root/arch/x86/kernel/process_32.c

DEFINITIONS

1. __show_regs
2. release_thread
3. copy_thread_tls
4. start_thread
5. __switch_to
6. SYSCALL_DEFINE2

   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 
  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 #include <asm/resctrl_sched.h>
  57 #include <asm/proto.h>
  58 
  59 #include "process.h"
  60 
  61 void __show_regs(struct pt_regs *regs, enum show_regs_mode mode)
  62 {
  63         unsigned long cr0 = 0L, cr2 = 0L, cr3 = 0L, cr4 = 0L;
  64         unsigned long d0, d1, d2, d3, d6, d7;
  65         unsigned short gs;
  66 
  67         if (user_mode(regs))
  68                 gs = get_user_gs(regs);
  69         else
  70                 savesegment(gs, gs);
  71 
  72         show_ip(regs, KERN_DEFAULT);
  73 
  74         printk(KERN_DEFAULT "EAX: %08lx EBX: %08lx ECX: %08lx EDX: %08lx\n",
  75                 regs->ax, regs->bx, regs->cx, regs->dx);
  76         printk(KERN_DEFAULT "ESI: %08lx EDI: %08lx EBP: %08lx ESP: %08lx\n",
  77                 regs->si, regs->di, regs->bp, regs->sp);
  78         printk(KERN_DEFAULT "DS: %04x ES: %04x FS: %04x GS: %04x SS: %04x EFLAGS: %08lx\n",
  79                (u16)regs->ds, (u16)regs->es, (u16)regs->fs, gs, regs->ss, regs->flags);
  80 
  81         if (mode != SHOW_REGS_ALL)
  82                 return;
  83 
  84         cr0 = read_cr0();
  85         cr2 = read_cr2();
  86         cr3 = __read_cr3();
  87         cr4 = __read_cr4();
  88         printk(KERN_DEFAULT "CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n",
  89                         cr0, cr2, cr3, cr4);
  90 
  91         get_debugreg(d0, 0);
  92         get_debugreg(d1, 1);
  93         get_debugreg(d2, 2);
  94         get_debugreg(d3, 3);
  95         get_debugreg(d6, 6);
  96         get_debugreg(d7, 7);
  97 
  98         /* Only print out debug registers if they are in their non-default state. */
  99         if ((d0 == 0) && (d1 == 0) && (d2 == 0) && (d3 == 0) &&
 100             (d6 == DR6_RESERVED) && (d7 == 0x400))
 101                 return;
 102 
 103         printk(KERN_DEFAULT "DR0: %08lx DR1: %08lx DR2: %08lx DR3: %08lx\n",
 104                         d0, d1, d2, d3);
 105         printk(KERN_DEFAULT "DR6: %08lx DR7: %08lx\n",
 106                         d6, d7);
 107 }
 108 
 109 void release_thread(struct task_struct *dead_task)
 110 {
 111         BUG_ON(dead_task->mm);
 112         release_vm86_irqs(dead_task);
 113 }
 114 
 115 int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
 116         unsigned long arg, struct task_struct *p, unsigned long tls)
 117 {
 118         struct pt_regs *childregs = task_pt_regs(p);
 119         struct fork_frame *fork_frame = container_of(childregs, struct fork_frame, regs);
 120         struct inactive_task_frame *frame = &fork_frame->frame;
 121         struct task_struct *tsk;
 122         int err;
 123 
 124         /*
 125          * For a new task use the RESET flags value since there is no before.
 126          * All the status flags are zero; DF and all the system flags must also
 127          * be 0, specifically IF must be 0 because we context switch to the new
 128          * task with interrupts disabled.
 129          */
 130         frame->flags = X86_EFLAGS_FIXED;
 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 
 236         /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
 237 
 238         if (!test_thread_flag(TIF_NEED_FPU_LOAD))
 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         switch_to_extra(prev_p, next_p);
 268 
 269         /*
 270          * Leave lazy mode, flushing any hypercalls made here.
 271          * This must be done before restoring TLS segments so
 272          * the GDT and LDT are properly updated.
 273          */
 274         arch_end_context_switch(next_p);
 275 
 276         /*
 277          * Reload esp0 and cpu_current_top_of_stack.  This changes
 278          * current_thread_info().  Refresh the SYSENTER configuration in
 279          * case prev or next is vm86.
 280          */
 281         update_task_stack(next_p);
 282         refresh_sysenter_cs(next);
 283         this_cpu_write(cpu_current_top_of_stack,
 284                        (unsigned long)task_stack_page(next_p) +
 285                        THREAD_SIZE);
 286 
 287         /*
 288          * Restore %gs if needed (which is common)
 289          */
 290         if (prev->gs | next->gs)
 291                 lazy_load_gs(next->gs);
 292 
 293         this_cpu_write(current_task, next_p);
 294 
 295         switch_fpu_finish(next_fpu);
 296 
 297         /* Load the Intel cache allocation PQR MSR. */
 298         resctrl_sched_in();
 299 
 300         return prev_p;
 301 }
 302 
 303 SYSCALL_DEFINE2(arch_prctl, int, option, unsigned long, arg2)
 304 {
 305         return do_arch_prctl_common(current, option, arg2);
 306 }