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Linux/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/i387.h>
 43 #include <asm/fpu-internal.h>
 44 #include <asm/desc.h>
 45 #ifdef CONFIG_MATH_EMULATION
 46 #include <asm/math_emu.h>
 47 #endif
 48 
 49 #include <linux/err.h>
 50 
 51 #include <asm/tlbflush.h>
 52 #include <asm/cpu.h>
 53 #include <asm/idle.h>
 54 #include <asm/syscalls.h>
 55 #include <asm/debugreg.h>
 56 #include <asm/switch_to.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(unsigned long clone_flags, unsigned long sp,
133         unsigned long arg, struct task_struct *p)
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 *)childregs->si, 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         int cpu = smp_processor_id();
247         struct tss_struct *tss = &per_cpu(cpu_tss, cpu);
248         fpu_switch_t fpu;
249 
250         /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
251 
252         fpu = switch_fpu_prepare(prev_p, next_p, cpu);
253 
254         /*
255          * Save away %gs. No need to save %fs, as it was saved on the
256          * stack on entry.  No need to save %es and %ds, as those are
257          * always kernel segments while inside the kernel.  Doing this
258          * before setting the new TLS descriptors avoids the situation
259          * where we temporarily have non-reloadable segments in %fs
260          * and %gs.  This could be an issue if the NMI handler ever
261          * used %fs or %gs (it does not today), or if the kernel is
262          * running inside of a hypervisor layer.
263          */
264         lazy_save_gs(prev->gs);
265 
266         /*
267          * Load the per-thread Thread-Local Storage descriptor.
268          */
269         load_TLS(next, cpu);
270 
271         /*
272          * Restore IOPL if needed.  In normal use, the flags restore
273          * in the switch assembly will handle this.  But if the kernel
274          * is running virtualized at a non-zero CPL, the popf will
275          * not restore flags, so it must be done in a separate step.
276          */
277         if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
278                 set_iopl_mask(next->iopl);
279 
280         /*
281          * If it were not for PREEMPT_ACTIVE we could guarantee that the
282          * preempt_count of all tasks was equal here and this would not be
283          * needed.
284          */
285         task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count);
286         this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);
287 
288         /*
289          * Now maybe handle debug registers and/or IO bitmaps
290          */
291         if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
292                      task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
293                 __switch_to_xtra(prev_p, next_p, tss);
294 
295         /*
296          * Leave lazy mode, flushing any hypercalls made here.
297          * This must be done before restoring TLS segments so
298          * the GDT and LDT are properly updated, and must be
299          * done before math_state_restore, so the TS bit is up
300          * to date.
301          */
302         arch_end_context_switch(next_p);
303 
304         /*
305          * Reload esp0, kernel_stack, and current_top_of_stack.  This changes
306          * current_thread_info().
307          */
308         load_sp0(tss, next);
309         this_cpu_write(kernel_stack,
310                        (unsigned long)task_stack_page(next_p) +
311                        THREAD_SIZE);
312         this_cpu_write(cpu_current_top_of_stack,
313                        (unsigned long)task_stack_page(next_p) +
314                        THREAD_SIZE);
315 
316         /*
317          * Restore %gs if needed (which is common)
318          */
319         if (prev->gs | next->gs)
320                 lazy_load_gs(next->gs);
321 
322         switch_fpu_finish(next_p, fpu);
323 
324         this_cpu_write(current_task, next_p);
325 
326         return prev_p;
327 }
328 
329 #define top_esp                (THREAD_SIZE - sizeof(unsigned long))
330 #define top_ebp                (THREAD_SIZE - 2*sizeof(unsigned long))
331 
332 unsigned long get_wchan(struct task_struct *p)
333 {
334         unsigned long bp, sp, ip;
335         unsigned long stack_page;
336         int count = 0;
337         if (!p || p == current || p->state == TASK_RUNNING)
338                 return 0;
339         stack_page = (unsigned long)task_stack_page(p);
340         sp = p->thread.sp;
341         if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
342                 return 0;
343         /* include/asm-i386/system.h:switch_to() pushes bp last. */
344         bp = *(unsigned long *) sp;
345         do {
346                 if (bp < stack_page || bp > top_ebp+stack_page)
347                         return 0;
348                 ip = *(unsigned long *) (bp+4);
349                 if (!in_sched_functions(ip))
350                         return ip;
351                 bp = *(unsigned long *) bp;
352         } while (count++ < 16);
353         return 0;
354 }
355 
356 

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