LXR linux/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
  23SYSCALL_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 */
  39SYSCALL_DEFINE0(arc_gettls)
  40{
  41        return task_thread_info(current)->thr_ptr;
  42}
  43
  44void arch_cpu_idle(void)
  45{
  46        /* sleep, but enable all interrupts before committing */
  47        __asm__("sleep 0x3");
  48}
  49
  50asmlinkage 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 */
  83int 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 * Do necessary setup to start up a new user task
 155 */
 156void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long usp)
 157{
 158        set_fs(USER_DS); /* user space */
 159
 160        regs->sp = usp;
 161        regs->ret = pc;
 162
 163        /*
 164         * [U]ser Mode bit set
 165         * [L] ZOL loop inhibited to begin with - cleared by a LP insn
 166         * Interrupts enabled
 167         */
 168        regs->status32 = STATUS_U_MASK | STATUS_L_MASK |
 169                         STATUS_E1_MASK | STATUS_E2_MASK;
 170
 171        /* bogus seed values for debugging */
 172        regs->lp_start = 0x10;
 173        regs->lp_end = 0x80;
 174}
 175
 176/*
 177 * Some archs flush debug and FPU info here
 178 */
 179void flush_thread(void)
 180{
 181}
 182
 183/*
 184 * Free any architecture-specific thread data structures, etc.
 185 */
 186void exit_thread(void)
 187{
 188}
 189
 190int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 191{
 192        return 0;
 193}
 194
 195/*
 196 * API: expected by schedular Code: If thread is sleeping where is that.
 197 * What is this good for? it will be always the scheduler or ret_from_fork.
 198 * So we hard code that anyways.
 199 */
 200unsigned long thread_saved_pc(struct task_struct *t)
 201{
 202        struct pt_regs *regs = task_pt_regs(t);
 203        unsigned long blink = 0;
 204
 205        /*
 206         * If the thread being queried for in not itself calling this, then it
 207         * implies it is not executing, which in turn implies it is sleeping,
 208         * which in turn implies it got switched OUT by the schedular.
 209         * In that case, it's kernel mode blink can reliably retrieved as per
 210         * the picture above (right above pt_regs).
 211         */
 212        if (t != current && t->state != TASK_RUNNING)
 213                blink = *((unsigned int *)regs - 1);
 214
 215        return blink;
 216}
 217
 218int elf_check_arch(const struct elf32_hdr *x)
 219{
 220        unsigned int eflags;
 221
 222        if (x->e_machine != EM_ARCOMPACT)
 223                return 0;
 224
 225        eflags = x->e_flags;
 226        if ((eflags & EF_ARC_OSABI_MSK) < EF_ARC_OSABI_CURRENT) {
 227                pr_err("ABI mismatch - you need newer toolchain\n");
 228                force_sigsegv(SIGSEGV, current);
 229                return 0;
 230        }
 231
 232        return 1;
 233}
 234EXPORT_SYMBOL(elf_check_arch);
 235