LXR linux/arch/x86/kernel/process

   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/init.h>
  28#include <linux/mc146818rtc.h>
  29#include <linux/module.h>
  30#include <linux/kallsyms.h>
  31#include <linux/ptrace.h>
  32#include <linux/personality.h>
  33#include <linux/percpu.h>
  34#include <linux/prctl.h>
  35#include <linux/ftrace.h>
  36#include <linux/uaccess.h>
  37#include <linux/io.h>
  38#include <linux/kdebug.h>
  39
  40#include <asm/pgtable.h>
  41#include <asm/ldt.h>
  42#include <asm/processor.h>
  43#include <asm/i387.h>
  44#include <asm/fpu-internal.h>
  45#include <asm/desc.h>
  46#ifdef CONFIG_MATH_EMULATION
  47#include <asm/math_emu.h>
  48#endif
  49
  50#include <linux/err.h>
  51
  52#include <asm/tlbflush.h>
  53#include <asm/cpu.h>
  54#include <asm/idle.h>
  55#include <asm/syscalls.h>
  56#include <asm/debugreg.h>
  57#include <asm/switch_to.h>
  58
  59asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
  60
  61/*
  62 * Return saved PC of a blocked thread.
  63 */
  64unsigned long thread_saved_pc(struct task_struct *tsk)
  65{
  66        return ((unsigned long *)tsk->thread.sp)[3];
  67}
  68
  69void __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_vm(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        show_regs_common();
  87
  88        printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
  89                        (u16)regs->cs, regs->ip, regs->flags,
  90                        smp_processor_id());
  91        print_symbol("EIP is at %s\n", regs->ip);
  92
  93        printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
  94                regs->ax, regs->bx, regs->cx, regs->dx);
  95        printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
  96                regs->si, regs->di, regs->bp, sp);
  97        printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n",
  98               (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss);
  99
 100        if (!all)
 101                return;
 102
 103        cr0 = read_cr0();
 104        cr2 = read_cr2();
 105        cr3 = read_cr3();
 106        cr4 = read_cr4_safe();
 107        printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
 108                        cr0, cr2, cr3, cr4);
 109
 110        get_debugreg(d0, 0);
 111        get_debugreg(d1, 1);
 112        get_debugreg(d2, 2);
 113        get_debugreg(d3, 3);
 114        printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
 115                        d0, d1, d2, d3);
 116
 117        get_debugreg(d6, 6);
 118        get_debugreg(d7, 7);
 119        printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
 120                        d6, d7);
 121}
 122
 123void release_thread(struct task_struct *dead_task)
 124{
 125        BUG_ON(dead_task->mm);
 126        release_vm86_irqs(dead_task);
 127}
 128
 129int copy_thread(unsigned long clone_flags, unsigned long sp,
 130        unsigned long unused,
 131        struct task_struct *p, struct pt_regs *regs)
 132{
 133        struct pt_regs *childregs;
 134        struct task_struct *tsk;
 135        int err;
 136
 137        childregs = task_pt_regs(p);
 138        *childregs = *regs;
 139        childregs->ax = 0;
 140        childregs->sp = sp;
 141
 142        p->thread.sp = (unsigned long) childregs;
 143        p->thread.sp0 = (unsigned long) (childregs+1);
 144
 145        p->thread.ip = (unsigned long) ret_from_fork;
 146
 147        task_user_gs(p) = get_user_gs(regs);
 148
 149        p->fpu_counter = 0;
 150        p->thread.io_bitmap_ptr = NULL;
 151        tsk = current;
 152        err = -ENOMEM;
 153
 154        memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 155
 156        if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
 157                p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
 158                                                IO_BITMAP_BYTES, GFP_KERNEL);
 159                if (!p->thread.io_bitmap_ptr) {
 160                        p->thread.io_bitmap_max = 0;
 161                        return -ENOMEM;
 162                }
 163                set_tsk_thread_flag(p, TIF_IO_BITMAP);
 164        }
 165
 166        err = 0;
 167
 168        /*
 169         * Set a new TLS for the child thread?
 170         */
 171        if (clone_flags & CLONE_SETTLS)
 172                err = do_set_thread_area(p, -1,
 173                        (struct user_desc __user *)childregs->si, 0);
 174
 175        if (err && p->thread.io_bitmap_ptr) {
 176                kfree(p->thread.io_bitmap_ptr);
 177                p->thread.io_bitmap_max = 0;
 178        }
 179        return err;
 180}
 181
 182void
 183start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 184{
 185        set_user_gs(regs, 0);
 186        regs->fs                = 0;
 187        regs->ds                = __USER_DS;
 188        regs->es                = __USER_DS;
 189        regs->ss                = __USER_DS;
 190        regs->cs                = __USER_CS;
 191        regs->ip                = new_ip;
 192        regs->sp                = new_sp;
 193        /*
 194         * Free the old FP and other extended state
 195         */
 196        free_thread_xstate(current);
 197}
 198EXPORT_SYMBOL_GPL(start_thread);
 199
 200
 201/*
 202 *      switch_to(x,y) should switch tasks from x to y.
 203 *
 204 * We fsave/fwait so that an exception goes off at the right time
 205 * (as a call from the fsave or fwait in effect) rather than to
 206 * the wrong process. Lazy FP saving no longer makes any sense
 207 * with modern CPU's, and this simplifies a lot of things (SMP
 208 * and UP become the same).
 209 *
 210 * NOTE! We used to use the x86 hardware context switching. The
 211 * reason for not using it any more becomes apparent when you
 212 * try to recover gracefully from saved state that is no longer
 213 * valid (stale segment register values in particular). With the
 214 * hardware task-switch, there is no way to fix up bad state in
 215 * a reasonable manner.
 216 *
 217 * The fact that Intel documents the hardware task-switching to
 218 * be slow is a fairly red herring - this code is not noticeably
 219 * faster. However, there _is_ some room for improvement here,
 220 * so the performance issues may eventually be a valid point.
 221 * More important, however, is the fact that this allows us much
 222 * more flexibility.
 223 *
 224 * The return value (in %ax) will be the "prev" task after
 225 * the task-switch, and shows up in ret_from_fork in entry.S,
 226 * for example.
 227 */
 228__notrace_funcgraph struct task_struct *
 229__switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 230{
 231        struct thread_struct *prev = &prev_p->thread,
 232                                 *next = &next_p->thread;
 233        int cpu = smp_processor_id();
 234        struct tss_struct *tss = &per_cpu(init_tss, cpu);
 235        fpu_switch_t fpu;
 236
 237        /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
 238
 239        fpu = switch_fpu_prepare(prev_p, next_p, cpu);
 240
 241        /*
 242         * Reload esp0.
 243         */
 244        load_sp0(tss, next);
 245
 246        /*
 247         * Save away %gs. No need to save %fs, as it was saved on the
 248         * stack on entry.  No need to save %es and %ds, as those are
 249         * always kernel segments while inside the kernel.  Doing this
 250         * before setting the new TLS descriptors avoids the situation
 251         * where we temporarily have non-reloadable segments in %fs
 252         * and %gs.  This could be an issue if the NMI handler ever
 253         * used %fs or %gs (it does not today), or if the kernel is
 254         * running inside of a hypervisor layer.
 255         */
 256        lazy_save_gs(prev->gs);
 257
 258        /*
 259         * Load the per-thread Thread-Local Storage descriptor.
 260         */
 261        load_TLS(next, cpu);
 262
 263        /*
 264         * Restore IOPL if needed.  In normal use, the flags restore
 265         * in the switch assembly will handle this.  But if the kernel
 266         * is running virtualized at a non-zero CPL, the popf will
 267         * not restore flags, so it must be done in a separate step.
 268         */
 269        if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
 270                set_iopl_mask(next->iopl);
 271
 272        /*
 273         * Now maybe handle debug registers and/or IO bitmaps
 274         */
 275        if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
 276                     task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
 277                __switch_to_xtra(prev_p, next_p, tss);
 278
 279        /*
 280         * Leave lazy mode, flushing any hypercalls made here.
 281         * This must be done before restoring TLS segments so
 282         * the GDT and LDT are properly updated, and must be
 283         * done before math_state_restore, so the TS bit is up
 284         * to date.
 285         */
 286        arch_end_context_switch(next_p);
 287
 288        /*
 289         * Restore %gs if needed (which is common)
 290         */
 291        if (prev->gs | next->gs)
 292                lazy_load_gs(next->gs);
 293
 294        switch_fpu_finish(next_p, fpu);
 295
 296        this_cpu_write(current_task, next_p);
 297
 298        return prev_p;
 299}
 300
 301#define top_esp                (THREAD_SIZE - sizeof(unsigned long))
 302#define top_ebp                (THREAD_SIZE - 2*sizeof(unsigned long))
 303
 304unsigned long get_wchan(struct task_struct *p)
 305{
 306        unsigned long bp, sp, ip;
 307        unsigned long stack_page;
 308        int count = 0;
 309        if (!p || p == current || p->state == TASK_RUNNING)
 310                return 0;
 311        stack_page = (unsigned long)task_stack_page(p);
 312        sp = p->thread.sp;
 313        if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
 314                return 0;
 315        /* include/asm-i386/system.h:switch_to() pushes bp last. */
 316        bp = *(unsigned long *) sp;
 317        do {
 318                if (bp < stack_page || bp > top_ebp+stack_page)
 319                        return 0;
 320                ip = *(unsigned long *) (bp+4);
 321                if (!in_sched_functions(ip))
 322                        return ip;
 323                bp = *(unsigned long *) bp;
 324        } while (count++ < 16);
 325        return 0;
 326}
 327
 328