Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 | /*
* linux/arch/i386/kernel/process.c
*
* Copyright (C) 1995 Linus Torvalds
*/
/*
* This file handles the architecture-dependent parts of process handling..
*/
#define __KERNEL_SYSCALLS__
#include <stdarg.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/malloc.h>
#include <linux/vmalloc.h>
#include <linux/user.h>
#include <linux/a.out.h>
#include <linux/interrupt.h>
#include <linux/config.h>
#include <linux/unistd.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/mc146818rtc.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/io.h>
#include <asm/ldt.h>
#include <asm/processor.h>
#include <asm/desc.h>
#ifdef CONFIG_MATH_EMULATION
#include <asm/math_emu.h>
#endif
#include "irq.h"
spinlock_t semaphore_wake_lock = SPIN_LOCK_UNLOCKED;
asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
int hlt_counter=0;
#define HARD_IDLE_TIMEOUT (HZ / 3)
/*
* Powermanagement idle function, if any..
*/
void (*acpi_idle)(void) = NULL;
/*
* Power off function, if any
*/
void (*acpi_power_off)(void) = NULL;
void disable_hlt(void)
{
hlt_counter++;
}
void enable_hlt(void)
{
hlt_counter--;
}
#ifndef CONFIG_SMP
/*
* The idle loop on a uniprocessor i386..
*/
static int cpu_idle(void *unused)
{
int work = 1;
unsigned long start_idle = 0;
/* endless idle loop with no priority at all */
current->priority = 0;
current->counter = -100;
for (;;) {
if (work)
start_idle = jiffies;
if (acpi_idle && (jiffies - start_idle > HARD_IDLE_TIMEOUT))
acpi_idle();
else {
if (boot_cpu_data.hlt_works_ok && !hlt_counter && !current->need_resched)
__asm__("hlt");
}
work = current->need_resched;
schedule();
check_pgt_cache();
}
}
#else
/*
* This is being executed in task 0 'user space'.
*/
int cpu_idle(void *unused)
{
/* endless idle loop with no priority at all */
current->priority = 0;
current->counter = -100;
while(1) {
if (current_cpu_data.hlt_works_ok && !hlt_counter &&
!current->need_resched)
__asm__("hlt");
/*
* although we are an idle CPU, we do not want to
* get into the scheduler unnecessarily.
*/
if (current->need_resched) {
schedule();
check_pgt_cache();
}
}
}
#endif
asmlinkage int sys_idle(void)
{
if (current->pid != 0)
return -EPERM;
cpu_idle(NULL);
return 0;
}
/*
* This routine reboots the machine by asking the keyboard
* controller to pulse the reset-line low. We try that for a while,
* and if it doesn't work, we do some other stupid things.
*/
static long no_idt[2] = {0, 0};
static int reboot_mode = 0;
static int reboot_thru_bios = 0;
__initfunc(void reboot_setup(char *str, int *ints))
{
while(1) {
switch (*str) {
case 'w': /* "warm" reboot (no memory testing etc) */
reboot_mode = 0x1234;
break;
case 'c': /* "cold" reboot (with memory testing etc) */
reboot_mode = 0x0;
break;
case 'b': /* "bios" reboot by jumping through the BIOS */
reboot_thru_bios = 1;
break;
case 'h': /* "hard" reboot by toggling RESET and/or crashing the CPU */
reboot_thru_bios = 0;
break;
}
if((str = strchr(str,',')) != NULL)
str++;
else
break;
}
}
/* The following code and data reboots the machine by switching to real
mode and jumping to the BIOS reset entry point, as if the CPU has
really been reset. The previous version asked the keyboard
controller to pulse the CPU reset line, which is more thorough, but
doesn't work with at least one type of 486 motherboard. It is easy
to stop this code working; hence the copious comments. */
static unsigned long long
real_mode_gdt_entries [3] =
{
0x0000000000000000ULL, /* Null descriptor */
0x00009a000000ffffULL, /* 16-bit real-mode 64k code at 0x00000000 */
0x000092000100ffffULL /* 16-bit real-mode 64k data at 0x00000100 */
};
static struct
{
unsigned short size __attribute__ ((packed));
unsigned long long * base __attribute__ ((packed));
}
real_mode_gdt = { sizeof (real_mode_gdt_entries) - 1, real_mode_gdt_entries },
real_mode_idt = { 0x3ff, 0 };
/* This is 16-bit protected mode code to disable paging and the cache,
switch to real mode and jump to the BIOS reset code.
The instruction that switches to real mode by writing to CR0 must be
followed immediately by a far jump instruction, which set CS to a
valid value for real mode, and flushes the prefetch queue to avoid
running instructions that have already been decoded in protected
mode.
Clears all the flags except ET, especially PG (paging), PE
(protected-mode enable) and TS (task switch for coprocessor state
save). Flushes the TLB after paging has been disabled. Sets CD and
NW, to disable the cache on a 486, and invalidates the cache. This
is more like the state of a 486 after reset. I don't know if
something else should be done for other chips.
More could be done here to set up the registers as if a CPU reset had
occurred; hopefully real BIOSs don't assume much. */
static unsigned char real_mode_switch [] =
{
0x66, 0x0f, 0x20, 0xc0, /* movl %cr0,%eax */
0x66, 0x83, 0xe0, 0x11, /* andl $0x00000011,%eax */
0x66, 0x0d, 0x00, 0x00, 0x00, 0x60, /* orl $0x60000000,%eax */
0x66, 0x0f, 0x22, 0xc0, /* movl %eax,%cr0 */
0x66, 0x0f, 0x22, 0xd8, /* movl %eax,%cr3 */
0x66, 0x0f, 0x20, 0xc3, /* movl %cr0,%ebx */
0x66, 0x81, 0xe3, 0x00, 0x00, 0x00, 0x60, /* andl $0x60000000,%ebx */
0x74, 0x02, /* jz f */
0x0f, 0x08, /* invd */
0x24, 0x10, /* f: andb $0x10,al */
0x66, 0x0f, 0x22, 0xc0 /* movl %eax,%cr0 */
};
static unsigned char jump_to_bios [] =
{
0xea, 0x00, 0x00, 0xff, 0xff /* ljmp $0xffff,$0x0000 */
};
static inline void kb_wait(void)
{
int i;
for (i=0; i<0x10000; i++)
if ((inb_p(0x64) & 0x02) == 0)
break;
}
/*
* Switch to real mode and then execute the code
* specified by the code and length parameters.
* We assume that length will aways be less that 100!
*/
void machine_real_restart(unsigned char *code, int length)
{
unsigned long flags;
cli();
/* Write zero to CMOS register number 0x0f, which the BIOS POST
routine will recognize as telling it to do a proper reboot. (Well
that's what this book in front of me says -- it may only apply to
the Phoenix BIOS though, it's not clear). At the same time,
disable NMIs by setting the top bit in the CMOS address register,
as we're about to do peculiar things to the CPU. I'm not sure if
`outb_p' is needed instead of just `outb'. Use it to be on the
safe side. */
spin_lock_irqsave(&rtc_lock, flags);
CMOS_WRITE(0x00, 0x8f);
spin_unlock_irqrestore(&rtc_lock, flags);
/* Remap the kernel at virtual address zero, as well as offset zero
from the kernel segment. This assumes the kernel segment starts at
virtual address PAGE_OFFSET. */
memcpy (swapper_pg_dir, swapper_pg_dir + USER_PGD_PTRS,
sizeof (swapper_pg_dir [0]) * KERNEL_PGD_PTRS);
/* Make sure the first page is mapped to the start of physical memory.
It is normally not mapped, to trap kernel NULL pointer dereferences. */
pg0[0] = _PAGE_RW | _PAGE_PRESENT;
/*
* Use `swapper_pg_dir' as our page directory. We bother with
* `SET_PAGE_DIR' because although might be rebooting, but if we change
* the way we set root page dir in the future, then we wont break a
* seldom used feature ;)
*/
SET_PAGE_DIR(current,swapper_pg_dir);
/* Write 0x1234 to absolute memory location 0x472. The BIOS reads
this on booting to tell it to "Bypass memory test (also warm
boot)". This seems like a fairly standard thing that gets set by
REBOOT.COM programs, and the previous reset routine did this
too. */
*((unsigned short *)0x472) = reboot_mode;
/* For the switch to real mode, copy some code to low memory. It has
to be in the first 64k because it is running in 16-bit mode, and it
has to have the same physical and virtual address, because it turns
off paging. Copy it near the end of the first page, out of the way
of BIOS variables. */
memcpy ((void *) (0x1000 - sizeof (real_mode_switch) - 100),
real_mode_switch, sizeof (real_mode_switch));
memcpy ((void *) (0x1000 - 100), code, length);
/* Set up the IDT for real mode. */
__asm__ __volatile__ ("lidt %0" : : "m" (real_mode_idt));
/* Set up a GDT from which we can load segment descriptors for real
mode. The GDT is not used in real mode; it is just needed here to
prepare the descriptors. */
__asm__ __volatile__ ("lgdt %0" : : "m" (real_mode_gdt));
/* Load the data segment registers, and thus the descriptors ready for
real mode. The base address of each segment is 0x100, 16 times the
selector value being loaded here. This is so that the segment
registers don't have to be reloaded after switching to real mode:
the values are consistent for real mode operation already. */
__asm__ __volatile__ ("movl $0x0010,%%eax\n"
"\tmovl %%ax,%%ds\n"
"\tmovl %%ax,%%es\n"
"\tmovl %%ax,%%fs\n"
"\tmovl %%ax,%%gs\n"
"\tmovl %%ax,%%ss" : : : "eax");
/* Jump to the 16-bit code that we copied earlier. It disables paging
and the cache, switches to real mode, and jumps to the BIOS reset
entry point. */
__asm__ __volatile__ ("ljmp $0x0008,%0"
:
: "i" ((void *) (0x1000 - sizeof (real_mode_switch) - 100)));
}
void machine_restart(char * __unused)
{
#if CONFIG_SMP
/*
* turn off the IO-APIC, so we can do a clean reboot
*/
init_pic_mode();
#endif
if(!reboot_thru_bios) {
/* rebooting needs to touch the page at absolute addr 0 */
*((unsigned short *)__va(0x472)) = reboot_mode;
for (;;) {
int i;
for (i=0; i<100; i++) {
kb_wait();
udelay(50);
outb(0xfe,0x64); /* pulse reset low */
udelay(50);
}
/* That didn't work - force a triple fault.. */
__asm__ __volatile__("lidt %0": :"m" (no_idt));
__asm__ __volatile__("int3");
}
}
machine_real_restart(jump_to_bios, sizeof(jump_to_bios));
}
void machine_halt(void)
{
}
void machine_power_off(void)
{
if (acpi_power_off)
acpi_power_off();
}
void show_regs(struct pt_regs * regs)
{
long cr0 = 0L, cr2 = 0L, cr3 = 0L;
printk("\n");
printk("EIP: %04x:[<%08lx>]",0xffff & regs->xcs,regs->eip);
if (regs->xcs & 3)
printk(" ESP: %04x:%08lx",0xffff & regs->xss,regs->esp);
printk(" EFLAGS: %08lx\n",regs->eflags);
printk("EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
regs->eax,regs->ebx,regs->ecx,regs->edx);
printk("ESI: %08lx EDI: %08lx EBP: %08lx",
regs->esi, regs->edi, regs->ebp);
printk(" DS: %04x ES: %04x\n",
0xffff & regs->xds,0xffff & regs->xes);
__asm__("movl %%cr0, %0": "=r" (cr0));
__asm__("movl %%cr2, %0": "=r" (cr2));
__asm__("movl %%cr3, %0": "=r" (cr3));
printk("CR0: %08lx CR2: %08lx CR3: %08lx\n", cr0, cr2, cr3);
}
/*
* Allocation and freeing of basic task resources.
*
* NOTE! The task struct and the stack go together
*
* The task structure is a two-page thing, and as such
* not reliable to allocate using the basic page alloc
* functions. We have a small cache of structures for
* when the allocations fail..
*
* This extra buffer essentially acts to make for less
* "jitter" in the allocations..
*
* On SMP we don't do this right now because:
* - we aren't holding any locks when called, and we might
* as well just depend on the generic memory management
* to do proper locking for us instead of complicating it
* here.
* - if you use SMP you have a beefy enough machine that
* this shouldn't matter..
*/
#ifndef CONFIG_SMP
#define EXTRA_TASK_STRUCT 16
static struct task_struct * task_struct_stack[EXTRA_TASK_STRUCT];
static int task_struct_stack_ptr = -1;
#endif
struct task_struct * alloc_task_struct(void)
{
#ifndef EXTRA_TASK_STRUCT
return (struct task_struct *) __get_free_pages(GFP_KERNEL,1);
#else
int index;
struct task_struct *ret;
index = task_struct_stack_ptr;
if (index >= EXTRA_TASK_STRUCT/2)
goto use_cache;
ret = (struct task_struct *) __get_free_pages(GFP_KERNEL,1);
if (!ret) {
index = task_struct_stack_ptr;
if (index >= 0) {
use_cache:
ret = task_struct_stack[index];
task_struct_stack_ptr = index-1;
}
}
return ret;
#endif
}
void free_task_struct(struct task_struct *p)
{
#ifdef EXTRA_TASK_STRUCT
int index = task_struct_stack_ptr+1;
if (index < EXTRA_TASK_STRUCT) {
task_struct_stack[index] = p;
task_struct_stack_ptr = index;
} else
#endif
free_pages((unsigned long) p, 1);
}
void release_segments(struct mm_struct *mm)
{
if (mm->segments) {
void * ldt = mm->segments;
mm->segments = NULL;
vfree(ldt);
}
}
void forget_segments(void)
{
/* forget local segments */
__asm__ __volatile__("movl %w0,%%fs ; movl %w0,%%gs"
: /* no outputs */
: "r" (0));
/*
* Get the LDT entry from init_task.
*/
current->tss.ldt = _LDT(0);
load_ldt(0);
}
/*
* Create a kernel thread
*/
int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
{
long retval, d0;
__asm__ __volatile__(
"movl %%esp,%%esi\n\t"
"int $0x80\n\t" /* Linux/i386 system call */
"cmpl %%esp,%%esi\n\t" /* child or parent? */
"je 1f\n\t" /* parent - jump */
/* Load the argument into eax, and push it. That way, it does
* not matter whether the called function is compiled with
* -mregparm or not. */
"movl %4,%%eax\n\t"
"pushl %%eax\n\t"
"call *%5\n\t" /* call fn */
"movl %3,%0\n\t" /* exit */
"int $0x80\n"
"1:\t"
:"=&a" (retval), "=&S" (d0)
:"0" (__NR_clone), "i" (__NR_exit),
"r" (arg), "r" (fn),
"b" (flags | CLONE_VM)
: "memory");
return retval;
}
/*
* Free current thread data structures etc..
*/
void exit_thread(void)
{
/* nothing to do ... */
}
void flush_thread(void)
{
int i;
struct task_struct *tsk = current;
for (i=0 ; i<8 ; i++)
tsk->tss.debugreg[i] = 0;
/*
* Forget coprocessor state..
*/
clear_fpu(tsk);
tsk->used_math = 0;
}
void release_thread(struct task_struct *dead_task)
{
}
/*
* If new_mm is NULL, we're being called to set up the LDT descriptor
* for a clone task. Each clone must have a separate entry in the GDT.
*/
void copy_segments(int nr, struct task_struct *p, struct mm_struct *new_mm)
{
struct mm_struct * old_mm = current->mm;
void * old_ldt = old_mm->segments, * ldt = old_ldt;
/* default LDT - use the one from init_task */
p->tss.ldt = _LDT(0);
if (old_ldt) {
if (new_mm) {
ldt = vmalloc(LDT_ENTRIES*LDT_ENTRY_SIZE);
new_mm->segments = ldt;
if (!ldt) {
printk(KERN_WARNING "ldt allocation failed\n");
return;
}
memcpy(ldt, old_ldt, LDT_ENTRIES*LDT_ENTRY_SIZE);
}
p->tss.ldt = _LDT(nr);
set_ldt_desc(nr, ldt, LDT_ENTRIES);
return;
}
}
/*
* Save a segment.
*/
#define savesegment(seg,value) \
asm volatile("movl %%" #seg ",%0":"=m" (*(int *)&(value)))
int copy_thread(int nr, unsigned long clone_flags, unsigned long esp,
struct task_struct * p, struct pt_regs * regs)
{
struct pt_regs * childregs;
childregs = ((struct pt_regs *) (2*PAGE_SIZE + (unsigned long) p)) - 1;
*childregs = *regs;
childregs->eax = 0;
childregs->esp = esp;
p->tss.esp = (unsigned long) childregs;
p->tss.esp0 = (unsigned long) (childregs+1);
p->tss.ss0 = __KERNEL_DS;
p->tss.tr = _TSS(nr);
set_tss_desc(nr,&(p->tss));
p->tss.eip = (unsigned long) ret_from_fork;
savesegment(fs,p->tss.fs);
savesegment(gs,p->tss.gs);
/*
* a bitmap offset pointing outside of the TSS limit causes a nicely
* controllable SIGSEGV. The first sys_ioperm() call sets up the
* bitmap properly.
*/
p->tss.bitmap = sizeof(struct thread_struct);
unlazy_fpu(current);
p->tss.i387 = current->tss.i387;
return 0;
}
/*
* fill in the FPU structure for a core dump.
*/
int dump_fpu (struct pt_regs * regs, struct user_i387_struct* fpu)
{
int fpvalid;
struct task_struct *tsk = current;
fpvalid = tsk->used_math;
if (fpvalid) {
unlazy_fpu(tsk);
memcpy(fpu,&tsk->tss.i387.hard,sizeof(*fpu));
}
return fpvalid;
}
/*
* fill in the user structure for a core dump..
*/
void dump_thread(struct pt_regs * regs, struct user * dump)
{
int i;
/* changed the size calculations - should hopefully work better. lbt */
dump->magic = CMAGIC;
dump->start_code = 0;
dump->start_stack = regs->esp & ~(PAGE_SIZE - 1);
dump->u_tsize = ((unsigned long) current->mm->end_code) >> PAGE_SHIFT;
dump->u_dsize = ((unsigned long) (current->mm->brk + (PAGE_SIZE-1))) >> PAGE_SHIFT;
dump->u_dsize -= dump->u_tsize;
dump->u_ssize = 0;
for (i = 0; i < 8; i++)
dump->u_debugreg[i] = current->tss.debugreg[i];
if (dump->start_stack < TASK_SIZE)
dump->u_ssize = ((unsigned long) (TASK_SIZE - dump->start_stack)) >> PAGE_SHIFT;
dump->regs.ebx = regs->ebx;
dump->regs.ecx = regs->ecx;
dump->regs.edx = regs->edx;
dump->regs.esi = regs->esi;
dump->regs.edi = regs->edi;
dump->regs.ebp = regs->ebp;
dump->regs.eax = regs->eax;
dump->regs.ds = regs->xds;
dump->regs.es = regs->xes;
savesegment(fs,dump->regs.fs);
savesegment(gs,dump->regs.gs);
dump->regs.orig_eax = regs->orig_eax;
dump->regs.eip = regs->eip;
dump->regs.cs = regs->xcs;
dump->regs.eflags = regs->eflags;
dump->regs.esp = regs->esp;
dump->regs.ss = regs->xss;
dump->u_fpvalid = dump_fpu (regs, &dump->i387);
}
/*
* This special macro can be used to load a debugging register
*/
#define loaddebug(tsk,register) \
__asm__("movl %0,%%db" #register \
: /* no output */ \
:"r" (tsk->tss.debugreg[register]))
/*
* switch_to(x,yn) should switch tasks from x to y.
*
* We fsave/fwait so that an exception goes off at the right time
* (as a call from the fsave or fwait in effect) rather than to
* the wrong process. Lazy FP saving no longer makes any sense
* with modern CPU's, and this simplifies a lot of things (SMP
* and UP become the same).
*
* NOTE! We used to use the x86 hardware context switching. The
* reason for not using it any more becomes apparent when you
* try to recover gracefully from saved state that is no longer
* valid (stale segment register values in particular). With the
* hardware task-switch, there is no way to fix up bad state in
* a reasonable manner.
*
* The fact that Intel documents the hardware task-switching to
* be slow is a fairly red herring - this code is not noticeably
* faster. However, there _is_ some room for improvement here,
* so the performance issues may eventually be a valid point.
* More important, however, is the fact that this allows us much
* more flexibility.
*/
void __switch_to(struct task_struct *prev, struct task_struct *next)
{
/* Do the FPU save and set TS if it wasn't set before.. */
unlazy_fpu(prev);
/*
* Reload TR, LDT and the page table pointers..
*
* We need TR for the IO permission bitmask (and
* the vm86 bitmasks in case we ever use enhanced
* v86 mode properly).
*
* We may want to get rid of the TR register some
* day, and copy the bitmaps around by hand. Oh,
* well. In the meantime we have to clear the busy
* bit in the TSS entry, ugh.
*/
gdt_table[next->tss.tr >> 3].b &= 0xfffffdff;
asm volatile("ltr %0": :"g" (*(unsigned short *)&next->tss.tr));
/*
* Save away %fs and %gs. No need to save %es and %ds, as
* those are always kernel segments while inside the kernel.
*/
asm volatile("movl %%fs,%0":"=m" (*(int *)&prev->tss.fs));
asm volatile("movl %%gs,%0":"=m" (*(int *)&prev->tss.gs));
/* Re-load LDT if necessary */
if (next->mm->segments != prev->mm->segments)
asm volatile("lldt %0": :"g" (*(unsigned short *)&next->tss.ldt));
/* Re-load page tables */
{
unsigned long new_cr3 = next->tss.cr3;
if (new_cr3 != prev->tss.cr3)
asm volatile("movl %0,%%cr3": :"r" (new_cr3));
}
/*
* Restore %fs and %gs.
*/
loadsegment(fs,next->tss.fs);
loadsegment(gs,next->tss.gs);
/*
* Now maybe reload the debug registers
*/
if (next->tss.debugreg[7]){
loaddebug(next,0);
loaddebug(next,1);
loaddebug(next,2);
loaddebug(next,3);
loaddebug(next,6);
loaddebug(next,7);
}
}
asmlinkage int sys_fork(struct pt_regs regs)
{
return do_fork(SIGCHLD, regs.esp, ®s);
}
asmlinkage int sys_clone(struct pt_regs regs)
{
unsigned long clone_flags;
unsigned long newsp;
clone_flags = regs.ebx;
newsp = regs.ecx;
if (!newsp)
newsp = regs.esp;
return do_fork(clone_flags, newsp, ®s);
}
/*
* This is trivial, and on the face of it looks like it
* could equally well be done in user mode.
*
* Not so, for quite unobvious reasons - register pressure.
* In user mode vfork() cannot have a stack frame, and if
* done by calling the "clone()" system call directly, you
* do not have enough call-clobbered registers to hold all
* the information you need.
*/
asmlinkage int sys_vfork(struct pt_regs regs)
{
return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs.esp, ®s);
}
/*
* sys_execve() executes a new program.
*/
asmlinkage int sys_execve(struct pt_regs regs)
{
int error;
char * filename;
lock_kernel();
filename = getname((char *) regs.ebx);
error = PTR_ERR(filename);
if (IS_ERR(filename))
goto out;
error = do_execve(filename, (char **) regs.ecx, (char **) regs.edx, ®s);
if (error == 0)
current->flags &= ~PF_DTRACE;
putname(filename);
out:
unlock_kernel();
return error;
}
|