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