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 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         u32 uval;
  48         int ret;
  49
  50         /*
  51          * This is only for old cores lacking LLOCK/SCOND, which by defintion
  52          * can't possibly be SMP. Thus doesn't need to be SMP safe.
  53          * And this also helps reduce the overhead for serializing in
  54          * the UP case
  55          */
  56         WARN_ON_ONCE(IS_ENABLED(CONFIG_SMP));
  57
  58         /* Z indicates to userspace if operation succeded */
  59         regs->status32 &= ~STATUS_Z_MASK;
  60
  61         ret = access_ok(uaddr, sizeof(*uaddr));
  62         if (!ret)
  63                  goto fail;
  64
  65 again:
  66         preempt_disable();
  67
  68         ret = __get_user(uval, uaddr);
  69         if (ret)
  70                  goto fault;
  71
  72         if (uval != expected)
  73                  goto out;
  74
  75         ret = __put_user(new, uaddr);
  76         if (ret)
  77                  goto fault;
  78
  79         regs->status32 |= STATUS_Z_MASK;
  80
  81 out:
  82         preempt_enable();
  83         return uval;
  84
  85 fault:
  86         preempt_enable();
  87
  88         if (unlikely(ret != -EFAULT))
  89                  goto fail;
  90
  91         down_read(&current->mm->mmap_sem);
  92         ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
  93                                FAULT_FLAG_WRITE, NULL);
  94         up_read(&current->mm->mmap_sem);
  95
  96         if (likely(!ret))
  97                  goto again;
  98
  99 fail:
 100         force_sig(SIGSEGV);
 101         return ret;
 102 }
 103
 104 #ifdef CONFIG_ISA_ARCV2
 105
 106 void arch_cpu_idle(void)
 107 {
 108         /* Re-enable interrupts <= default irq priority before commiting SLEEP */
 109         const unsigned int arg = 0x10 | ARCV2_IRQ_DEF_PRIO;
 110
 111         __asm__ __volatile__(
 112                 "sleep %0       \n"
 113                 :
 114                 :"I"(arg)); /* can't be "r" has to be embedded const */
 115 }
 116
 117 #elif defined(CONFIG_EZNPS_MTM_EXT)     /* ARC700 variant in NPS */
 118
 119 void arch_cpu_idle(void)
 120 {
 121         /* only the calling HW thread needs to sleep */
 122         __asm__ __volatile__(
 123                 ".word %0       \n"
 124                 :
 125                 :"i"(CTOP_INST_HWSCHD_WFT_IE12));
 126 }
 127
 128 #else   /* ARC700 */
 129
 130 void arch_cpu_idle(void)
 131 {
 132         /* sleep, but enable both set E1/E2 (levels of interrutps) before committing */
 133         __asm__ __volatile__("sleep 0x3 \n");
 134 }
 135
 136 #endif
 137
 138 asmlinkage void ret_from_fork(void);
 139
 140 /*
 141  * Copy architecture-specific thread state
 142  *
 143  * Layout of Child kernel mode stack as setup at the end of this function is
 144  *
 145  * |     ...        |
 146  * |     ...        |
 147  * |    unused      |
 148  * |                |
 149  * ------------------
 150  * |     r25        |   <==== top of Stack (thread.ksp)
 151  * ~                ~
 152  * |    --to--      |   (CALLEE Regs of kernel mode)
 153  * |     r13        |
 154  * ------------------
 155  * |     fp         |
 156  * |    blink       |   @ret_from_fork
 157  * ------------------
 158  * |                |
 159  * ~                ~
 160  * ~                ~
 161  * |                |
 162  * ------------------
 163  * |     r12        |
 164  * ~                ~
 165  * |    --to--      |   (scratch Regs of user mode)
 166  * |     r0         |
 167  * ------------------
 168  * |      SP        |
 169  * |    orig_r0     |
 170  * |    event/ECR   |
 171  * |    user_r25    |
 172  * ------------------  <===== END of PAGE
 173  */
 174 int copy_thread(unsigned long clone_flags,
 175                 unsigned long usp, unsigned long kthread_arg,
 176                 struct task_struct *p)
 177 {
 178         struct pt_regs *c_regs;        /* child's pt_regs */
 179         unsigned long *childksp;       /* to unwind out of __switch_to() */
 180         struct callee_regs *c_callee;  /* child's callee regs */
 181         struct callee_regs *parent_callee;  /* paren't callee */
 182         struct pt_regs *regs = current_pt_regs();
 183
 184         /* Mark the specific anchors to begin with (see pic above) */
 185         c_regs = task_pt_regs(p);
 186         childksp = (unsigned long *)c_regs - 2;  /* 2 words for FP/BLINK */
 187         c_callee = ((struct callee_regs *)childksp) - 1;
 188
 189         /*
 190          * __switch_to() uses thread.ksp to start unwinding stack
 191          * For kernel threads we don't need to create callee regs, the
 192          * stack layout nevertheless needs to remain the same.
 193          * Also, since __switch_to anyways unwinds callee regs, we use
 194          * this to populate kernel thread entry-pt/args into callee regs,
 195          * so that ret_from_kernel_thread() becomes simpler.
 196          */
 197         p->thread.ksp = (unsigned long)c_callee;        /* THREAD_KSP */
 198
 199         /* __switch_to expects FP(0), BLINK(return addr) at top */
 200         childksp[0] = 0;                        /* fp */
 201         childksp[1] = (unsigned long)ret_from_fork; /* blink */
 202
 203         if (unlikely(p->flags & PF_KTHREAD)) {
 204                 memset(c_regs, 0, sizeof(struct pt_regs));
 205
 206                 c_callee->r13 = kthread_arg;
 207                 c_callee->r14 = usp;  /* function */
 208
 209                 return 0;
 210         }
 211
 212         /*--------- User Task Only --------------*/
 213
 214         /* __switch_to expects FP(0), BLINK(return addr) at top of stack */
 215         childksp[0] = 0;                                /* for POP fp */
 216         childksp[1] = (unsigned long)ret_from_fork;     /* for POP blink */
 217
 218         /* Copy parents pt regs on child's kernel mode stack */
 219         *c_regs = *regs;
 220
 221         if (usp)
 222                 c_regs->sp = usp;
 223
 224         c_regs->r0 = 0;         /* fork returns 0 in child */
 225
 226         parent_callee = ((struct callee_regs *)regs) - 1;
 227         *c_callee = *parent_callee;
 228
 229         if (unlikely(clone_flags & CLONE_SETTLS)) {
 230                 /*
 231                  * set task's userland tls data ptr from 4th arg
 232                  * clone C-lib call is difft from clone sys-call
 233                  */
 234                 task_thread_info(p)->thr_ptr = regs->r3;
 235         } else {
 236                 /* Normal fork case: set parent's TLS ptr in child */
 237                 task_thread_info(p)->thr_ptr =
 238                 task_thread_info(current)->thr_ptr;
 239         }
 240
 241
 242         /*
 243          * setup usermode thread pointer #1:
 244          * when child is picked by scheduler, __switch_to() uses @c_callee to
 245          * populate usermode callee regs: this works (despite being in a kernel
 246          * function) since special return path for child @ret_from_fork()
 247          * ensures those regs are not clobbered all the way to RTIE to usermode
 248          */
 249         c_callee->r25 = task_thread_info(p)->thr_ptr;
 250
 251 #ifdef CONFIG_ARC_CURR_IN_REG
 252         /*
 253          * setup usermode thread pointer #2:
 254          * however for this special use of r25 in kernel, __switch_to() sets
 255          * r25 for kernel needs and only in the final return path is usermode
 256          * r25 setup, from pt_regs->user_r25. So set that up as well
 257          */
 258         c_regs->user_r25 = c_callee->r25;
 259 #endif
 260
 261         return 0;
 262 }
 263
 264 /*
 265  * Do necessary setup to start up a new user task
 266  */
 267 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long usp)
 268 {
 269         regs->sp = usp;
 270         regs->ret = pc;
 271
 272         /*
 273          * [U]ser Mode bit set
 274          * [L] ZOL loop inhibited to begin with - cleared by a LP insn
 275          * Interrupts enabled
 276          */
 277         regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;
 278
 279 #ifdef CONFIG_EZNPS_MTM_EXT
 280         regs->eflags = 0;
 281 #endif
 282
 283         /* bogus seed values for debugging */
 284         regs->lp_start = 0x10;
 285         regs->lp_end = 0x80;
 286 }
 287
 288 /*
 289  * Some archs flush debug and FPU info here
 290  */
 291 void flush_thread(void)
 292 {
 293 }
 294
 295 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 296 {
 297         return 0;
 298 }
 299
 300 int elf_check_arch(const struct elf32_hdr *x)
 301 {
 302         unsigned int eflags;
 303
 304         if (x->e_machine != EM_ARC_INUSE) {
 305                 pr_err("ELF not built for %s ISA\n",
 306                         is_isa_arcompact() ? "ARCompact":"ARCv2");
 307                 return 0;
 308         }
 309
 310         eflags = x->e_flags;
 311         if ((eflags & EF_ARC_OSABI_MSK) != EF_ARC_OSABI_CURRENT) {
 312                 pr_err("ABI mismatch - you need newer toolchain\n");
 313                 force_sigsegv(SIGSEGV);
 314                 return 0;
 315         }
 316
 317         return 1;
 318 }
 319 EXPORT_SYMBOL(elf_check_arch);