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         if (is_isa_arcompact()) {
  48                 __asm__("sleep 0x3");
  49         } else {
  50                 /* default irq priority (<=) which can interrupt the doze */
  51                 const int arg = 0x10 | ARCV2_IRQ_DEF_PRIO;
  52
  53                 __asm__ __volatile__(
  54                 "sleep %0       \n"
  55                 :
  56                 :"r"(arg));
  57         }
  58 }
  59
  60 asmlinkage void ret_from_fork(void);
  61
  62 /*
  63  * Copy architecture-specific thread state
  64  *
  65  * Layout of Child kernel mode stack as setup at the end of this function is
  66  *
  67  * |     ...        |
  68  * |     ...        |
  69  * |    unused      |
  70  * |                |
  71  * ------------------
  72  * |     r25        |   <==== top of Stack (thread.ksp)
  73  * ~                ~
  74  * |    --to--      |   (CALLEE Regs of user mode)
  75  * |     r13        |
  76  * ------------------
  77  * |     fp         |
  78  * |    blink       |   @ret_from_fork
  79  * ------------------
  80  * |                |
  81  * ~                ~
  82  * ~                ~
  83  * |                |
  84  * ------------------
  85  * |     r12        |
  86  * ~                ~
  87  * |    --to--      |   (scratch Regs of user mode)
  88  * |     r0         |
  89  * ------------------
  90  * |      SP        |
  91  * |    orig_r0     |
  92  * |    event/ECR   |
  93  * |    user_r25    |
  94  * ------------------  <===== END of PAGE
  95  */
  96 int copy_thread(unsigned long clone_flags,
  97                 unsigned long usp, unsigned long kthread_arg,
  98                 struct task_struct *p)
  99 {
 100         struct pt_regs *c_regs;        /* child's pt_regs */
 101         unsigned long *childksp;       /* to unwind out of __switch_to() */
 102         struct callee_regs *c_callee;  /* child's callee regs */
 103         struct callee_regs *parent_callee;  /* paren't callee */
 104         struct pt_regs *regs = current_pt_regs();
 105
 106         /* Mark the specific anchors to begin with (see pic above) */
 107         c_regs = task_pt_regs(p);
 108         childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
 109         c_callee = ((struct callee_regs *)childksp) - 1;
 110
 111         /*
 112          * __switch_to() uses thread.ksp to start unwinding stack
 113          * For kernel threads we don't need to create callee regs, the
 114          * stack layout nevertheless needs to remain the same.
 115          * Also, since __switch_to anyways unwinds callee regs, we use
 116          * this to populate kernel thread entry-pt/args into callee regs,
 117          * so that ret_from_kernel_thread() becomes simpler.
 118          */
 119         p->thread.ksp = (unsigned long)c_callee;        /* THREAD_KSP */
 120
 121         /* __switch_to expects FP(0), BLINK(return addr) at top */
 122         childksp[0] = 0;                        /* fp */
 123         childksp[1] = (unsigned long)ret_from_fork; /* blink */
 124
 125         if (unlikely(p->flags & PF_KTHREAD)) {
 126                 memset(c_regs, 0, sizeof(struct pt_regs));
 127
 128                 c_callee->r13 = kthread_arg;
 129                 c_callee->r14 = usp;  /* function */
 130
 131                 return 0;
 132         }
 133
 134         /*--------- User Task Only --------------*/
 135
 136         /* __switch_to expects FP(0), BLINK(return addr) at top of stack */
 137         childksp[0] = 0;                                /* for POP fp */
 138         childksp[1] = (unsigned long)ret_from_fork;     /* for POP blink */
 139
 140         /* Copy parents pt regs on child's kernel mode stack */
 141         *c_regs = *regs;
 142
 143         if (usp)
 144                 c_regs->sp = usp;
 145
 146         c_regs->r0 = 0;         /* fork returns 0 in child */
 147
 148         parent_callee = ((struct callee_regs *)regs) - 1;
 149         *c_callee = *parent_callee;
 150
 151         if (unlikely(clone_flags & CLONE_SETTLS)) {
 152                 /*
 153                  * set task's userland tls data ptr from 4th arg
 154                  * clone C-lib call is difft from clone sys-call
 155                  */
 156                 task_thread_info(p)->thr_ptr = regs->r3;
 157         } else {
 158                 /* Normal fork case: set parent's TLS ptr in child */
 159                 task_thread_info(p)->thr_ptr =
 160                 task_thread_info(current)->thr_ptr;
 161         }
 162
 163         return 0;
 164 }
 165
 166 /*
 167  * Do necessary setup to start up a new user task
 168  */
 169 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long usp)
 170 {
 171         regs->sp = usp;
 172         regs->ret = pc;
 173
 174         /*
 175          * [U]ser Mode bit set
 176          * [L] ZOL loop inhibited to begin with - cleared by a LP insn
 177          * Interrupts enabled
 178          */
 179         regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;
 180
 181         /* bogus seed values for debugging */
 182         regs->lp_start = 0x10;
 183         regs->lp_end = 0x80;
 184 }
 185
 186 /*
 187  * Some archs flush debug and FPU info here
 188  */
 189 void flush_thread(void)
 190 {
 191 }
 192
 193 /*
 194  * Free any architecture-specific thread data structures, etc.
 195  */
 196 void exit_thread(void)
 197 {
 198 }
 199
 200 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 201 {
 202         return 0;
 203 }
 204
 205 int elf_check_arch(const struct elf32_hdr *x)
 206 {
 207         unsigned int eflags;
 208
 209         if (x->e_machine != EM_ARC_INUSE) {
 210                 pr_err("ELF not built for %s ISA\n",
 211                         is_isa_arcompact() ? "ARCompact":"ARCv2");
 212                 return 0;
 213         }
 214
 215         eflags = x->e_flags;
 216         if ((eflags & EF_ARC_OSABI_MSK) < EF_ARC_OSABI_CURRENT) {
 217                 pr_err("ABI mismatch - you need newer toolchain\n");
 218                 force_sigsegv(SIGSEGV, current);
 219                 return 0;
 220         }
 221
 222         return 1;
 223 }
 224 EXPORT_SYMBOL(elf_check_arch);