2 * Copyright (C) 1995 Linus Torvalds
4 * Pentium III FXSR, SSE support
5 * Gareth Hughes <gareth@valinux.com>, May 2000
9 * This file handles the architecture-dependent parts of process handling..
12 #include <linux/cpu.h>
13 #include <linux/errno.h>
14 #include <linux/sched.h>
16 #include <linux/kernel.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>
37 #include <linux/kdebug.h>
39 #include <asm/pgtable.h>
41 #include <asm/processor.h>
43 #include <asm/fpu-internal.h>
45 #ifdef CONFIG_MATH_EMULATION
46 #include <asm/math_emu.h>
49 #include <linux/err.h>
51 #include <asm/tlbflush.h>
54 #include <asm/syscalls.h>
55 #include <asm/debugreg.h>
56 #include <asm/switch_to.h>
58 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
59 asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");
62 * Return saved PC of a blocked thread.
64 unsigned long thread_saved_pc(struct task_struct *tsk)
66 return ((unsigned long *)tsk->thread.sp)[3];
69 void __show_regs(struct pt_regs *regs, int all)
71 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
72 unsigned long d0, d1, d2, d3, d6, d7;
74 unsigned short ss, gs;
76 if (user_mode_vm(regs)) {
78 ss = regs->ss & 0xffff;
79 gs = get_user_gs(regs);
81 sp = kernel_stack_pointer(regs);
86 printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n",
87 (u16)regs->cs, regs->ip, regs->flags,
89 print_symbol("EIP is at %s\n", regs->ip);
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);
104 cr4 = read_cr4_safe();
105 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
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))
120 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
122 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
126 void release_thread(struct task_struct *dead_task)
128 BUG_ON(dead_task->mm);
129 release_vm86_irqs(dead_task);
132 int copy_thread(unsigned long clone_flags, unsigned long sp,
133 unsigned long arg, struct task_struct *p)
135 struct pt_regs *childregs = task_pt_regs(p);
136 struct task_struct *tsk;
139 p->thread.sp = (unsigned long) childregs;
140 p->thread.sp0 = (unsigned long) (childregs+1);
142 if (unlikely(p->flags & PF_KTHREAD)) {
144 memset(childregs, 0, sizeof(struct pt_regs));
145 p->thread.ip = (unsigned long) ret_from_kernel_thread;
146 task_user_gs(p) = __KERNEL_STACK_CANARY;
147 childregs->ds = __USER_DS;
148 childregs->es = __USER_DS;
149 childregs->fs = __KERNEL_PERCPU;
150 childregs->bx = sp; /* function */
152 childregs->orig_ax = -1;
153 childregs->cs = __KERNEL_CS | get_kernel_rpl();
154 childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
155 p->thread.fpu_counter = 0;
156 p->thread.io_bitmap_ptr = NULL;
157 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
160 *childregs = *current_pt_regs();
165 p->thread.ip = (unsigned long) ret_from_fork;
166 task_user_gs(p) = get_user_gs(current_pt_regs());
168 p->thread.fpu_counter = 0;
169 p->thread.io_bitmap_ptr = NULL;
173 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
175 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
176 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
177 IO_BITMAP_BYTES, GFP_KERNEL);
178 if (!p->thread.io_bitmap_ptr) {
179 p->thread.io_bitmap_max = 0;
182 set_tsk_thread_flag(p, TIF_IO_BITMAP);
188 * Set a new TLS for the child thread?
190 if (clone_flags & CLONE_SETTLS)
191 err = do_set_thread_area(p, -1,
192 (struct user_desc __user *)childregs->si, 0);
194 if (err && p->thread.io_bitmap_ptr) {
195 kfree(p->thread.io_bitmap_ptr);
196 p->thread.io_bitmap_max = 0;
202 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
204 set_user_gs(regs, 0);
206 regs->ds = __USER_DS;
207 regs->es = __USER_DS;
208 regs->ss = __USER_DS;
209 regs->cs = __USER_CS;
212 regs->flags = X86_EFLAGS_IF;
214 * force it to the iret return path by making it look as if there was
217 set_thread_flag(TIF_NOTIFY_RESUME);
219 EXPORT_SYMBOL_GPL(start_thread);
223 * switch_to(x,y) should switch tasks from x to y.
225 * We fsave/fwait so that an exception goes off at the right time
226 * (as a call from the fsave or fwait in effect) rather than to
227 * the wrong process. Lazy FP saving no longer makes any sense
228 * with modern CPU's, and this simplifies a lot of things (SMP
229 * and UP become the same).
231 * NOTE! We used to use the x86 hardware context switching. The
232 * reason for not using it any more becomes apparent when you
233 * try to recover gracefully from saved state that is no longer
234 * valid (stale segment register values in particular). With the
235 * hardware task-switch, there is no way to fix up bad state in
236 * a reasonable manner.
238 * The fact that Intel documents the hardware task-switching to
239 * be slow is a fairly red herring - this code is not noticeably
240 * faster. However, there _is_ some room for improvement here,
241 * so the performance issues may eventually be a valid point.
242 * More important, however, is the fact that this allows us much
245 * The return value (in %ax) will be the "prev" task after
246 * the task-switch, and shows up in ret_from_fork in entry.S,
249 __visible __notrace_funcgraph struct task_struct *
250 __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
252 struct thread_struct *prev = &prev_p->thread,
253 *next = &next_p->thread;
254 int cpu = smp_processor_id();
255 struct tss_struct *tss = &per_cpu(init_tss, cpu);
258 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
260 fpu = switch_fpu_prepare(prev_p, next_p, cpu);
268 * Save away %gs. No need to save %fs, as it was saved on the
269 * stack on entry. No need to save %es and %ds, as those are
270 * always kernel segments while inside the kernel. Doing this
271 * before setting the new TLS descriptors avoids the situation
272 * where we temporarily have non-reloadable segments in %fs
273 * and %gs. This could be an issue if the NMI handler ever
274 * used %fs or %gs (it does not today), or if the kernel is
275 * running inside of a hypervisor layer.
277 lazy_save_gs(prev->gs);
280 * Load the per-thread Thread-Local Storage descriptor.
285 * Restore IOPL if needed. In normal use, the flags restore
286 * in the switch assembly will handle this. But if the kernel
287 * is running virtualized at a non-zero CPL, the popf will
288 * not restore flags, so it must be done in a separate step.
290 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl))
291 set_iopl_mask(next->iopl);
294 * If it were not for PREEMPT_ACTIVE we could guarantee that the
295 * preempt_count of all tasks was equal here and this would not be
298 task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count);
299 this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count);
302 * Now maybe handle debug registers and/or IO bitmaps
304 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV ||
305 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
306 __switch_to_xtra(prev_p, next_p, tss);
309 * Leave lazy mode, flushing any hypercalls made here.
310 * This must be done before restoring TLS segments so
311 * the GDT and LDT are properly updated, and must be
312 * done before math_state_restore, so the TS bit is up
315 arch_end_context_switch(next_p);
317 this_cpu_write(kernel_stack,
318 (unsigned long)task_stack_page(next_p) +
319 THREAD_SIZE - KERNEL_STACK_OFFSET);
322 * Restore %gs if needed (which is common)
324 if (prev->gs | next->gs)
325 lazy_load_gs(next->gs);
327 switch_fpu_finish(next_p, fpu);
329 this_cpu_write(current_task, next_p);
334 #define top_esp (THREAD_SIZE - sizeof(unsigned long))
335 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long))
337 unsigned long get_wchan(struct task_struct *p)
339 unsigned long bp, sp, ip;
340 unsigned long stack_page;
342 if (!p || p == current || p->state == TASK_RUNNING)
344 stack_page = (unsigned long)task_stack_page(p);
346 if (!stack_page || sp < stack_page || sp > top_esp+stack_page)
348 /* include/asm-i386/system.h:switch_to() pushes bp last. */
349 bp = *(unsigned long *) sp;
351 if (bp < stack_page || bp > top_ebp+stack_page)
353 ip = *(unsigned long *) (bp+4);
354 if (!in_sched_functions(ip))
356 bp = *(unsigned long *) bp;
357 } while (count++ < 16);