linux/arch/arc/kernel/process.c
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   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
  25SYSCALL_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 */
  41SYSCALL_DEFINE0(arc_gettls)
  42{
  43        return task_thread_info(current)->thr_ptr;
  44}
  45
  46SYSCALL_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 definition
  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 succeeded */
  61        regs->status32 &= ~STATUS_Z_MASK;
  62
  63        ret = access_ok(uaddr, sizeof(*uaddr));
  64        if (!ret)
  65                 goto fail;
  66
  67again:
  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
  83out:
  84        preempt_enable();
  85        return uval;
  86
  87fault:
  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
 101fail:
 102        force_sig(SIGSEGV);
 103        return ret;
 104}
 105
 106#ifdef CONFIG_ISA_ARCV2
 107
 108void arch_cpu_idle(void)
 109{
 110        /* Re-enable interrupts <= default irq priority before committing 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
 121void arch_cpu_idle(void)
 122{
 123        /* sleep, but enable both set E1/E2 (levels of interrupts) before committing */
 124        __asm__ __volatile__("sleep 0x3 \n");
 125}
 126
 127#endif
 128
 129asmlinkage 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 */
 165int 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 | PF_IO_WORKER))) {
 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 */
 258void 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 */
 280void flush_thread(void)
 281{
 282}
 283
 284int 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}
 303EXPORT_SYMBOL(elf_check_arch);
 304