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         u32 uval;
  51         int ret;
  52
  53         /*
  54          * This is only for old cores lacking LLOCK/SCOND, which by defintion
  55          * can't possibly be SMP. Thus doesn't need to be SMP safe.
  56          * And this also helps reduce the overhead for serializing in
  57          * the UP case
  58          */
  59         WARN_ON_ONCE(IS_ENABLED(CONFIG_SMP));
  60
  61         /* Z indicates to userspace if operation succeded */
  62         regs->status32 &= ~STATUS_Z_MASK;
  63
  64         ret = access_ok(VERIFY_WRITE, uaddr, sizeof(*uaddr));
  65         if (!ret)
  66                  goto fail;
  67
  68 again:
  69         preempt_disable();
  70
  71         ret = __get_user(uval, uaddr);
  72         if (ret)
  73                  goto fault;
  74
  75         if (uval != expected)
  76                  goto out;
  77
  78         ret = __put_user(new, uaddr);
  79         if (ret)
  80                  goto fault;
  81
  82         regs->status32 |= STATUS_Z_MASK;
  83
  84 out:
  85         preempt_enable();
  86         return uval;
  87
  88 fault:
  89         preempt_enable();
  90
  91         if (unlikely(ret != -EFAULT))
  92                  goto fail;
  93
  94         down_read(&current->mm->mmap_sem);
  95         ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
  96                                FAULT_FLAG_WRITE, NULL);
  97         up_read(&current->mm->mmap_sem);
  98
  99         if (likely(!ret))
 100                  goto again;
 101
 102 fail:
 103         force_sig(SIGSEGV, current);
 104         return ret;
 105 }
 106
 107 #ifdef CONFIG_ISA_ARCV2
 108
 109 void arch_cpu_idle(void)
 110 {
 111         /* Re-enable interrupts <= default irq priority before commiting SLEEP */
 112         const unsigned int arg = 0x10 | ARCV2_IRQ_DEF_PRIO;
 113
 114         __asm__ __volatile__(
 115                 "sleep %0       \n"
 116                 :
 117                 :"I"(arg)); /* can't be "r" has to be embedded const */
 118 }
 119
 120 #elif defined(CONFIG_EZNPS_MTM_EXT)     /* ARC700 variant in NPS */
 121
 122 void arch_cpu_idle(void)
 123 {
 124         /* only the calling HW thread needs to sleep */
 125         __asm__ __volatile__(
 126                 ".word %0       \n"
 127                 :
 128                 :"i"(CTOP_INST_HWSCHD_WFT_IE12));
 129 }
 130
 131 #else   /* ARC700 */
 132
 133 void arch_cpu_idle(void)
 134 {
 135         /* sleep, but enable both set E1/E2 (levels of interrutps) before committing */
 136         __asm__ __volatile__("sleep 0x3 \n");
 137 }
 138
 139 #endif
 140
 141 asmlinkage void ret_from_fork(void);
 142
 143 /*
 144  * Copy architecture-specific thread state
 145  *
 146  * Layout of Child kernel mode stack as setup at the end of this function is
 147  *
 148  * |     ...        |
 149  * |     ...        |
 150  * |    unused      |
 151  * |                |
 152  * ------------------
 153  * |     r25        |   <==== top of Stack (thread.ksp)
 154  * ~                ~
 155  * |    --to--      |   (CALLEE Regs of kernel mode)
 156  * |     r13        |
 157  * ------------------
 158  * |     fp         |
 159  * |    blink       |   @ret_from_fork
 160  * ------------------
 161  * |                |
 162  * ~                ~
 163  * ~                ~
 164  * |                |
 165  * ------------------
 166  * |     r12        |
 167  * ~                ~
 168  * |    --to--      |   (scratch Regs of user mode)
 169  * |     r0         |
 170  * ------------------
 171  * |      SP        |
 172  * |    orig_r0     |
 173  * |    event/ECR   |
 174  * |    user_r25    |
 175  * ------------------  <===== END of PAGE
 176  */
 177 int copy_thread(unsigned long clone_flags,
 178                 unsigned long usp, unsigned long kthread_arg,
 179                 struct task_struct *p)
 180 {
 181         struct pt_regs *c_regs;        /* child's pt_regs */
 182         unsigned long *childksp;       /* to unwind out of __switch_to() */
 183         struct callee_regs *c_callee;  /* child's callee regs */
 184         struct callee_regs *parent_callee;  /* paren't callee */
 185         struct pt_regs *regs = current_pt_regs();
 186
 187         /* Mark the specific anchors to begin with (see pic above) */
 188         c_regs = task_pt_regs(p);
 189         childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
 190         c_callee = ((struct callee_regs *)childksp) - 1;
 191
 192         /*
 193          * __switch_to() uses thread.ksp to start unwinding stack
 194          * For kernel threads we don't need to create callee regs, the
 195          * stack layout nevertheless needs to remain the same.
 196          * Also, since __switch_to anyways unwinds callee regs, we use
 197          * this to populate kernel thread entry-pt/args into callee regs,
 198          * so that ret_from_kernel_thread() becomes simpler.
 199          */
 200         p->thread.ksp = (unsigned long)c_callee;        /* THREAD_KSP */
 201
 202         /* __switch_to expects FP(0), BLINK(return addr) at top */
 203         childksp[0] = 0;                        /* fp */
 204         childksp[1] = (unsigned long)ret_from_fork; /* blink */
 205
 206         if (unlikely(p->flags & PF_KTHREAD)) {
 207                 memset(c_regs, 0, sizeof(struct pt_regs));
 208
 209                 c_callee->r13 = kthread_arg;
 210                 c_callee->r14 = usp;  /* function */
 211
 212                 return 0;
 213         }
 214
 215         /*--------- User Task Only --------------*/
 216
 217         /* __switch_to expects FP(0), BLINK(return addr) at top of stack */
 218         childksp[0] = 0;                                /* for POP fp */
 219         childksp[1] = (unsigned long)ret_from_fork;     /* for POP blink */
 220
 221         /* Copy parents pt regs on child's kernel mode stack */
 222         *c_regs = *regs;
 223
 224         if (usp)
 225                 c_regs->sp = usp;
 226
 227         c_regs->r0 = 0;         /* fork returns 0 in child */
 228
 229         parent_callee = ((struct callee_regs *)regs) - 1;
 230         *c_callee = *parent_callee;
 231
 232         if (unlikely(clone_flags & CLONE_SETTLS)) {
 233                 /*
 234                  * set task's userland tls data ptr from 4th arg
 235                  * clone C-lib call is difft from clone sys-call
 236                  */
 237                 task_thread_info(p)->thr_ptr = regs->r3;
 238         } else {
 239                 /* Normal fork case: set parent's TLS ptr in child */
 240                 task_thread_info(p)->thr_ptr =
 241                 task_thread_info(current)->thr_ptr;
 242         }
 243
 244
 245         /*
 246          * setup usermode thread pointer #1:
 247          * when child is picked by scheduler, __switch_to() uses @c_callee to
 248          * populate usermode callee regs: this works (despite being in a kernel
 249          * function) since special return path for child @ret_from_fork()
 250          * ensures those regs are not clobbered all the way to RTIE to usermode
 251          */
 252         c_callee->r25 = task_thread_info(p)->thr_ptr;
 253
 254 #ifdef CONFIG_ARC_CURR_IN_REG
 255         /*
 256          * setup usermode thread pointer #2:
 257          * however for this special use of r25 in kernel, __switch_to() sets
 258          * r25 for kernel needs and only in the final return path is usermode
 259          * r25 setup, from pt_regs->user_r25. So set that up as well
 260          */
 261         c_regs->user_r25 = c_callee->r25;
 262 #endif
 263
 264         return 0;
 265 }
 266
 267 /*
 268  * Do necessary setup to start up a new user task
 269  */
 270 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long usp)
 271 {
 272         regs->sp = usp;
 273         regs->ret = pc;
 274
 275         /*
 276          * [U]ser Mode bit set
 277          * [L] ZOL loop inhibited to begin with - cleared by a LP insn
 278          * Interrupts enabled
 279          */
 280         regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;
 281
 282 #ifdef CONFIG_EZNPS_MTM_EXT
 283         regs->eflags = 0;
 284 #endif
 285
 286         /* bogus seed values for debugging */
 287         regs->lp_start = 0x10;
 288         regs->lp_end = 0x80;
 289 }
 290
 291 /*
 292  * Some archs flush debug and FPU info here
 293  */
 294 void flush_thread(void)
 295 {
 296 }
 297
 298 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 299 {
 300         return 0;
 301 }
 302
 303 int elf_check_arch(const struct elf32_hdr *x)
 304 {
 305         unsigned int eflags;
 306
 307         if (x->e_machine != EM_ARC_INUSE) {
 308                 pr_err("ELF not built for %s ISA\n",
 309                         is_isa_arcompact() ? "ARCompact":"ARCv2");
 310                 return 0;
 311         }
 312
 313         eflags = x->e_flags;
 314         if ((eflags & EF_ARC_OSABI_MSK) != EF_ARC_OSABI_CURRENT) {
 315                 pr_err("ABI mismatch - you need newer toolchain\n");
 316                 force_sigsegv(SIGSEGV, current);
 317                 return 0;
 318         }
 319
 320         return 1;
 321 }
 322 EXPORT_SYMBOL(elf_check_arch);