p_memmap[D].mem_phys << CLICK_SHIFT,
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;
}
/*===========================================================================*
* check_segments *
*===========================================================================*/
PUBLIC 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 (RTS_ISSET(rp, SLOT_FREE))
continue;
if( (iskernelp(rp)))
privilege = TASK_PRIVILEGE;
else
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 != -2) {
CHECK(rp->p_reg.es, ds);
}
CHECK(rp->p_reg.ds, ds);
}
if(fail) {
printf("%d/%d checks failed\n", fail, checked);
minix_panic("wrong", fail);
}
}
/*===========================================================================*
* printseg *
*===========================================================================*/
PUBLIC void printseg(char *banner, int iscs, struct proc *pr, u32_t selector)
{
u32_t base, limit, index, dpl;
struct segdesc_s *desc;
if(banner) { kprintf("%s", banner); }
index = selector >> 3;
kprintf("RPL %d, ind %d of ",
(selector & RPL_MASK), index);
if(selector & TI) {
kprintf("LDT");
if(index < 0 || index >= LDT_SIZE) {
kprintf("invalid index in ldt\n");
return;
}
if(!pr) {
kprintf("local selector but unknown process\n");
return;
}
desc = &pr->p_seg.p_ldt[index];
} else {
kprintf("GDT");
if(index < 0 || index >= GDT_SIZE) {
kprintf("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);
kprintf(" -> base 0x%08lx size 0x%08lx ", base, limit+1);
if(iscs) {
if(!(desc->granularity & BIG))
kprintf("16bit ");
} else {
if(!(desc->granularity & BIG))
kprintf("not big ");
}
if(desc->granularity & 0x20) { /* reserved */
minix_panic("granularity reserved field set", NO_NUM);
}
if(!(desc->access & PRESENT))
kprintf("notpresent ");
if(!(desc->access & SEGMENT))
kprintf("system ");
if(desc->access & EXECUTABLE) {
kprintf(" exec ");
if(desc->access & CONFORMING) kprintf("conforming ");
if(!(desc->access & READABLE)) kprintf("non-readable ");
} else {
kprintf("nonexec ");
if(desc->access & EXPAND_DOWN) kprintf("non-expand-down ");
if(!(desc->access & WRITEABLE)) kprintf("non-writable ");
}
if(!(desc->access & ACCESSED)) {
kprintf("nonacc ");
}
dpl = ((u32_t) desc->access & DPL) >> DPL_SHIFT;
kprintf("DPL %d\n", dpl);
return;
}
/*===========================================================================*
* prot_set_kern_seg_limit *
*===========================================================================*/
PUBLIC int prot_set_kern_seg_limit(vir_bytes limit)
{
struct proc *rp;
vir_bytes prev;
int orig_click;
int incr_clicks;
if(limit <= kinfo.data_base) {
kprintf("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 (RTS_ISSET(rp, SLOT_FREE) || !iskernelp(rp))
continue;
rp->p_memmap[S].mem_len += incr_clicks;
alloc_segments(rp);
}
return OK;
}
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