// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2003, 2004, 2007  Maciej W. Rozycki
 */
#include <linux/context_tracking.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/stddef.h>

#include <asm/bugs.h>
#include <asm/compiler.h>
#include <asm/cpu.h>
#include <asm/fpu.h>
#include <asm/mipsregs.h>
#include <asm/setup.h>
#include <asm/traps.h>

static char bug64hit[] __initdata =
        "reliable operation impossible!\n%s";
static char nowar[] __initdata =
        "Please report to <linux-mips@vger.kernel.org>.";
static char r4kwar[] __initdata =
        "Enable CPU_R4000_WORKAROUNDS to rectify.";
static char daddiwar[] __initdata =
        "Enable CPU_DADDI_WORKAROUNDS to rectify.";

static __always_inline __init
void align_mod(const int align, const int mod)
{
        asm volatile(
                ".set   push\n\t"
                ".set   noreorder\n\t"
                ".balign %0\n\t"
                ".rept  %1\n\t"
                "nop\n\t"
                ".endr\n\t"
                ".set   pop"
                :
                : "n"(align), "n"(mod));
}

static __always_inline __init
void mult_sh_align_mod(long *v1, long *v2, long *w,
                       const int align, const int mod)
{
        unsigned long flags;
        int m1, m2;
        long p, s, lv1, lv2, lw;

        /*
         * We want the multiply and the shift to be isolated from the
         * rest of the code to disable gcc optimizations.  Hence the
         * asm statements that execute nothing, but make gcc not know
         * what the values of m1, m2 and s are and what lv2 and p are
         * used for.
         */

        local_irq_save(flags);
        /*
         * The following code leads to a wrong result of the first
         * dsll32 when executed on R4000 rev. 2.2 or 3.0 (PRId
         * 00000422 or 00000430, respectively).
         *
         * See "MIPS R4000PC/SC Errata, Processor Revision 2.2 and
         * 3.0" by MIPS Technologies, Inc., errata #16 and #28 for
         * details.  I got no permission to duplicate them here,
         * sigh... --macro
         */
        asm volatile(
                ""
                : "=r" (m1), "=r" (m2), "=r" (s)
                : "0" (5), "1" (8), "2" (5));
        align_mod(align, mod);
        /*
         * The trailing nop is needed to fulfill the two-instruction
         * requirement between reading hi/lo and staring a mult/div.
         * Leaving it out may cause gas insert a nop itself breaking
         * the desired alignment of the next chunk.
         */
        asm volatile(
                ".set   push\n\t"
                ".set   noat\n\t"
                ".set   noreorder\n\t"
                ".set   nomacro\n\t"
                "mult   %2, %3\n\t"
                "dsll32 %0, %4, %5\n\t"
                "mflo   $0\n\t"
                "dsll32 %1, %4, %5\n\t"
                "nop\n\t"
                ".set   pop"
                : "=&r" (lv1), "=r" (lw)
                : "r" (m1), "r" (m2), "r" (s), "I" (0)
                : "hi", "lo", "$0");
        /* We have to use single integers for m1 and m2 and a double
         * one for p to be sure the mulsidi3 gcc's RTL multiplication
         * instruction has the workaround applied.  Older versions of
         * gcc have correct umulsi3 and mulsi3, but other
         * multiplication variants lack the workaround.
         */
        asm volatile(
                ""
                : "=r" (m1), "=r" (m2), "=r" (s)
                : "0" (m1), "1" (m2), "2" (s));
        align_mod(align, mod);
        p = m1 * m2;
        lv2 = s << 32;
        asm volatile(
                ""
                : "=r" (lv2)
                : "0" (lv2), "r" (p));
        local_irq_restore(flags);

        *v1 = lv1;
        *v2 = lv2;
        *w = lw;
}

static __always_inline __init void check_mult_sh(void)
{
        long v1[8], v2[8], w[8];
        int bug, fix, i;

        printk("Checking for the multiply/shift bug... ");

        /*
         * Testing discovered false negatives for certain code offsets
         * into cache lines.  Hence we test all possible offsets for
         * the worst assumption of an R4000 I-cache line width of 32
         * bytes.
         *
         * We can't use a loop as alignment directives need to be
         * immediates.
         */
        mult_sh_align_mod(&v1[0], &v2[0], &w[0], 32, 0);
        mult_sh_align_mod(&v1[1], &v2[1], &w[1], 32, 1);
        mult_sh_align_mod(&v1[2], &v2[2], &w[2], 32, 2);
        mult_sh_align_mod(&v1[3], &v2[3], &w[3], 32, 3);
        mult_sh_align_mod(&v1[4], &v2[4], &w[4], 32, 4);
        mult_sh_align_mod(&v1[5], &v2[5], &w[5], 32, 5);
        mult_sh_align_mod(&v1[6], &v2[6], &w[6], 32, 6);
        mult_sh_align_mod(&v1[7], &v2[7], &w[7], 32, 7);

        bug = 0;
        for (i = 0; i < 8; i++)
                if (v1[i] != w[i])
                        bug = 1;

        if (bug == 0) {
                pr_cont("no.\n");
                return;
        }

        pr_cont("yes, workaround... ");

        fix = 1;
        for (i = 0; i < 8; i++)
                if (v2[i] != w[i])
                        fix = 0;

        if (fix == 1) {
                pr_cont("yes.\n");
                return;
        }

        pr_cont("no.\n");
        panic(bug64hit,
              IS_ENABLED(CONFIG_CPU_R4000_WORKAROUNDS) ? nowar : r4kwar);
}

static volatile int daddi_ov;

asmlinkage void __init do_daddi_ov(struct pt_regs *regs)
{
        enum ctx_state prev_state;

        prev_state = exception_enter();
        daddi_ov = 1;
        regs->cp0_epc += 4;
        exception_exit(prev_state);
}

static __init void check_daddi(void)
{
        extern asmlinkage void handle_daddi_ov(void);
        unsigned long flags;
        void *handler;
        long v, tmp;

        printk("Checking for the daddi bug... ");

        local_irq_save(flags);
        handler = set_except_vector(EXCCODE_OV, handle_daddi_ov);
        /*
         * The following code fails to trigger an overflow exception
         * when executed on R4000 rev. 2.2 or 3.0 (PRId 00000422 or
         * 00000430, respectively).
         *
         * See "MIPS R4000PC/SC Errata, Processor Revision 2.2 and
         * 3.0" by MIPS Technologies, Inc., erratum #23 for details.
         * I got no permission to duplicate it here, sigh... --macro
         */
        asm volatile(
                ".set   push\n\t"
                ".set   noat\n\t"
                ".set   noreorder\n\t"
                ".set   nomacro\n\t"
                "addiu  %1, $0, %2\n\t"
                "dsrl   %1, %1, 1\n\t"
#ifdef HAVE_AS_SET_DADDI
                ".set   daddi\n\t"
#endif
                "daddi  %0, %1, %3\n\t"
                ".set   pop"
                : "=r" (v), "=&r" (tmp)
                : "I" (0xffffffffffffdb9aUL), "I" (0x1234));
        set_except_vector(EXCCODE_OV, handler);
        local_irq_restore(flags);

        if (daddi_ov) {
                pr_cont("no.\n");
                return;
        }

        pr_cont("yes, workaround... ");

        local_irq_save(flags);
        handler = set_except_vector(EXCCODE_OV, handle_daddi_ov);
        asm volatile(
                "addiu  %1, $0, %2\n\t"
                "dsrl   %1, %1, 1\n\t"
                "daddi  %0, %1, %3"
                : "=r" (v), "=&r" (tmp)
                : "I" (0xffffffffffffdb9aUL), "I" (0x1234));
        set_except_vector(EXCCODE_OV, handler);
        local_irq_restore(flags);

        if (daddi_ov) {
                pr_cont("yes.\n");
                return;
        }

        pr_cont("no.\n");
        panic(bug64hit,
              IS_ENABLED(CONFIG_CPU_DADDI_WORKAROUNDS) ? nowar : daddiwar);
}

int daddiu_bug  = -1;

static __init void check_daddiu(void)
{
        long v, w, tmp;

        printk("Checking for the daddiu bug... ");

        /*
         * The following code leads to a wrong result of daddiu when
         * executed on R4400 rev. 1.0 (PRId 00000440).
         *
         * See "MIPS R4400PC/SC Errata, Processor Revision 1.0" by
         * MIPS Technologies, Inc., erratum #7 for details.
         *
         * According to "MIPS R4000PC/SC Errata, Processor Revision
         * 2.2 and 3.0" by MIPS Technologies, Inc., erratum #41 this
         * problem affects R4000 rev. 2.2 and 3.0 (PRId 00000422 and
         * 00000430, respectively), too.  Testing failed to trigger it
         * so far.
         *
         * I got no permission to duplicate the errata here, sigh...
         * --macro
         */
        asm volatile(
                ".set   push\n\t"
                ".set   noat\n\t"
                ".set   noreorder\n\t"
                ".set   nomacro\n\t"
                "addiu  %2, $0, %3\n\t"
                "dsrl   %2, %2, 1\n\t"
#ifdef HAVE_AS_SET_DADDI
                ".set   daddi\n\t"
#endif
                "daddiu %0, %2, %4\n\t"
                "addiu  %1, $0, %4\n\t"
                "daddu  %1, %2\n\t"
                ".set   pop"
                : "=&r" (v), "=&r" (w), "=&r" (tmp)
                : "I" (0xffffffffffffdb9aUL), "I" (0x1234));

        daddiu_bug = v != w;

        if (!daddiu_bug) {
                pr_cont("no.\n");
                return;
        }

        pr_cont("yes, workaround... ");

        asm volatile(
                "addiu  %2, $0, %3\n\t"
                "dsrl   %2, %2, 1\n\t"
                "daddiu %0, %2, %4\n\t"
                "addiu  %1, $0, %4\n\t"
                "daddu  %1, %2"
                : "=&r" (v), "=&r" (w), "=&r" (tmp)
                : "I" (0xffffffffffffdb9aUL), "I" (0x1234));

        if (v == w) {
                pr_cont("yes.\n");
                return;
        }

        pr_cont("no.\n");
        panic(bug64hit,
              IS_ENABLED(CONFIG_CPU_DADDI_WORKAROUNDS) ? nowar : daddiwar);
}

void __init check_bugs64_early(void)
{
        check_mult_sh();
        check_daddiu();
}

void __init check_bugs64(void)
{
        check_daddi();
}