i86pc/os/dtrace_subr.c

/*
 * 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))
{
#ifdef __amd64
    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);
#else
    extern void *device_arena_contains(void *, size_t, size_t *);
    caddr_t vaddr;
    size_t  len;

    for (vaddr = (caddr_t)kernelbase; vaddr < (caddr_t)KERNEL_TEXT;
        vaddr += len) {
        len = (caddr_t)KERNEL_TEXT - vaddr;
        vaddr = device_arena_contains(vaddr, len, &len);
        if (vaddr == NULL)
            break;
        (*func)((uintptr_t)vaddr, (uintptr_t)vaddr + len);
    }
#endif
    (*func)(0, _userlimit);
}

static int
dtrace_xcall_func(dtrace_xcall_t func, void *arg)
{
    (*func)(arg);

    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),
        (xc_func_t)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) {
#ifdef __amd64
        /*
         * 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;
            }
        }
#endif
        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
}