arch/arm64/kernel/sys_compat.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Based on arch/arm/kernel/sys_arm.c
   4  *
   5  * Copyright (C) People who wrote linux/arch/i386/kernel/sys_i386.c
   6  * Copyright (C) 1995, 1996 Russell King.
   7  * Copyright (C) 2012 ARM Ltd.
   8  */
   9
  10 #include <linux/compat.h>
  11 #include <linux/cpufeature.h>
  12 #include <linux/sched.h>
  13 #include <linux/sched/signal.h>
  14 #include <linux/slab.h>
  15 #include <linux/syscalls.h>
  16 #include <linux/uaccess.h>
  17
  18 #include <asm/cacheflush.h>
  19 #include <asm/system_misc.h>
  20 #include <asm/tlbflush.h>
  21 #include <asm/unistd.h>
  22
  23 static long
  24 __do_compat_cache_op(unsigned long start, unsigned long end)
  25 {
  26         long ret;
  27
  28         do {
  29                 unsigned long chunk = min(PAGE_SIZE, end - start);
  30
  31                 if (fatal_signal_pending(current))
  32                         return 0;
  33
  34                 if (cpus_have_final_cap(ARM64_WORKAROUND_1542419)) {
  35                         /*
  36                          * The workaround requires an inner-shareable tlbi.
  37                          * We pick the reserved-ASID to minimise the impact.
  38                          */
  39                         __tlbi(aside1is, __TLBI_VADDR(0, 0));
  40                         dsb(ish);
  41                 }
  42
  43                 ret = caches_clean_inval_user_pou(start, start + chunk);
  44                 if (ret)
  45                         return ret;
  46
  47                 cond_resched();
  48                 start += chunk;
  49         } while (start < end);
  50
  51         return 0;
  52 }
  53
  54 static inline long
  55 do_compat_cache_op(unsigned long start, unsigned long end, int flags)
  56 {
  57         if (end < start || flags)
  58                 return -EINVAL;
  59
  60         if (!access_ok((const void __user *)start, end - start))
  61                 return -EFAULT;
  62
  63         return __do_compat_cache_op(start, end);
  64 }
  65 /*
  66  * Handle all unrecognised system calls.
  67  */
  68 long compat_arm_syscall(struct pt_regs *regs, int scno)
  69 {
  70         unsigned long addr;
  71
  72         switch (scno) {
  73         /*
  74          * Flush a region from virtual address 'r0' to virtual address 'r1'
  75          * _exclusive_.  There is no alignment requirement on either address;
  76          * user space does not need to know the hardware cache layout.
  77          *
  78          * r2 contains flags.  It should ALWAYS be passed as ZERO until it
  79          * is defined to be something else.  For now we ignore it, but may
  80          * the fires of hell burn in your belly if you break this rule. ;)
  81          *
  82          * (at a later date, we may want to allow this call to not flush
  83          * various aspects of the cache.  Passing '0' will guarantee that
  84          * everything necessary gets flushed to maintain consistency in
  85          * the specified region).
  86          */
  87         case __ARM_NR_compat_cacheflush:
  88                 return do_compat_cache_op(regs->regs[0], regs->regs[1], regs->regs[2]);
  89
  90         case __ARM_NR_compat_set_tls:
  91                 current->thread.uw.tp_value = regs->regs[0];
  92
  93                 /*
  94                  * Protect against register corruption from context switch.
  95                  * See comment in tls_thread_flush.
  96                  */
  97                 barrier();
  98                 write_sysreg(regs->regs[0], tpidrro_el0);
  99                 return 0;
 100
 101         default:
 102                 /*
 103                  * Calls 0xf0xxx..0xf07ff are defined to return -ENOSYS
 104                  * if not implemented, rather than raising SIGILL. This
 105                  * way the calling program can gracefully determine whether
 106                  * a feature is supported.
 107                  */
 108                 if (scno < __ARM_NR_COMPAT_END)
 109                         return -ENOSYS;
 110                 break;
 111         }
 112
 113         addr = instruction_pointer(regs) - (compat_thumb_mode(regs) ? 2 : 4);
 114
 115         arm64_notify_die("Oops - bad compat syscall(2)", regs,
 116                          SIGILL, ILL_ILLTRP, addr, 0);
 117         return 0;
 118 }