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 asmlinkage void ret_from_kernel_thread(void) __asm__("ret_from_kernel_thread"); 61 62 /* 63 * Return saved PC of a blocked thread. 64 */ 65 unsigned long thread_saved_pc(struct task_struct *tsk) 66 { 67 return ((unsigned long *)tsk->thread.sp)[3]; 68 } 69 70 void __show_regs(struct pt_regs *regs, int all) 71 { 72 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L; 73 unsigned long d0, d1, d2, d3, d6, d7; 74 unsigned long sp; 75 unsigned short ss, gs; 76 77 if (user_mode_vm(regs)) { 78 sp = regs->sp; 79 ss = regs->ss & 0xffff; 80 gs = get_user_gs(regs); 81 } else { 82 sp = kernel_stack_pointer(regs); 83 savesegment(ss, ss); 84 savesegment(gs, gs); 85 } 86 87 printk(KERN_DEFAULT "EIP: %04x:[<%08lx>] EFLAGS: %08lx CPU: %d\n", 88 (u16)regs->cs, regs->ip, regs->flags, 89 smp_processor_id()); 90 print_symbol("EIP is at %s\n", regs->ip); 91 92 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n", 93 regs->ax, regs->bx, regs->cx, regs->dx); 94 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n", 95 regs->si, regs->di, regs->bp, sp); 96 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n", 97 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss); 98 99 if (!all) 100 return; 101 102 cr0 = read_cr0(); 103 cr2 = read_cr2(); 104 cr3 = read_cr3(); 105 cr4 = read_cr4_safe(); 106 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", 107 cr0, cr2, cr3, cr4); 108 109 get_debugreg(d0, 0); 110 get_debugreg(d1, 1); 111 get_debugreg(d2, 2); 112 get_debugreg(d3, 3); 113 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n", 114 d0, d1, d2, d3); 115 116 get_debugreg(d6, 6); 117 get_debugreg(d7, 7); 118 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n", 119 d6, d7); 120 } 121 122 void release_thread(struct task_struct *dead_task) 123 { 124 BUG_ON(dead_task->mm); 125 release_vm86_irqs(dead_task); 126 } 127 128 int copy_thread(unsigned long clone_flags, unsigned long sp, 129 unsigned long arg, struct task_struct *p) 130 { 131 struct pt_regs *childregs = task_pt_regs(p); 132 struct task_struct *tsk; 133 int err; 134 135 p->thread.sp = (unsigned long) childregs; 136 p->thread.sp0 = (unsigned long) (childregs+1); 137 138 if (unlikely(p->flags & PF_KTHREAD)) { 139 /* kernel thread */ 140 memset(childregs, 0, sizeof(struct pt_regs)); 141 p->thread.ip = (unsigned long) ret_from_kernel_thread; 142 task_user_gs(p) = __KERNEL_STACK_CANARY; 143 childregs->ds = __USER_DS; 144 childregs->es = __USER_DS; 145 childregs->fs = __KERNEL_PERCPU; 146 childregs->bx = sp; /* function */ 147 childregs->bp = arg; 148 childregs->orig_ax = -1; 149 childregs->cs = __KERNEL_CS | get_kernel_rpl(); 150 childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_BIT1; 151 p->fpu_counter = 0; 152 p->thread.io_bitmap_ptr = NULL; 153 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); 154 return 0; 155 } 156 *childregs = *current_pt_regs(); 157 childregs->ax = 0; 158 if (sp) 159 childregs->sp = sp; 160 161 p->thread.ip = (unsigned long) ret_from_fork; 162 task_user_gs(p) = get_user_gs(current_pt_regs()); 163 164 p->fpu_counter = 0; 165 p->thread.io_bitmap_ptr = NULL; 166 tsk = current; 167 err = -ENOMEM; 168 169 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); 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 /* 210 * force it to the iret return path by making it look as if there was 211 * some work pending. 212 */ 213 set_thread_flag(TIF_NOTIFY_RESUME); 214 } 215 EXPORT_SYMBOL_GPL(start_thread); 216 217 218 /* 219 * switch_to(x,y) should switch tasks from x to y. 220 * 221 * We fsave/fwait so that an exception goes off at the right time 222 * (as a call from the fsave or fwait in effect) rather than to 223 * the wrong process. Lazy FP saving no longer makes any sense 224 * with modern CPU's, and this simplifies a lot of things (SMP 225 * and UP become the same). 226 * 227 * NOTE! We used to use the x86 hardware context switching. The 228 * reason for not using it any more becomes apparent when you 229 * try to recover gracefully from saved state that is no longer 230 * valid (stale segment register values in particular). With the 231 * hardware task-switch, there is no way to fix up bad state in 232 * a reasonable manner. 233 * 234 * The fact that Intel documents the hardware task-switching to 235 * be slow is a fairly red herring - this code is not noticeably 236 * faster. However, there _is_ some room for improvement here, 237 * so the performance issues may eventually be a valid point. 238 * More important, however, is the fact that this allows us much 239 * more flexibility. 240 * 241 * The return value (in %ax) will be the "prev" task after 242 * the task-switch, and shows up in ret_from_fork in entry.S, 243 * for example. 244 */ 245 __notrace_funcgraph struct task_struct * 246 __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 247 { 248 struct thread_struct *prev = &prev_p->thread, 249 *next = &next_p->thread; 250 int cpu = smp_processor_id(); 251 struct tss_struct *tss = &per_cpu(init_tss, cpu); 252 fpu_switch_t fpu; 253 254 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ 255 256 fpu = switch_fpu_prepare(prev_p, next_p, cpu); 257 258 /* 259 * Reload esp0. 260 */ 261 load_sp0(tss, next); 262 263 /* 264 * Save away %gs. No need to save %fs, as it was saved on the 265 * stack on entry. No need to save %es and %ds, as those are 266 * always kernel segments while inside the kernel. Doing this 267 * before setting the new TLS descriptors avoids the situation 268 * where we temporarily have non-reloadable segments in %fs 269 * and %gs. This could be an issue if the NMI handler ever 270 * used %fs or %gs (it does not today), or if the kernel is 271 * running inside of a hypervisor layer. 272 */ 273 lazy_save_gs(prev->gs); 274 275 /* 276 * Load the per-thread Thread-Local Storage descriptor. 277 */ 278 load_TLS(next, cpu); 279 280 /* 281 * Restore IOPL if needed. In normal use, the flags restore 282 * in the switch assembly will handle this. But if the kernel 283 * is running virtualized at a non-zero CPL, the popf will 284 * not restore flags, so it must be done in a separate step. 285 */ 286 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) 287 set_iopl_mask(next->iopl); 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 math_state_restore, so the TS bit is up 301 * to date. 302 */ 303 arch_end_context_switch(next_p); 304 305 /* 306 * Restore %gs if needed (which is common) 307 */ 308 if (prev->gs | next->gs) 309 lazy_load_gs(next->gs); 310 311 switch_fpu_finish(next_p, fpu); 312 313 this_cpu_write(current_task, next_p); 314 315 return prev_p; 316 } 317 318 #define top_esp (THREAD_SIZE - sizeof(unsigned long)) 319 #define top_ebp (THREAD_SIZE - 2*sizeof(unsigned long)) 320 321 unsigned long get_wchan(struct task_struct *p) 322 { 323 unsigned long bp, sp, ip; 324 unsigned long stack_page; 325 int count = 0; 326 if (!p || p == current || p->state == TASK_RUNNING) 327 return 0; 328 stack_page = (unsigned long)task_stack_page(p); 329 sp = p->thread.sp; 330 if (!stack_page || sp < stack_page || sp > top_esp+stack_page) 331 return 0; 332 /* include/asm-i386/system.h:switch_to() pushes bp last. */ 333 bp = *(unsigned long *) sp; 334 do { 335 if (bp < stack_page || bp > top_ebp+stack_page) 336 return 0; 337 ip = *(unsigned long *) (bp+4); 338 if (!in_sched_functions(ip)) 339 return ip; 340 bp = *(unsigned long *) bp; 341 } while (count++ < 16); 342 return 0; 343 } 344 345