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 /*
  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  */
  86 int 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  */
 159 void 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  */
 180 void flush_thread(void)
 181 {
 182 }
 183
 184 /*
 185  * Free any architecture-specific thread data structures, etc.
 186  */
 187 void exit_thread(void)
 188 {
 189 }
 190
 191 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 192 {
 193         return 0;
 194 }
 195
 196 int 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 }
 212 EXPORT_SYMBOL(elf_check_arch);