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/export.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/syscalls.h> 53 #include <asm/debugreg.h> 54 #include <asm/switch_to.h> 55 #include <asm/vm86.h> 56 57 void __show_regs(struct pt_regs *regs, int all) 58 { 59 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L; 60 unsigned long d0, d1, d2, d3, d6, d7; 61 unsigned long sp; 62 unsigned short ss, gs; 63 64 if (user_mode(regs)) { 65 sp = regs->sp; 66 ss = regs->ss & 0xffff; 67 gs = get_user_gs(regs); 68 } else { 69 sp = kernel_stack_pointer(regs); 70 savesegment(ss, ss); 71 savesegment(gs, gs); 72 } 73 74 printk(KERN_DEFAULT "EIP: %pS\n", (void *)regs->ip); 75 printk(KERN_DEFAULT "EFLAGS: %08lx CPU: %d\n", regs->flags, 76 smp_processor_id()); 77 78 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n", 79 regs->ax, regs->bx, regs->cx, regs->dx); 80 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n", 81 regs->si, regs->di, regs->bp, sp); 82 printk(KERN_DEFAULT " DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x\n", 83 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss); 84 85 if (!all) 86 return; 87 88 cr0 = read_cr0(); 89 cr2 = read_cr2(); 90 cr3 = read_cr3(); 91 cr4 = __read_cr4(); 92 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", 93 cr0, cr2, cr3, cr4); 94 95 get_debugreg(d0, 0); 96 get_debugreg(d1, 1); 97 get_debugreg(d2, 2); 98 get_debugreg(d3, 3); 99 get_debugreg(d6, 6); 100 get_debugreg(d7, 7); 101 102 /* Only print out debug registers if they are in their non-default state. */ 103 if ((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) && 104 (d6 == DR6_RESERVED) && (d7 == 0x400)) 105 return; 106 107 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n", 108 d0, d1, d2, d3); 109 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n", 110 d6, d7); 111 } 112 113 void release_thread(struct task_struct *dead_task) 114 { 115 BUG_ON(dead_task->mm); 116 release_vm86_irqs(dead_task); 117 } 118 119 int copy_thread_tls(unsigned long clone_flags, unsigned long sp, 120 unsigned long arg, struct task_struct *p, unsigned long tls) 121 { 122 struct pt_regs *childregs = task_pt_regs(p); 123 struct fork_frame *fork_frame = container_of(childregs, struct fork_frame, regs); 124 struct inactive_task_frame *frame = &fork_frame->frame; 125 struct task_struct *tsk; 126 int err; 127 128 frame->bp = 0; 129 frame->ret_addr = (unsigned long) ret_from_fork; 130 p->thread.sp = (unsigned long) fork_frame; 131 p->thread.sp0 = (unsigned long) (childregs+1); 132 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); 133 134 if (unlikely(p->flags & PF_KTHREAD)) { 135 /* kernel thread */ 136 memset(childregs, 0, sizeof(struct pt_regs)); 137 frame->bx = sp; /* function */ 138 frame->di = arg; 139 p->thread.io_bitmap_ptr = NULL; 140 return 0; 141 } 142 frame->bx = 0; 143 *childregs = *current_pt_regs(); 144 childregs->ax = 0; 145 if (sp) 146 childregs->sp = sp; 147 148 task_user_gs(p) = get_user_gs(current_pt_regs()); 149 150 p->thread.io_bitmap_ptr = NULL; 151 tsk = current; 152 err = -ENOMEM; 153 154 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { 155 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, 156 IO_BITMAP_BYTES, GFP_KERNEL); 157 if (!p->thread.io_bitmap_ptr) { 158 p->thread.io_bitmap_max = 0; 159 return -ENOMEM; 160 } 161 set_tsk_thread_flag(p, TIF_IO_BITMAP); 162 } 163 164 err = 0; 165 166 /* 167 * Set a new TLS for the child thread? 168 */ 169 if (clone_flags & CLONE_SETTLS) 170 err = do_set_thread_area(p, -1, 171 (struct user_desc __user *)tls, 0); 172 173 if (err && p->thread.io_bitmap_ptr) { 174 kfree(p->thread.io_bitmap_ptr); 175 p->thread.io_bitmap_max = 0; 176 } 177 return err; 178 } 179 180 void 181 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) 182 { 183 set_user_gs(regs, 0); 184 regs->fs = 0; 185 regs->ds = __USER_DS; 186 regs->es = __USER_DS; 187 regs->ss = __USER_DS; 188 regs->cs = __USER_CS; 189 regs->ip = new_ip; 190 regs->sp = new_sp; 191 regs->flags = X86_EFLAGS_IF; 192 force_iret(); 193 } 194 EXPORT_SYMBOL_GPL(start_thread); 195 196 197 /* 198 * switch_to(x,y) should switch tasks from x to y. 199 * 200 * We fsave/fwait so that an exception goes off at the right time 201 * (as a call from the fsave or fwait in effect) rather than to 202 * the wrong process. Lazy FP saving no longer makes any sense 203 * with modern CPU's, and this simplifies a lot of things (SMP 204 * and UP become the same). 205 * 206 * NOTE! We used to use the x86 hardware context switching. The 207 * reason for not using it any more becomes apparent when you 208 * try to recover gracefully from saved state that is no longer 209 * valid (stale segment register values in particular). With the 210 * hardware task-switch, there is no way to fix up bad state in 211 * a reasonable manner. 212 * 213 * The fact that Intel documents the hardware task-switching to 214 * be slow is a fairly red herring - this code is not noticeably 215 * faster. However, there _is_ some room for improvement here, 216 * so the performance issues may eventually be a valid point. 217 * More important, however, is the fact that this allows us much 218 * more flexibility. 219 * 220 * The return value (in %ax) will be the "prev" task after 221 * the task-switch, and shows up in ret_from_fork in entry.S, 222 * for example. 223 */ 224 __visible __notrace_funcgraph struct task_struct * 225 __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 226 { 227 struct thread_struct *prev = &prev_p->thread, 228 *next = &next_p->thread; 229 struct fpu *prev_fpu = &prev->fpu; 230 struct fpu *next_fpu = &next->fpu; 231 int cpu = smp_processor_id(); 232 struct tss_struct *tss = &per_cpu(cpu_tss, cpu); 233 234 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ 235 236 switch_fpu_prepare(prev_fpu, cpu); 237 238 /* 239 * Save away %gs. No need to save %fs, as it was saved on the 240 * stack on entry. No need to save %es and %ds, as those are 241 * always kernel segments while inside the kernel. Doing this 242 * before setting the new TLS descriptors avoids the situation 243 * where we temporarily have non-reloadable segments in %fs 244 * and %gs. This could be an issue if the NMI handler ever 245 * used %fs or %gs (it does not today), or if the kernel is 246 * running inside of a hypervisor layer. 247 */ 248 lazy_save_gs(prev->gs); 249 250 /* 251 * Load the per-thread Thread-Local Storage descriptor. 252 */ 253 load_TLS(next, cpu); 254 255 /* 256 * Restore IOPL if needed. In normal use, the flags restore 257 * in the switch assembly will handle this. But if the kernel 258 * is running virtualized at a non-zero CPL, the popf will 259 * not restore flags, so it must be done in a separate step. 260 */ 261 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) 262 set_iopl_mask(next->iopl); 263 264 /* 265 * Now maybe handle debug registers and/or IO bitmaps 266 */ 267 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV || 268 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT)) 269 __switch_to_xtra(prev_p, next_p, tss); 270 271 /* 272 * Leave lazy mode, flushing any hypercalls made here. 273 * This must be done before restoring TLS segments so 274 * the GDT and LDT are properly updated, and must be 275 * done before fpu__restore(), so the TS bit is up 276 * to date. 277 */ 278 arch_end_context_switch(next_p); 279 280 /* 281 * Reload esp0 and cpu_current_top_of_stack. This changes 282 * current_thread_info(). 283 */ 284 load_sp0(tss, next); 285 this_cpu_write(cpu_current_top_of_stack, 286 (unsigned long)task_stack_page(next_p) + 287 THREAD_SIZE); 288 289 /* 290 * Restore %gs if needed (which is common) 291 */ 292 if (prev->gs | next->gs) 293 lazy_load_gs(next->gs); 294 295 switch_fpu_finish(next_fpu, cpu); 296 297 this_cpu_write(current_task, next_p); 298 299 return prev_p; 300 } 301