// SPDX-License-Identifier: GPL-2.0 /* * MMU fault handling support. * * Copyright (C) 1998-2002 Hewlett-Packard Co * David Mosberger-Tang <davidm@hpl.hp.com> */ #include <linux/sched/signal.h> #include <linux/kernel.h> #include <linux/mm.h> #include <linux/extable.h> #include <linux/interrupt.h> #include <linux/kprobes.h> #include <linux/kdebug.h> #include <linux/prefetch.h> #include <linux/uaccess.h> #include <linux/perf_event.h> #include <asm/processor.h> #include <asm/exception.h> extern int die(char *, struct pt_regs *, long); /* * Return TRUE if ADDRESS points at a page in the kernel's mapped segment * (inside region 5, on ia64) and that page is present. */ static int mapped_kernel_page_is_present (unsigned long address) { pgd_t *pgd; p4d_t *p4d; pud_t *pud; pmd_t *pmd; pte_t *ptep, pte; pgd = pgd_offset_k(address); if (pgd_none(*pgd) || pgd_bad(*pgd)) return 0; p4d = p4d_offset(pgd, address); if (p4d_none(*p4d) || p4d_bad(*p4d)) return 0; pud = pud_offset(p4d, address); if (pud_none(*pud) || pud_bad(*pud)) return 0; pmd = pmd_offset(pud, address); if (pmd_none(*pmd) || pmd_bad(*pmd)) return 0; ptep = pte_offset_kernel(pmd, address); if (!ptep) return 0; pte = *ptep; return pte_present(pte); } # define VM_READ_BIT 0 # define VM_WRITE_BIT 1 # define VM_EXEC_BIT 2 void __kprobes ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs) { int signal = SIGSEGV, code = SEGV_MAPERR; struct vm_area_struct *vma, *prev_vma; struct mm_struct *mm = current->mm; unsigned long mask; vm_fault_t fault; unsigned int flags = FAULT_FLAG_DEFAULT; mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT) | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT)); /* mmap_lock is performance critical.... */ prefetchw(&mm->mmap_lock); /* * If we're in an interrupt or have no user context, we must not take the fault.. */ if (faulthandler_disabled() || !mm) goto no_context; #ifdef CONFIG_VIRTUAL_MEM_MAP /* * If fault is in region 5 and we are in the kernel, we may already * have the mmap_lock (pfn_valid macro is called during mmap). There * is no vma for region 5 addr's anyway, so skip getting the semaphore * and go directly to the exception handling code. */ if ((REGION_NUMBER(address) == 5) && !user_mode(regs)) goto bad_area_no_up; #endif /* * This is to handle the kprobes on user space access instructions */ if (kprobe_page_fault(regs, TRAP_BRKPT)) return; if (user_mode(regs)) flags |= FAULT_FLAG_USER; if (mask & VM_WRITE) flags |= FAULT_FLAG_WRITE; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); retry: mmap_read_lock(mm); vma = find_vma_prev(mm, address, &prev_vma); if (!vma && !prev_vma ) goto bad_area; /* * find_vma_prev() returns vma such that address < vma->vm_end or NULL * * May find no vma, but could be that the last vm area is the * register backing store that needs to expand upwards, in * this case vma will be null, but prev_vma will ne non-null */ if (( !vma && prev_vma ) || (address < vma->vm_start) ) goto check_expansion; good_area: code = SEGV_ACCERR; /* OK, we've got a good vm_area for this memory area. Check the access permissions: */ # if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \ || (1 << VM_EXEC_BIT) != VM_EXEC) # error File is out of sync with <linux/mm.h>. Please update. # endif if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE)))) goto bad_area; if ((vma->vm_flags & mask) != mask) goto bad_area; /* * If for any reason at all we couldn't handle the fault, make * sure we exit gracefully rather than endlessly redo the * fault. */ fault = handle_mm_fault(vma, address, flags, regs); if (fault_signal_pending(fault, regs)) return; if (unlikely(fault & VM_FAULT_ERROR)) { /* * We ran out of memory, or some other thing happened * to us that made us unable to handle the page fault * gracefully. */ if (fault & VM_FAULT_OOM) { goto out_of_memory; } else if (fault & VM_FAULT_SIGSEGV) { goto bad_area; } else if (fault & VM_FAULT_SIGBUS) { signal = SIGBUS; goto bad_area; } BUG(); } if (flags & FAULT_FLAG_ALLOW_RETRY) { if (fault & VM_FAULT_RETRY) { flags |= FAULT_FLAG_TRIED; /* No need to mmap_read_unlock(mm) as we would * have already released it in __lock_page_or_retry * in mm/filemap.c. */ goto retry; } } mmap_read_unlock(mm); return; check_expansion: if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) { if (!vma) goto bad_area; if (!(vma->vm_flags & VM_GROWSDOWN)) goto bad_area; if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) || REGION_OFFSET(address) >= RGN_MAP_LIMIT) goto bad_area; if (expand_stack(vma, address)) goto bad_area; } else { vma = prev_vma; if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) || REGION_OFFSET(address) >= RGN_MAP_LIMIT) goto bad_area; /* * Since the register backing store is accessed sequentially, * we disallow growing it by more than a page at a time. */ if (address > vma->vm_end + PAGE_SIZE - sizeof(long)) goto bad_area; if (expand_upwards(vma, address)) goto bad_area; } goto good_area; bad_area: mmap_read_unlock(mm); #ifdef CONFIG_VIRTUAL_MEM_MAP bad_area_no_up: #endif if ((isr & IA64_ISR_SP) || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) { /* * This fault was due to a speculative load or lfetch.fault, set the "ed" * bit in the psr to ensure forward progress. (Target register will get a * NaT for ld.s, lfetch will be canceled.) */ ia64_psr(regs)->ed = 1; return; } if (user_mode(regs)) { force_sig_fault(signal, code, (void __user *) address, 0, __ISR_VALID, isr); return; } no_context: if ((isr & IA64_ISR_SP) || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) { /* * This fault was due to a speculative load or lfetch.fault, set the "ed" * bit in the psr to ensure forward progress. (Target register will get a * NaT for ld.s, lfetch will be canceled.) */ ia64_psr(regs)->ed = 1; return; } /* * Since we have no vma's for region 5, we might get here even if the address is * valid, due to the VHPT walker inserting a non present translation that becomes * stale. If that happens, the non present fault handler already purged the stale * translation, which fixed the problem. So, we check to see if the translation is * valid, and return if it is. */ if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address)) return; if (ia64_done_with_exception(regs)) return; /* * Oops. The kernel tried to access some bad page. We'll have to terminate things * with extreme prejudice. */ bust_spinlocks(1); if (address < PAGE_SIZE) printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address); else printk(KERN_ALERT "Unable to handle kernel paging request at " "virtual address %016lx\n", address); if (die("Oops", regs, isr)) regs = NULL; bust_spinlocks(0); if (regs) do_exit(SIGKILL); return; out_of_memory: mmap_read_unlock(mm); if (!user_mode(regs)) goto no_context; pagefault_out_of_memory(); }