/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright (c) 2012, Joyent, Inc. All rights reserved.
 * Copyright (c) 2013, 2014 by Delphix. All rights reserved.
 * Copyright 2024 Oxide Computer Company
 */

#include <sys/modctl.h>
#include <sys/sunddi.h>
#include <sys/dtrace.h>
#include <sys/kobj.h>
#include <sys/stat.h>
#include <sys/conf.h>
#include <vm/seg_kmem.h>
#include <sys/stack.h>
#include <sys/frame.h>
#include <sys/dtrace_impl.h>
#include <sys/cmn_err.h>
#include <sys/sysmacros.h>
#include <sys/privregs.h>
#include <sys/sdt_impl.h>

#define SDT_PATCHVAL    0xf0
#define SDT_ADDR2NDX(addr)      ((((uintptr_t)(addr)) >> 4) & sdt_probetab_mask)
#define SDT_PROBETAB_SIZE       0x1000          /* 4k entries -- 16K total */

static dev_info_t               *sdt_devi;
static int                      sdt_verbose = 0;
static sdt_probe_t              **sdt_probetab;
static int                      sdt_probetab_size;
static int                      sdt_probetab_mask;

/*ARGSUSED*/
static int
sdt_invop(uintptr_t addr, uintptr_t *stack, uintptr_t eax)
{
        uintptr_t stack0, stack1, stack2, stack3, stack4;
        int i = 0;
        sdt_probe_t *sdt = sdt_probetab[SDT_ADDR2NDX(addr)];

        /*
         * On amd64, stack[0] contains the dereferenced stack pointer,
         * stack[1] contains savfp, stack[2] contains savpc.  We want
         * to step over these entries.
         */
        i += 3;

        for (; sdt != NULL; sdt = sdt->sdp_hashnext) {
                if ((uintptr_t)sdt->sdp_patchpoint == addr) {
                        /*
                         * When accessing the arguments on the stack, we must
                         * protect against accessing beyond the stack.  We can
                         * safely set NOFAULT here -- we know that interrupts
                         * are already disabled.
                         */
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        stack0 = stack[i++];
                        stack1 = stack[i++];
                        stack2 = stack[i++];
                        stack3 = stack[i++];
                        stack4 = stack[i++];
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT |
                            CPU_DTRACE_BADADDR);

                        dtrace_probe(sdt->sdp_id, stack0, stack1,
                            stack2, stack3, stack4);

                        return (DTRACE_INVOP_NOP);
                }
        }

        return (0);
}

/*ARGSUSED*/
static void
sdt_provide_module(void *arg, struct modctl *ctl)
{
        struct module *mp = ctl->mod_mp;
        char *modname = ctl->mod_modname;
        sdt_probedesc_t *sdpd;
        sdt_probe_t *sdp, *old;
        sdt_provider_t *prov;
        int len;

        /*
         * One for all, and all for one:  if we haven't yet registered all of
         * our providers, we'll refuse to provide anything.
         */
        for (prov = sdt_providers; prov->sdtp_name != NULL; prov++) {
                if (prov->sdtp_id == DTRACE_PROVNONE)
                        return;
        }

        if (mp->sdt_nprobes != 0 || (sdpd = mp->sdt_probes) == NULL)
                return;

        for (sdpd = mp->sdt_probes; sdpd != NULL; sdpd = sdpd->sdpd_next) {
                char *name = sdpd->sdpd_name, *func, *nname;
                int i, j;
                sdt_provider_t *prov;
                ulong_t offs;
                dtrace_id_t id;

                for (prov = sdt_providers; prov->sdtp_prefix != NULL; prov++) {
                        char *prefix = prov->sdtp_prefix;

                        if (strncmp(name, prefix, strlen(prefix)) == 0) {
                                name += strlen(prefix);
                                break;
                        }
                }

                nname = kmem_alloc(len = strlen(name) + 1, KM_SLEEP);

                for (i = 0, j = 0; name[j] != '\0'; i++) {
                        if (name[j] == '_' && name[j + 1] == '_') {
                                nname[i] = '-';
                                j += 2;
                        } else {
                                nname[i] = name[j++];
                        }
                }

                nname[i] = '\0';

                sdp = kmem_zalloc(sizeof (sdt_probe_t), KM_SLEEP);
                sdp->sdp_loadcnt = ctl->mod_loadcnt;
                sdp->sdp_ctl = ctl;
                sdp->sdp_name = nname;
                sdp->sdp_namelen = len;
                sdp->sdp_provider = prov;

                func = kobj_searchsym(mp, sdpd->sdpd_offset, &offs);

                if (func == NULL)
                        func = "<unknown>";

                /*
                 * We have our provider.  Now create the probe.
                 */
                if ((id = dtrace_probe_lookup(prov->sdtp_id, modname,
                    func, nname)) != DTRACE_IDNONE) {
                        old = dtrace_probe_arg(prov->sdtp_id, id);
                        ASSERT(old != NULL);

                        sdp->sdp_next = old->sdp_next;
                        sdp->sdp_id = id;
                        old->sdp_next = sdp;
                } else {
                        sdp->sdp_id = dtrace_probe_create(prov->sdtp_id,
                            modname, func, nname, 3, sdp);

                        mp->sdt_nprobes++;
                }

                sdp->sdp_hashnext =
                    sdt_probetab[SDT_ADDR2NDX(sdpd->sdpd_offset)];
                sdt_probetab[SDT_ADDR2NDX(sdpd->sdpd_offset)] = sdp;

                sdp->sdp_patchval = SDT_PATCHVAL;
                sdp->sdp_patchpoint = (uint8_t *)sdpd->sdpd_offset;
                sdp->sdp_savedval = *sdp->sdp_patchpoint;
                sdp->sdp_is_tailcall =
                    sdp->sdp_patchpoint[SDT_OFF_RET_IDX] == SDT_RET;
        }
}

/*ARGSUSED*/
static void
sdt_destroy(void *arg, dtrace_id_t id, void *parg)
{
        sdt_probe_t *sdp = parg, *old, *last, *hash;
        struct modctl *ctl = sdp->sdp_ctl;
        int ndx;

        if (ctl != NULL && ctl->mod_loadcnt == sdp->sdp_loadcnt) {
                if ((ctl->mod_loadcnt == sdp->sdp_loadcnt &&
                    ctl->mod_loaded)) {
                        ((struct module *)(ctl->mod_mp))->sdt_nprobes--;
                }
        }

        while (sdp != NULL) {
                old = sdp;

                /*
                 * Now we need to remove this probe from the sdt_probetab.
                 */
                ndx = SDT_ADDR2NDX(sdp->sdp_patchpoint);
                last = NULL;
                hash = sdt_probetab[ndx];

                while (hash != sdp) {
                        ASSERT(hash != NULL);
                        last = hash;
                        hash = hash->sdp_hashnext;
                }

                if (last != NULL) {
                        last->sdp_hashnext = sdp->sdp_hashnext;
                } else {
                        sdt_probetab[ndx] = sdp->sdp_hashnext;
                }

                kmem_free(sdp->sdp_name, sdp->sdp_namelen);
                sdp = sdp->sdp_next;
                kmem_free(old, sizeof (sdt_probe_t));
        }
}

/*ARGSUSED*/
static int
sdt_enable(void *arg, dtrace_id_t id, void *parg)
{
        sdt_probe_t *sdp = parg;
        struct modctl *ctl = sdp->sdp_ctl;

        ctl->mod_nenabled++;

        /*
         * If this module has disappeared since we discovered its probes,
         * refuse to enable it.
         */
        if (!ctl->mod_loaded) {
                if (sdt_verbose) {
                        cmn_err(CE_NOTE, "sdt is failing for probe %s "
                            "(module %s unloaded)",
                            sdp->sdp_name, ctl->mod_modname);
                }
                goto err;
        }

        /*
         * Now check that our modctl has the expected load count.  If it
         * doesn't, this module must have been unloaded and reloaded -- and
         * we're not going to touch it.
         */
        if (ctl->mod_loadcnt != sdp->sdp_loadcnt) {
                if (sdt_verbose) {
                        cmn_err(CE_NOTE, "sdt is failing for probe %s "
                            "(module %s reloaded)",
                            sdp->sdp_name, ctl->mod_modname);
                }
                goto err;
        }

        while (sdp != NULL) {
                *sdp->sdp_patchpoint = sdp->sdp_patchval;
                sdp = sdp->sdp_next;
        }
err:
        return (0);
}

/*ARGSUSED*/
static void
sdt_disable(void *arg, dtrace_id_t id, void *parg)
{
        sdt_probe_t *sdp = parg;
        struct modctl *ctl = sdp->sdp_ctl;

        ctl->mod_nenabled--;

        if (!ctl->mod_loaded || ctl->mod_loadcnt != sdp->sdp_loadcnt)
                goto err;

        while (sdp != NULL) {
                *sdp->sdp_patchpoint = sdp->sdp_savedval;
                sdp = sdp->sdp_next;
        }

err:
        ;
}

/*ARGSUSED*/
uint64_t
sdt_getarg(void *arg, dtrace_id_t id, void *parg, int argno, int aframes)
{
        sdt_probe_t *sdp = parg;
        uintptr_t val;
        struct frame *fp = (struct frame *)dtrace_getfp();
        uintptr_t *stack;
        int i;
        /*
         * A total of 6 arguments are passed via registers; any argument with
         * index of 5 or lower is therefore in a register.
         */
        int inreg = 5;

        for (i = 1; i <= aframes; i++) {
                fp = (struct frame *)(fp->fr_savfp);

                if (fp->fr_savpc == (pc_t)dtrace_invop_callsite) {
                        /*
                         * In the case of amd64, we will use the pointer to the
                         * regs structure that was pushed when we took the
                         * trap.  To get this structure, we must increment
                         * beyond the frame structure, the calling RIP, and
                         * padding stored in dtrace_invop().  If the argument
                         * that we're seeking is passed on the stack, we'll
                         * pull the true stack pointer out of the saved
                         * registers and decrement our argument by the number
                         * of arguments passed in registers; if the argument
                         * we're seeking is passed in regsiters, we can just
                         * load it directly.
                         */
                        struct regs *rp = (struct regs *)((uintptr_t)&fp[1] +
                            sizeof (uintptr_t) * 2);

                        if (argno <= inreg) {
                                stack = (uintptr_t *)&rp->r_rdi;
                        } else {
                                stack = (uintptr_t *)(rp->r_rsp);
                                argno -= (inreg + 1);

                                /*
                                 * If the probe was invoked as a tail call, the
                                 * compiler leaves the stack as if we had just
                                 * entered the fictitious  __dtrace_probe_[name]
                                 * function, meaning we need to skip over the
                                 * saved return address to get to the stack
                                 * arguments.
                                 */
                                if (sdp->sdp_is_tailcall)
                                        argno++;
                        }
                        goto load;
                }
        }

        /*
         * We know that we did not come through a trap to get into
         * dtrace_probe() -- the provider simply called dtrace_probe()
         * directly.  As this is the case, we need to shift the argument
         * that we're looking for:  the probe ID is the first argument to
         * dtrace_probe(), so the argument n will actually be found where
         * one would expect to find argument (n + 1).
         */
        argno++;

        if (argno <= inreg) {
                /*
                 * This shouldn't happen.  If the argument is passed in a
                 * register then it should have been, well, passed in a
                 * register...
                 */
                DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                return (0);
        }

        argno -= (inreg + 1);
        stack = (uintptr_t *)&fp[1];

load:
        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
        val = stack[argno];
        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

        return (val);
}

static dtrace_pops_t sdt_pops = {
        NULL,
        sdt_provide_module,
        sdt_enable,
        sdt_disable,
        NULL,
        NULL,
        sdt_getargdesc,
        sdt_getarg,
        NULL,
        sdt_destroy
};

/*ARGSUSED*/
static int
sdt_attach(dev_info_t *devi, ddi_attach_cmd_t cmd)
{
        sdt_provider_t *prov;

        if (ddi_create_minor_node(devi, "sdt", S_IFCHR,
            0, DDI_PSEUDO, 0) == DDI_FAILURE) {
                cmn_err(CE_NOTE, "/dev/sdt couldn't create minor node");
                ddi_remove_minor_node(devi, NULL);
                return (DDI_FAILURE);
        }

        ddi_report_dev(devi);
        sdt_devi = devi;

        if (sdt_probetab_size == 0)
                sdt_probetab_size = SDT_PROBETAB_SIZE;

        sdt_probetab_mask = sdt_probetab_size - 1;
        sdt_probetab =
            kmem_zalloc(sdt_probetab_size * sizeof (sdt_probe_t *), KM_SLEEP);
        dtrace_invop_add(sdt_invop);

        for (prov = sdt_providers; prov->sdtp_name != NULL; prov++) {
                uint32_t priv;

                if (prov->sdtp_priv == DTRACE_PRIV_NONE) {
                        priv = DTRACE_PRIV_KERNEL;
                        sdt_pops.dtps_mode = NULL;
                } else {
                        priv = prov->sdtp_priv;
                        ASSERT(priv == DTRACE_PRIV_USER);
                        sdt_pops.dtps_mode = sdt_mode;
                }

                if (dtrace_register(prov->sdtp_name, prov->sdtp_attr,
                    priv, NULL, &sdt_pops, prov, &prov->sdtp_id) != 0) {
                        cmn_err(CE_WARN, "failed to register sdt provider %s",
                            prov->sdtp_name);
                }
        }

        return (DDI_SUCCESS);
}

/*ARGSUSED*/
static int
sdt_detach(dev_info_t *dip, ddi_detach_cmd_t cmd)
{
        sdt_provider_t *prov;

        switch (cmd) {
        case DDI_DETACH:
                break;

        case DDI_SUSPEND:
                return (DDI_SUCCESS);

        default:
                return (DDI_FAILURE);
        }

        for (prov = sdt_providers; prov->sdtp_name != NULL; prov++) {
                if (prov->sdtp_id != DTRACE_PROVNONE) {
                        if (dtrace_unregister(prov->sdtp_id) != 0)
                                return (DDI_FAILURE);

                        prov->sdtp_id = DTRACE_PROVNONE;
                }
        }

        dtrace_invop_remove(sdt_invop);
        kmem_free(sdt_probetab, sdt_probetab_size * sizeof (sdt_probe_t *));

        return (DDI_SUCCESS);
}

/*ARGSUSED*/
static int
sdt_info(dev_info_t *dip, ddi_info_cmd_t infocmd, void *arg, void **result)
{
        int error;

        switch (infocmd) {
        case DDI_INFO_DEVT2DEVINFO:
                *result = (void *)sdt_devi;
                error = DDI_SUCCESS;
                break;
        case DDI_INFO_DEVT2INSTANCE:
                *result = (void *)0;
                error = DDI_SUCCESS;
                break;
        default:
                error = DDI_FAILURE;
        }
        return (error);
}

/*ARGSUSED*/
static int
sdt_open(dev_t *devp, int flag, int otyp, cred_t *cred_p)
{
        return (0);
}

static struct cb_ops sdt_cb_ops = {
        sdt_open,               /* open */
        nodev,                  /* close */
        nulldev,                /* strategy */
        nulldev,                /* print */
        nodev,                  /* dump */
        nodev,                  /* read */
        nodev,                  /* write */
        nodev,                  /* ioctl */
        nodev,                  /* devmap */
        nodev,                  /* mmap */
        nodev,                  /* segmap */
        nochpoll,               /* poll */
        ddi_prop_op,            /* cb_prop_op */
        0,                      /* streamtab  */
        D_NEW | D_MP            /* Driver compatibility flag */
};

static struct dev_ops sdt_ops = {
        DEVO_REV,               /* devo_rev, */
        0,                      /* refcnt  */
        sdt_info,               /* get_dev_info */
        nulldev,                /* identify */
        nulldev,                /* probe */
        sdt_attach,             /* attach */
        sdt_detach,             /* detach */
        nodev,                  /* reset */
        &sdt_cb_ops,            /* driver operations */
        NULL,                   /* bus operations */
        nodev,                  /* dev power */
        ddi_quiesce_not_needed,         /* quiesce */
};

/*
 * Module linkage information for the kernel.
 */
static struct modldrv modldrv = {
        &mod_driverops,         /* module type (this is a pseudo driver) */
        "Statically Defined Tracing",   /* name of module */
        &sdt_ops,               /* driver ops */
};

static struct modlinkage modlinkage = {
        MODREV_1,
        (void *)&modldrv,
        NULL
};

int
_init(void)
{
        return (mod_install(&modlinkage));
}

int
_info(struct modinfo *modinfop)
{
        return (mod_info(&modlinkage, modinfop));
}

int
_fini(void)
{
        return (mod_remove(&modlinkage));
}