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