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/*
  53 * Copy architecture-specific thread state
  54 *
  55 * Layout of Child kernel mode stack as setup at the end of this function is
  56 *
  57 * |     ...        |
  58 * |     ...        |
  59 * |    unused      |
  60 * |                |
  61 * ------------------
  62 * |     r25        |   <==== top of Stack (thread.ksp)
  63 * ~                ~
  64 * |    --to--      |   (CALLEE Regs of user mode)
  65 * |     r13        |
  66 * ------------------
  67 * |     fp         |
  68 * |    blink       |   @ret_from_fork
  69 * ------------------
  70 * |                |
  71 * ~                ~
  72 * ~                ~
  73 * |                |
  74 * ------------------
  75 * |     r12        |
  76 * ~                ~
  77 * |    --to--      |   (scratch Regs of user mode)
  78 * |     r0         |
  79 * ------------------
  80 * |      SP        |
  81 * |    orig_r0     |
  82 * |    event/ECR   |
  83 * |    user_r25    |
  84 * ------------------  <===== END of PAGE
  85 */
  86int copy_thread(unsigned long clone_flags,
  87                unsigned long usp, unsigned long kthread_arg,
  88                struct task_struct *p)
  89{
  90        struct pt_regs *c_regs;        /* child's pt_regs */
  91        unsigned long *childksp;       /* to unwind out of __switch_to() */
  92        struct callee_regs *c_callee;  /* child's callee regs */
  93        struct callee_regs *parent_callee;  /* paren't callee */
  94        struct pt_regs *regs = current_pt_regs();
  95
  96        /* Mark the specific anchors to begin with (see pic above) */
  97        c_regs = task_pt_regs(p);
  98        childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
  99        c_callee = ((struct callee_regs *)childksp) - 1;
 100
 101        /*
 102         * __switch_to() uses thread.ksp to start unwinding stack
 103         * For kernel threads we don't need to create callee regs, the
 104         * stack layout nevertheless needs to remain the same.
 105         * Also, since __switch_to anyways unwinds callee regs, we use
 106         * this to populate kernel thread entry-pt/args into callee regs,
 107         * so that ret_from_kernel_thread() becomes simpler.
 108         */
 109        p->thread.ksp = (unsigned long)c_callee;        /* THREAD_KSP */
 110
 111        /* __switch_to expects FP(0), BLINK(return addr) at top */
 112        childksp[0] = 0;                        /* fp */
 113        childksp[1] = (unsigned long)ret_from_fork; /* blink */
 114
 115        if (unlikely(p->flags & PF_KTHREAD)) {
 116                memset(c_regs, 0, sizeof(struct pt_regs));
 117
 118                c_callee->r13 = kthread_arg;
 119                c_callee->r14 = usp;  /* function */
 120
 121                return 0;
 122        }
 123
 124        /*--------- User Task Only --------------*/
 125
 126        /* __switch_to expects FP(0), BLINK(return addr) at top of stack */
 127        childksp[0] = 0;                                /* for POP fp */
 128        childksp[1] = (unsigned long)ret_from_fork;     /* for POP blink */
 129
 130        /* Copy parents pt regs on child's kernel mode stack */
 131        *c_regs = *regs;
 132
 133        if (usp)
 134                c_regs->sp = usp;
 135
 136        c_regs->r0 = 0;         /* fork returns 0 in child */
 137
 138        parent_callee = ((struct callee_regs *)regs) - 1;
 139        *c_callee = *parent_callee;
 140
 141        if (unlikely(clone_flags & CLONE_SETTLS)) {
 142                /*
 143                 * set task's userland tls data ptr from 4th arg
 144                 * clone C-lib call is difft from clone sys-call
 145                 */
 146                task_thread_info(p)->thr_ptr = regs->r3;
 147        } else {
 148                /* Normal fork case: set parent's TLS ptr in child */
 149                task_thread_info(p)->thr_ptr =
 150                task_thread_info(current)->thr_ptr;
 151        }
 152
 153        return 0;
 154}
 155
 156/*
 157 * Do necessary setup to start up a new user task
 158 */
 159void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long usp)
 160{
 161        regs->sp = usp;
 162        regs->ret = pc;
 163
 164        /*
 165         * [U]ser Mode bit set
 166         * [L] ZOL loop inhibited to begin with - cleared by a LP insn
 167         * Interrupts enabled
 168         */
 169        regs->status32 = STATUS_U_MASK | STATUS_L_MASK |
 170                         STATUS_E1_MASK | STATUS_E2_MASK;
 171
 172        /* bogus seed values for debugging */
 173        regs->lp_start = 0x10;
 174        regs->lp_end = 0x80;
 175}
 176
 177/*
 178 * Some archs flush debug and FPU info here
 179 */
 180void flush_thread(void)
 181{
 182}
 183
 184/*
 185 * Free any architecture-specific thread data structures, etc.
 186 */
 187void exit_thread(void)
 188{
 189}
 190
 191int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 192{
 193        return 0;
 194}
 195
 196int elf_check_arch(const struct elf32_hdr *x)
 197{
 198        unsigned int eflags;
 199
 200        if (x->e_machine != EM_ARCOMPACT)
 201                return 0;
 202
 203        eflags = x->e_flags;
 204        if ((eflags & EF_ARC_OSABI_MSK) < EF_ARC_OSABI_CURRENT) {
 205                pr_err("ABI mismatch - you need newer toolchain\n");
 206                force_sigsegv(SIGSEGV, current);
 207                return 0;
 208        }
 209
 210        return 1;
 211}
 212EXPORT_SYMBOL(elf_check_arch);
 213