arch/loongarch/mm/fault.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
   4  *
   5  * Derived from MIPS:
   6  * Copyright (C) 1995 - 2000 by Ralf Baechle
   7  */
   8 #include <linux/context_tracking.h>
   9 #include <linux/signal.h>
  10 #include <linux/sched.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/kernel.h>
  13 #include <linux/entry-common.h>
  14 #include <linux/errno.h>
  15 #include <linux/string.h>
  16 #include <linux/types.h>
  17 #include <linux/ptrace.h>
  18 #include <linux/ratelimit.h>
  19 #include <linux/mman.h>
  20 #include <linux/mm.h>
  21 #include <linux/smp.h>
  22 #include <linux/kdebug.h>
  23 #include <linux/perf_event.h>
  24 #include <linux/uaccess.h>
  25 #include <linux/kfence.h>
  26
  27 #include <asm/branch.h>
  28 #include <asm/exception.h>
  29 #include <asm/mmu_context.h>
  30 #include <asm/ptrace.h>
  31
  32 int show_unhandled_signals = 1;
  33
  34 static void __kprobes no_context(struct pt_regs *regs,
  35                         unsigned long write, unsigned long address)
  36 {
  37         const int field = sizeof(unsigned long) * 2;
  38
  39         /* Are we prepared to handle this kernel fault?  */
  40         if (fixup_exception(regs))
  41                 return;
  42
  43         if (kfence_handle_page_fault(address, write, regs))
  44                 return;
  45
  46         /*
  47          * Oops. The kernel tried to access some bad page. We'll have to
  48          * terminate things with extreme prejudice.
  49          */
  50         bust_spinlocks(1);
  51
  52         pr_alert("CPU %d Unable to handle kernel paging request at "
  53                "virtual address %0*lx, era == %0*lx, ra == %0*lx\n",
  54                raw_smp_processor_id(), field, address, field, regs->csr_era,
  55                field,  regs->regs[1]);
  56         die("Oops", regs);
  57 }
  58
  59 static void __kprobes do_out_of_memory(struct pt_regs *regs,
  60                         unsigned long write, unsigned long address)
  61 {
  62         /*
  63          * We ran out of memory, call the OOM killer, and return the userspace
  64          * (which will retry the fault, or kill us if we got oom-killed).
  65          */
  66         if (!user_mode(regs)) {
  67                 no_context(regs, write, address);
  68                 return;
  69         }
  70         pagefault_out_of_memory();
  71 }
  72
  73 static void __kprobes do_sigbus(struct pt_regs *regs,
  74                 unsigned long write, unsigned long address, int si_code)
  75 {
  76         /* Kernel mode? Handle exceptions or die */
  77         if (!user_mode(regs)) {
  78                 no_context(regs, write, address);
  79                 return;
  80         }
  81
  82         /*
  83          * Send a sigbus, regardless of whether we were in kernel
  84          * or user mode.
  85          */
  86         current->thread.csr_badvaddr = address;
  87         current->thread.trap_nr = read_csr_excode();
  88         force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
  89 }
  90
  91 static void __kprobes do_sigsegv(struct pt_regs *regs,
  92                 unsigned long write, unsigned long address, int si_code)
  93 {
  94         const int field = sizeof(unsigned long) * 2;
  95         static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
  96
  97         /* Kernel mode? Handle exceptions or die */
  98         if (!user_mode(regs)) {
  99                 no_context(regs, write, address);
 100                 return;
 101         }
 102
 103         /* User mode accesses just cause a SIGSEGV */
 104         current->thread.csr_badvaddr = address;
 105         if (!write)
 106                 current->thread.error_code = 1;
 107         else
 108                 current->thread.error_code = 2;
 109         current->thread.trap_nr = read_csr_excode();
 110
 111         if (show_unhandled_signals &&
 112             unhandled_signal(current, SIGSEGV) && __ratelimit(&ratelimit_state)) {
 113                 pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n",
 114                         current->comm,
 115                         write ? "write access to" : "read access from",
 116                         field, address);
 117                 pr_info("era = %0*lx in", field,
 118                         (unsigned long) regs->csr_era);
 119                 print_vma_addr(KERN_CONT " ", regs->csr_era);
 120                 pr_cont("\n");
 121                 pr_info("ra  = %0*lx in", field,
 122                         (unsigned long) regs->regs[1]);
 123                 print_vma_addr(KERN_CONT " ", regs->regs[1]);
 124                 pr_cont("\n");
 125         }
 126         force_sig_fault(SIGSEGV, si_code, (void __user *)address);
 127 }
 128
 129 /*
 130  * This routine handles page faults.  It determines the address,
 131  * and the problem, and then passes it off to one of the appropriate
 132  * routines.
 133  */
 134 static void __kprobes __do_page_fault(struct pt_regs *regs,
 135                         unsigned long write, unsigned long address)
 136 {
 137         int si_code = SEGV_MAPERR;
 138         unsigned int flags = FAULT_FLAG_DEFAULT;
 139         struct task_struct *tsk = current;
 140         struct mm_struct *mm = tsk->mm;
 141         struct vm_area_struct *vma = NULL;
 142         vm_fault_t fault;
 143
 144         if (kprobe_page_fault(regs, current->thread.trap_nr))
 145                 return;
 146
 147         /*
 148          * We fault-in kernel-space virtual memory on-demand. The
 149          * 'reference' page table is init_mm.pgd.
 150          *
 151          * NOTE! We MUST NOT take any locks for this case. We may
 152          * be in an interrupt or a critical region, and should
 153          * only copy the information from the master page table,
 154          * nothing more.
 155          */
 156         if (address & __UA_LIMIT) {
 157                 if (!user_mode(regs))
 158                         no_context(regs, write, address);
 159                 else
 160                         do_sigsegv(regs, write, address, si_code);
 161                 return;
 162         }
 163
 164         /*
 165          * If we're in an interrupt or have no user
 166          * context, we must not take the fault..
 167          */
 168         if (faulthandler_disabled() || !mm) {
 169                 do_sigsegv(regs, write, address, si_code);
 170                 return;
 171         }
 172
 173         if (user_mode(regs))
 174                 flags |= FAULT_FLAG_USER;
 175
 176         perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 177 retry:
 178         vma = lock_mm_and_find_vma(mm, address, regs);
 179         if (unlikely(!vma))
 180                 goto bad_area_nosemaphore;
 181         goto good_area;
 182
 183 /*
 184  * Something tried to access memory that isn't in our memory map..
 185  * Fix it, but check if it's kernel or user first..
 186  */
 187 bad_area:
 188         mmap_read_unlock(mm);
 189 bad_area_nosemaphore:
 190         do_sigsegv(regs, write, address, si_code);
 191         return;
 192
 193 /*
 194  * Ok, we have a good vm_area for this memory access, so
 195  * we can handle it..
 196  */
 197 good_area:
 198         si_code = SEGV_ACCERR;
 199
 200         if (write) {
 201                 flags |= FAULT_FLAG_WRITE;
 202                 if (!(vma->vm_flags & VM_WRITE))
 203                         goto bad_area;
 204         } else {
 205                 if (!(vma->vm_flags & VM_READ) && address != exception_era(regs))
 206                         goto bad_area;
 207                 if (!(vma->vm_flags & VM_EXEC) && address == exception_era(regs))
 208                         goto bad_area;
 209         }
 210
 211         /*
 212          * If for any reason at all we couldn't handle the fault,
 213          * make sure we exit gracefully rather than endlessly redo
 214          * the fault.
 215          */
 216         fault = handle_mm_fault(vma, address, flags, regs);
 217
 218         if (fault_signal_pending(fault, regs)) {
 219                 if (!user_mode(regs))
 220                         no_context(regs, write, address);
 221                 return;
 222         }
 223
 224         /* The fault is fully completed (including releasing mmap lock) */
 225         if (fault & VM_FAULT_COMPLETED)
 226                 return;
 227
 228         if (unlikely(fault & VM_FAULT_RETRY)) {
 229                 flags |= FAULT_FLAG_TRIED;
 230
 231                 /*
 232                  * No need to mmap_read_unlock(mm) as we would
 233                  * have already released it in __lock_page_or_retry
 234                  * in mm/filemap.c.
 235                  */
 236                 goto retry;
 237         }
 238         if (unlikely(fault & VM_FAULT_ERROR)) {
 239                 mmap_read_unlock(mm);
 240                 if (fault & VM_FAULT_OOM) {
 241                         do_out_of_memory(regs, write, address);
 242                         return;
 243                 } else if (fault & VM_FAULT_SIGSEGV) {
 244                         do_sigsegv(regs, write, address, si_code);
 245                         return;
 246                 } else if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
 247                         do_sigbus(regs, write, address, si_code);
 248                         return;
 249                 }
 250                 BUG();
 251         }
 252
 253         mmap_read_unlock(mm);
 254 }
 255
 256 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
 257                         unsigned long write, unsigned long address)
 258 {
 259         irqentry_state_t state = irqentry_enter(regs);
 260
 261         /* Enable interrupt if enabled in parent context */
 262         if (likely(regs->csr_prmd & CSR_PRMD_PIE))
 263                 local_irq_enable();
 264
 265         __do_page_fault(regs, write, address);
 266
 267         local_irq_disable();
 268
 269         irqentry_exit(regs, state);
 270 }