// SPDX-License-Identifier: GPL-2.0
/*
 * fault.c:  Page fault handlers for the Sparc.
 *
 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 * Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be)
 * Copyright (C) 1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
 */

#include <asm/head.h>

#include <linux/string.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/threads.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/perf_event.h>
#include <linux/interrupt.h>
#include <linux/kdebug.h>
#include <linux/uaccess.h>
#include <linux/extable.h>

#include <asm/page.h>
#include <asm/openprom.h>
#include <asm/oplib.h>
#include <asm/setup.h>
#include <asm/smp.h>
#include <asm/traps.h>

#include "mm_32.h"

int show_unhandled_signals = 1;

static void __noreturn unhandled_fault(unsigned long address,
                                       struct task_struct *tsk,
                                       struct pt_regs *regs)
{
        if ((unsigned long) address < PAGE_SIZE) {
                printk(KERN_ALERT
                    "Unable to handle kernel NULL pointer dereference\n");
        } else {
                printk(KERN_ALERT "Unable to handle kernel paging request at virtual address %08lx\n",
                       address);
        }
        printk(KERN_ALERT "tsk->{mm,active_mm}->context = %08lx\n",
                (tsk->mm ? tsk->mm->context : tsk->active_mm->context));
        printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %08lx\n",
                (tsk->mm ? (unsigned long) tsk->mm->pgd :
                        (unsigned long) tsk->active_mm->pgd));
        die_if_kernel("Oops", regs);
}

static inline void
show_signal_msg(struct pt_regs *regs, int sig, int code,
                unsigned long address, struct task_struct *tsk)
{
        if (!unhandled_signal(tsk, sig))
                return;

        if (!printk_ratelimit())
                return;

        printk("%s%s[%d]: segfault at %lx ip %px (rpc %px) sp %px error %x",
               task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
               tsk->comm, task_pid_nr(tsk), address,
               (void *)regs->pc, (void *)regs->u_regs[UREG_I7],
               (void *)regs->u_regs[UREG_FP], code);

        print_vma_addr(KERN_CONT " in ", regs->pc);

        printk(KERN_CONT "\n");
}

static void __do_fault_siginfo(int code, int sig, struct pt_regs *regs,
                               unsigned long addr)
{
        if (unlikely(show_unhandled_signals))
                show_signal_msg(regs, sig, code,
                                addr, current);

        force_sig_fault(sig, code, (void __user *) addr);
}

static unsigned long compute_si_addr(struct pt_regs *regs, int text_fault)
{
        unsigned int insn;

        if (text_fault)
                return regs->pc;

        if (regs->psr & PSR_PS)
                insn = *(unsigned int *) regs->pc;
        else
                __get_user(insn, (unsigned int *) regs->pc);

        return safe_compute_effective_address(regs, insn);
}

static noinline void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
                                      int text_fault)
{
        unsigned long addr = compute_si_addr(regs, text_fault);

        __do_fault_siginfo(code, sig, regs, addr);
}

asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
                               unsigned long address)
{
        struct vm_area_struct *vma;
        struct task_struct *tsk = current;
        struct mm_struct *mm = tsk->mm;
        int from_user = !(regs->psr & PSR_PS);
        int code;
        vm_fault_t fault;
        unsigned int flags = FAULT_FLAG_DEFAULT;

        if (text_fault)
                address = regs->pc;

        /*
         * We fault-in kernel-space virtual memory on-demand. The
         * 'reference' page table is init_mm.pgd.
         *
         * 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.
         */
        code = SEGV_MAPERR;
        if (address >= TASK_SIZE)
                goto vmalloc_fault;

        /*
         * If we're in an interrupt or have no user
         * context, we must not take the fault..
         */
        if (pagefault_disabled() || !mm)
                goto no_context;

        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);

retry:
        mmap_read_lock(mm);

        if (!from_user && address >= PAGE_OFFSET)
                goto bad_area;

        vma = find_vma(mm, address);
        if (!vma)
                goto bad_area;
        if (vma->vm_start <= address)
                goto good_area;
        if (!(vma->vm_flags & VM_GROWSDOWN))
                goto bad_area;
        if (expand_stack(vma, address))
                goto bad_area;
        /*
         * Ok, we have a good vm_area for this memory access, so
         * we can handle it..
         */
good_area:
        code = SEGV_ACCERR;
        if (write) {
                if (!(vma->vm_flags & VM_WRITE))
                        goto bad_area;
        } else {
                /* Allow reads even for write-only mappings */
                if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
                        goto bad_area;
        }

        if (from_user)
                flags |= FAULT_FLAG_USER;
        if (write)
                flags |= FAULT_FLAG_WRITE;

        /*
         * 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)) {
                if (fault & VM_FAULT_OOM)
                        goto out_of_memory;
                else if (fault & VM_FAULT_SIGSEGV)
                        goto bad_area;
                else if (fault & VM_FAULT_SIGBUS)
                        goto do_sigbus;
                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;

        /*
         * Something tried to access memory that isn't in our memory map..
         * Fix it, but check if it's kernel or user first..
         */
bad_area:
        mmap_read_unlock(mm);

bad_area_nosemaphore:
        /* User mode accesses just cause a SIGSEGV */
        if (from_user) {
                do_fault_siginfo(code, SIGSEGV, regs, text_fault);
                return;
        }

        /* Is this in ex_table? */
no_context:
        if (!from_user) {
                const struct exception_table_entry *entry;

                entry = search_exception_tables(regs->pc);
#ifdef DEBUG_EXCEPTIONS
                printk("Exception: PC<%08lx> faddr<%08lx>\n",
                       regs->pc, address);
                printk("EX_TABLE: insn<%08lx> fixup<%08x>\n",
                        regs->pc, entry->fixup);
#endif
                regs->pc = entry->fixup;
                regs->npc = regs->pc + 4;
                return;
        }

        unhandled_fault(address, tsk, regs);
        do_exit(SIGKILL);

/*
 * We ran out of memory, or some other thing happened to us that made
 * us unable to handle the page fault gracefully.
 */
out_of_memory:
        mmap_read_unlock(mm);
        if (from_user) {
                pagefault_out_of_memory();
                return;
        }
        goto no_context;

do_sigbus:
        mmap_read_unlock(mm);
        do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, text_fault);
        if (!from_user)
                goto no_context;

vmalloc_fault:
        {
                /*
                 * Synchronize this task's top level page-table
                 * with the 'reference' page table.
                 */
                int offset = pgd_index(address);
                pgd_t *pgd, *pgd_k;
                p4d_t *p4d, *p4d_k;
                pud_t *pud, *pud_k;
                pmd_t *pmd, *pmd_k;

                pgd = tsk->active_mm->pgd + offset;
                pgd_k = init_mm.pgd + offset;

                if (!pgd_present(*pgd)) {
                        if (!pgd_present(*pgd_k))
                                goto bad_area_nosemaphore;
                        pgd_val(*pgd) = pgd_val(*pgd_k);
                        return;
                }

                p4d = p4d_offset(pgd, address);
                pud = pud_offset(p4d, address);
                pmd = pmd_offset(pud, address);

                p4d_k = p4d_offset(pgd_k, address);
                pud_k = pud_offset(p4d_k, address);
                pmd_k = pmd_offset(pud_k, address);

                if (pmd_present(*pmd) || !pmd_present(*pmd_k))
                        goto bad_area_nosemaphore;

                *pmd = *pmd_k;
                return;
        }
}

/* This always deals with user addresses. */
static void force_user_fault(unsigned long address, int write)
{
        struct vm_area_struct *vma;
        struct task_struct *tsk = current;
        struct mm_struct *mm = tsk->mm;
        unsigned int flags = FAULT_FLAG_USER;
        int code;

        code = SEGV_MAPERR;

        mmap_read_lock(mm);
        vma = find_vma(mm, address);
        if (!vma)
                goto bad_area;
        if (vma->vm_start <= address)
                goto good_area;
        if (!(vma->vm_flags & VM_GROWSDOWN))
                goto bad_area;
        if (expand_stack(vma, address))
                goto bad_area;
good_area:
        code = SEGV_ACCERR;
        if (write) {
                if (!(vma->vm_flags & VM_WRITE))
                        goto bad_area;
                flags |= FAULT_FLAG_WRITE;
        } else {
                if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
                        goto bad_area;
        }
        switch (handle_mm_fault(vma, address, flags, NULL)) {
        case VM_FAULT_SIGBUS:
        case VM_FAULT_OOM:
                goto do_sigbus;
        }
        mmap_read_unlock(mm);
        return;
bad_area:
        mmap_read_unlock(mm);
        __do_fault_siginfo(code, SIGSEGV, tsk->thread.kregs, address);
        return;

do_sigbus:
        mmap_read_unlock(mm);
        __do_fault_siginfo(BUS_ADRERR, SIGBUS, tsk->thread.kregs, address);
}

static void check_stack_aligned(unsigned long sp)
{
        if (sp & 0x7UL)
                force_sig(SIGILL);
}

void window_overflow_fault(void)
{
        unsigned long sp;

        sp = current_thread_info()->rwbuf_stkptrs[0];
        if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
                force_user_fault(sp + 0x38, 1);
        force_user_fault(sp, 1);

        check_stack_aligned(sp);
}

void window_underflow_fault(unsigned long sp)
{
        if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
                force_user_fault(sp + 0x38, 0);
        force_user_fault(sp, 0);

        check_stack_aligned(sp);
}

void window_ret_fault(struct pt_regs *regs)
{
        unsigned long sp;

        sp = regs->u_regs[UREG_FP];
        if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
                force_user_fault(sp + 0x38, 0);
        force_user_fault(sp, 0);

        check_stack_aligned(sp);
}