kernel/arch/x86/thread.cc

   1 // arch/x86/thread.cc -- Thread switching
   2 //
   3 // This software is copyright (c) 2006 Scott Wood <scott@buserror.net>.
   4 //
   5 // This software is provided 'as-is', without any express or implied warranty.
   6 // In no event will the authors or contributors be held liable for any damages
   7 // arising from the use of this software.
   8 //
   9 // Permission is hereby granted to everyone, free of charge, to use, copy,
  10 // modify, prepare derivative works of, publish, distribute, perform,
  11 // sublicense, and/or sell copies of the Software, provided that the above
  12 // copyright notice and disclaimer of warranty be included in all copies or
  13 // substantial portions of this software.
  14
  15 #include <kern/thread.h>
  16 #include <kern/mem.h>
  17 #include <kern/pagetable.h>
  18 #include <kern/process.h>
  19
  20 namespace Arch {
  21         void set_aspace(Mem::ProcAddrSpace *aspace)
  22         {
  23                 u32 cr3 = Mem::kvirt_to_phys(aspace->page_table->toplevel);
  24                 asm volatile("movl %0, %%cr3" : : "r" (cr3) : "memory");
  25         }
  26
  27         void switch_thread(Threads::Thread *dest, Threads::Thread *src)
  28         {
  29                 u32 dummy1, dummy2;
  30
  31                 if (dest->addr_space) {
  32                         assert(dest->addr_space == dest->active_addr_space);
  33
  34                         if (dest->addr_space != src->active_addr_space)
  35                                 set_aspace(dest->addr_space);
  36                 } else {
  37                         dest->active_addr_space = src->active_addr_space;
  38                 }
  39
  40                 Priv::tss.esp0 = reinterpret_cast<u32>(dest);
  41
  42                 asm volatile("movl %%esp, (%0);"
  43                              "movl %%ebp, 4(%0);"
  44                              "movb $0, 8(%0);"
  45                              "movb 8(%1), %%al;"
  46                              "cmpb $0, %%al;"
  47                              "movl (%1), %%esp;"
  48                              "movl 4(%1), %%ebp;"
  49                              "jnz x86_new_thread;" :
  50                              "=a" (dummy1), "=c" (dummy2) :
  51                              "0" (&src->arch.esp), "1" (&dest->arch.esp) :
  52                              "ebx", "edx", "esi", "edi", "memory");
  53         }
  54 }