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 57 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); 58 asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread"); 59 60 /* 61 * Return saved PC of a blocked thread. 62 */ 63 unsigned long thread_saved_pc(struct task_struct *tsk) 64 { 65 return ((unsigned long *)tsk->thread.sp)[3]; 66 } 67 68 void __show_regs(struct pt_regs *regs, int all) 69 { 70 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L; 71 unsigned long d0, d1, d2, d3, d6, d7; 72 unsigned long sp; 73 unsigned short ss, gs; 74 75 if (user_mode(regs)) { 76 sp = regs->sp; 77 ss = regs->ss & 0xffff; 78 gs = get_user_gs(regs); 79 } else { 80 sp = kernel_stack_pointer(regs); 81 savesegment(ss, ss); 82 savesegment(gs, gs); 83 } 84 85 printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n", 86 (u16)regs->cs, regs->ip, regs->flags, 87 smp_processor_id()); 88 print_symbol("EIP is at %s\n", regs->ip); 89 90 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n", 91 regs->ax, regs->bx, regs->cx, regs->dx); 92 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n", 93 regs->si, regs->di, regs->bp, sp); 94 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n", 95 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss); 96 97 if (!all) 98 return; 99 100 cr0 = read_cr0(); 101 cr2 = read_cr2(); 102 cr3 = read_cr3(); 103 cr4 = __read_cr4_safe(); 104 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", 105 cr0, cr2, cr3, cr4); 106 107 get_debugreg(d0, 0); 108 get_debugreg(d1, 1); 109 get_debugreg(d2, 2); 110 get_debugreg(d3, 3); 111 get_debugreg(d6, 6); 112 get_debugreg(d7, 7); 113 114 /* Only print out debug registers if they are in their non-default state. */ 115 if ((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) && 116 (d6 == DR6_RESERVED) && (d7 == 0x400)) 117 return; 118 119 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n", 120 d0, d1, d2, d3); 121 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n", 122 d6, d7); 123 } 124 125 void release_thread(struct task_struct *dead_task) 126 { 127 BUG_ON(dead_task->mm); 128 release_vm86_irqs(dead_task); 129 } 130 131 int copy_thread_tls(unsigned long clone_flags, unsigned long sp, 132 unsigned long arg, struct task_struct *p, unsigned long tls) 133 { 134 struct pt_regs *childregs = task_pt_regs(p); 135 struct task_struct *tsk; 136 int err; 137 138 p->thread.sp = (unsigned long) childregs; 139 p->thread.sp0 = (unsigned long) (childregs+1); 140 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); 141 142 if (unlikely(p->flags & PF_KTHREAD)) { 143 /* kernel thread */ 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 */ 151 childregs->bp = arg; 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.io_bitmap_ptr = NULL; 156 return 0; 157 } 158 *childregs = *current_pt_regs(); 159 childregs->ax = 0; 160 if (sp) 161 childregs->sp = sp; 162 163 p->thread.ip = (unsigned long) ret_from_fork; 164 task_user_gs(p) = get_user_gs(current_pt_regs()); 165 166 p->thread.io_bitmap_ptr = NULL; 167 tsk = current; 168 err = -ENOMEM; 169 170 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { 171 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, 172 IO_BITMAP_BYTES, GFP_KERNEL); 173 if (!p->thread.io_bitmap_ptr) { 174 p->thread.io_bitmap_max = 0; 175 return -ENOMEM; 176 } 177 set_tsk_thread_flag(p, TIF_IO_BITMAP); 178 } 179 180 err = 0; 181 182 /* 183 * Set a new TLS for the child thread? 184 */ 185 if (clone_flags & CLONE_SETTLS) 186 err = do_set_thread_area(p, -1, 187 (struct user_desc __user *)tls, 0); 188 189 if (err && p->thread.io_bitmap_ptr) { 190 kfree(p->thread.io_bitmap_ptr); 191 p->thread.io_bitmap_max = 0; 192 } 193 return err; 194 } 195 196 void 197 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) 198 { 199 set_user_gs(regs, 0); 200 regs->fs = 0; 201 regs->ds = __USER_DS; 202 regs->es = __USER_DS; 203 regs->ss = __USER_DS; 204 regs->cs = __USER_CS; 205 regs->ip = new_ip; 206 regs->sp = new_sp; 207 regs->flags = X86_EFLAGS_IF; 208 force_iret(); 209 } 210 EXPORT_SYMBOL_GPL(start_thread); 211 212 213 /* 214 * switch_to(x,y) should switch tasks from x to y. 215 * 216 * We fsave/fwait so that an exception goes off at the right time 217 * (as a call from the fsave or fwait in effect) rather than to 218 * the wrong process. Lazy FP saving no longer makes any sense 219 * with modern CPU's, and this simplifies a lot of things (SMP 220 * and UP become the same). 221 * 222 * NOTE! We used to use the x86 hardware context switching. The 223 * reason for not using it any more becomes apparent when you 224 * try to recover gracefully from saved state that is no longer 225 * valid (stale segment register values in particular). With the 226 * hardware task-switch, there is no way to fix up bad state in 227 * a reasonable manner. 228 * 229 * The fact that Intel documents the hardware task-switching to 230 * be slow is a fairly red herring - this code is not noticeably 231 * faster. However, there _is_ some room for improvement here, 232 * so the performance issues may eventually be a valid point. 233 * More important, however, is the fact that this allows us much 234 * more flexibility. 235 * 236 * The return value (in %ax) will be the "prev" task after 237 * the task-switch, and shows up in ret_from_fork in entry.S, 238 * for example. 239 */ 240 __visible __notrace_funcgraph struct task_struct * 241 __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 242 { 243 struct thread_struct *prev = &prev_p->thread, 244 *next = &next_p->thread; 245 struct fpu *prev_fpu = &prev->fpu; 246 struct fpu *next_fpu = &next->fpu; 247 int cpu = smp_processor_id(); 248 struct tss_struct *tss = &per_cpu(cpu_tss, cpu); 249 fpu_switch_t fpu_switch; 250 251 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ 252 253 fpu_switch = switch_fpu_prepare(prev_fpu, next_fpu, cpu); 254 255 /* 256 * Save away %gs. No need to save %fs, as it was saved on the 257 * stack on entry. No need to save %es and %ds, as those are 258 * always kernel segments while inside the kernel. Doing this 259 * before setting the new TLS descriptors avoids the situation 260 * where we temporarily have non-reloadable segments in %fs 261 * and %gs. This could be an issue if the NMI handler ever 262 * used %fs or %gs (it does not today), or if the kernel is 263 * running inside of a hypervisor layer. 264 */ 265 lazy_save_gs(prev->gs); 266 267 /* 268 * Load the per-thread Thread-Local Storage descriptor. 269 */ 270 load_TLS(next, cpu); 271 272 /* 273 * Restore IOPL if needed. In normal use, the flags restore 274 * in the switch assembly will handle this. But if the kernel 275 * is running virtualized at a non-zero CPL, the popf will 276 * not restore flags, so it must be done in a separate step. 277 */ 278 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) 279 set_iopl_mask(next->iopl); 280 281 /* 282 * If it were not for PREEMPT_ACTIVE we could guarantee that the 283 * preempt_count of all tasks was equal here and this would not be 284 * needed. 285 */ 286 task_thread_info(prev_p)->saved_preempt_count = this_cpu_read(__preempt_count); 287 this_cpu_write(__preempt_count, task_thread_info(next_p)->saved_preempt_count); 288 289 /* 290 * Now maybe handle debug registers and/or IO bitmaps 291 */ 292 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV || 293 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT)) 294 __switch_to_xtra(prev_p, next_p, tss); 295 296 /* 297 * Leave lazy mode, flushing any hypercalls made here. 298 * This must be done before restoring TLS segments so 299 * the GDT and LDT are properly updated, and must be 300 * done before fpu__restore(), so the TS bit is up 301 * to date. 302 */ 303 arch_end_context_switch(next_p); 304 305 /* 306 * Reload esp0 and cpu_current_top_of_stack. This changes 307 * current_thread_info(). 308 */ 309 load_sp0(tss, next); 310 this_cpu_write(cpu_current_top_of_stack, 311 (unsigned long)task_stack_page(next_p) + 312 THREAD_SIZE); 313 314 /* 315 * Restore %gs if needed (which is common) 316 */ 317 if (prev->gs | next->gs) 318 lazy_load_gs(next->gs); 319 320 switch_fpu_finish(next_fpu, fpu_switch); 321 322 this_cpu_write(current_task, next_p); 323 324 return prev_p; 325 } 326 327 #define top_esp (THREAD_SIZE - sizeof(unsigned long)) 328 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long)) 329 330 unsigned long get_wchan(struct task_struct *p) 331 { 332 unsigned long bp, sp, ip; 333 unsigned long stack_page; 334 int count = 0; 335 if (!p || p == current || p->state == TASK_RUNNING) 336 return 0; 337 stack_page = (unsigned long)task_stack_page(p); 338 sp = p->thread.sp; 339 if (!stack_page || sp < stack_page || sp > top_esp+stack_page) 340 return 0; 341 /* include/asm-i386/system.h:switch_to() pushes bp last. */ 342 bp = *(unsigned long *) sp; 343 do { 344 if (bp < stack_page || bp > top_ebp+stack_page) 345 return 0; 346 ip = *(unsigned long *) (bp+4); 347 if (!in_sched_functions(ip)) 348 return ip; 349 bp = *(unsigned long *) bp; 350 } while (count++ < 16); 351 return 0; 352 } 353 354