fasttrap.c

Sun Solaris 10 中的 DTrace 组件的源代码。请参看: http://www.sun.com/software/solaris/observability.jsp

		sprunlock(p);
	} else {
		/*
		 * If the process is dead, we're just waiting for the
		 * last probe to be disabled to be able to free it.
		 */
		if (provider->ftp_rcount == 0 && !provider->ftp_marked)
			whack = provider->ftp_marked = 1;
		mutex_exit(&provider->ftp_mtx);
	}

	if (whack)
		fasttrap_pid_cleanup();

	probe->ftp_enabled = 0;

	ASSERT(MUTEX_HELD(&cpu_lock));
	fasttrap_disable_common(&fasttrap_pid_count, &dtrace_pid_probe_ptr,
	    &dtrace_return_probe_ptr);
}

/*ARGSUSED*/
static void
fasttrap_pid_getargdesc(void *arg, dtrace_id_t id, void *parg,
    dtrace_argdesc_t *desc)
{
	fasttrap_probe_t *probe = parg;
	char *str;
	int i;

	desc->dtargd_native[0] = '\0';
	desc->dtargd_xlate[0] = '\0';

	if (probe->ftp_prov->ftp_defunct != 0 ||
	    desc->dtargd_ndx >= probe->ftp_nargs) {
		desc->dtargd_ndx = DTRACE_ARGNONE;
		return;
	}

	/*
	 * We only need to set this member if the argument is remapped.
	 */
	if (probe->ftp_argmap != NULL)
		desc->dtargd_mapping = probe->ftp_argmap[desc->dtargd_ndx];

	str = probe->ftp_ntypes;
	for (i = 0; i < desc->dtargd_mapping; i++) {
		str += strlen(str) + 1;
	}

	ASSERT(strlen(str + 1) < sizeof (desc->dtargd_native));
	(void) strcpy(desc->dtargd_native, str);

	if (probe->ftp_xtypes == NULL)
		return;

	str = probe->ftp_xtypes;
	for (i = 0; i < desc->dtargd_ndx; i++) {
		str += strlen(str) + 1;
	}

	ASSERT(strlen(str + 1) < sizeof (desc->dtargd_xlate));
	(void) strcpy(desc->dtargd_xlate, str);
}

/*ARGSUSED*/
static void
fasttrap_destroy(void *arg, dtrace_id_t id, void *parg)
{
	ASSERT(arg == NULL);
	ASSERT(id == fasttrap_probe_id);
}

/*ARGSUSED*/
static void
fasttrap_pid_destroy(void *arg, dtrace_id_t id, void *parg)
{
	fasttrap_probe_t *probe = parg;
	int i;
	size_t size;

	ASSERT(probe != NULL);
	ASSERT(!probe->ftp_enabled);
	ASSERT(fasttrap_total >= probe->ftp_ntps);

	atomic_add_32(&fasttrap_total, -probe->ftp_ntps);
	size = sizeof (fasttrap_probe_t) +
	    sizeof (probe->ftp_tps[0]) * (probe->ftp_ntps - 1);

	if (probe->ftp_gen + 1 >= fasttrap_mod_gen)
		fasttrap_mod_barrier(probe->ftp_gen);

	for (i = 0; i < probe->ftp_ntps; i++) {
		kmem_free(probe->ftp_tps[i].fit_tp,
		    sizeof (fasttrap_tracepoint_t));
	}

	kmem_free(probe, size);
}


static const dtrace_pattr_t fasttrap_attr = {
{ DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_ISA },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
{ DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_ISA },
{ DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_ISA },
};

static dtrace_pops_t fasttrap_pops = {
	fasttrap_provide,
	NULL,
	fasttrap_enable,
	fasttrap_disable,
	NULL,
	NULL,
	NULL,
	fasttrap_getarg,
	NULL,
	fasttrap_destroy
};

static const dtrace_pattr_t pid_attr = {
{ DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_ISA },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
{ DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_ISA },
{ DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN },
};

static dtrace_pops_t pid_pops = {
	fasttrap_pid_provide,
	NULL,
	fasttrap_pid_enable,
	fasttrap_pid_disable,
	NULL,
	NULL,
	fasttrap_pid_getargdesc,
	fasttrap_getarg,
	NULL,
	fasttrap_pid_destroy
};

static dtrace_pops_t usdt_pops = {
	fasttrap_pid_provide,
	NULL,
	fasttrap_pid_enable,
	fasttrap_pid_disable,
	NULL,
	NULL,
	fasttrap_pid_getargdesc,
	fasttrap_usdt_getarg,
	NULL,
	fasttrap_pid_destroy
};

/*
 * Lookup a fasttrap-managed provider based on its name and associated pid.
 * If the pattr argument is non-NULL, this function instantiates the provider
 * if it doesn't exist otherwise it returns NULL. The provider is returned
 * with its lock held.
 */
static fasttrap_provider_t *
fasttrap_provider_lookup(pid_t pid, const char *name,
    const dtrace_pattr_t *pattr)
{
	fasttrap_provider_t *fp, *new_fp = NULL;
	fasttrap_bucket_t *bucket;
	char provname[DTRACE_PROVNAMELEN];
	proc_t *p;
	uid_t uid = (uid_t)-1;

	ASSERT(strlen(name) < sizeof (fp->ftp_name));

	bucket = &fasttrap_provs.fth_table[FASTTRAP_PROVS_INDEX(pid, name)];
	mutex_enter(&bucket->ftb_mtx);

	/*
	 * Take a lap through the list and return the match if we find it.
	 */
	for (fp = bucket->ftb_data; fp != NULL; fp = fp->ftp_next) {
		if (fp->ftp_pid == pid && strcmp(fp->ftp_name, name) == 0 &&
		    !fp->ftp_defunct) {
			mutex_enter(&fp->ftp_mtx);
			mutex_exit(&bucket->ftb_mtx);
			return (fp);
		}
	}

	/*
	 * Drop the bucket lock so we don't try to perform a sleeping
	 * allocation under it.
	 */
	mutex_exit(&bucket->ftb_mtx);

	if (pattr == NULL)
		return (NULL);

	/*
	 * Make sure the process exists, isn't a child created as the result
	 * of a vfork(2), and isn't a zombie (but may be in fork). Record the
	 * process's uid to pass to dtrace_register().
	 */
	mutex_enter(&pidlock);
	if ((p = prfind(pid)) == NULL ||
	    (p->p_flag & (SVFORK | SEXITLWPS)) ||
	    (p->p_lwpcnt == 0 && p->p_lwpdir != NULL)) {
		mutex_exit(&pidlock);
		return (NULL);
	}
	mutex_enter(&p->p_lock);
	mutex_exit(&pidlock);

	/*
	 * Increment p_dtrace_probes so that the process knows to inform us
	 * when it exits or execs. fasttrap_provider_free() decrements this
	 * when we're done with this provider.
	 */
	p->p_dtrace_probes++;

	mutex_enter(&p->p_crlock);
	uid = crgetruid(p->p_cred);
	mutex_exit(&p->p_crlock);
	mutex_exit(&p->p_lock);

	new_fp = kmem_zalloc(sizeof (fasttrap_provider_t), KM_SLEEP);

	mutex_enter(&bucket->ftb_mtx);

	/*
	 * Take another lap through the list to make sure a provider hasn't
	 * been created for this pid while we weren't under the bucket lock.
	 */
	for (fp = bucket->ftb_data; fp != NULL; fp = fp->ftp_next) {
		if (fp->ftp_pid == pid && strcmp(fp->ftp_name, name) == 0 &&
		    !fp->ftp_defunct) {
			mutex_enter(&fp->ftp_mtx);
			mutex_exit(&bucket->ftb_mtx);
			fasttrap_provider_free(new_fp);
			return (fp);
		}
	}

	new_fp->ftp_pid = pid;
	(void) strcpy(new_fp->ftp_name, name);

	/*
	 * Fail and return NULL if either the provider name is too long
	 * or we fail to register this new provider with the DTrace
	 * framework. Note that this is the only place we ever construct
	 * the full provider name -- we keep it in pieces in the provider
	 * structure.
	 */
	if (snprintf(provname, sizeof (provname), "%s%u", name, (uint_t)pid) >=
	    sizeof (provname) ||
	    dtrace_register(provname, pattr,
	    DTRACE_PRIV_PROC | DTRACE_PRIV_OWNER, uid,
	    pattr == &pid_attr ? &pid_pops : &usdt_pops, new_fp,
	    &new_fp->ftp_provid) != 0) {
		mutex_exit(&bucket->ftb_mtx);
		fasttrap_provider_free(new_fp);
		return (NULL);
	}

	new_fp->ftp_next = bucket->ftb_data;
	bucket->ftb_data = new_fp;

	mutex_enter(&new_fp->ftp_mtx);
	mutex_exit(&bucket->ftb_mtx);

	return (new_fp);
}

static void
fasttrap_provider_free(fasttrap_provider_t *provider)
{
	pid_t pid = provider->ftp_pid;
	proc_t *p;

	/*
	 * There need to be no consumers using this provider and no
	 * associated enabled probes.
	 */
	ASSERT(provider->ftp_ccount == 0);
	ASSERT(provider->ftp_rcount == 0);

	kmem_free(provider, sizeof (fasttrap_provider_t));

	/*
	 * Decrement p_dtrace_probes on the process whose provider we're
	 * freeing. We don't have to worry about clobbering somone else's
	 * modifications to it because we have locked the bucket that
	 * corresponds to this process's hash chain in the provider hash
	 * table. Don't sweat it if we can't find the process.
	 */
	mutex_enter(&pidlock);
	if ((p = prfind(pid)) == NULL) {
		mutex_exit(&pidlock);
		return;
	}

	mutex_enter(&p->p_lock);
	mutex_exit(&pidlock);

	p->p_dtrace_probes--;
	mutex_exit(&p->p_lock);
}

static void
fasttrap_provider_retire(fasttrap_provider_t *provider)
{
	dtrace_provider_id_t provid = provider->ftp_provid;

	/*
	 * Mark the provider to be removed in our post-processing step
	 * and mark it as defunct. The former indicates that we should try
	 * to remove it, the latter indicates that even if we were unable
	 * to remove it, this provider shouldn't be used to create probes
	 * in the future.
	 */
	provider->ftp_defunct = 1;
	provider->ftp_marked = 1;
	mutex_exit(&provider->ftp_mtx);

	/*
	 * We don't have to worry about invalidating the same provider twice
	 * since fasttrap_provider_lookup() will ignore provider that have
	 * been marked as defunct.
	 */
	dtrace_invalidate(provid);

	fasttrap_pid_cleanup();
}

static int
fasttrap_add_probe(fasttrap_probe_spec_t *pdata)
{
	fasttrap_provider_t *provider;
	fasttrap_probe_t *pp;
	fasttrap_tracepoint_t *tp;
	char *name;
	size_t size;
	int i, aframes, whack;

	switch (pdata->ftps_type) {
	case DTFTP_ENTRY:
		name = "entry";
		aframes = FASTTRAP_ENTRY_AFRAMES;
		break;
	case DTFTP_RETURN:
		name = "return";
		aframes = FASTTRAP_RETURN_AFRAMES;
		break;
	case DTFTP_OFFSETS:
		name = NULL;
		break;
	default:
		return (EINVAL);
	}

	if ((provider = fasttrap_provider_lookup(pdata->ftps_pid,
	    FASTTRAP_PID_NAME, &pid_attr)) == NULL)
		return (ESRCH);

	/*
	 * Increment this reference count to indicate that a consumer is
	 * actively adding a new probe associated with this provider.
	 */
	provider->ftp_ccount++;
	mutex_exit(&provider->ftp_mtx);

	if (name != NULL) {
		if (dtrace_probe_lookup(provider->ftp_provid,
		    pdata->ftps_mod, pdata->ftps_func, name) != 0)
			goto done;

		atomic_add_32(&fasttrap_total, pdata->ftps_noffs);

		if (fasttrap_total > fasttrap_max) {
			atomic_add_32(&fasttrap_total, -pdata->ftps_noffs);
			goto no_mem;
		}

		ASSERT(pdata->ftps_noffs > 0);
		size = sizeof (fasttrap_probe_t) +
		    sizeof (pp->ftp_tps[0]) * (pdata->ftps_noffs - 1);

		pp = kmem_zalloc(size, KM_SLEEP);

		pp->ftp_prov = provider;
		pp->ftp_faddr = pdata->ftps_pc;
		pp->ftp_fsize = pdata->ftps_size;
		pp->ftp_pid = pdata->ftps_pid;
		pp->ftp_ntps = pdata->ftps_noffs;
		pp->ftp_type = pdata->ftps_type;

		for (i = 0; i < pdata->ftps_noffs; i++) {
			tp = kmem_zalloc(sizeof (fasttrap_tracepoint_t),
			    KM_SLEEP);

			tp->ftt_prov = provider;
			tp->ftt_pc = pdata->ftps_offs[i] + pdata->ftps_pc;
			tp->ftt_pid = pdata->ftps_pid;

			pp->ftp_tps[i].fit_tp = tp;
			pp->ftp_tps[i].fit_id.fti_probe = pp;
		}

		pp->ftp_id = dtrace_probe_create(provider->ftp_provid,
		    pdata->ftps_mod, pdata->ftps_func, name, aframes, pp);
	} else {
		for (i = 0; i < pdata->ftps_noffs; i++) {
			char name_str[17];

			(void) sprintf(name_str, "%llx",
			    (unsigned long long)pdata->ftps_offs[i]);

			if (dtrace_probe_lookup(provider->ftp_provid,
			    pdata->ftps_mod, pdata->ftps_func, name_str) != 0)
				continue;

			atomic_add_32(&fasttrap_total, 1);

			if (fasttrap_total > fasttrap_max) {
				atomic_add_32(&fasttrap_total, -1);
				goto no_mem;
			}

			pp = kmem_zalloc(sizeof (fasttrap_probe_t), KM_SLEEP);

			pp->ftp_prov = provider;
			pp->ftp_faddr = pdata->ftps_pc;
			pp->ftp_fsize = pdata->ftps_size;
			pp->ftp_pid = pdata->ftps_pid;
			pp->ftp_ntps = 1;
			pp->ftp_type = pdata->ftps_type;

			tp = kmem_zalloc(sizeof (fasttrap_tracepoint_t),
			    KM_SLEEP);

			tp->ftt_prov = provider;
			tp->ftt_pc = pdata->ftps_offs[i] + pdata->ftps_pc;
			tp->ftt_pid = pdata->ftps_pid;

			pp->ftp_tps[0].fit_tp = tp;
			pp->ftp_tps[0].fit_id.fti_probe = pp;

			pp->ftp_id = dtrace_probe_create(provider->ftp_provid,
			    pdata->ftps_mod, pdata->ftps_func, name_str,
			    FASTTRAP_OFFSET_AFRAMES, pp);
		}
	}

done:
	/*
	 * We know that the provider is still valid since we incremented the
	 * reference count. If someone tried to free this provider while we
	 * were using it (e.g. because the process called exec(2) or exit(2)),
	 * take note of that and try to free it now.
	 */
	mutex_enter(&provider->ftp_mtx);
	provider->ftp_ccount--;
	whack = provider->ftp_defunct;
	mutex_exit(&provider->ftp_mtx);

	if (whack)
		fasttrap_pid_cleanup();

	return (0);

no_mem:
	/*
	 * If we've exhausted the allowable resources, we'll try to remove
	 * this provider to free some up. This is to cover the case where
	 * the user has accidentally created many more probes than was
	 * intended (e.g. pid123:::).
	 */
	mutex_enter(&provider->ftp_mtx);
	provider->ftp_ccount--;
	provider->ftp_marked = 1;
	mutex_exit(&provider->ftp_mtx);

	fasttrap_pid_cleanup();

	return (ENOMEM);
}

/*ARGSUSED*/