arch/arc/kernel/process.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   4  *
   5  * Amit Bhor, Kanika Nema: Codito Technologies 2004
   6  */
   7
   8 #include <linux/errno.h>
   9 #include <linux/module.h>
  10 #include <linux/sched.h>
  11 #include <linux/sched/task.h>
  12 #include <linux/sched/task_stack.h>
  13
  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 #include <asm/fpu.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         u32 uval;
  50         int ret;
  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         ret = access_ok(uaddr, sizeof(*uaddr));
  64         if (!ret)
  65                  goto fail;
  66
  67 again:
  68         preempt_disable();
  69
  70         ret = __get_user(uval, uaddr);
  71         if (ret)
  72                  goto fault;
  73
  74         if (uval != expected)
  75                  goto out;
  76
  77         ret = __put_user(new, uaddr);
  78         if (ret)
  79                  goto fault;
  80
  81         regs->status32 |= STATUS_Z_MASK;
  82
  83 out:
  84         preempt_enable();
  85         return uval;
  86
  87 fault:
  88         preempt_enable();
  89
  90         if (unlikely(ret != -EFAULT))
  91                  goto fail;
  92
  93         mmap_read_lock(current->mm);
  94         ret = fixup_user_fault(current->mm, (unsigned long) uaddr,
  95                                FAULT_FLAG_WRITE, NULL);
  96         mmap_read_unlock(current->mm);
  97
  98         if (likely(!ret))
  99                  goto again;
 100
 101 fail:
 102         force_sig(SIGSEGV);
 103         return ret;
 104 }
 105
 106 #ifdef CONFIG_ISA_ARCV2
 107
 108 void arch_cpu_idle(void)
 109 {
 110         /* Re-enable interrupts <= default irq priority before commiting SLEEP */
 111         const unsigned int arg = 0x10 | ARCV2_IRQ_DEF_PRIO;
 112
 113         __asm__ __volatile__(
 114                 "sleep %0       \n"
 115                 :
 116                 :"I"(arg)); /* can't be "r" has to be embedded const */
 117 }
 118
 119 #else   /* ARC700 */
 120
 121 void arch_cpu_idle(void)
 122 {
 123         /* sleep, but enable both set E1/E2 (levels of interrutps) before committing */
 124         __asm__ __volatile__("sleep 0x3 \n");
 125 }
 126
 127 #endif
 128
 129 asmlinkage void ret_from_fork(void);
 130
 131 /*
 132  * Copy architecture-specific thread state
 133  *
 134  * Layout of Child kernel mode stack as setup at the end of this function is
 135  *
 136  * |     ...        |
 137  * |     ...        |
 138  * |    unused      |
 139  * |                |
 140  * ------------------
 141  * |     r25        |   <==== top of Stack (thread.ksp)
 142  * ~                ~
 143  * |    --to--      |   (CALLEE Regs of kernel mode)
 144  * |     r13        |
 145  * ------------------
 146  * |     fp         |
 147  * |    blink       |   @ret_from_fork
 148  * ------------------
 149  * |                |
 150  * ~                ~
 151  * ~                ~
 152  * |                |
 153  * ------------------
 154  * |     r12        |
 155  * ~                ~
 156  * |    --to--      |   (scratch Regs of user mode)
 157  * |     r0         |
 158  * ------------------
 159  * |      SP        |
 160  * |    orig_r0     |
 161  * |    event/ECR   |
 162  * |    user_r25    |
 163  * ------------------  <===== END of PAGE
 164  */
 165 int copy_thread(unsigned long clone_flags, unsigned long usp,
 166                 unsigned long kthread_arg, struct task_struct *p,
 167                 unsigned long tls)
 168 {
 169         struct pt_regs *c_regs;        /* child's pt_regs */
 170         unsigned long *childksp;       /* to unwind out of __switch_to() */
 171         struct callee_regs *c_callee;  /* child's callee regs */
 172         struct callee_regs *parent_callee;  /* paren't callee */
 173         struct pt_regs *regs = current_pt_regs();
 174
 175         /* Mark the specific anchors to begin with (see pic above) */
 176         c_regs = task_pt_regs(p);
 177         childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
 178         c_callee = ((struct callee_regs *)childksp) - 1;
 179
 180         /*
 181          * __switch_to() uses thread.ksp to start unwinding stack
 182          * For kernel threads we don't need to create callee regs, the
 183          * stack layout nevertheless needs to remain the same.
 184          * Also, since __switch_to anyways unwinds callee regs, we use
 185          * this to populate kernel thread entry-pt/args into callee regs,
 186          * so that ret_from_kernel_thread() becomes simpler.
 187          */
 188         p->thread.ksp = (unsigned long)c_callee;        /* THREAD_KSP */
 189
 190         /* __switch_to expects FP(0), BLINK(return addr) at top */
 191         childksp[0] = 0;                        /* fp */
 192         childksp[1] = (unsigned long)ret_from_fork; /* blink */
 193
 194         if (unlikely(p->flags & PF_KTHREAD)) {
 195                 memset(c_regs, 0, sizeof(struct pt_regs));
 196
 197                 c_callee->r13 = kthread_arg;
 198                 c_callee->r14 = usp;  /* function */
 199
 200                 return 0;
 201         }
 202
 203         /*--------- User Task Only --------------*/
 204
 205         /* __switch_to expects FP(0), BLINK(return addr) at top of stack */
 206         childksp[0] = 0;                                /* for POP fp */
 207         childksp[1] = (unsigned long)ret_from_fork;     /* for POP blink */
 208
 209         /* Copy parents pt regs on child's kernel mode stack */
 210         *c_regs = *regs;
 211
 212         if (usp)
 213                 c_regs->sp = usp;
 214
 215         c_regs->r0 = 0;         /* fork returns 0 in child */
 216
 217         parent_callee = ((struct callee_regs *)regs) - 1;
 218         *c_callee = *parent_callee;
 219
 220         if (unlikely(clone_flags & CLONE_SETTLS)) {
 221                 /*
 222                  * set task's userland tls data ptr from 4th arg
 223                  * clone C-lib call is difft from clone sys-call
 224                  */
 225                 task_thread_info(p)->thr_ptr = tls;
 226         } else {
 227                 /* Normal fork case: set parent's TLS ptr in child */
 228                 task_thread_info(p)->thr_ptr =
 229                 task_thread_info(current)->thr_ptr;
 230         }
 231
 232
 233         /*
 234          * setup usermode thread pointer #1:
 235          * when child is picked by scheduler, __switch_to() uses @c_callee to
 236          * populate usermode callee regs: this works (despite being in a kernel
 237          * function) since special return path for child @ret_from_fork()
 238          * ensures those regs are not clobbered all the way to RTIE to usermode
 239          */
 240         c_callee->r25 = task_thread_info(p)->thr_ptr;
 241
 242 #ifdef CONFIG_ARC_CURR_IN_REG
 243         /*
 244          * setup usermode thread pointer #2:
 245          * however for this special use of r25 in kernel, __switch_to() sets
 246          * r25 for kernel needs and only in the final return path is usermode
 247          * r25 setup, from pt_regs->user_r25. So set that up as well
 248          */
 249         c_regs->user_r25 = c_callee->r25;
 250 #endif
 251
 252         return 0;
 253 }
 254
 255 /*
 256  * Do necessary setup to start up a new user task
 257  */
 258 void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long usp)
 259 {
 260         regs->sp = usp;
 261         regs->ret = pc;
 262
 263         /*
 264          * [U]ser Mode bit set
 265          * [L] ZOL loop inhibited to begin with - cleared by a LP insn
 266          * Interrupts enabled
 267          */
 268         regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;
 269
 270         fpu_init_task(regs);
 271
 272         /* bogus seed values for debugging */
 273         regs->lp_start = 0x10;
 274         regs->lp_end = 0x80;
 275 }
 276
 277 /*
 278  * Some archs flush debug and FPU info here
 279  */
 280 void flush_thread(void)
 281 {
 282 }
 283
 284 int elf_check_arch(const struct elf32_hdr *x)
 285 {
 286         unsigned int eflags;
 287
 288         if (x->e_machine != EM_ARC_INUSE) {
 289                 pr_err("ELF not built for %s ISA\n",
 290                         is_isa_arcompact() ? "ARCompact":"ARCv2");
 291                 return 0;
 292         }
 293
 294         eflags = x->e_flags;
 295         if ((eflags & EF_ARC_OSABI_MSK) != EF_ARC_OSABI_CURRENT) {
 296                 pr_err("ABI mismatch - you need newer toolchain\n");
 297                 force_sigsegv(SIGSEGV);
 298                 return 0;
 299         }
 300
 301         return 1;
 302 }
 303 EXPORT_SYMBOL(elf_check_arch);