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
58asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
59asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread");
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(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
126void release_thread(struct task_struct *dead_task)
127{
128	BUG_ON(dead_task->mm);
129	release_vm86_irqs(dead_task);
130}
131
132int 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
197void
198start_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}
211EXPORT_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}
319