Linux 3.12.28

[linux/fpc-iii.git] / arch / arm64 / mm / fault.c

/*
 * 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/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);
                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;
        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_WRITE               (1 << 6)
#define ESR_CM                  (1 << 8)
#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_WRITE) && !(esr & ESR_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;
                        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, esr);

        return 0;
}