// SPDX-License-Identifier: GPL-2.0
/*
 *  S390 version
 *    Copyright IBM Corp. 1999
 *    Author(s): Hartmut Penner (hp@de.ibm.com)
 *               Ulrich Weigand (uweigand@de.ibm.com)
 *
 *  Derived from "arch/i386/mm/fault.c"
 *    Copyright (C) 1995  Linus Torvalds
 */

#include <linux/kernel_stat.h>
#include <linux/mmu_context.h>
#include <linux/cpufeature.h>
#include <linux/perf_event.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kdebug.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/extable.h>
#include <linux/hardirq.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <linux/hugetlb.h>
#include <linux/kfence.h>
#include <linux/pagewalk.h>
#include <asm/asm-extable.h>
#include <asm/asm-offsets.h>
#include <asm/ptrace.h>
#include <asm/fault.h>
#include <asm/diag.h>
#include <asm/irq.h>
#include <asm/facility.h>
#include <asm/uv.h>
#include "../kernel/entry.h"

/*
 * Find out which address space caused the exception.
 */
static bool is_kernel_fault(struct pt_regs *regs)
{
        union teid teid = { .val = regs->int_parm_long };

        if (user_mode(regs))
                return false;
        if (teid.as == PSW_BITS_AS_SECONDARY)
                return false;
        return true;
}

static unsigned long get_fault_address(struct pt_regs *regs)
{
        union teid teid = { .val = regs->int_parm_long };

        return teid.addr * PAGE_SIZE;
}

static __always_inline bool fault_is_write(struct pt_regs *regs)
{
        union teid teid = { .val = regs->int_parm_long };

        if (test_facility(75))
                return teid.fsi == TEID_FSI_STORE;
        return false;
}

static void dump_pagetable(unsigned long asce, unsigned long address)
{
        unsigned long entry, *table = __va(asce & _ASCE_ORIGIN);

        pr_alert("AS:%016lx ", asce);
        switch (asce & _ASCE_TYPE_MASK) {
        case _ASCE_TYPE_REGION1:
                table += (address & _REGION1_INDEX) >> _REGION1_SHIFT;
                if (get_kernel_nofault(entry, table))
                        goto bad;
                pr_cont("R1:%016lx ", entry);
                if (entry & _REGION_ENTRY_INVALID)
                        goto out;
                table = __va(entry & _REGION_ENTRY_ORIGIN);
                fallthrough;
        case _ASCE_TYPE_REGION2:
                table += (address & _REGION2_INDEX) >> _REGION2_SHIFT;
                if (get_kernel_nofault(entry, table))
                        goto bad;
                pr_cont("R2:%016lx ", entry);
                if (entry & _REGION_ENTRY_INVALID)
                        goto out;
                table = __va(entry & _REGION_ENTRY_ORIGIN);
                fallthrough;
        case _ASCE_TYPE_REGION3:
                table += (address & _REGION3_INDEX) >> _REGION3_SHIFT;
                if (get_kernel_nofault(entry, table))
                        goto bad;
                pr_cont("R3:%016lx ", entry);
                if (entry & (_REGION_ENTRY_INVALID | _REGION3_ENTRY_LARGE))
                        goto out;
                table = __va(entry & _REGION_ENTRY_ORIGIN);
                fallthrough;
        case _ASCE_TYPE_SEGMENT:
                table += (address & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
                if (get_kernel_nofault(entry, table))
                        goto bad;
                pr_cont("S:%016lx ", entry);
                if (entry & (_SEGMENT_ENTRY_INVALID | _SEGMENT_ENTRY_LARGE))
                        goto out;
                table = __va(entry & _SEGMENT_ENTRY_ORIGIN);
        }
        table += (address & _PAGE_INDEX) >> PAGE_SHIFT;
        if (get_kernel_nofault(entry, table))
                goto bad;
        pr_cont("P:%016lx ", entry);
out:
        pr_cont("\n");
        return;
bad:
        pr_cont("BAD\n");
}

static void dump_fault_info(struct pt_regs *regs)
{
        union teid teid = { .val = regs->int_parm_long };
        unsigned long asce;

        pr_alert("Failing address: %016lx TEID: %016lx",
                 get_fault_address(regs), teid.val);
        if (test_facility(131))
                pr_cont(" ESOP-2");
        else if (machine_has_esop())
                pr_cont(" ESOP-1");
        else
                pr_cont(" SOP");
        if (test_facility(75))
                pr_cont(" FSI");
        pr_cont("\n");
        pr_alert("Fault in ");
        switch (teid.as) {
        case PSW_BITS_AS_HOME:
                pr_cont("home space ");
                break;
        case PSW_BITS_AS_SECONDARY:
                pr_cont("secondary space ");
                break;
        case PSW_BITS_AS_ACCREG:
                pr_cont("access register ");
                break;
        case PSW_BITS_AS_PRIMARY:
                pr_cont("primary space ");
                break;
        }
        pr_cont("mode while using ");
        if (is_kernel_fault(regs)) {
                asce = get_lowcore()->kernel_asce.val;
                pr_cont("kernel ");
        } else {
                asce = get_lowcore()->user_asce.val;
                pr_cont("user ");
        }
        pr_cont("ASCE.\n");
        dump_pagetable(asce, get_fault_address(regs));
}

int show_unhandled_signals = 1;

static const struct ctl_table s390_fault_sysctl_table[] = {
        {
                .procname       = "userprocess_debug",
                .data           = &show_unhandled_signals,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = proc_dointvec,
        },
};

static int __init init_s390_fault_sysctls(void)
{
        register_sysctl_init("kernel", s390_fault_sysctl_table);
        return 0;
}
arch_initcall(init_s390_fault_sysctls);

void report_user_fault(struct pt_regs *regs, long signr, int is_mm_fault)
{
        static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);

        if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
                return;
        if (!unhandled_signal(current, signr))
                return;
        if (!__ratelimit(&rs))
                return;
        pr_alert("User process fault: interruption code %04x ilc:%d ",
                 regs->int_code & 0xffff, regs->int_code >> 17);
        print_vma_addr(KERN_CONT "in ", regs->psw.addr);
        pr_cont("\n");
        if (is_mm_fault)
                dump_fault_info(regs);
        show_regs(regs);
}

static void do_sigsegv(struct pt_regs *regs, int si_code)
{
        report_user_fault(regs, SIGSEGV, 1);
        force_sig_fault(SIGSEGV, si_code, (void __user *)get_fault_address(regs));
}

static void handle_fault_error_nolock(struct pt_regs *regs, int si_code)
{
        unsigned long address;
        bool is_write;

        if (user_mode(regs)) {
                if (WARN_ON_ONCE(!si_code))
                        si_code = SEGV_MAPERR;
                return do_sigsegv(regs, si_code);
        }
        if (fixup_exception(regs))
                return;
        if (is_kernel_fault(regs)) {
                address = get_fault_address(regs);
                is_write = fault_is_write(regs);
                if (kfence_handle_page_fault(address, is_write, regs))
                        return;
                pr_alert("Unable to handle kernel pointer dereference in virtual kernel address space\n");
        } else {
                pr_alert("Unable to handle kernel paging request in virtual user address space\n");
        }
        dump_fault_info(regs);
        die(regs, "Oops");
}

static void handle_fault_error(struct pt_regs *regs, int si_code)
{
        struct mm_struct *mm = current->mm;

        mmap_read_unlock(mm);
        handle_fault_error_nolock(regs, si_code);
}

static void do_sigbus(struct pt_regs *regs)
{
        force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)get_fault_address(regs));
}

/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 *
 * interruption code (int_code):
 *   04       Protection           ->  Write-Protection  (suppression)
 *   10       Segment translation  ->  Not present       (nullification)
 *   11       Page translation     ->  Not present       (nullification)
 *   3b       Region third trans.  ->  Not present       (nullification)
 */
static void do_exception(struct pt_regs *regs, int access)
{
        struct vm_area_struct *vma;
        unsigned long address;
        struct mm_struct *mm;
        unsigned int flags;
        vm_fault_t fault;
        bool is_write;

        /*
         * The instruction that caused the program check has
         * been nullified. Don't signal single step via SIGTRAP.
         */
        clear_thread_flag(TIF_PER_TRAP);
        if (kprobe_page_fault(regs, 14))
                return;
        mm = current->mm;
        address = get_fault_address(regs);
        is_write = fault_is_write(regs);
        if (is_kernel_fault(regs) || faulthandler_disabled() || !mm)
                return handle_fault_error_nolock(regs, 0);
        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
        flags = FAULT_FLAG_DEFAULT;
        if (user_mode(regs))
                flags |= FAULT_FLAG_USER;
        if (is_write)
                access = VM_WRITE;
        if (access == VM_WRITE)
                flags |= FAULT_FLAG_WRITE;
        if (!(flags & FAULT_FLAG_USER))
                goto lock_mmap;
        vma = lock_vma_under_rcu(mm, address);
        if (!vma)
                goto lock_mmap;
        if (!(vma->vm_flags & access)) {
                vma_end_read(vma);
                count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
                return handle_fault_error_nolock(regs, SEGV_ACCERR);
        }
        fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs);
        if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
                vma_end_read(vma);
        if (!(fault & VM_FAULT_RETRY)) {
                count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
                goto done;
        }
        count_vm_vma_lock_event(VMA_LOCK_RETRY);
        if (fault & VM_FAULT_MAJOR)
                flags |= FAULT_FLAG_TRIED;
        /* Quick path to respond to signals */
        if (fault_signal_pending(fault, regs)) {
                if (!user_mode(regs))
                        handle_fault_error_nolock(regs, 0);
                return;
        }
lock_mmap:
retry:
        vma = lock_mm_and_find_vma(mm, address, regs);
        if (!vma)
                return handle_fault_error_nolock(regs, SEGV_MAPERR);
        if (unlikely(!(vma->vm_flags & access)))
                return handle_fault_error(regs, SEGV_ACCERR);
        fault = handle_mm_fault(vma, address, flags, regs);
        if (fault_signal_pending(fault, regs)) {
                if (!user_mode(regs))
                        handle_fault_error_nolock(regs, 0);
                return;
        }
        /* The fault is fully completed (including releasing mmap lock) */
        if (fault & VM_FAULT_COMPLETED)
                return;
        if (fault & VM_FAULT_RETRY) {
                flags |= FAULT_FLAG_TRIED;
                goto retry;
        }
        mmap_read_unlock(mm);
done:
        if (!(fault & VM_FAULT_ERROR))
                return;
        if (fault & VM_FAULT_OOM) {
                if (!user_mode(regs))
                        handle_fault_error_nolock(regs, 0);
                else
                        pagefault_out_of_memory();
        } else if (fault & VM_FAULT_SIGSEGV) {
                if (!user_mode(regs))
                        handle_fault_error_nolock(regs, 0);
                else
                        do_sigsegv(regs, SEGV_MAPERR);
        } else if (fault & (VM_FAULT_SIGBUS | VM_FAULT_HWPOISON |
                            VM_FAULT_HWPOISON_LARGE)) {
                if (!user_mode(regs))
                        handle_fault_error_nolock(regs, 0);
                else
                        do_sigbus(regs);
        } else {
                pr_emerg("Unexpected fault flags: %08x\n", fault);
                BUG();
        }
}

void do_protection_exception(struct pt_regs *regs)
{
        union teid teid = { .val = regs->int_parm_long };

        /*
         * Protection exceptions are suppressing, decrement psw address.
         * The exception to this rule are aborted transactions, for these
         * the PSW already points to the correct location.
         */
        if (!(regs->int_code & 0x200)) {
                regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
                set_pt_regs_flag(regs, PIF_PSW_ADDR_ADJUSTED);
        }
        /*
         * If bit 61 if the TEID is not set, the remainder of the
         * TEID is unpredictable. Special handling is required.
         */
        if (unlikely(!teid.b61)) {
                if (user_mode(regs)) {
                        dump_fault_info(regs);
                        die(regs, "Unexpected TEID");
                }
                /* Assume low-address protection in kernel mode. */
                return handle_fault_error_nolock(regs, 0);
        }
        if (unlikely(cpu_has_nx() && teid.b56)) {
                regs->int_parm_long = (teid.addr * PAGE_SIZE) | (regs->psw.addr & PAGE_MASK);
                return handle_fault_error_nolock(regs, SEGV_ACCERR);
        }
        do_exception(regs, VM_WRITE);
}
NOKPROBE_SYMBOL(do_protection_exception);

void do_dat_exception(struct pt_regs *regs)
{
        do_exception(regs, VM_ACCESS_FLAGS);
}
NOKPROBE_SYMBOL(do_dat_exception);

#if IS_ENABLED(CONFIG_KVM)

void do_secure_storage_access(struct pt_regs *regs)
{
        union teid teid = { .val = regs->int_parm_long };
        unsigned long addr = get_fault_address(regs);
        struct vm_area_struct *vma;
        struct folio_walk fw;
        struct mm_struct *mm;
        struct folio *folio;
        int rc;

        /*
         * Bit 61 indicates if the address is valid, if it is not the
         * kernel should be stopped or SIGSEGV should be sent to the
         * process. Bit 61 is not reliable without the misc UV feature,
         * therefore this needs to be checked too.
         */
        if (uv_has_feature(BIT_UV_FEAT_MISC) && !teid.b61) {
                /*
                 * When this happens, userspace did something that it
                 * was not supposed to do, e.g. branching into secure
                 * memory. Trigger a segmentation fault.
                 */
                if (user_mode(regs)) {
                        send_sig(SIGSEGV, current, 0);
                        return;
                }
                /*
                 * The kernel should never run into this case and
                 * there is no way out of this situation.
                 */
                panic("Unexpected PGM 0x3d with TEID bit 61=0");
        }
        if (is_kernel_fault(regs)) {
                folio = phys_to_folio(addr);
                if (unlikely(!folio_try_get(folio)))
                        return;
                rc = uv_convert_from_secure(folio_to_phys(folio));
                if (!rc)
                        clear_bit(PG_arch_1, &folio->flags.f);
                folio_put(folio);
                /*
                 * There are some valid fixup types for kernel
                 * accesses to donated secure memory. zeropad is one
                 * of them.
                 */
                if (rc)
                        return handle_fault_error_nolock(regs, 0);
        } else {
                if (faulthandler_disabled())
                        return handle_fault_error_nolock(regs, 0);
                mm = current->mm;
                mmap_read_lock(mm);
                vma = find_vma(mm, addr);
                if (!vma)
                        return handle_fault_error(regs, SEGV_MAPERR);
                folio = folio_walk_start(&fw, vma, addr, 0);
                if (!folio) {
                        mmap_read_unlock(mm);
                        return;
                }
                /* arch_make_folio_accessible() needs a raised refcount. */
                folio_get(folio);
                rc = arch_make_folio_accessible(folio);
                folio_put(folio);
                folio_walk_end(&fw, vma);
                if (rc)
                        send_sig(SIGSEGV, current, 0);
                mmap_read_unlock(mm);
        }
}
NOKPROBE_SYMBOL(do_secure_storage_access);

#endif /* CONFIG_KVM */