// SPDX-License-Identifier: GPL-2.0
/*
 *  S390 version
 *    Copyright IBM Corp. 1999, 2000
 *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com),
 *               Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com),
 *
 *  Derived from "arch/i386/kernel/traps.c"
 *    Copyright (C) 1991, 1992 Linus Torvalds
 */

#include <linux/cpufeature.h>
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/randomize_kstack.h>
#include <linux/extable.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/cpu.h>
#include <linux/entry-common.h>
#include <linux/kmsan.h>
#include <linux/bug.h>
#include <asm/asm-extable.h>
#include <asm/irqflags.h>
#include <asm/ptrace.h>
#include <asm/vtime.h>
#include <asm/fpu.h>
#include <asm/fault.h>
#include "entry.h"

static inline void __user *get_trap_ip(struct pt_regs *regs)
{
        unsigned long address;

        if (regs->int_code & 0x200)
                address = current->thread.trap_tdb.data[3];
        else
                address = regs->psw.addr;
        return (void __user *)(address - (regs->int_code >> 16));
}

#ifdef CONFIG_GENERIC_BUG
int is_valid_bugaddr(unsigned long addr)
{
        return 1;
}
#endif

void do_report_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)
{
        if (user_mode(regs)) {
                force_sig_fault(si_signo, si_code, get_trap_ip(regs));
                report_user_fault(regs, si_signo, 0);
        } else {
                if (!fixup_exception(regs))
                        die(regs, str);
        }
}

static void do_trap(struct pt_regs *regs, int si_signo, int si_code, char *str)
{
        if (notify_die(DIE_TRAP, str, regs, 0, regs->int_code, si_signo) == NOTIFY_STOP)
                return;
        do_report_trap(regs, si_signo, si_code, str);
}
NOKPROBE_SYMBOL(do_trap);

void do_per_trap(struct pt_regs *regs)
{
        if (notify_die(DIE_SSTEP, "sstep", regs, 0, 0, SIGTRAP) == NOTIFY_STOP)
                return;
        if (!current->ptrace)
                return;
        force_sig_fault(SIGTRAP, TRAP_HWBKPT, (void __force __user *)current->thread.per_event.address);
}
NOKPROBE_SYMBOL(do_per_trap);

static void default_trap_handler(struct pt_regs *regs)
{
        if (user_mode(regs)) {
                report_user_fault(regs, SIGSEGV, 0);
                force_exit_sig(SIGSEGV);
        } else
                die(regs, "Unknown program exception");
}

#define DO_ERROR_INFO(name, signr, sicode, str) \
static void name(struct pt_regs *regs)          \
{                                               \
        do_trap(regs, signr, sicode, str);      \
}

DO_ERROR_INFO(addressing_exception, SIGILL, ILL_ILLADR, "addressing exception")
DO_ERROR_INFO(divide_exception, SIGFPE, FPE_INTDIV, "fixpoint divide exception")
DO_ERROR_INFO(execute_exception, SIGILL, ILL_ILLOPN, "execute exception")
DO_ERROR_INFO(hfp_divide_exception, SIGFPE, FPE_FLTDIV, "HFP divide exception")
DO_ERROR_INFO(hfp_overflow_exception, SIGFPE, FPE_FLTOVF, "HFP overflow exception")
DO_ERROR_INFO(hfp_significance_exception, SIGFPE, FPE_FLTRES, "HFP significance exception")
DO_ERROR_INFO(hfp_sqrt_exception, SIGFPE, FPE_FLTINV, "HFP square root exception")
DO_ERROR_INFO(hfp_underflow_exception, SIGFPE, FPE_FLTUND, "HFP underflow exception")
DO_ERROR_INFO(operand_exception, SIGILL, ILL_ILLOPN, "operand exception")
DO_ERROR_INFO(overflow_exception, SIGFPE, FPE_INTOVF, "fixpoint overflow exception")
DO_ERROR_INFO(privileged_op, SIGILL, ILL_PRVOPC, "privileged operation")
DO_ERROR_INFO(special_op_exception, SIGILL, ILL_ILLOPN, "special operation exception")
DO_ERROR_INFO(specification_exception, SIGILL, ILL_ILLOPN, "specification exception");
DO_ERROR_INFO(transaction_exception, SIGILL, ILL_ILLOPN, "transaction constraint exception")

static inline void do_fp_trap(struct pt_regs *regs, __u32 fpc)
{
        int si_code = 0;

        /* FPC[2] is Data Exception Code */
        if ((fpc & 0x00000300) == 0) {
                /* bits 6 and 7 of DXC are 0 iff IEEE exception */
                if (fpc & 0x8000) /* invalid fp operation */
                        si_code = FPE_FLTINV;
                else if (fpc & 0x4000) /* div by 0 */
                        si_code = FPE_FLTDIV;
                else if (fpc & 0x2000) /* overflow */
                        si_code = FPE_FLTOVF;
                else if (fpc & 0x1000) /* underflow */
                        si_code = FPE_FLTUND;
                else if (fpc & 0x0800) /* inexact */
                        si_code = FPE_FLTRES;
        }
        do_trap(regs, SIGFPE, si_code, "floating point exception");
}

static void translation_specification_exception(struct pt_regs *regs)
{
        /* May never happen. */
        panic("Translation-Specification Exception");
}

static void illegal_op(struct pt_regs *regs)
{
        int is_uprobe_insn = 0;
        u16 __user *location;
        int signal = 0;
        u16 opcode;

        location = get_trap_ip(regs);
        if (user_mode(regs)) {
                if (get_user(opcode, location))
                        return;
                if (opcode == S390_BREAKPOINT_U16) {
                        if (current->ptrace)
                                force_sig_fault(SIGTRAP, TRAP_BRKPT, location);
                        else
                                signal = SIGILL;
#ifdef CONFIG_UPROBES
                } else if (opcode == UPROBE_SWBP_INSN) {
                        is_uprobe_insn = 1;
#endif
                } else {
                        signal = SIGILL;
                }
        }
        /*
         * This is either an illegal op in kernel mode, or user space trapped
         * on a uprobes illegal instruction. See if kprobes or uprobes picks
         * it up. If not, SIGILL.
         */
        if (is_uprobe_insn || !user_mode(regs)) {
                if (notify_die(DIE_BPT, "bpt", regs, 0, 3, SIGTRAP) != NOTIFY_STOP)
                        signal = SIGILL;
        }
        if (signal)
                do_trap(regs, signal, ILL_ILLOPC, "illegal operation");
}
NOKPROBE_SYMBOL(illegal_op);

static void vector_exception(struct pt_regs *regs)
{
        int si_code, vic;

        /* get vector interrupt code from fpc */
        save_user_fpu_regs();
        vic = (current->thread.ufpu.fpc & 0xf00) >> 8;
        switch (vic) {
        case 1: /* invalid vector operation */
                si_code = FPE_FLTINV;
                break;
        case 2: /* division by zero */
                si_code = FPE_FLTDIV;
                break;
        case 3: /* overflow */
                si_code = FPE_FLTOVF;
                break;
        case 4: /* underflow */
                si_code = FPE_FLTUND;
                break;
        case 5: /* inexact */
                si_code = FPE_FLTRES;
                break;
        default: /* unknown cause */
                si_code = 0;
        }
        do_trap(regs, SIGFPE, si_code, "vector exception");
}

static void data_exception(struct pt_regs *regs)
{
        save_user_fpu_regs();
        if (current->thread.ufpu.fpc & FPC_DXC_MASK)
                do_fp_trap(regs, current->thread.ufpu.fpc);
        else
                do_trap(regs, SIGILL, ILL_ILLOPN, "data exception");
}

static void space_switch_exception(struct pt_regs *regs)
{
        /* Set user psw back to home space mode. */
        if (user_mode(regs))
                regs->psw.mask |= PSW_ASC_HOME;
        /* Send SIGILL. */
        do_trap(regs, SIGILL, ILL_PRVOPC, "space switch event");
}

#if defined(CONFIG_BUG) && defined(CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS)

void *__warn_args(struct arch_va_list *args, struct pt_regs *regs)
{
        struct stack_frame *stack_frame;

        /*
         * Generate va_list from pt_regs. See ELF Application Binary Interface
         * s390x Supplement documentation for details.
         *
         * - __overflow_arg_area needs to point to the parameter area, which
         *   is right above the standard stack frame (160 bytes)
         *
         * - __reg_save_area needs to point to a register save area where
         *   general registers (%r2 - %r6) can be found at offset 16. Which
         *   means that the gprs save area of pt_regs can be used
         *
         * - __gpr must be set to one, since the first parameter has been
         *   processed (pointer to bug_entry)
         */
        stack_frame = (struct stack_frame *)regs->gprs[15];
        args->__overflow_arg_area = stack_frame + 1;
        args->__reg_save_area = regs->gprs;
        args->__gpr = 1;
        return args;
}

#endif /* CONFIG_BUG && CONFIG_CC_HAS_ASM_IMMEDIATE_STRINGS */

static void monitor_event_exception(struct pt_regs *regs)
{
        enum bug_trap_type btt;

        if (user_mode(regs))
                return;
        if (regs->monitor_code == MONCODE_BUG_ARG) {
                regs->psw.addr = regs->gprs[14];
                btt = report_bug_entry((struct bug_entry *)regs->gprs[2], regs);
        } else {
                btt = report_bug(regs->psw.addr - (regs->int_code >> 16), regs);
        }
        switch (btt) {
        case BUG_TRAP_TYPE_NONE:
                fixup_exception(regs);
                break;
        case BUG_TRAP_TYPE_WARN:
                break;
        case BUG_TRAP_TYPE_BUG:
                die(regs, "monitor event");
                break;
        }
}

void kernel_stack_invalid(struct pt_regs *regs)
{
        /*
         * Normally regs are unpoisoned by the generic entry code, but
         * kernel_stack_overflow() is a rare case that is called bypassing it.
         */
        kmsan_unpoison_entry_regs(regs);
        bust_spinlocks(1);
        pr_emerg("Kernel stack pointer invalid\n");
        show_regs(regs);
        bust_spinlocks(0);
        panic("Invalid kernel stack pointer, cannot continue");
}
NOKPROBE_SYMBOL(kernel_stack_invalid);

static void __init test_monitor_call(void)
{
        int val = 1;

        if (!IS_ENABLED(CONFIG_BUG))
                return;
        asm_inline volatile(
                "       mc      %[monc](%%r0),0\n"
                "0:     lhi     %[val],0\n"
                "1:\n"
                EX_TABLE(0b, 1b)
                : [val] "+d" (val)
                : [monc] "i" (MONCODE_BUG));
        if (!val)
                panic("Monitor call doesn't work!\n");
}

void __init trap_init(void)
{
        struct lowcore *lc = get_lowcore();
        unsigned long flags;
        struct ctlreg cr0;

        local_irq_save(flags);
        cr0 = local_ctl_clear_bit(0, CR0_LOW_ADDRESS_PROTECTION_BIT);
        psw_bits(lc->external_new_psw).mcheck = 1;
        psw_bits(lc->program_new_psw).mcheck = 1;
        psw_bits(lc->svc_new_psw).mcheck = 1;
        psw_bits(lc->io_new_psw).mcheck = 1;
        local_ctl_load(0, &cr0);
        local_irq_restore(flags);
        local_mcck_enable();
        test_monitor_call();
}

static void (*pgm_check_table[128])(struct pt_regs *regs);

void noinstr __do_pgm_check(struct pt_regs *regs)
{
        struct lowcore *lc = get_lowcore();
        irqentry_state_t state;
        unsigned int trapnr;
        union teid teid;

        teid.val = lc->trans_exc_code;
        regs->int_code = lc->pgm_int_code;
        regs->int_parm_long = teid.val;
        regs->monitor_code = lc->monitor_code;
        /*
         * In case of a guest fault, short-circuit the fault handler and return.
         * This way the sie64a() function will return 0; fault address and
         * other relevant bits are saved in current->thread.gmap_teid, and
         * the fault number in current->thread.gmap_int_code. KVM will be
         * able to use this information to handle the fault.
         */
        if (test_pt_regs_flag(regs, PIF_GUEST_FAULT)) {
                current->thread.gmap_teid.val = regs->int_parm_long;
                current->thread.gmap_int_code = regs->int_code & 0xffff;
                return;
        }
        state = irqentry_enter(regs);
        if (user_mode(regs)) {
                update_timer_sys();
                if (!cpu_has_bear()) {
                        if (regs->last_break < 4096)
                                regs->last_break = 1;
                }
                current->thread.last_break = regs->last_break;
        }
        if (lc->pgm_code & 0x0200) {
                /* transaction abort */
                current->thread.trap_tdb = lc->pgm_tdb;
        }
        if (lc->pgm_code & PGM_INT_CODE_PER) {
                if (user_mode(regs)) {
                        struct per_event *ev = &current->thread.per_event;

                        set_thread_flag(TIF_PER_TRAP);
                        ev->address = lc->per_address;
                        ev->cause = lc->per_code_combined;
                        ev->paid = lc->per_access_id;
                } else {
                        /* PER event in kernel is kprobes */
                        __arch_local_irq_ssm(regs->psw.mask & ~PSW_MASK_PER);
                        do_per_trap(regs);
                        goto out;
                }
        }
        if (!irqs_disabled_flags(regs->psw.mask))
                trace_hardirqs_on();
        __arch_local_irq_ssm(regs->psw.mask & ~PSW_MASK_PER);
        trapnr = regs->int_code & PGM_INT_CODE_MASK;
        if (trapnr)
                pgm_check_table[trapnr](regs);
out:
        local_irq_disable();
        irqentry_exit(regs, state);
}

/*
 * The program check table contains exactly 128 (0x00-0x7f) entries. Each
 * line defines the function to be called corresponding to the program check
 * interruption code.
 */
static void (*pgm_check_table[128])(struct pt_regs *regs) = {
        [0x00]          = default_trap_handler,
        [0x01]          = illegal_op,
        [0x02]          = privileged_op,
        [0x03]          = execute_exception,
        [0x04]          = do_protection_exception,
        [0x05]          = addressing_exception,
        [0x06]          = specification_exception,
        [0x07]          = data_exception,
        [0x08]          = overflow_exception,
        [0x09]          = divide_exception,
        [0x0a]          = overflow_exception,
        [0x0b]          = divide_exception,
        [0x0c]          = hfp_overflow_exception,
        [0x0d]          = hfp_underflow_exception,
        [0x0e]          = hfp_significance_exception,
        [0x0f]          = hfp_divide_exception,
        [0x10]          = do_dat_exception,
        [0x11]          = do_dat_exception,
        [0x12]          = translation_specification_exception,
        [0x13]          = special_op_exception,
        [0x14]          = default_trap_handler,
        [0x15]          = operand_exception,
        [0x16]          = default_trap_handler,
        [0x17]          = default_trap_handler,
        [0x18]          = transaction_exception,
        [0x19]          = default_trap_handler,
        [0x1a]          = default_trap_handler,
        [0x1b]          = vector_exception,
        [0x1c]          = space_switch_exception,
        [0x1d]          = hfp_sqrt_exception,
        [0x1e ... 0x37] = default_trap_handler,
        [0x38]          = do_dat_exception,
        [0x39]          = do_dat_exception,
        [0x3a]          = do_dat_exception,
        [0x3b]          = do_dat_exception,
        [0x3c]          = default_trap_handler,
        [0x3d]          = do_secure_storage_access,
        [0x3e]          = default_trap_handler,
        [0x3f]          = default_trap_handler,
        [0x40]          = monitor_event_exception,
        [0x41 ... 0x7f] = default_trap_handler,
};

#define COND_TRAP(x) asm(                       \
        ".weak " __stringify(x) "\n\t"          \
        ".set  " __stringify(x) ","             \
        __stringify(default_trap_handler))

COND_TRAP(do_secure_storage_access);