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/init.h> 28 #include <linux/mc146818rtc.h> 29 #include <linux/module.h> 30 #include <linux/kallsyms.h> 31 #include <linux/ptrace.h> 32 #include <linux/personality.h> 33 #include <linux/percpu.h> 34 #include <linux/prctl.h> 35 #include <linux/ftrace.h> 36 #include <linux/uaccess.h> 37 #include <linux/io.h> 38 #include <linux/kdebug.h> 39 40 #include <asm/pgtable.h> 41 #include <asm/ldt.h> 42 #include <asm/processor.h> 43 #include <asm/i387.h> 44 #include <asm/fpu-internal.h> 45 #include <asm/desc.h> 46 #ifdef CONFIG_MATH_EMULATION 47 #include <asm/math_emu.h> 48 #endif 49 50 #include <linux/err.h> 51 52 #include <asm/tlbflush.h> 53 #include <asm/cpu.h> 54 #include <asm/idle.h> 55 #include <asm/syscalls.h> 56 #include <asm/debugreg.h> 57 #include <asm/switch_to.h> 58 59 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); 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_vm(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 show_regs_common(); 87 88 printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n", 89 (u16)regs->cs, regs->ip, regs->flags, 90 smp_processor_id()); 91 print_symbol("EIP is at %s\n", regs->ip); 92 93 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n", 94 regs->ax, regs->bx, regs->cx, regs->dx); 95 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n", 96 regs->si, regs->di, regs->bp, sp); 97 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n", 98 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss); 99 100 if (!all) 101 return; 102 103 cr0 = read_cr0(); 104 cr2 = read_cr2(); 105 cr3 = read_cr3(); 106 cr4 = read_cr4_safe(); 107 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", 108 cr0, cr2, cr3, cr4); 109 110 get_debugreg(d0, 0); 111 get_debugreg(d1, 1); 112 get_debugreg(d2, 2); 113 get_debugreg(d3, 3); 114 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n", 115 d0, d1, d2, d3); 116 117 get_debugreg(d6, 6); 118 get_debugreg(d7, 7); 119 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n", 120 d6, d7); 121 } 122 123 void release_thread(struct task_struct *dead_task) 124 { 125 BUG_ON(dead_task->mm); 126 release_vm86_irqs(dead_task); 127 } 128 129 /* 130 * This gets called before we allocate a new thread and copy 131 * the current task into it. 132 */ 133 void prepare_to_copy(struct task_struct *tsk) 134 { 135 unlazy_fpu(tsk); 136 } 137 138 int copy_thread(unsigned long clone_flags, unsigned long sp, 139 unsigned long unused, 140 struct task_struct *p, struct pt_regs *regs) 141 { 142 struct pt_regs *childregs; 143 struct task_struct *tsk; 144 int err; 145 146 childregs = task_pt_regs(p); 147 *childregs = *regs; 148 childregs->ax = 0; 149 childregs->sp = sp; 150 151 p->thread.sp = (unsigned long) childregs; 152 p->thread.sp0 = (unsigned long) (childregs+1); 153 154 p->thread.ip = (unsigned long) ret_from_fork; 155 156 task_user_gs(p) = get_user_gs(regs); 157 158 p->fpu_counter = 0; 159 p->thread.io_bitmap_ptr = NULL; 160 tsk = current; 161 err = -ENOMEM; 162 163 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); 164 165 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { 166 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, 167 IO_BITMAP_BYTES, GFP_KERNEL); 168 if (!p->thread.io_bitmap_ptr) { 169 p->thread.io_bitmap_max = 0; 170 return -ENOMEM; 171 } 172 set_tsk_thread_flag(p, TIF_IO_BITMAP); 173 } 174 175 err = 0; 176 177 /* 178 * Set a new TLS for the child thread? 179 */ 180 if (clone_flags & CLONE_SETTLS) 181 err = do_set_thread_area(p, -1, 182 (struct user_desc __user *)childregs->si, 0); 183 184 if (err && p->thread.io_bitmap_ptr) { 185 kfree(p->thread.io_bitmap_ptr); 186 p->thread.io_bitmap_max = 0; 187 } 188 return err; 189 } 190 191 void 192 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) 193 { 194 set_user_gs(regs, 0); 195 regs->fs = 0; 196 regs->ds = __USER_DS; 197 regs->es = __USER_DS; 198 regs->ss = __USER_DS; 199 regs->cs = __USER_CS; 200 regs->ip = new_ip; 201 regs->sp = new_sp; 202 /* 203 * Free the old FP and other extended state 204 */ 205 free_thread_xstate(current); 206 } 207 EXPORT_SYMBOL_GPL(start_thread); 208 209 210 /* 211 * switch_to(x,y) should switch tasks from x to y. 212 * 213 * We fsave/fwait so that an exception goes off at the right time 214 * (as a call from the fsave or fwait in effect) rather than to 215 * the wrong process. Lazy FP saving no longer makes any sense 216 * with modern CPU's, and this simplifies a lot of things (SMP 217 * and UP become the same). 218 * 219 * NOTE! We used to use the x86 hardware context switching. The 220 * reason for not using it any more becomes apparent when you 221 * try to recover gracefully from saved state that is no longer 222 * valid (stale segment register values in particular). With the 223 * hardware task-switch, there is no way to fix up bad state in 224 * a reasonable manner. 225 * 226 * The fact that Intel documents the hardware task-switching to 227 * be slow is a fairly red herring - this code is not noticeably 228 * faster. However, there _is_ some room for improvement here, 229 * so the performance issues may eventually be a valid point. 230 * More important, however, is the fact that this allows us much 231 * more flexibility. 232 * 233 * The return value (in %ax) will be the "prev" task after 234 * the task-switch, and shows up in ret_from_fork in entry.S, 235 * for example. 236 */ 237 __notrace_funcgraph struct task_struct * 238 __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 239 { 240 struct thread_struct *prev = &prev_p->thread, 241 *next = &next_p->thread; 242 int cpu = smp_processor_id(); 243 struct tss_struct *tss = &per_cpu(init_tss, cpu); 244 fpu_switch_t fpu; 245 246 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ 247 248 fpu = switch_fpu_prepare(prev_p, next_p, cpu); 249 250 /* 251 * Reload esp0. 252 */ 253 load_sp0(tss, next); 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 * Now maybe handle debug registers and/or IO bitmaps 283 */ 284 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV || 285 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT)) 286 __switch_to_xtra(prev_p, next_p, tss); 287 288 /* 289 * Leave lazy mode, flushing any hypercalls made here. 290 * This must be done before restoring TLS segments so 291 * the GDT and LDT are properly updated, and must be 292 * done before math_state_restore, so the TS bit is up 293 * to date. 294 */ 295 arch_end_context_switch(next_p); 296 297 /* 298 * Restore %gs if needed (which is common) 299 */ 300 if (prev->gs | next->gs) 301 lazy_load_gs(next->gs); 302 303 switch_fpu_finish(next_p, fpu); 304 305 percpu_write(current_task, next_p); 306 307 return prev_p; 308 } 309 310 #define top_esp (THREAD_SIZE - sizeof(unsigned long)) 311 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long)) 312 313 unsigned long get_wchan(struct task_struct *p) 314 { 315 unsigned long bp, sp, ip; 316 unsigned long stack_page; 317 int count = 0; 318 if (!p || p == current || p->state == TASK_RUNNING) 319 return 0; 320 stack_page = (unsigned long)task_stack_page(p); 321 sp = p->thread.sp; 322 if (!stack_page || sp < stack_page || sp > top_esp+stack_page) 323 return 0; 324 /* include/asm-i386/system.h:switch_to() pushes bp last. */ 325 bp = *(unsigned long *) sp; 326 do { 327 if (bp < stack_page || bp > top_ebp+stack_page) 328 return 0; 329 ip = *(unsigned long *) (bp+4); 330 if (!in_sched_functions(ip)) 331 return ip; 332 bp = *(unsigned long *) bp; 333 } while (count++ < 16); 334 return 0; 335 } 336 337