arch/x86/kernel/process_32.c

   1 /*
   2  *  Copyright (C) 1995  Linus Torvalds
   3  *
   4  *  Pentium III FXSR, SSE support
   5  *      Gareth Hughes <gareth@valinux.com>, May 2000
   6  */
   7
   8 /*
   9  * This file handles the architecture-dependent parts of process handling..
  10  */
  11
  12 #include <linux/cpu.h>
  13 #include <linux/errno.h>
  14 #include <linux/sched.h>
  15 #include <linux/fs.h>
  16 #include <linux/kernel.h>
  17 #include <linux/mm.h>
  18 #include <linux/elfcore.h>
  19 #include <linux/smp.h>
  20 #include <linux/stddef.h>
  21 #include <linux/slab.h>
  22 #include <linux/vmalloc.h>
  23 #include <linux/user.h>
  24 #include <linux/interrupt.h>
  25 #include <linux/delay.h>
  26 #include <linux/reboot.h>
  27 #include <linux/mc146818rtc.h>
  28 #include <linux/module.h>
  29 #include <linux/kallsyms.h>
  30 #include <linux/ptrace.h>
  31 #include <linux/personality.h>
  32 #include <linux/percpu.h>
  33 #include <linux/prctl.h>
  34 #include <linux/ftrace.h>
  35 #include <linux/uaccess.h>
  36 #include <linux/io.h>
  37 #include <linux/kdebug.h>
  38
  39 #include <asm/pgtable.h>
  40 #include <asm/ldt.h>
  41 #include <asm/processor.h>
  42 #include <asm/fpu/internal.h>
  43 #include <asm/desc.h>
  44 #ifdef CONFIG_MATH_EMULATION
  45 #include <asm/math_emu.h>
  46 #endif
  47
  48 #include <linux/err.h>
  49
  50 #include <asm/tlbflush.h>
  51 #include <asm/cpu.h>
  52 #include <asm/idle.h>
  53 #include <asm/syscalls.h>
  54 #include <asm/debugreg.h>
  55 #include <asm/switch_to.h>
  56 #include <asm/vm86.h>
  57
  58 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
  59 asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");
  60
  61 /*
  62  * Return saved PC of a blocked thread.
  63  */
  64 unsigned long thread_saved_pc(struct task_struct *tsk)
  65 {
  66         return ((unsigned long *)tsk->thread.sp)[3];
  67 }
  68
  69 void __show_regs(struct pt_regs *regs, int all)
  70 {
  71         unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
  72         unsigned long d0, d1, d2, d3, d6, d7;
  73         unsigned long sp;
  74         unsigned short ss, gs;
  75
  76         if (user_mode(regs)) {
  77                 sp = regs->sp;
  78                 ss = regs->ss & 0xffff;
  79                 gs = get_user_gs(regs);
  80         } else {
  81                 sp = kernel_stack_pointer(regs);
  82                 savesegment(ss, ss);
  83                 savesegment(gs, gs);
  84         }
  85
  86         printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
  87                         (u16)regs->cs, regs->ip, regs->flags,
  88                         smp_processor_id());
  89         print_symbol("EIP is at %s\n", regs->ip);
  90
  91         printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
  92                 regs->ax, regs->bx, regs->cx, regs->dx);
  93         printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
  94                 regs->si, regs->di, regs->bp, sp);
  95         printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
  96                (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
  97
  98         if (!all)
  99                 return;
 100
 101         cr0 = read_cr0();
 102         cr2 = read_cr2();
 103         cr3 = read_cr3();
 104         cr4 = __read_cr4_safe();
 105         printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
 106                         cr0, cr2, cr3, cr4);
 107
 108         get_debugreg(d0, 0);
 109         get_debugreg(d1, 1);
 110         get_debugreg(d2, 2);
 111         get_debugreg(d3, 3);
 112         get_debugreg(d6, 6);
 113         get_debugreg(d7, 7);
 114
 115         /* Only print out debug registers if they are in their non-default state. */
 116         if ((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) &&
 117             (d6 == DR6_RESERVED) && (d7 == 0x400))
 118                 return;
 119
 120         printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
 121                         d0, d1, d2, d3);
 122         printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
 123                         d6, d7);
 124 }
 125
 126 void release_thread(struct task_struct *dead_task)
 127 {
 128         BUG_ON(dead_task->mm);
 129         release_vm86_irqs(dead_task);
 130 }
 131
 132 int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 133         unsigned long arg, struct task_struct *p, unsigned long tls)
 134 {
 135         struct pt_regs *childregs = task_pt_regs(p);
 136         struct task_struct *tsk;
 137         int err;
 138
 139         p->thread.sp = (unsigned long) childregs;
 140         p->thread.sp0 = (unsigned long) (childregs+1);
 141         memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 142
 143         if (unlikely(p->flags & PF_KTHREAD)) {
 144                 /* kernel thread */
 145                 memset(childregs, 0, sizeof(struct pt_regs));
 146                 p->thread.ip = (unsigned long) ret_from_kernel_thread;
 147                 task_user_gs(p) = __KERNEL_STACK_CANARY;
 148                 childregs->ds = __USER_DS;
 149                 childregs->es = __USER_DS;
 150                 childregs->fs = __KERNEL_PERCPU;
 151                 childregs->bx = sp;     /* function */
 152                 childregs->bp = arg;
 153                 childregs->orig_ax = -1;
 154                 childregs->cs = __KERNEL_CS | get_kernel_rpl();
 155                 childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
 156                 p->thread.io_bitmap_ptr = NULL;
 157                 return 0;
 158         }
 159         *childregs = *current_pt_regs();
 160         childregs->ax = 0;
 161         if (sp)
 162                 childregs->sp = sp;
 163
 164         p->thread.ip = (unsigned long) ret_from_fork;
 165         task_user_gs(p) = get_user_gs(current_pt_regs());
 166
 167         p->thread.io_bitmap_ptr = NULL;
 168         tsk = current;
 169         err = -ENOMEM;
 170
 171         if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
 172                 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
 173                                                 IO_BITMAP_BYTES, GFP_KERNEL);
 174                 if (!p->thread.io_bitmap_ptr) {
 175                         p->thread.io_bitmap_max = 0;
 176                         return -ENOMEM;
 177                 }
 178                 set_tsk_thread_flag(p, TIF_IO_BITMAP);
 179         }
 180
 181         err = 0;
 182
 183         /*
 184          * Set a new TLS for the child thread?
 185          */
 186         if (clone_flags & CLONE_SETTLS)
 187                 err = do_set_thread_area(p, -1,
 188                         (struct user_desc __user *)tls, 0);
 189
 190         if (err && p->thread.io_bitmap_ptr) {
 191                 kfree(p->thread.io_bitmap_ptr);
 192                 p->thread.io_bitmap_max = 0;
 193         }
 194         return err;
 195 }
 196
 197 void
 198 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 199 {
 200         set_user_gs(regs, 0);
 201         regs->fs                = 0;
 202         regs->ds                = __USER_DS;
 203         regs->es                = __USER_DS;
 204         regs->ss                = __USER_DS;
 205         regs->cs                = __USER_CS;
 206         regs->ip                = new_ip;
 207         regs->sp                = new_sp;
 208         regs->flags             = X86_EFLAGS_IF;
 209         force_iret();
 210 }
 211 EXPORT_SYMBOL_GPL(start_thread);
 212
 213
 214 /*
 215  *      switch_to(x,y) should switch tasks from x to y.
 216  *
 217  * We fsave/fwait so that an exception goes off at the right time
 218  * (as a call from the fsave or fwait in effect) rather than to
 219  * the wrong process. Lazy FP saving no longer makes any sense
 220  * with modern CPU's, and this simplifies a lot of things (SMP
 221  * and UP become the same).
 222  *
 223  * NOTE! We used to use the x86 hardware context switching. The
 224  * reason for not using it any more becomes apparent when you
 225  * try to recover gracefully from saved state that is no longer
 226  * valid (stale segment register values in particular). With the
 227  * hardware task-switch, there is no way to fix up bad state in
 228  * a reasonable manner.
 229  *
 230  * The fact that Intel documents the hardware task-switching to
 231  * be slow is a fairly red herring - this code is not noticeably
 232  * faster. However, there _is_ some room for improvement here,
 233  * so the performance issues may eventually be a valid point.
 234  * More important, however, is the fact that this allows us much
 235  * more flexibility.
 236  *
 237  * The return value (in %ax) will be the "prev" task after
 238  * the task-switch, and shows up in ret_from_fork in entry.S,
 239  * for example.
 240  */
 241 __visible __notrace_funcgraph struct task_struct *
 242 __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 243 {
 244         struct thread_struct *prev = &prev_p->thread,
 245                              *next = &next_p->thread;
 246         struct fpu *prev_fpu = &prev->fpu;
 247         struct fpu *next_fpu = &next->fpu;
 248         int cpu = smp_processor_id();
 249         struct tss_struct *tss = &per_cpu(cpu_tss, cpu);
 250         fpu_switch_t fpu_switch;
 251
 252         /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
 253
 254         fpu_switch = switch_fpu_prepare(prev_fpu, next_fpu, cpu);
 255
 256         /*
 257          * Save away %gs. No need to save %fs, as it was saved on the
 258          * stack on entry.  No need to save %es and %ds, as those are
 259          * always kernel segments while inside the kernel.  Doing this
 260          * before setting the new TLS descriptors avoids the situation
 261          * where we temporarily have non-reloadable segments in %fs
 262          * and %gs.  This could be an issue if the NMI handler ever
 263          * used %fs or %gs (it does not today), or if the kernel is
 264          * running inside of a hypervisor layer.
 265          */
 266         lazy_save_gs(prev->gs);
 267
 268         /*
 269          * Load the per-thread Thread-Local Storage descriptor.
 270          */
 271         load_TLS(next, cpu);
 272
 273         /*
 274          * Restore IOPL if needed.  In normal use, the flags restore
 275          * in the switch assembly will handle this.  But if the kernel
 276          * is running virtualized at a non-zero CPL, the popf will
 277          * not restore flags, so it must be done in a separate step.
 278          */
 279         if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
 280                 set_iopl_mask(next->iopl);
 281
 282         /*
 283          * Now maybe handle debug registers and/or IO bitmaps
 284          */
 285         if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
 286                      task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
 287                 __switch_to_xtra(prev_p, next_p, tss);
 288
 289         /*
 290          * Leave lazy mode, flushing any hypercalls made here.
 291          * This must be done before restoring TLS segments so
 292          * the GDT and LDT are properly updated, and must be
 293          * done before fpu__restore(), so the TS bit is up
 294          * to date.
 295          */
 296         arch_end_context_switch(next_p);
 297
 298         /*
 299          * Reload esp0 and cpu_current_top_of_stack.  This changes
 300          * current_thread_info().
 301          */
 302         load_sp0(tss, next);
 303         this_cpu_write(cpu_current_top_of_stack,
 304                        (unsigned long)task_stack_page(next_p) +
 305                        THREAD_SIZE);
 306
 307         /*
 308          * Restore %gs if needed (which is common)
 309          */
 310         if (prev->gs | next->gs)
 311                 lazy_load_gs(next->gs);
 312
 313         switch_fpu_finish(next_fpu, fpu_switch);
 314
 315         this_cpu_write(current_task, next_p);
 316
 317         return prev_p;
 318 }