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/sched/task.h>
  15
  16 #include <linux/mm.h>
  17 #include <linux/fs.h>
  18 #include <linux/unistd.h>
  19 #include <linux/ptrace.h>
  20 #include <linux/slab.h>
  21 #include <linux/syscalls.h>
  22 #include <linux/elf.h>
  23 #include <linux/tick.h>
  24
  25 SYSCALL_DEFINE1(arc_settls, void *, user_tls_data_ptr)
  26 {
  27         task_thread_info(current)->thr_ptr = (unsigned int)user_tls_data_ptr;
  28         return 0;
  29 }
  30
  31 /*
  32  * We return the user space TLS data ptr as sys-call return code
  33  * Ideally it should be copy to user.
  34  * However we can cheat by the fact that some sys-calls do return
  35  * absurdly high values
  36  * Since the tls dat aptr is not going to be in range of 0xFFFF_xxxx
  37  * it won't be considered a sys-call error
  38  * and it will be loads better than copy-to-user, which is a definite
  39  * D-TLB Miss
  40  */
  41 SYSCALL_DEFINE0(arc_gettls)
  42 {
  43         return task_thread_info(current)->thr_ptr;
  44 }
  45
  46 SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
  47 {
  48         struct pt_regs *regs = current_pt_regs();
  49         int uval = -EFAULT;
  50
  51         /*
  52          * This is only for old cores lacking LLOCK/SCOND, which by defintion
  53          * can't possibly be SMP. Thus doesn't need to be SMP safe.
  54          * And this also helps reduce the overhead for serializing in
  55          * the UP case
  56          */
  57         WARN_ON_ONCE(IS_ENABLED(CONFIG_SMP));
  58
  59         /* Z indicates to userspace if operation succeded */
  60         regs->status32 &= ~STATUS_Z_MASK;
  61
  62         if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
  63                 return -EFAULT;
  64
  65         preempt_disable();
  66
  67         if (__get_user(uval, uaddr))
  68                 goto done;
  69
  70         if (uval == expected) {
  71                 if (!__put_user(new, uaddr))
  72                         regs->status32 |= STATUS_Z_MASK;
  73         }
  74
  75 done:
  76         preempt_enable();
  77
  78         return uval;
  79 }
  80
  81 void arch_cpu_idle(void)
  82 {
  83         /* sleep, but enable all interrupts before committing */
  84         __asm__ __volatile__(
  85                 "sleep %0       \n"
  86                 :
  87                 :"I"(ISA_SLEEP_ARG)); /* can't be "r" has to be embedded const */
  88 }
  89
  90 asmlinkage void ret_from_fork(void);
  91
  92 /*
  93  * Copy architecture-specific thread state
  94  *
  95  * Layout of Child kernel mode stack as setup at the end of this function is
  96  *
  97  * |     ...        |
  98  * |     ...        |
  99  * |    unused      |
 100  * |                |
 101  * ------------------
 102  * |     r25        |   <==== top of Stack (thread.ksp)
 103  * ~                ~
 104  * |    --to--      |   (CALLEE Regs of kernel mode)
 105  * |     r13        |
 106  * ------------------
 107  * |     fp         |
 108  * |    blink       |   @ret_from_fork
 109  * ------------------
 110  * |                |
 111  * ~                ~
 112  * ~                ~
 113  * |                |
 114  * ------------------
 115  * |     r12        |
 116  * ~                ~
 117  * |    --to--      |   (scratch Regs of user mode)
 118  * |     r0         |
 119  * ------------------
 120  * |      SP        |
 121  * |    orig_r0     |
 122  * |    event/ECR   |
 123  * |    user_r25    |
 124  * ------------------  <===== END of PAGE
 125  */
 126 int copy_thread(unsigned long clone_flags,
 127                 unsigned long usp, unsigned long kthread_arg,
 128                 struct task_struct *p)
 129 {
 130         struct pt_regs *c_regs;        /* child's pt_regs */
 131         unsigned long *childksp;       /* to unwind out of __switch_to() */
 132         struct callee_regs *c_callee;  /* child's callee regs */
 133         struct callee_regs *parent_callee;  /* paren't callee */
 134         struct pt_regs *regs = current_pt_regs();
 135
 136         /* Mark the specific anchors to begin with (see pic above) */
 137         c_regs = task_pt_regs(p);
 138         childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
 139         c_callee = ((struct callee_regs *)childksp) - 1;
 140
 141         /*
 142          * __switch_to() uses thread.ksp to start unwinding stack
 143          * For kernel threads we don't need to create callee regs, the
 144          * stack layout nevertheless needs to remain the same.
 145          * Also, since __switch_to anyways unwinds callee regs, we use
 146          * this to populate kernel thread entry-pt/args into callee regs,
 147          * so that ret_from_kernel_thread() becomes simpler.
 148          */
 149         p->thread.ksp = (unsigned long)c_callee;        /* THREAD_KSP */
 150
 151         /* __switch_to expects FP(0), BLINK(return addr) at top */
 152         childksp[0] = 0;                        /* fp */
 153         childksp[1] = (unsigned long)ret_from_fork; /* blink */
 154
 155         if (unlikely(p->flags & PF_KTHREAD)) {
 156                 memset(c_regs, 0, sizeof(struct pt_regs));
 157
 158                 c_callee->r13 = kthread_arg;
 159                 c_callee->r14 = usp;  /* function */
 160
 161                 return 0;
 162         }
 163
 164         /*--------- User Task Only --------------*/
 165
 166         /* __switch_to expects FP(0), BLINK(return addr) at top of stack */
 167         childksp[0] = 0;                                /* for POP fp */
 168         childksp[1] = (unsigned long)ret_from_fork;     /* for POP blink */
 169
 170         /* Copy parents pt regs on child's kernel mode stack */
 171         *c_regs = *regs;
 172
 173         if (usp)
 174                 c_regs->sp = usp;
 175
 176         c_regs->r0 = 0;         /* fork returns 0 in child */
 177
 178         parent_callee = ((struct callee_regs *)regs) - 1;
 179         *c_callee = *parent_callee;
 180
 181         if (unlikely(clone_flags & CLONE_SETTLS)) {
 182                 /*
 183                  * set task's userland tls data ptr from 4th arg
 184                  * clone C-lib call is difft from clone sys-call
 185                  */
 186                 task_thread_info(p)->thr_ptr = regs->r3;
 187         } else {
 188                 /* Normal fork case: set parent's TLS ptr in child */
 189                 task_thread_info(p)->thr_ptr =
 190                 task_thread_info(current)->thr_ptr;
 191         }
 192
 193         return 0;
 194 }
 195
 196 /*
 197  * Do necessary setup to start up a new user task
 198  */
 199 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long usp)
 200 {
 201         regs->sp = usp;
 202         regs->ret = pc;
 203
 204         /*
 205          * [U]ser Mode bit set
 206          * [L] ZOL loop inhibited to begin with - cleared by a LP insn
 207          * Interrupts enabled
 208          */
 209         regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;
 210
 211         /* bogus seed values for debugging */
 212         regs->lp_start = 0x10;
 213         regs->lp_end = 0x80;
 214 }
 215
 216 /*
 217  * Some archs flush debug and FPU info here
 218  */
 219 void flush_thread(void)
 220 {
 221 }
 222
 223 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 224 {
 225         return 0;
 226 }
 227
 228 int elf_check_arch(const struct elf32_hdr *x)
 229 {
 230         unsigned int eflags;
 231
 232         if (x->e_machine != EM_ARC_INUSE) {
 233                 pr_err("ELF not built for %s ISA\n",
 234                         is_isa_arcompact() ? "ARCompact":"ARCv2");
 235                 return 0;
 236         }
 237
 238         eflags = x->e_flags;
 239         if ((eflags & EF_ARC_OSABI_MSK) != EF_ARC_OSABI_CURRENT) {
 240                 pr_err("ABI mismatch - you need newer toolchain\n");
 241                 force_sigsegv(SIGSEGV, current);
 242                 return 0;
 243         }
 244
 245         return 1;
 246 }
 247 EXPORT_SYMBOL(elf_check_arch);