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 void arch_cpu_idle(void)
  45 {
  46         /* sleep, but enable all interrupts before committing */
  47         __asm__("sleep 0x3");
  48 }
  49
  50 asmlinkage void ret_from_fork(void);
  51
  52 /* Layout of Child kernel mode stack as setup at the end of this function is
  53  *
  54  * |     ...        |
  55  * |     ...        |
  56  * |    unused      |
  57  * |                |
  58  * ------------------
  59  * |     r25        |   <==== top of Stack (thread.ksp)
  60  * ~                ~
  61  * |    --to--      |   (CALLEE Regs of user mode)
  62  * |     r13        |
  63  * ------------------
  64  * |     fp         |
  65  * |    blink       |   @ret_from_fork
  66  * ------------------
  67  * |                |
  68  * ~                ~
  69  * ~                ~
  70  * |                |
  71  * ------------------
  72  * |     r12        |
  73  * ~                ~
  74  * |    --to--      |   (scratch Regs of user mode)
  75  * |     r0         |
  76  * ------------------
  77  * |      SP        |
  78  * |    orig_r0     |
  79  * |    event/ECR   |
  80  * |    user_r25    |
  81  * ------------------  <===== END of PAGE
  82  */
  83 int copy_thread(unsigned long clone_flags,
  84                 unsigned long usp, unsigned long arg,
  85                 struct task_struct *p)
  86 {
  87         struct pt_regs *c_regs;        /* child's pt_regs */
  88         unsigned long *childksp;       /* to unwind out of __switch_to() */
  89         struct callee_regs *c_callee;  /* child's callee regs */
  90         struct callee_regs *parent_callee;  /* paren't callee */
  91         struct pt_regs *regs = current_pt_regs();
  92
  93         /* Mark the specific anchors to begin with (see pic above) */
  94         c_regs = task_pt_regs(p);
  95         childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
  96         c_callee = ((struct callee_regs *)childksp) - 1;
  97
  98         /*
  99          * __switch_to() uses thread.ksp to start unwinding stack
 100          * For kernel threads we don't need to create callee regs, the
 101          * stack layout nevertheless needs to remain the same.
 102          * Also, since __switch_to anyways unwinds callee regs, we use
 103          * this to populate kernel thread entry-pt/args into callee regs,
 104          * so that ret_from_kernel_thread() becomes simpler.
 105          */
 106         p->thread.ksp = (unsigned long)c_callee;        /* THREAD_KSP */
 107
 108         /* __switch_to expects FP(0), BLINK(return addr) at top */
 109         childksp[0] = 0;                        /* fp */
 110         childksp[1] = (unsigned long)ret_from_fork; /* blink */
 111
 112         if (unlikely(p->flags & PF_KTHREAD)) {
 113                 memset(c_regs, 0, sizeof(struct pt_regs));
 114
 115                 c_callee->r13 = arg; /* argument to kernel thread */
 116                 c_callee->r14 = usp;  /* function */
 117
 118                 return 0;
 119         }
 120
 121         /*--------- User Task Only --------------*/
 122
 123         /* __switch_to expects FP(0), BLINK(return addr) at top of stack */
 124         childksp[0] = 0;                                /* for POP fp */
 125         childksp[1] = (unsigned long)ret_from_fork;     /* for POP blink */
 126
 127         /* Copy parents pt regs on child's kernel mode stack */
 128         *c_regs = *regs;
 129
 130         if (usp)
 131                 c_regs->sp = usp;
 132
 133         c_regs->r0 = 0;         /* fork returns 0 in child */
 134
 135         parent_callee = ((struct callee_regs *)regs) - 1;
 136         *c_callee = *parent_callee;
 137
 138         if (unlikely(clone_flags & CLONE_SETTLS)) {
 139                 /*
 140                  * set task's userland tls data ptr from 4th arg
 141                  * clone C-lib call is difft from clone sys-call
 142                  */
 143                 task_thread_info(p)->thr_ptr = regs->r3;
 144         } else {
 145                 /* Normal fork case: set parent's TLS ptr in child */
 146                 task_thread_info(p)->thr_ptr =
 147                 task_thread_info(current)->thr_ptr;
 148         }
 149
 150         return 0;
 151 }
 152
 153 /*
 154  * Some archs flush debug and FPU info here
 155  */
 156 void flush_thread(void)
 157 {
 158 }
 159
 160 /*
 161  * Free any architecture-specific thread data structures, etc.
 162  */
 163 void exit_thread(void)
 164 {
 165 }
 166
 167 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 168 {
 169         return 0;
 170 }
 171
 172 /*
 173  * API: expected by schedular Code: If thread is sleeping where is that.
 174  * What is this good for? it will be always the scheduler or ret_from_fork.
 175  * So we hard code that anyways.
 176  */
 177 unsigned long thread_saved_pc(struct task_struct *t)
 178 {
 179         struct pt_regs *regs = task_pt_regs(t);
 180         unsigned long blink = 0;
 181
 182         /*
 183          * If the thread being queried for in not itself calling this, then it
 184          * implies it is not executing, which in turn implies it is sleeping,
 185          * which in turn implies it got switched OUT by the schedular.
 186          * In that case, it's kernel mode blink can reliably retrieved as per
 187          * the picture above (right above pt_regs).
 188          */
 189         if (t != current && t->state != TASK_RUNNING)
 190                 blink = *((unsigned int *)regs - 1);
 191
 192         return blink;
 193 }
 194
 195 int elf_check_arch(const struct elf32_hdr *x)
 196 {
 197         unsigned int eflags;
 198
 199         if (x->e_machine != EM_ARCOMPACT)
 200                 return 0;
 201
 202         eflags = x->e_flags;
 203         if ((eflags & EF_ARC_OSABI_MSK) < EF_ARC_OSABI_CURRENT) {
 204                 pr_err("ABI mismatch - you need newer toolchain\n");
 205                 force_sigsegv(SIGSEGV, current);
 206                 return 0;
 207         }
 208
 209         return 1;
 210 }
 211 EXPORT_SYMBOL(elf_check_arch);