/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 *
 * Copyright (C) 1995, 1996, 1997, 1998 by Ralf Baechle
 * Copyright 1999 SuSE GmbH (Philipp Rumpf, prumpf@tux.org)
 * Copyright 1999 Hewlett Packard Co.
 *
 */

#include <linux/mm.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/interrupt.h>
#include <linux/extable.h>
#include <linux/uaccess.h>
#include <linux/hugetlb.h>
#include <linux/perf_event.h>

#include <asm/traps.h>

/* Various important other fields */
#define bit22set(x)             (x & 0x00000200)
#define bits23_25set(x)         (x & 0x000001c0)
#define isGraphicsFlushRead(x)  ((x & 0xfc003fdf) == 0x04001a80)
                                /* extended opcode is 0x6a */

#define BITSSET         0x1c0   /* for identifying LDCW */


int show_unhandled_signals = 1;

/*
 * parisc_acctyp(unsigned int inst) --
 *    Given a PA-RISC memory access instruction, determine if the
 *    the instruction would perform a memory read or memory write
 *    operation.
 *
 *    This function assumes that the given instruction is a memory access
 *    instruction (i.e. you should really only call it if you know that
 *    the instruction has generated some sort of a memory access fault).
 *
 * Returns:
 *   VM_READ  if read operation
 *   VM_WRITE if write operation
 *   VM_EXEC  if execute operation
 */
static unsigned long
parisc_acctyp(unsigned long code, unsigned int inst)
{
        if (code == 6 || code == 16)
            return VM_EXEC;

        switch (inst & 0xf0000000) {
        case 0x40000000: /* load */
        case 0x50000000: /* new load */
                return VM_READ;

        case 0x60000000: /* store */
        case 0x70000000: /* new store */
                return VM_WRITE;

        case 0x20000000: /* coproc */
        case 0x30000000: /* coproc2 */
                if (bit22set(inst))
                        return VM_WRITE;
                fallthrough;

        case 0x0: /* indexed/memory management */
                if (bit22set(inst)) {
                        /*
                         * Check for the 'Graphics Flush Read' instruction.
                         * It resembles an FDC instruction, except for bits
                         * 20 and 21. Any combination other than zero will
                         * utilize the block mover functionality on some
                         * older PA-RISC platforms.  The case where a block
                         * move is performed from VM to graphics IO space
                         * should be treated as a READ.
                         *
                         * The significance of bits 20,21 in the FDC
                         * instruction is:
                         *
                         *   00  Flush data cache (normal instruction behavior)
                         *   01  Graphics flush write  (IO space -> VM)
                         *   10  Graphics flush read   (VM -> IO space)
                         *   11  Graphics flush read/write (VM <-> IO space)
                         */
                        if (isGraphicsFlushRead(inst))
                                return VM_READ;
                        return VM_WRITE;
                } else {
                        /*
                         * Check for LDCWX and LDCWS (semaphore instructions).
                         * If bits 23 through 25 are all 1's it is one of
                         * the above two instructions and is a write.
                         *
                         * Note: With the limited bits we are looking at,
                         * this will also catch PROBEW and PROBEWI. However,
                         * these should never get in here because they don't
                         * generate exceptions of the type:
                         *   Data TLB miss fault/data page fault
                         *   Data memory protection trap
                         */
                        if (bits23_25set(inst) == BITSSET)
                                return VM_WRITE;
                }
                return VM_READ; /* Default */
        }
        return VM_READ; /* Default */
}

#undef bit22set
#undef bits23_25set
#undef isGraphicsFlushRead
#undef BITSSET


#if 0
/* This is the treewalk to find a vma which is the highest that has
 * a start < addr.  We're using find_vma_prev instead right now, but
 * we might want to use this at some point in the future.  Probably
 * not, but I want it committed to CVS so I don't lose it :-)
 */
                        while (tree != vm_avl_empty) {
                                if (tree->vm_start > addr) {
                                        tree = tree->vm_avl_left;
                                } else {
                                        prev = tree;
                                        if (prev->vm_next == NULL)
                                                break;
                                        if (prev->vm_next->vm_start > addr)
                                                break;
                                        tree = tree->vm_avl_right;
                                }
                        }
#endif

int fixup_exception(struct pt_regs *regs)
{
        const struct exception_table_entry *fix;

        fix = search_exception_tables(regs->iaoq[0]);
        if (fix) {
                /*
                 * Fix up get_user() and put_user().
                 * ASM_EXCEPTIONTABLE_ENTRY_EFAULT() sets the least-significant
                 * bit in the relative address of the fixup routine to indicate
                 * that %r8 should be loaded with -EFAULT to report a userspace
                 * access error.
                 */
                if (fix->fixup & 1) {
                        regs->gr[8] = -EFAULT;

                        /* zero target register for get_user() */
                        if (parisc_acctyp(0, regs->iir) == VM_READ) {
                                int treg = regs->iir & 0x1f;
                                BUG_ON(treg == 0);
                                regs->gr[treg] = 0;
                        }
                }

                regs->iaoq[0] = (unsigned long)&fix->fixup + fix->fixup;
                regs->iaoq[0] &= ~3;
                /*
                 * NOTE: In some cases the faulting instruction
                 * may be in the delay slot of a branch. We
                 * don't want to take the branch, so we don't
                 * increment iaoq[1], instead we set it to be
                 * iaoq[0]+4, and clear the B bit in the PSW
                 */
                regs->iaoq[1] = regs->iaoq[0] + 4;
                regs->gr[0] &= ~PSW_B; /* IPSW in gr[0] */

                return 1;
        }

        return 0;
}

/*
 * parisc hardware trap list
 *
 * Documented in section 3 "Addressing and Access Control" of the
 * "PA-RISC 1.1 Architecture and Instruction Set Reference Manual"
 * https://parisc.wiki.kernel.org/index.php/File:Pa11_acd.pdf
 *
 * For implementation see handle_interruption() in traps.c
 */
static const char * const trap_description[] = {
        [1] "High-priority machine check (HPMC)",
        [2] "Power failure interrupt",
        [3] "Recovery counter trap",
        [5] "Low-priority machine check",
        [6] "Instruction TLB miss fault",
        [7] "Instruction access rights / protection trap",
        [8] "Illegal instruction trap",
        [9] "Break instruction trap",
        [10] "Privileged operation trap",
        [11] "Privileged register trap",
        [12] "Overflow trap",
        [13] "Conditional trap",
        [14] "FP Assist Exception trap",
        [15] "Data TLB miss fault",
        [16] "Non-access ITLB miss fault",
        [17] "Non-access DTLB miss fault",
        [18] "Data memory protection/unaligned access trap",
        [19] "Data memory break trap",
        [20] "TLB dirty bit trap",
        [21] "Page reference trap",
        [22] "Assist emulation trap",
        [25] "Taken branch trap",
        [26] "Data memory access rights trap",
        [27] "Data memory protection ID trap",
        [28] "Unaligned data reference trap",
};

const char *trap_name(unsigned long code)
{
        const char *t = NULL;

        if (code < ARRAY_SIZE(trap_description))
                t = trap_description[code];

        return t ? t : "Unknown trap";
}

/*
 * Print out info about fatal segfaults, if the show_unhandled_signals
 * sysctl is set:
 */
static inline void
show_signal_msg(struct pt_regs *regs, unsigned long code,
                unsigned long address, struct task_struct *tsk,
                struct vm_area_struct *vma)
{
        if (!unhandled_signal(tsk, SIGSEGV))
                return;

        if (!printk_ratelimit())
                return;

        pr_warn("\n");
        pr_warn("do_page_fault() command='%s' type=%lu address=0x%08lx",
            tsk->comm, code, address);
        print_vma_addr(KERN_CONT " in ", regs->iaoq[0]);

        pr_cont("\ntrap #%lu: %s%c", code, trap_name(code),
                vma ? ',':'\n');

        if (vma)
                pr_cont(" vm_start = 0x%08lx, vm_end = 0x%08lx\n",
                        vma->vm_start, vma->vm_end);

        show_regs(regs);
}

void do_page_fault(struct pt_regs *regs, unsigned long code,
                              unsigned long address)
{
        struct vm_area_struct *vma, *prev_vma;
        struct task_struct *tsk;
        struct mm_struct *mm;
        unsigned long acc_type;
        vm_fault_t fault = 0;
        unsigned int flags;

        if (faulthandler_disabled())
                goto no_context;

        tsk = current;
        mm = tsk->mm;
        if (!mm)
                goto no_context;

        flags = FAULT_FLAG_DEFAULT;
        if (user_mode(regs))
                flags |= FAULT_FLAG_USER;

        acc_type = parisc_acctyp(code, regs->iir);
        if (acc_type & 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 || address < vma->vm_start)
                goto check_expansion;
/*
 * Ok, we have a good vm_area for this memory access. We still need to
 * check the access permissions.
 */

good_area:

        if ((vma->vm_flags & acc_type) != acc_type)
                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 hit a shared mapping outside of the file, 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|VM_FAULT_HWPOISON|
                                  VM_FAULT_HWPOISON_LARGE))
                        goto bad_area;
                BUG();
        }
        if (flags & FAULT_FLAG_ALLOW_RETRY) {
                if (fault & VM_FAULT_RETRY) {
                        /*
                         * No need to mmap_read_unlock(mm) as we would
                         * have already released it in __lock_page_or_retry
                         * in mm/filemap.c.
                         */
                        flags |= FAULT_FLAG_TRIED;
                        goto retry;
                }
        }
        mmap_read_unlock(mm);
        return;

check_expansion:
        vma = prev_vma;
        if (vma && (expand_stack(vma, address) == 0))
                goto good_area;

/*
 * Something tried to access memory that isn't in our memory map..
 */
bad_area:
        mmap_read_unlock(mm);

        if (user_mode(regs)) {
                int signo, si_code;

                switch (code) {
                case 15:        /* Data TLB miss fault/Data page fault */
                        /* send SIGSEGV when outside of vma */
                        if (!vma ||
                            address < vma->vm_start || address >= vma->vm_end) {
                                signo = SIGSEGV;
                                si_code = SEGV_MAPERR;
                                break;
                        }

                        /* send SIGSEGV for wrong permissions */
                        if ((vma->vm_flags & acc_type) != acc_type) {
                                signo = SIGSEGV;
                                si_code = SEGV_ACCERR;
                                break;
                        }

                        /* probably address is outside of mapped file */
                        fallthrough;
                case 17:        /* NA data TLB miss / page fault */
                case 18:        /* Unaligned access - PCXS only */
                        signo = SIGBUS;
                        si_code = (code == 18) ? BUS_ADRALN : BUS_ADRERR;
                        break;
                case 16:        /* Non-access instruction TLB miss fault */
                case 26:        /* PCXL: Data memory access rights trap */
                default:
                        signo = SIGSEGV;
                        si_code = (code == 26) ? SEGV_ACCERR : SEGV_MAPERR;
                        break;
                }
#ifdef CONFIG_MEMORY_FAILURE
                if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
                        unsigned int lsb = 0;
                        printk(KERN_ERR
        "MCE: Killing %s:%d due to hardware memory corruption fault at %08lx\n",
                        tsk->comm, tsk->pid, address);
                        /*
                         * Either small page or large page may be poisoned.
                         * In other words, VM_FAULT_HWPOISON_LARGE and
                         * VM_FAULT_HWPOISON are mutually exclusive.
                         */
                        if (fault & VM_FAULT_HWPOISON_LARGE)
                                lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
                        else if (fault & VM_FAULT_HWPOISON)
                                lsb = PAGE_SHIFT;

                        force_sig_mceerr(BUS_MCEERR_AR, (void __user *) address,
                                         lsb);
                        return;
                }
#endif
                show_signal_msg(regs, code, address, tsk, vma);

                force_sig_fault(signo, si_code, (void __user *) address);
                return;
        }

no_context:

        if (!user_mode(regs) && fixup_exception(regs)) {
                return;
        }

        parisc_terminate("Bad Address (null pointer deref?)", regs, code, address);

  out_of_memory:
        mmap_read_unlock(mm);
        if (!user_mode(regs))
                goto no_context;
        pagefault_out_of_memory();
}