arch/arc/kernel/process.c

   1 /*
   2  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * Amit Bhor, Kanika Nema: Codito Technologies 2004
   9  */
  10
  11 #include <linux/errno.h>
  12 #include <linux/module.h>
  13 #include <linux/sched.h>
  14 #include <linux/mm.h>
  15 #include <linux/fs.h>
  16 #include <linux/unistd.h>
  17 #include <linux/ptrace.h>
  18 #include <linux/slab.h>
  19 #include <linux/syscalls.h>
  20 #include <linux/elf.h>
  21 #include <linux/tick.h>
  22
  23 SYSCALL_DEFINE1(arc_settls, void *, user_tls_data_ptr)
  24 {
  25         task_thread_info(current)->thr_ptr = (unsigned int)user_tls_data_ptr;
  26         return 0;
  27 }
  28
  29 /*
  30  * We return the user space TLS data ptr as sys-call return code
  31  * Ideally it should be copy to user.
  32  * However we can cheat by the fact that some sys-calls do return
  33  * absurdly high values
  34  * Since the tls dat aptr is not going to be in range of 0xFFFF_xxxx
  35  * it won't be considered a sys-call error
  36  * and it will be loads better than copy-to-user, which is a definite
  37  * D-TLB Miss
  38  */
  39 SYSCALL_DEFINE0(arc_gettls)
  40 {
  41         return task_thread_info(current)->thr_ptr;
  42 }
  43
  44 static inline void arch_idle(void)
  45 {
  46         /* sleep, but enable all interrupts before committing */
  47         __asm__("sleep 0x3");
  48 }
  49
  50 void cpu_idle(void)
  51 {
  52         /* Since we SLEEP in idle loop, TIF_POLLING_NRFLAG can't be set */
  53
  54         /* endless idle loop with no priority at all */
  55         while (1) {
  56                 tick_nohz_idle_enter();
  57                 rcu_idle_enter();
  58
  59 doze:
  60                 local_irq_disable();
  61                 if (!need_resched()) {
  62                         arch_idle();
  63                         goto doze;
  64                 } else {
  65                         local_irq_enable();
  66                 }
  67
  68                 rcu_idle_exit();
  69                 tick_nohz_idle_exit();
  70
  71                 schedule_preempt_disabled();
  72         }
  73 }
  74
  75 asmlinkage void ret_from_fork(void);
  76
  77 /* Layout of Child kernel mode stack as setup at the end of this function is
  78  *
  79  * |     ...        |
  80  * |     ...        |
  81  * |    unused      |
  82  * |                |
  83  * ------------------  <==== top of Stack (thread.ksp)
  84  * |   UNUSED 1 word|
  85  * ------------------
  86  * |     r25        |
  87  * ~                ~
  88  * |    --to--      |   (CALLEE Regs of user mode)
  89  * |     r13        |
  90  * ------------------
  91  * |     fp         |
  92  * |    blink       |   @ret_from_fork
  93  * ------------------
  94  * |                |
  95  * ~                ~
  96  * ~                ~
  97  * |                |
  98  * ------------------
  99  * |     r12        |
 100  * ~                ~
 101  * |    --to--      |   (scratch Regs of user mode)
 102  * |     r0         |
 103  * ------------------
 104  * |   UNUSED 1 word|
 105  * ------------------  <===== END of PAGE
 106  */
 107 int copy_thread(unsigned long clone_flags,
 108                 unsigned long usp, unsigned long arg,
 109                 struct task_struct *p)
 110 {
 111         struct pt_regs *c_regs;        /* child's pt_regs */
 112         unsigned long *childksp;       /* to unwind out of __switch_to() */
 113         struct callee_regs *c_callee;  /* child's callee regs */
 114         struct callee_regs *parent_callee;  /* paren't callee */
 115         struct pt_regs *regs = current_pt_regs();
 116
 117         /* Mark the specific anchors to begin with (see pic above) */
 118         c_regs = task_pt_regs(p);
 119         childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
 120         c_callee = ((struct callee_regs *)childksp) - 1;
 121
 122         /*
 123          * __switch_to() uses thread.ksp to start unwinding stack
 124          * For kernel threads we don't need to create callee regs, the
 125          * stack layout nevertheless needs to remain the same.
 126          * Also, since __switch_to anyways unwinds callee regs, we use
 127          * this to populate kernel thread entry-pt/args into callee regs,
 128          * so that ret_from_kernel_thread() becomes simpler.
 129          */
 130         p->thread.ksp = (unsigned long)c_callee;        /* THREAD_KSP */
 131
 132         /* __switch_to expects FP(0), BLINK(return addr) at top */
 133         childksp[0] = 0;                        /* fp */
 134         childksp[1] = (unsigned long)ret_from_fork; /* blink */
 135
 136         if (unlikely(p->flags & PF_KTHREAD)) {
 137                 memset(c_regs, 0, sizeof(struct pt_regs));
 138
 139                 c_callee->r13 = arg; /* argument to kernel thread */
 140                 c_callee->r14 = usp;  /* function */
 141
 142                 return 0;
 143         }
 144
 145         /*--------- User Task Only --------------*/
 146
 147         /* __switch_to expects FP(0), BLINK(return addr) at top of stack */
 148         childksp[0] = 0;                                /* for POP fp */
 149         childksp[1] = (unsigned long)ret_from_fork;     /* for POP blink */
 150
 151         /* Copy parents pt regs on child's kernel mode stack */
 152         *c_regs = *regs;
 153
 154         if (usp)
 155                 c_regs->sp = usp;
 156
 157         c_regs->r0 = 0;         /* fork returns 0 in child */
 158
 159         parent_callee = ((struct callee_regs *)regs) - 1;
 160         *c_callee = *parent_callee;
 161
 162         if (unlikely(clone_flags & CLONE_SETTLS)) {
 163                 /*
 164                  * set task's userland tls data ptr from 4th arg
 165                  * clone C-lib call is difft from clone sys-call
 166                  */
 167                 task_thread_info(p)->thr_ptr = regs->r3;
 168         } else {
 169                 /* Normal fork case: set parent's TLS ptr in child */
 170                 task_thread_info(p)->thr_ptr =
 171                 task_thread_info(current)->thr_ptr;
 172         }
 173
 174         return 0;
 175 }
 176
 177 /*
 178  * Some archs flush debug and FPU info here
 179  */
 180 void flush_thread(void)
 181 {
 182 }
 183
 184 /*
 185  * Free any architecture-specific thread data structures, etc.
 186  */
 187 void exit_thread(void)
 188 {
 189 }
 190
 191 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 192 {
 193         return 0;
 194 }
 195
 196 /*
 197  * API: expected by schedular Code: If thread is sleeping where is that.
 198  * What is this good for? it will be always the scheduler or ret_from_fork.
 199  * So we hard code that anyways.
 200  */
 201 unsigned long thread_saved_pc(struct task_struct *t)
 202 {
 203         struct pt_regs *regs = task_pt_regs(t);
 204         unsigned long blink = 0;
 205
 206         /*
 207          * If the thread being queried for in not itself calling this, then it
 208          * implies it is not executing, which in turn implies it is sleeping,
 209          * which in turn implies it got switched OUT by the schedular.
 210          * In that case, it's kernel mode blink can reliably retrieved as per
 211          * the picture above (right above pt_regs).
 212          */
 213         if (t != current && t->state != TASK_RUNNING)
 214                 blink = *((unsigned int *)regs - 1);
 215
 216         return blink;
 217 }
 218
 219 int elf_check_arch(const struct elf32_hdr *x)
 220 {
 221         unsigned int eflags;
 222
 223         if (x->e_machine != EM_ARCOMPACT)
 224                 return 0;
 225
 226         eflags = x->e_flags;
 227         if ((eflags & EF_ARC_OSABI_MSK) < EF_ARC_OSABI_V2) {
 228                 pr_err("ABI mismatch - you need newer toolchain\n");
 229                 force_sigsegv(SIGSEGV, current);
 230                 return 0;
 231         }
 232
 233         return 1;
 234 }
 235 EXPORT_SYMBOL(elf_check_arch);