xref: /illumos-gate/usr/src/uts/i86pc/os/dtrace_subr.c (revision 86ef0a63)

/*
 * 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) 2011, Joyent, Inc. All rights reserved.
 */

#include <sys/dtrace.h>
#include <sys/fasttrap.h>
#include <sys/x_call.h>
#include <sys/cmn_err.h>
#include <sys/trap.h>
#include <sys/psw.h>
#include <sys/privregs.h>
#include <sys/machsystm.h>
#include <vm/seg_kmem.h>

typedef struct dtrace_invop_hdlr {
	int (*dtih_func)(uintptr_t, uintptr_t *, uintptr_t);
	struct dtrace_invop_hdlr *dtih_next;
} dtrace_invop_hdlr_t;

dtrace_invop_hdlr_t *dtrace_invop_hdlr;

int
dtrace_invop(uintptr_t addr, uintptr_t *stack, uintptr_t eax)
{
	dtrace_invop_hdlr_t *hdlr;
	int rval;

	for (hdlr = dtrace_invop_hdlr; hdlr != NULL; hdlr = hdlr->dtih_next) {
		if ((rval = hdlr->dtih_func(addr, stack, eax)) != 0)
			return (rval);
	}

	return (0);
}

void
dtrace_invop_add(int (*func)(uintptr_t, uintptr_t *, uintptr_t))
{
	dtrace_invop_hdlr_t *hdlr;

	hdlr = kmem_alloc(sizeof (dtrace_invop_hdlr_t), KM_SLEEP);
	hdlr->dtih_func = func;
	hdlr->dtih_next = dtrace_invop_hdlr;
	dtrace_invop_hdlr = hdlr;
}

void
dtrace_invop_remove(int (*func)(uintptr_t, uintptr_t *, uintptr_t))
{
	dtrace_invop_hdlr_t *hdlr = dtrace_invop_hdlr, *prev = NULL;

	for (;;) {
		if (hdlr == NULL)
			panic("attempt to remove non-existent invop handler");

		if (hdlr->dtih_func == func)
			break;

		prev = hdlr;
		hdlr = hdlr->dtih_next;
	}

	if (prev == NULL) {
		ASSERT(dtrace_invop_hdlr == hdlr);
		dtrace_invop_hdlr = hdlr->dtih_next;
	} else {
		ASSERT(dtrace_invop_hdlr != hdlr);
		prev->dtih_next = hdlr->dtih_next;
	}

	kmem_free(hdlr, sizeof (dtrace_invop_hdlr_t));
}

int
dtrace_getipl(void)
{
	return (CPU->cpu_pri);
}

/*ARGSUSED*/
void
dtrace_toxic_ranges(void (*func)(uintptr_t base, uintptr_t limit))
{
	extern uintptr_t toxic_addr;
	extern size_t toxic_size;

	(*func)(0, _userlimit);

	if (hole_end > hole_start)
		(*func)(hole_start, hole_end);
	(*func)(toxic_addr, toxic_addr + toxic_size);
	(*func)(0, _userlimit);
}

static int
dtrace_xcall_func(xc_arg_t arg1, xc_arg_t arg2, xc_arg_t arg3 __unused)
{
	dtrace_xcall_t func = (dtrace_xcall_t)arg1;
	(*func)((void*)arg2);

	return (0);
}

/*ARGSUSED*/
void
dtrace_xcall(processorid_t cpu, dtrace_xcall_t func, void *arg)
{
	cpuset_t set;

	CPUSET_ZERO(set);

	if (cpu == DTRACE_CPUALL) {
		CPUSET_ALL(set);
	} else {
		CPUSET_ADD(set, cpu);
	}

	kpreempt_disable();
	xc_sync((xc_arg_t)func, (xc_arg_t)arg, 0, CPUSET2BV(set),
	    dtrace_xcall_func);
	kpreempt_enable();
}

void
dtrace_sync_func(void)
{}

void
dtrace_sync(void)
{
	dtrace_xcall(DTRACE_CPUALL, (dtrace_xcall_t)dtrace_sync_func, NULL);
}

int (*dtrace_pid_probe_ptr)(struct regs *);
int (*dtrace_return_probe_ptr)(struct regs *);

void
dtrace_user_probe(struct regs *rp, caddr_t addr, processorid_t cpuid)
{
	krwlock_t *rwp;
	proc_t *p = curproc;
	extern void trap(struct regs *, caddr_t, processorid_t);

	if (USERMODE(rp->r_cs) || (rp->r_ps & PS_VM)) {
		if (curthread->t_cred != p->p_cred) {
			cred_t *oldcred = curthread->t_cred;
			/*
			 * DTrace accesses t_cred in probe context.  t_cred
			 * must always be either NULL, or point to a valid,
			 * allocated cred structure.
			 */
			curthread->t_cred = crgetcred();
			crfree(oldcred);
		}
	}

	if (rp->r_trapno == T_DTRACE_RET) {
		uint8_t step = curthread->t_dtrace_step;
		uint8_t ret = curthread->t_dtrace_ret;
		uintptr_t npc = curthread->t_dtrace_npc;

		if (curthread->t_dtrace_ast) {
			aston(curthread);
			curthread->t_sig_check = 1;
		}

		/*
		 * Clear all user tracing flags.
		 */
		curthread->t_dtrace_ft = 0;

		/*
		 * If we weren't expecting to take a return probe trap, kill
		 * the process as though it had just executed an unassigned
		 * trap instruction.
		 */
		if (step == 0) {
			tsignal(curthread, SIGILL);
			return;
		}

		/*
		 * If we hit this trap unrelated to a return probe, we're
		 * just here to reset the AST flag since we deferred a signal
		 * until after we logically single-stepped the instruction we
		 * copied out.
		 */
		if (ret == 0) {
			rp->r_pc = npc;
			return;
		}

		/*
		 * We need to wait until after we've called the
		 * dtrace_return_probe_ptr function pointer to set %pc.
		 */
		rwp = &CPU->cpu_ft_lock;
		rw_enter(rwp, RW_READER);
		if (dtrace_return_probe_ptr != NULL)
			(void) (*dtrace_return_probe_ptr)(rp);
		rw_exit(rwp);
		rp->r_pc = npc;

	} else if (rp->r_trapno == T_BPTFLT) {
		uint8_t instr, instr2;
		caddr_t linearpc;
		rwp = &CPU->cpu_ft_lock;

		/*
		 * The DTrace fasttrap provider uses the breakpoint trap
		 * (int 3). We let DTrace take the first crack at handling
		 * this trap; if it's not a probe that DTrace knowns about,
		 * we call into the trap() routine to handle it like a
		 * breakpoint placed by a conventional debugger.
		 */
		rw_enter(rwp, RW_READER);
		if (dtrace_pid_probe_ptr != NULL &&
		    (*dtrace_pid_probe_ptr)(rp) == 0) {
			rw_exit(rwp);
			return;
		}
		rw_exit(rwp);

		if (dtrace_linear_pc(rp, p, &linearpc) != 0) {
			trap(rp, addr, cpuid);
			return;
		}

		/*
		 * If the instruction that caused the breakpoint trap doesn't
		 * look like an int 3 anymore, it may be that this tracepoint
		 * was removed just after the user thread executed it. In
		 * that case, return to user land to retry the instuction.
		 * Note that we assume the length of the instruction to retry
		 * is 1 byte because that's the length of FASTTRAP_INSTR.
		 * We check for r_pc > 0 and > 2 so that we don't have to
		 * deal with segment wraparound.
		 */
		if (rp->r_pc > 0 && fuword8(linearpc - 1, &instr) == 0 &&
		    instr != FASTTRAP_INSTR &&
		    (instr != 3 || (rp->r_pc >= 2 &&
		    (fuword8(linearpc - 2, &instr2) != 0 || instr2 != 0xCD)))) {
			rp->r_pc--;
			return;
		}

		trap(rp, addr, cpuid);

	} else {
		trap(rp, addr, cpuid);
	}
}

void
dtrace_safe_synchronous_signal(void)
{
	kthread_t *t = curthread;
	struct regs *rp = lwptoregs(ttolwp(t));
	size_t isz = t->t_dtrace_npc - t->t_dtrace_pc;

	ASSERT(t->t_dtrace_on);

	/*
	 * If we're not in the range of scratch addresses, we're not actually
	 * tracing user instructions so turn off the flags. If the instruction
	 * we copied out caused a synchonous trap, reset the pc back to its
	 * original value and turn off the flags.
	 */
	if (rp->r_pc < t->t_dtrace_scrpc ||
	    rp->r_pc > t->t_dtrace_astpc + isz) {
		t->t_dtrace_ft = 0;
	} else if (rp->r_pc == t->t_dtrace_scrpc ||
	    rp->r_pc == t->t_dtrace_astpc) {
		rp->r_pc = t->t_dtrace_pc;
		t->t_dtrace_ft = 0;
	}
}

int
dtrace_safe_defer_signal(void)
{
	kthread_t *t = curthread;
	struct regs *rp = lwptoregs(ttolwp(t));
	size_t isz = t->t_dtrace_npc - t->t_dtrace_pc;

	ASSERT(t->t_dtrace_on);

	/*
	 * If we're not in the range of scratch addresses, we're not actually
	 * tracing user instructions so turn off the flags.
	 */
	if (rp->r_pc < t->t_dtrace_scrpc ||
	    rp->r_pc > t->t_dtrace_astpc + isz) {
		t->t_dtrace_ft = 0;
		return (0);
	}

	/*
	 * If we have executed the original instruction, but we have performed
	 * neither the jmp back to t->t_dtrace_npc nor the clean up of any
	 * registers used to emulate %rip-relative instructions in 64-bit mode,
	 * we'll save ourselves some effort by doing that here and taking the
	 * signal right away.  We detect this condition by seeing if the program
	 * counter is the range [scrpc + isz, astpc).
	 */
	if (rp->r_pc >= t->t_dtrace_scrpc + isz &&
	    rp->r_pc < t->t_dtrace_astpc) {
		/*
		 * If there is a scratch register and we're on the
		 * instruction immediately after the modified instruction,
		 * restore the value of that scratch register.
		 */
		if (t->t_dtrace_reg != 0 &&
		    rp->r_pc == t->t_dtrace_scrpc + isz) {
			switch (t->t_dtrace_reg) {
			case REG_RAX:
				rp->r_rax = t->t_dtrace_regv;
				break;
			case REG_RCX:
				rp->r_rcx = t->t_dtrace_regv;
				break;
			case REG_R8:
				rp->r_r8 = t->t_dtrace_regv;
				break;
			case REG_R9:
				rp->r_r9 = t->t_dtrace_regv;
				break;
			}
		}
		rp->r_pc = t->t_dtrace_npc;
		t->t_dtrace_ft = 0;
		return (0);
	}

	/*
	 * Otherwise, make sure we'll return to the kernel after executing
	 * the copied out instruction and defer the signal.
	 */
	if (!t->t_dtrace_step) {
		ASSERT(rp->r_pc < t->t_dtrace_astpc);
		rp->r_pc += t->t_dtrace_astpc - t->t_dtrace_scrpc;
		t->t_dtrace_step = 1;
	}

	t->t_dtrace_ast = 1;

	return (1);
}

/*
 * Additional artificial frames for the machine type. For i86pc, we're already
 * accounted for, so return 0. On the hypervisor, we have an additional frame
 * (xen_callback_handler).
 */
int
dtrace_mach_aframes(void)
{
#ifdef __xpv
	return (1);
#else
	return (0);
#endif
}