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