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