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/sched/task.h> 16 #include <linux/sched/task_stack.h> 17 #include <linux/fs.h> 18 #include <linux/kernel.h> 19 #include <linux/mm.h> 20 #include <linux/elfcore.h> 21 #include <linux/smp.h> 22 #include <linux/stddef.h> 23 #include <linux/slab.h> 24 #include <linux/vmalloc.h> 25 #include <linux/user.h> 26 #include <linux/interrupt.h> 27 #include <linux/delay.h> 28 #include <linux/reboot.h> 29 #include <linux/mc146818rtc.h> 30 #include <linux/export.h> 31 #include <linux/kallsyms.h> 32 #include <linux/ptrace.h> 33 #include <linux/personality.h> 34 #include <linux/percpu.h> 35 #include <linux/prctl.h> 36 #include <linux/ftrace.h> 37 #include <linux/uaccess.h> 38 #include <linux/io.h> 39 #include <linux/kdebug.h> 40 #include <linux/syscalls.h> 41 42 #include <asm/pgtable.h> 43 #include <asm/ldt.h> 44 #include <asm/processor.h> 45 #include <asm/fpu/internal.h> 46 #include <asm/desc.h> 47 #ifdef CONFIG_MATH_EMULATION 48 #include <asm/math_emu.h> 49 #endif 50 51 #include <linux/err.h> 52 53 #include <asm/tlbflush.h> 54 #include <asm/cpu.h> 55 #include <asm/syscalls.h> 56 #include <asm/debugreg.h> 57 #include <asm/switch_to.h> 58 #include <asm/vm86.h> 59 #include <asm/intel_rdt_sched.h> 60 #include <asm/proto.h> 61 62 void __show_regs(struct pt_regs *regs, int all) 63 { 64 unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L; 65 unsigned long d0, d1, d2, d3, d6, d7; 66 unsigned long sp; 67 unsigned short ss, gs; 68 69 if (user_mode(regs)) { 70 sp = regs->sp; 71 ss = regs->ss; 72 gs = get_user_gs(regs); 73 } else { 74 sp = kernel_stack_pointer(regs); 75 savesegment(ss, ss); 76 savesegment(gs, gs); 77 } 78 79 show_ip(regs, KERN_DEFAULT); 80 81 printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n", 82 regs->ax, regs->bx, regs->cx, regs->dx); 83 printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n", 84 regs->si, regs->di, regs->bp, sp); 85 printk(KERN_DEFAULT "DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x EFLAGS: %08lx\n", 86 (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, ss, regs->flags); 87 88 if (!all) 89 return; 90 91 cr0 = read_cr0(); 92 cr2 = read_cr2(); 93 cr3 = __read_cr3(); 94 cr4 = __read_cr4(); 95 printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", 96 cr0, cr2, cr3, cr4); 97 98 get_debugreg(d0, 0); 99 get_debugreg(d1, 1); 100 get_debugreg(d2, 2); 101 get_debugreg(d3, 3); 102 get_debugreg(d6, 6); 103 get_debugreg(d7, 7); 104 105 /* Only print out debug registers if they are in their non-default state. */ 106 if ((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) && 107 (d6 == DR6_RESERVED) && (d7 == 0x400)) 108 return; 109 110 printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n", 111 d0, d1, d2, d3); 112 printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n", 113 d6, d7); 114 } 115 116 void release_thread(struct task_struct *dead_task) 117 { 118 BUG_ON(dead_task->mm); 119 release_vm86_irqs(dead_task); 120 } 121 122 int copy_thread_tls(unsigned long clone_flags, unsigned long sp, 123 unsigned long arg, struct task_struct *p, unsigned long tls) 124 { 125 struct pt_regs *childregs = task_pt_regs(p); 126 struct fork_frame *fork_frame = container_of(childregs, struct fork_frame, regs); 127 struct inactive_task_frame *frame = &fork_frame->frame; 128 struct task_struct *tsk; 129 int err; 130 131 frame->bp = 0; 132 frame->ret_addr = (unsigned long) ret_from_fork; 133 p->thread.sp = (unsigned long) fork_frame; 134 p->thread.sp0 = (unsigned long) (childregs+1); 135 memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps)); 136 137 if (unlikely(p->flags & PF_KTHREAD)) { 138 /* kernel thread */ 139 memset(childregs, 0, sizeof(struct pt_regs)); 140 frame->bx = sp; /* function */ 141 frame->di = arg; 142 p->thread.io_bitmap_ptr = NULL; 143 return 0; 144 } 145 frame->bx = 0; 146 *childregs = *current_pt_regs(); 147 childregs->ax = 0; 148 if (sp) 149 childregs->sp = sp; 150 151 task_user_gs(p) = get_user_gs(current_pt_regs()); 152 153 p->thread.io_bitmap_ptr = NULL; 154 tsk = current; 155 err = -ENOMEM; 156 157 if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) { 158 p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr, 159 IO_BITMAP_BYTES, GFP_KERNEL); 160 if (!p->thread.io_bitmap_ptr) { 161 p->thread.io_bitmap_max = 0; 162 return -ENOMEM; 163 } 164 set_tsk_thread_flag(p, TIF_IO_BITMAP); 165 } 166 167 err = 0; 168 169 /* 170 * Set a new TLS for the child thread? 171 */ 172 if (clone_flags & CLONE_SETTLS) 173 err = do_set_thread_area(p, -1, 174 (struct user_desc __user *)tls, 0); 175 176 if (err && p->thread.io_bitmap_ptr) { 177 kfree(p->thread.io_bitmap_ptr); 178 p->thread.io_bitmap_max = 0; 179 } 180 return err; 181 } 182 183 void 184 start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) 185 { 186 set_user_gs(regs, 0); 187 regs->fs = 0; 188 regs->ds = __USER_DS; 189 regs->es = __USER_DS; 190 regs->ss = __USER_DS; 191 regs->cs = __USER_CS; 192 regs->ip = new_ip; 193 regs->sp = new_sp; 194 regs->flags = X86_EFLAGS_IF; 195 force_iret(); 196 } 197 EXPORT_SYMBOL_GPL(start_thread); 198 199 200 /* 201 * switch_to(x,y) should switch tasks from x to y. 202 * 203 * We fsave/fwait so that an exception goes off at the right time 204 * (as a call from the fsave or fwait in effect) rather than to 205 * the wrong process. Lazy FP saving no longer makes any sense 206 * with modern CPU's, and this simplifies a lot of things (SMP 207 * and UP become the same). 208 * 209 * NOTE! We used to use the x86 hardware context switching. The 210 * reason for not using it any more becomes apparent when you 211 * try to recover gracefully from saved state that is no longer 212 * valid (stale segment register values in particular). With the 213 * hardware task-switch, there is no way to fix up bad state in 214 * a reasonable manner. 215 * 216 * The fact that Intel documents the hardware task-switching to 217 * be slow is a fairly red herring - this code is not noticeably 218 * faster. However, there _is_ some room for improvement here, 219 * so the performance issues may eventually be a valid point. 220 * More important, however, is the fact that this allows us much 221 * more flexibility. 222 * 223 * The return value (in %ax) will be the "prev" task after 224 * the task-switch, and shows up in ret_from_fork in entry.S, 225 * for example. 226 */ 227 __visible __notrace_funcgraph struct task_struct * 228 __switch_to(struct task_struct *prev_p, struct task_struct *next_p) 229 { 230 struct thread_struct *prev = &prev_p->thread, 231 *next = &next_p->thread; 232 struct fpu *prev_fpu = &prev->fpu; 233 struct fpu *next_fpu = &next->fpu; 234 int cpu = smp_processor_id(); 235 struct tss_struct *tss = &per_cpu(cpu_tss_rw, cpu); 236 237 /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */ 238 239 switch_fpu_prepare(prev_fpu, cpu); 240 241 /* 242 * Save away %gs. No need to save %fs, as it was saved on the 243 * stack on entry. No need to save %es and %ds, as those are 244 * always kernel segments while inside the kernel. Doing this 245 * before setting the new TLS descriptors avoids the situation 246 * where we temporarily have non-reloadable segments in %fs 247 * and %gs. This could be an issue if the NMI handler ever 248 * used %fs or %gs (it does not today), or if the kernel is 249 * running inside of a hypervisor layer. 250 */ 251 lazy_save_gs(prev->gs); 252 253 /* 254 * Load the per-thread Thread-Local Storage descriptor. 255 */ 256 load_TLS(next, cpu); 257 258 /* 259 * Restore IOPL if needed. In normal use, the flags restore 260 * in the switch assembly will handle this. But if the kernel 261 * is running virtualized at a non-zero CPL, the popf will 262 * not restore flags, so it must be done in a separate step. 263 */ 264 if (get_kernel_rpl() && unlikely(prev->iopl != next->iopl)) 265 set_iopl_mask(next->iopl); 266 267 /* 268 * Now maybe handle debug registers and/or IO bitmaps 269 */ 270 if (unlikely(task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV || 271 task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT)) 272 __switch_to_xtra(prev_p, next_p, tss); 273 274 /* 275 * Leave lazy mode, flushing any hypercalls made here. 276 * This must be done before restoring TLS segments so 277 * the GDT and LDT are properly updated, and must be 278 * done before fpu__restore(), so the TS bit is up 279 * to date. 280 */ 281 arch_end_context_switch(next_p); 282 283 /* 284 * Reload esp0 and cpu_current_top_of_stack. This changes 285 * current_thread_info(). Refresh the SYSENTER configuration in 286 * case prev or next is vm86. 287 */ 288 update_task_stack(next_p); 289 refresh_sysenter_cs(next); 290 this_cpu_write(cpu_current_top_of_stack, 291 (unsigned long)task_stack_page(next_p) + 292 THREAD_SIZE); 293 294 /* 295 * Restore %gs if needed (which is common) 296 */ 297 if (prev->gs | next->gs) 298 lazy_load_gs(next->gs); 299 300 switch_fpu_finish(next_fpu, cpu); 301 302 this_cpu_write(current_task, next_p); 303 304 /* Load the Intel cache allocation PQR MSR. */ 305 intel_rdt_sched_in(); 306 307 return prev_p; 308 } 309 310 SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2) 311 { 312 return do_arch_prctl_common(current, option, arg2); 313 } 314