/* * Based on arch/arm/mm/fault.c * * Copyright (C) 1995 Linus Torvalds * Copyright (C) 1995-2004 Russell King * Copyright (C) 2012 ARM Ltd. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. */ #include <linux/module.h> #include <linux/signal.h> #include <linux/mm.h> #include <linux/hardirq.h> #include <linux/init.h> #include <linux/kprobes.h> #include <linux/uaccess.h> #include <linux/page-flags.h> #include <linux/sched.h> #include <linux/highmem.h> #include <linux/perf_event.h> #include <asm/exception.h> #include <asm/debug-monitors.h> #include <asm/esr.h> #include <asm/system_misc.h> #include <asm/pgtable.h> #include <asm/tlbflush.h> static const char *fault_name(unsigned int esr); /* * Dump out the page tables associated with 'addr' in mm 'mm'. */ void show_pte(struct mm_struct *mm, unsigned long addr) { pgd_t *pgd; if (!mm) mm = &init_mm; pr_alert("pgd = %p\n", mm->pgd); pgd = pgd_offset(mm, addr); pr_alert("[%08lx] *pgd=%016llx", addr, pgd_val(*pgd)); do { pud_t *pud; pmd_t *pmd; pte_t *pte; if (pgd_none(*pgd) || pgd_bad(*pgd)) break; pud = pud_offset(pgd, addr); printk(", *pud=%016llx", pud_val(*pud)); if (pud_none(*pud) || pud_bad(*pud)) break; pmd = pmd_offset(pud, addr); printk(", *pmd=%016llx", pmd_val(*pmd)); if (pmd_none(*pmd) || pmd_bad(*pmd)) break; pte = pte_offset_map(pmd, addr); printk(", *pte=%016llx", pte_val(*pte)); pte_unmap(pte); } while(0); printk("\n"); } /* * The kernel tried to access some page that wasn't present. */ static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int esr, struct pt_regs *regs) { /* * Are we prepared to handle this kernel fault? */ if (fixup_exception(regs)) return; /* * No handler, we'll have to terminate things with extreme prejudice. */ bust_spinlocks(1); pr_alert("Unable to handle kernel %s at virtual address %08lx\n", (addr < PAGE_SIZE) ? "NULL pointer dereference" : "paging request", addr); show_pte(mm, addr); die("Oops", regs, esr); bust_spinlocks(0); do_exit(SIGKILL); } /* * Something tried to access memory that isn't in our memory map. User mode * accesses just cause a SIGSEGV */ static void __do_user_fault(struct task_struct *tsk, unsigned long addr, unsigned int esr, unsigned int sig, int code, struct pt_regs *regs) { struct siginfo si; if (show_unhandled_signals && unhandled_signal(tsk, sig) && printk_ratelimit()) { pr_info("%s[%d]: unhandled %s (%d) at 0x%08lx, esr 0x%03x\n", tsk->comm, task_pid_nr(tsk), fault_name(esr), sig, addr, esr); show_pte(tsk->mm, addr); show_regs(regs); } tsk->thread.fault_address = addr; tsk->thread.fault_code = esr; si.si_signo = sig; si.si_errno = 0; si.si_code = code; si.si_addr = (void __user *)addr; force_sig_info(sig, &si, tsk); } static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs) { struct task_struct *tsk = current; struct mm_struct *mm = tsk->active_mm; /* * If we are in kernel mode at this point, we have no context to * handle this fault with. */ if (user_mode(regs)) __do_user_fault(tsk, addr, esr, SIGSEGV, SEGV_MAPERR, regs); else __do_kernel_fault(mm, addr, esr, regs); } #define VM_FAULT_BADMAP 0x010000 #define VM_FAULT_BADACCESS 0x020000 #define ESR_LNX_EXEC (1 << 24) static int __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int mm_flags, unsigned long vm_flags, struct task_struct *tsk) { struct vm_area_struct *vma; int fault; vma = find_vma(mm, addr); fault = VM_FAULT_BADMAP; if (unlikely(!vma)) goto out; if (unlikely(vma->vm_start > addr)) goto check_stack; /* * Ok, we have a good vm_area for this memory access, so we can handle * it. */ good_area: /* * Check that the permissions on the VMA allow for the fault which * occurred. If we encountered a write or exec fault, we must have * appropriate permissions, otherwise we allow any permission. */ if (!(vma->vm_flags & vm_flags)) { fault = VM_FAULT_BADACCESS; goto out; } return handle_mm_fault(mm, vma, addr & PAGE_MASK, mm_flags); check_stack: if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr)) goto good_area; out: return fault; } static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, struct pt_regs *regs) { struct task_struct *tsk; struct mm_struct *mm; int fault, sig, code; unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC; unsigned int mm_flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; tsk = current; mm = tsk->mm; /* Enable interrupts if they were enabled in the parent context. */ if (interrupts_enabled(regs)) local_irq_enable(); /* * If we're in an interrupt or have no user context, we must not take * the fault. */ if (in_atomic() || !mm) goto no_context; if (user_mode(regs)) mm_flags |= FAULT_FLAG_USER; if (esr & ESR_LNX_EXEC) { vm_flags = VM_EXEC; } else if ((esr & ESR_EL1_WRITE) && !(esr & ESR_EL1_CM)) { vm_flags = VM_WRITE; mm_flags |= FAULT_FLAG_WRITE; } /* * As per x86, we may deadlock here. However, since the kernel only * validly references user space from well defined areas of the code, * we can bug out early if this is from code which shouldn't. */ if (!down_read_trylock(&mm->mmap_sem)) { if (!user_mode(regs) && !search_exception_tables(regs->pc)) goto no_context; retry: down_read(&mm->mmap_sem); } else { /* * The above down_read_trylock() might have succeeded in which * case, we'll have missed the might_sleep() from down_read(). */ might_sleep(); #ifdef CONFIG_DEBUG_VM if (!user_mode(regs) && !search_exception_tables(regs->pc)) goto no_context; #endif } fault = __do_page_fault(mm, addr, mm_flags, vm_flags, tsk); /* * If we need to retry but a fatal signal is pending, handle the * signal first. We do not need to release the mmap_sem because it * would already be released in __lock_page_or_retry in mm/filemap.c. */ if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) return 0; /* * Major/minor page fault accounting is only done on the initial * attempt. If we go through a retry, it is extremely likely that the * page will be found in page cache at that point. */ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); if (mm_flags & FAULT_FLAG_ALLOW_RETRY) { if (fault & VM_FAULT_MAJOR) { tsk->maj_flt++; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, addr); } else { tsk->min_flt++; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, addr); } if (fault & VM_FAULT_RETRY) { /* * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk of * starvation. */ mm_flags &= ~FAULT_FLAG_ALLOW_RETRY; mm_flags |= FAULT_FLAG_TRIED; goto retry; } } up_read(&mm->mmap_sem); /* * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR */ if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS)))) return 0; /* * If we are in kernel mode at this point, we have no context to * handle this fault with. */ if (!user_mode(regs)) goto no_context; if (fault & VM_FAULT_OOM) { /* * We ran out of memory, call the OOM killer, and return to * userspace (which will retry the fault, or kill us if we got * oom-killed). */ pagefault_out_of_memory(); return 0; } if (fault & VM_FAULT_SIGBUS) { /* * We had some memory, but were unable to successfully fix up * this page fault. */ sig = SIGBUS; code = BUS_ADRERR; } else { /* * Something tried to access memory that isn't in our memory * map. */ sig = SIGSEGV; code = fault == VM_FAULT_BADACCESS ? SEGV_ACCERR : SEGV_MAPERR; } __do_user_fault(tsk, addr, esr, sig, code, regs); return 0; no_context: __do_kernel_fault(mm, addr, esr, regs); return 0; } /* * First Level Translation Fault Handler * * We enter here because the first level page table doesn't contain a valid * entry for the address. * * If the address is in kernel space (>= TASK_SIZE), then we are probably * faulting in the vmalloc() area. * * If the init_task's first level page tables contains the relevant entry, we * copy the it to this task. If not, we send the process a signal, fixup the * exception, or oops the kernel. * * NOTE! We MUST NOT take any locks for this case. We may be in an interrupt * or a critical region, and should only copy the information from the master * page table, nothing more. */ static int __kprobes do_translation_fault(unsigned long addr, unsigned int esr, struct pt_regs *regs) { if (addr < TASK_SIZE) return do_page_fault(addr, esr, regs); do_bad_area(addr, esr, regs); return 0; } /* * This abort handler always returns "fault". */ static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs) { return 1; } static struct fault_info { int (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs); int sig; int code; const char *name; } fault_info[] = { { do_bad, SIGBUS, 0, "ttbr address size fault" }, { do_bad, SIGBUS, 0, "level 1 address size fault" }, { do_bad, SIGBUS, 0, "level 2 address size fault" }, { do_bad, SIGBUS, 0, "level 3 address size fault" }, { do_translation_fault, SIGSEGV, SEGV_MAPERR, "input address range fault" }, { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 1 translation fault" }, { do_translation_fault, SIGSEGV, SEGV_MAPERR, "level 2 translation fault" }, { do_page_fault, SIGSEGV, SEGV_MAPERR, "level 3 translation fault" }, { do_bad, SIGBUS, 0, "reserved access flag fault" }, { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 access flag fault" }, { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 access flag fault" }, { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 access flag fault" }, { do_bad, SIGBUS, 0, "reserved permission fault" }, { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" }, { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 permission fault" }, { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 permission fault" }, { do_bad, SIGBUS, 0, "synchronous external abort" }, { do_bad, SIGBUS, 0, "asynchronous external abort" }, { do_bad, SIGBUS, 0, "unknown 18" }, { do_bad, SIGBUS, 0, "unknown 19" }, { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" }, { do_bad, SIGBUS, 0, "synchronous parity error" }, { do_bad, SIGBUS, 0, "asynchronous parity error" }, { do_bad, SIGBUS, 0, "unknown 26" }, { do_bad, SIGBUS, 0, "unknown 27" }, { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk" }, { do_bad, SIGBUS, 0, "unknown 32" }, { do_bad, SIGBUS, BUS_ADRALN, "alignment fault" }, { do_bad, SIGBUS, 0, "debug event" }, { do_bad, SIGBUS, 0, "unknown 35" }, { do_bad, SIGBUS, 0, "unknown 36" }, { do_bad, SIGBUS, 0, "unknown 37" }, { do_bad, SIGBUS, 0, "unknown 38" }, { do_bad, SIGBUS, 0, "unknown 39" }, { do_bad, SIGBUS, 0, "unknown 40" }, { do_bad, SIGBUS, 0, "unknown 41" }, { do_bad, SIGBUS, 0, "unknown 42" }, { do_bad, SIGBUS, 0, "unknown 43" }, { do_bad, SIGBUS, 0, "unknown 44" }, { do_bad, SIGBUS, 0, "unknown 45" }, { do_bad, SIGBUS, 0, "unknown 46" }, { do_bad, SIGBUS, 0, "unknown 47" }, { do_bad, SIGBUS, 0, "unknown 48" }, { do_bad, SIGBUS, 0, "unknown 49" }, { do_bad, SIGBUS, 0, "unknown 50" }, { do_bad, SIGBUS, 0, "unknown 51" }, { do_bad, SIGBUS, 0, "implementation fault (lockdown abort)" }, { do_bad, SIGBUS, 0, "unknown 53" }, { do_bad, SIGBUS, 0, "unknown 54" }, { do_bad, SIGBUS, 0, "unknown 55" }, { do_bad, SIGBUS, 0, "unknown 56" }, { do_bad, SIGBUS, 0, "unknown 57" }, { do_bad, SIGBUS, 0, "implementation fault (coprocessor abort)" }, { do_bad, SIGBUS, 0, "unknown 59" }, { do_bad, SIGBUS, 0, "unknown 60" }, { do_bad, SIGBUS, 0, "unknown 61" }, { do_bad, SIGBUS, 0, "unknown 62" }, { do_bad, SIGBUS, 0, "unknown 63" }, }; static const char *fault_name(unsigned int esr) { const struct fault_info *inf = fault_info + (esr & 63); return inf->name; } /* * Dispatch a data abort to the relevant handler. */ asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs) { const struct fault_info *inf = fault_info + (esr & 63); struct siginfo info; if (!inf->fn(addr, esr, regs)) return; pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n", inf->name, esr, addr); info.si_signo = inf->sig; info.si_errno = 0; info.si_code = inf->code; info.si_addr = (void __user *)addr; arm64_notify_die("", regs, &info, esr); } /* * Handle stack alignment exceptions. */ asmlinkage void __exception do_sp_pc_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs) { struct siginfo info; info.si_signo = SIGBUS; info.si_errno = 0; info.si_code = BUS_ADRALN; info.si_addr = (void __user *)addr; arm64_notify_die("", regs, &info, esr); } static struct fault_info debug_fault_info[] = { { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware breakpoint" }, { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware single-step" }, { do_bad, SIGTRAP, TRAP_HWBKPT, "hardware watchpoint" }, { do_bad, SIGBUS, 0, "unknown 3" }, { do_bad, SIGTRAP, TRAP_BRKPT, "aarch32 BKPT" }, { do_bad, SIGTRAP, 0, "aarch32 vector catch" }, { do_bad, SIGTRAP, TRAP_BRKPT, "aarch64 BRK" }, { do_bad, SIGBUS, 0, "unknown 7" }, }; void __init hook_debug_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *), int sig, int code, const char *name) { BUG_ON(nr < 0 || nr >= ARRAY_SIZE(debug_fault_info)); debug_fault_info[nr].fn = fn; debug_fault_info[nr].sig = sig; debug_fault_info[nr].code = code; debug_fault_info[nr].name = name; } asmlinkage int __exception do_debug_exception(unsigned long addr, unsigned int esr, struct pt_regs *regs) { const struct fault_info *inf = debug_fault_info + DBG_ESR_EVT(esr); struct siginfo info; if (!inf->fn(addr, esr, regs)) return 1; pr_alert("Unhandled debug exception: %s (0x%08x) at 0x%016lx\n", inf->name, esr, addr); info.si_signo = inf->sig; info.si_errno = 0; info.si_code = inf->code; info.si_addr = (void __user *)addr; arm64_notify_die("", regs, &info, 0); return 0; }