/*
 * 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 2017 Joyent, Inc.
 */

#include <sys/dtrace_impl.h>
#include <sys/atomic.h>
#include <sys/model.h>
#include <sys/frame.h>
#include <sys/stack.h>
#include <sys/machpcb.h>
#include <sys/procfs_isa.h>
#include <sys/cmn_err.h>
#include <sys/sysmacros.h>

#define DTRACE_FMT3OP3_MASK     0x81000000
#define DTRACE_FMT3OP3          0x80000000
#define DTRACE_FMT3RS1_SHIFT    14
#define DTRACE_FMT3RD_SHIFT     25
#define DTRACE_DISP22_SHIFT     10
#define DTRACE_RMASK            0x1f
#define DTRACE_REG_L0           16
#define DTRACE_REG_O7           15
#define DTRACE_REG_I0           24
#define DTRACE_REG_I6           30
#define DTRACE_RET              0x81c7e008
#define DTRACE_RETL             0x81c3e008
#define DTRACE_SAVE_MASK        0xc1f80000
#define DTRACE_SAVE             0x81e00000
#define DTRACE_RESTORE          0x81e80000
#define DTRACE_CALL_MASK        0xc0000000
#define DTRACE_CALL             0x40000000
#define DTRACE_JMPL_MASK        0x81f80000
#define DTRACE_JMPL             0x81c00000
#define DTRACE_BA_MASK          0xdfc00000
#define DTRACE_BA               0x10800000
#define DTRACE_BA_MAX           10

extern int dtrace_getupcstack_top(uint64_t *, int, uintptr_t *);
extern int dtrace_getustackdepth_top(uintptr_t *);
extern ulong_t dtrace_getreg_win(uint_t, uint_t);
extern void dtrace_putreg_win(uint_t, ulong_t);
extern int dtrace_fish(int, int, uintptr_t *);

int     dtrace_ustackdepth_max = 2048;

/*
 * This is similar in principle to getpcstack(), but there are several marked
 * differences in implementation:
 *
 * (a)  dtrace_getpcstack() is called from probe context.  Thus, the call
 *      to flush_windows() from getpcstack() is a call to the probe-safe
 *      equivalent here.
 *
 * (b)  dtrace_getpcstack() is willing to sacrifice some performance to get
 *      a correct stack.  While consumers of getpcstack() are largely
 *      subsystem-specific in-kernel debugging facilities, DTrace consumers
 *      are arbitrary user-level analysis tools; dtrace_getpcstack() must
 *      deliver as correct a stack as possible.  Details on the issues
 *      surrounding stack correctness are found below.
 *
 * (c)  dtrace_getpcstack() _always_ fills in pcstack_limit pc_t's -- filling
 *      in the difference between the stack depth and pcstack_limit with NULLs.
 *      Due to this behavior dtrace_getpcstack() returns void.
 *
 * (d)  dtrace_getpcstack() takes a third parameter, aframes, that
 *      denotes the number of _artificial frames_ on the bottom of the
 *      stack.  An artificial frame is one induced by the provider; all
 *      artificial frames are stripped off before frames are stored to
 *      pcstack.
 *
 * (e)  dtrace_getpcstack() takes a fourth parameter, pc, that indicates
 *      an interrupted program counter (if any).  This should be a non-NULL
 *      value if and only if the hit probe is unanchored.  (Anchored probes
 *      don't fire through an interrupt source.)  This parameter is used to
 *      assure (b), above.
 */
void
dtrace_getpcstack(pc_t *pcstack, int pcstack_limit, int aframes, uint32_t *pc)
{
        struct frame *fp, *nextfp, *minfp, *stacktop;
        int depth = 0;
        int on_intr, j = 0;
        uint32_t i, r;

        fp = (struct frame *)((caddr_t)dtrace_getfp() + STACK_BIAS);
        dtrace_flush_windows();

        if (pc != NULL) {
                /*
                 * If we've been passed a non-NULL pc, we need to determine
                 * whether or not the specified program counter falls in a leaf
                 * function.  If it falls within a leaf function, we know that
                 * %o7 is valid in its frame (and we can just drive on).  If
                 * it's a non-leaf, however, we know that %o7 is garbage in the
                 * bottom frame.  To trim this frame, we simply increment
                 * aframes and drop into the stack-walking loop.
                 *
                 * To quickly determine if the specified program counter is in
                 * a leaf function, we exploit the fact that leaf functions
                 * tend to be short and non-leaf functions tend to frequently
                 * perform operations that are only permitted in a non-leaf
                 * function (e.g., using the %i's or %l's; calling a function;
                 * performing a restore).  We exploit these tendencies by
                 * simply scanning forward from the specified %pc -- if we see
                 * an operation only permitted in a non-leaf, we know we're in
                 * a non-leaf; if we see a retl, we know we're in a leaf.
                 * Fortunately, one need not perform anywhere near full
                 * disassembly to effectively determine the former: determining
                 * that an instruction is a format-3 instruction and decoding
                 * its rd and rs1 fields, for example, requires very little
                 * manipulation.  Overall, this method of leaf determination
                 * performs quite well:  on average, we only examine between
                 * 1.5 and 2.5 instructions before making the determination.
                 * (Outliers do exist, however; of note is the non-leaf
                 * function ip_sioctl_not_ours() which -- as of this writing --
                 * has a whopping 455 straight instructions that manipulate
                 * only %g's and %o's.)
                 */
                int delay = 0, branches = 0, taken = 0;

                if (depth < pcstack_limit)
                        pcstack[depth++] = (pc_t)(uintptr_t)pc;

                /*
                 * Our heuristic is exactly that -- a heuristic -- and there
                 * exists a possibility that we could be either be vectored
                 * off into the weeds (by following a bogus branch) or could
                 * wander off the end of the function and off the end of a
                 * text mapping (by not following a conditional branch at the
                 * end of the function that is effectively always taken).  So
                 * as a precautionary measure, we set the NOFAULT flag.
                 */
                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);

                for (;;) {
                        i = pc[j++];

                        if ((i & DTRACE_FMT3OP3_MASK) == DTRACE_FMT3OP3) {
                                /*
                                 * This is a format-3 instruction.  We can
                                 * look at rd and rs1.
                                 */
                                r = (i >> DTRACE_FMT3RS1_SHIFT) & DTRACE_RMASK;

                                if (r >= DTRACE_REG_L0)
                                        goto nonleaf;

                                r = (i >> DTRACE_FMT3RD_SHIFT) & DTRACE_RMASK;

                                if (r >= DTRACE_REG_L0)
                                        goto nonleaf;

                                if ((i & DTRACE_JMPL_MASK) == DTRACE_JMPL) {
                                        delay = 1;
                                        continue;
                                }

                                /*
                                 * If we see explicit manipulation with %o7
                                 * as a destination register, we know that
                                 * %o7 is likely bogus -- and we treat this
                                 * function as a non-leaf.
                                 */
                                if (r == DTRACE_REG_O7) {
                                        if (delay)
                                                goto leaf;

                                        i &= DTRACE_JMPL_MASK;

                                        if (i == DTRACE_JMPL) {
                                                delay = 1;
                                                continue;
                                        }

                                        goto nonleaf;
                                }
                        } else {
                                /*
                                 * If this is a call, it may or may not be
                                 * a leaf; we need to check the delay slot.
                                 */
                                if ((i & DTRACE_CALL_MASK) == DTRACE_CALL) {
                                        delay = 1;
                                        continue;
                                }

                                /*
                                 * If we see a ret it's not a leaf; if we
                                 * see a retl, it is a leaf.
                                 */
                                if (i == DTRACE_RET)
                                        goto nonleaf;

                                if (i == DTRACE_RETL)
                                        goto leaf;

                                /*
                                 * If this is a ba (annulled or not), then we
                                 * need to actually follow the branch.  No, we
                                 * don't look at the delay slot -- hopefully
                                 * anything that can be gleaned from the delay
                                 * slot can also be gleaned from the branch
                                 * target.  To prevent ourselves from iterating
                                 * infinitely, we clamp the number of branches
                                 * that we'll follow, and we refuse to follow
                                 * the same branch twice consecutively.  In
                                 * both cases, we abort by deciding that we're
                                 * looking at a leaf.  While in theory this
                                 * could be wrong (we could be in the middle of
                                 * a loop in a non-leaf that ends with a ba and
                                 * only manipulates outputs and globals in the
                                 * body of the loop -- therefore leading us to
                                 * the wrong conclusion), this doesn't seem to
                                 * crop up in practice.  (Or rather, this
                                 * condition could not be deliberately induced,
                                 * despite concerted effort.)
                                 */
                                if ((i & DTRACE_BA_MASK) == DTRACE_BA) {
                                        if (++branches == DTRACE_BA_MAX ||
                                            taken == j)
                                                goto nonleaf;

                                        taken = j;
                                        j += ((int)(i << DTRACE_DISP22_SHIFT) >>
                                            DTRACE_DISP22_SHIFT) - 1;
                                        continue;
                                }

                                /*
                                 * Finally, if it's a save, it should be
                                 * treated as a leaf; if it's a restore it
                                 * should not be treated as a leaf.
                                 */
                                if ((i & DTRACE_SAVE_MASK) == DTRACE_SAVE)
                                        goto leaf;

                                if ((i & DTRACE_SAVE_MASK) == DTRACE_RESTORE)
                                        goto nonleaf;
                        }

                        if (delay) {
                                /*
                                 * If this was a delay slot instruction and
                                 * we didn't pick it up elsewhere, this is a
                                 * non-leaf.
                                 */
                                goto nonleaf;
                        }
                }
nonleaf:
                aframes++;
leaf:
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
        }

        if ((on_intr = CPU_ON_INTR(CPU)) != 0)
                stacktop = (struct frame *)(CPU->cpu_intr_stack + SA(MINFRAME));
        else
                stacktop = (struct frame *)curthread->t_stk;
        minfp = fp;

        while (depth < pcstack_limit) {
                nextfp = (struct frame *)((caddr_t)fp->fr_savfp + STACK_BIAS);
                if (nextfp <= minfp || nextfp >= stacktop) {
                        if (!on_intr && nextfp == stacktop && aframes != 0) {
                                /*
                                 * If we are exactly at the top of the stack
                                 * with a non-zero number of artificial frames,
                                 * it must be that the stack is filled with
                                 * nothing _but_ artificial frames.  In this
                                 * case, we assert that this is so, zero
                                 * pcstack, and return.
                                 */
                                ASSERT(aframes == 1);
                                ASSERT(depth == 0);

                                while (depth < pcstack_limit)
                                        pcstack[depth++] = 0;
                                return;
                        }

                        if (on_intr) {
                                /*
                                 * Hop from interrupt stack to thread stack.
                                 */
                                stacktop = (struct frame *)curthread->t_stk;
                                minfp = (struct frame *)curthread->t_stkbase;

                                on_intr = 0;

                                if (nextfp > minfp && nextfp < stacktop)
                                        continue;
                        } else {
                                /*
                                 * High-level interrupts may occur when %sp is
                                 * not necessarily contained in the stack
                                 * bounds implied by %g7 -- interrupt thread
                                 * management runs with %pil at DISP_LEVEL,
                                 * and high-level interrupts may thus occur
                                 * in windows when %sp and %g7 are not self-
                                 * consistent.  If we call dtrace_getpcstack()
                                 * from a high-level interrupt that has occurred
                                 * in such a window, we will fail the above test
                                 * of nextfp against minfp/stacktop.  If the
                                 * high-level interrupt has in turn interrupted
                                 * a non-passivated interrupt thread, we
                                 * will execute the below code with non-zero
                                 * aframes.  We therefore want to assert that
                                 * aframes is zero _or_ we are in a high-level
                                 * interrupt -- but because cpu_intr_actv is
                                 * updated with high-level interrupts enabled,
                                 * we must reduce this to only asserting that
                                 * %pil is greater than DISP_LEVEL.
                                 */
                                ASSERT(aframes == 0 ||
                                    dtrace_getipl() > DISP_LEVEL);
                                pcstack[depth++] = (pc_t)fp->fr_savpc;
                        }

                        while (depth < pcstack_limit)
                                pcstack[depth++] = 0;
                        return;
                }

                if (aframes > 0) {
                        aframes--;
                } else {
                        pcstack[depth++] = (pc_t)fp->fr_savpc;
                }

                fp = nextfp;
                minfp = fp;
        }
}

static int
dtrace_getustack_common(uint64_t *pcstack, int pcstack_limit, uintptr_t sp)
{
        proc_t *p = curproc;
        int ret = 0;
        uintptr_t oldsp;
        volatile uint16_t *flags =
            (volatile uint16_t *)&cpu_core[CPU->cpu_id].cpuc_dtrace_flags;

        ASSERT(pcstack == NULL || pcstack_limit > 0);
        ASSERT(dtrace_ustackdepth_max > 0);

        if (p->p_model == DATAMODEL_NATIVE) {
                for (;;) {
                        struct frame *fr = (struct frame *)(sp + STACK_BIAS);
                        uintptr_t pc;

                        if (sp == 0 || fr == NULL ||
                            !IS_P2ALIGNED((uintptr_t)fr, STACK_ALIGN))
                                break;

                        oldsp = sp;

                        pc = dtrace_fulword(&fr->fr_savpc);
                        sp = dtrace_fulword(&fr->fr_savfp);

                        if (pc == 0)
                                break;

                        /*
                         * We limit the number of times we can go around this
                         * loop to account for a circular stack.
                         */
                        if (sp == oldsp || ret++ >= dtrace_ustackdepth_max) {
                                *flags |= CPU_DTRACE_BADSTACK;
                                cpu_core[CPU->cpu_id].cpuc_dtrace_illval = sp;
                                break;
                        }

                        if (pcstack != NULL) {
                                *pcstack++ = pc;
                                pcstack_limit--;
                                if (pcstack_limit == 0)
                                        break;
                        }
                }
        } else {
                /*
                 * Truncate the stack pointer to 32-bits as there may be
                 * garbage in the upper bits which would normally be ignored
                 * by the processor in 32-bit mode.
                 */
                sp = (uint32_t)sp;

                for (;;) {
                        struct frame32 *fr = (struct frame32 *)sp;
                        uint32_t pc;

                        if (sp == 0 ||
                            !IS_P2ALIGNED((uintptr_t)fr, STACK_ALIGN32))
                                break;

                        oldsp = sp;

                        pc = dtrace_fuword32(&fr->fr_savpc);
                        sp = dtrace_fuword32(&fr->fr_savfp);

                        if (pc == 0)
                                break;

                        if (sp == oldsp || ret++ >= dtrace_ustackdepth_max) {
                                *flags |= CPU_DTRACE_BADSTACK;
                                cpu_core[CPU->cpu_id].cpuc_dtrace_illval = sp;
                                break;
                        }

                        if (pcstack != NULL) {
                                *pcstack++ = pc;
                                pcstack_limit--;
                                if (pcstack_limit == 0)
                                        break;
                        }
                }
        }

        return (ret);
}

void
dtrace_getupcstack(uint64_t *pcstack, int pcstack_limit)
{
        klwp_t *lwp = ttolwp(curthread);
        proc_t *p = curproc;
        struct regs *rp;
        uintptr_t sp;
        int n;

        ASSERT(DTRACE_CPUFLAG_ISSET(CPU_DTRACE_NOFAULT));

        if (pcstack_limit <= 0)
                return;

        /*
         * If there's no user context we still need to zero the stack.
         */
        if (lwp == NULL || p == NULL || (rp = lwp->lwp_regs) == NULL)
                goto zero;

        *pcstack++ = (uint64_t)p->p_pid;
        pcstack_limit--;

        if (pcstack_limit <= 0)
                return;

        *pcstack++ = (uint64_t)rp->r_pc;
        pcstack_limit--;

        if (pcstack_limit <= 0)
                return;

        if (DTRACE_CPUFLAG_ISSET(CPU_DTRACE_ENTRY)) {
                *pcstack++ = (uint64_t)rp->r_o7;
                pcstack_limit--;
                if (pcstack_limit <= 0)
                        return;
        }

        sp = rp->r_sp;

        n = dtrace_getupcstack_top(pcstack, pcstack_limit, &sp);
        ASSERT(n >= 0);
        ASSERT(n <= pcstack_limit);

        pcstack += n;
        pcstack_limit -= n;
        if (pcstack_limit <= 0)
                return;

        n = dtrace_getustack_common(pcstack, pcstack_limit, sp);
        ASSERT(n >= 0);
        ASSERT(n <= pcstack_limit);

        pcstack += n;
        pcstack_limit -= n;

zero:
        while (pcstack_limit-- > 0)
                *pcstack++ = 0;
}

int
dtrace_getustackdepth(void)
{
        klwp_t *lwp = ttolwp(curthread);
        proc_t *p = curproc;
        struct regs *rp;
        uintptr_t sp;
        int n = 1;

        if (lwp == NULL || p == NULL || (rp = lwp->lwp_regs) == NULL)
                return (0);

        if (DTRACE_CPUFLAG_ISSET(CPU_DTRACE_FAULT))
                return (-1);

        sp = rp->r_sp;

        n += dtrace_getustackdepth_top(&sp);
        n += dtrace_getustack_common(NULL, 0, sp);

        /*
         * Add one more to the stack depth if we're in an entry probe as long
         * as the return address is non-NULL or there are additional frames
         * beyond that NULL return address.
         */
        if (DTRACE_CPUFLAG_ISSET(CPU_DTRACE_ENTRY) &&
            (rp->r_o7 != 0 || n != 1))
                n++;

        return (n);
}

void
dtrace_getufpstack(uint64_t *pcstack, uint64_t *fpstack, int pcstack_limit)
{
        klwp_t *lwp = ttolwp(curthread);
        proc_t *p = ttoproc(curthread);
        struct regs *rp;
        uintptr_t sp;

        if (pcstack_limit <= 0)
                return;

        /*
         * If there's no user context we still need to zero the stack.
         */
        if (lwp == NULL || p == NULL || (rp = lwp->lwp_regs) == NULL)
                goto zero;

        *pcstack++ = (uint64_t)p->p_pid;
        pcstack_limit--;

        if (pcstack_limit <= 0)
                return;

        if (DTRACE_CPUFLAG_ISSET(CPU_DTRACE_ENTRY)) {
                *fpstack++ = 0;
                *pcstack++ = (uint64_t)rp->r_pc;
                pcstack_limit--;
                if (pcstack_limit <= 0)
                        return;

                *fpstack++ = (uint64_t)rp->r_sp;
                *pcstack++ = (uint64_t)rp->r_o7;
                pcstack_limit--;
        } else {
                *fpstack++ = (uint64_t)rp->r_sp;
                *pcstack++ = (uint64_t)rp->r_pc;
                pcstack_limit--;
        }

        if (pcstack_limit <= 0)
                return;

        sp = rp->r_sp;

        dtrace_flush_user_windows();

        if (p->p_model == DATAMODEL_NATIVE) {
                while (pcstack_limit > 0) {
                        struct frame *fr = (struct frame *)(sp + STACK_BIAS);
                        uintptr_t pc;

                        if (sp == 0 || fr == NULL ||
                            ((uintptr_t)&fr->fr_savpc & 3) != 0 ||
                            ((uintptr_t)&fr->fr_savfp & 3) != 0)
                                break;

                        pc = dtrace_fulword(&fr->fr_savpc);
                        sp = dtrace_fulword(&fr->fr_savfp);

                        if (pc == 0)
                                break;

                        *fpstack++ = sp;
                        *pcstack++ = pc;
                        pcstack_limit--;
                }
        } else {
                /*
                 * Truncate the stack pointer to 32-bits as there may be
                 * garbage in the upper bits which would normally be ignored
                 * by the processor in 32-bit mode.
                 */
                sp = (uint32_t)sp;

                while (pcstack_limit > 0) {
                        struct frame32 *fr = (struct frame32 *)sp;
                        uint32_t pc;

                        if (sp == 0 ||
                            ((uintptr_t)&fr->fr_savpc & 3) != 0 ||
                            ((uintptr_t)&fr->fr_savfp & 3) != 0)
                                break;

                        pc = dtrace_fuword32(&fr->fr_savpc);
                        sp = dtrace_fuword32(&fr->fr_savfp);

                        if (pc == 0)
                                break;

                        *fpstack++ = sp;
                        *pcstack++ = pc;
                        pcstack_limit--;
                }
        }

zero:
        while (pcstack_limit-- > 0)
                *pcstack++ = 0;
}

uint64_t
dtrace_getarg(int arg, int aframes)
{
        uintptr_t val;
        struct frame *fp;
        uint64_t rval;

        /*
         * Account for the fact that dtrace_getarg() consumes an additional
         * stack frame.
         */
        aframes++;

        if (arg < 6) {
                if (dtrace_fish(aframes, DTRACE_REG_I0 + arg, &val) == 0)
                        return (val);
        } else {
                if (dtrace_fish(aframes, DTRACE_REG_I6, &val) == 0) {
                        /*
                         * We have a stack pointer; grab the argument.
                         */
                        fp = (struct frame *)(val + STACK_BIAS);

                        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                        rval = fp->fr_argx[arg - 6];
                        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

                        return (rval);
                }
        }

        /*
         * There are other ways to do this.  But the slow, painful way works
         * just fine.  Because this requires some loads, we need to set
         * CPU_DTRACE_NOFAULT to protect against looking for an argument that
         * isn't there.
         */
        fp = (struct frame *)((caddr_t)dtrace_getfp() + STACK_BIAS);
        dtrace_flush_windows();

        DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);

        for (aframes -= 1; aframes; aframes--)
                fp = (struct frame *)((caddr_t)fp->fr_savfp + STACK_BIAS);

        if (arg < 6) {
                rval = fp->fr_arg[arg];
        } else {
                fp = (struct frame *)((caddr_t)fp->fr_savfp + STACK_BIAS);
                rval = fp->fr_argx[arg - 6];
        }

        DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);

        return (rval);
}

int
dtrace_getstackdepth(int aframes)
{
        struct frame *fp, *nextfp, *minfp, *stacktop;
        int depth = 0;
        int on_intr;

        fp = (struct frame *)((caddr_t)dtrace_getfp() + STACK_BIAS);
        dtrace_flush_windows();

        if ((on_intr = CPU_ON_INTR(CPU)) != 0)
                stacktop = (struct frame *)CPU->cpu_intr_stack + SA(MINFRAME);
        else
                stacktop = (struct frame *)curthread->t_stk;
        minfp = fp;

        for (;;) {
                nextfp = (struct frame *)((caddr_t)fp->fr_savfp + STACK_BIAS);
                if (nextfp <= minfp || nextfp >= stacktop) {
                        if (on_intr) {
                                /*
                                 * Hop from interrupt stack to thread stack.
                                 */
                                stacktop = (struct frame *)curthread->t_stk;
                                minfp = (struct frame *)curthread->t_stkbase;
                                on_intr = 0;
                                continue;
                        }

                        return (++depth);
                }

                if (aframes > 0) {
                        aframes--;
                } else {
                        depth++;
                }

                fp = nextfp;
                minfp = fp;
        }
}

/*
 * This uses the same register numbering scheme as in sys/procfs_isa.h.
 */
ulong_t
dtrace_getreg(struct regs *rp, uint_t reg)
{
        ulong_t value;
        uintptr_t fp;
        struct machpcb *mpcb;

        if (reg == R_G0)
                return (0);

        if (reg <= R_G7)
                return ((&rp->r_g1)[reg - 1]);

        if (reg > R_I7) {
                switch (reg) {
                case R_CCR:
                        return ((rp->r_tstate >> TSTATE_CCR_SHIFT) &
                            TSTATE_CCR_MASK);
                case R_PC:
                        return (rp->r_pc);
                case R_nPC:
                        return (rp->r_npc);
                case R_Y:
                        return (rp->r_y);
                case R_ASI:
                        return ((rp->r_tstate >> TSTATE_ASI_SHIFT) &
                            TSTATE_ASI_MASK);
                case R_FPRS:
                        return (dtrace_getfprs());
                default:
                        DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
                        return (0);
                }
        }

        /*
         * We reach go to the fake restore case if the probe we hit was a pid
         * return probe on a restore instruction. We partially emulate the
         * restore in the kernel and then execute a simple restore
         * instruction that we've secreted away to do the actual register
         * window manipulation. We need to go one register window further
         * down to get at the %ls, and %is and we need to treat %os like %is
         * to pull them out of the topmost user frame.
         */
        if (DTRACE_CPUFLAG_ISSET(CPU_DTRACE_FAKERESTORE)) {
                if (reg > R_O7)
                        goto fake_restore;
                else
                        reg += R_I0 - R_O0;

        } else if (reg <= R_O7) {
                return ((&rp->r_g1)[reg - 1]);
        }

        if (dtrace_getotherwin() > 0)
                return (dtrace_getreg_win(reg, 1));

        mpcb = (struct machpcb *)((caddr_t)rp - REGOFF);

        if (curproc->p_model == DATAMODEL_NATIVE) {
                struct frame *fr = (void *)(rp->r_sp + STACK_BIAS);

                if (mpcb->mpcb_wbcnt > 0) {
                        struct rwindow *rwin = (void *)mpcb->mpcb_wbuf;
                        int i = mpcb->mpcb_wbcnt;
                        do {
                                i--;
                                if ((long)mpcb->mpcb_spbuf[i] == rp->r_sp)
                                        return (rwin[i].rw_local[reg - 16]);
                        } while (i > 0);
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                value = dtrace_fulword(&fr->fr_local[reg - 16]);
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
        } else {
                struct frame32 *fr = (void *)(uintptr_t)(caddr32_t)rp->r_sp;

                if (mpcb->mpcb_wbcnt > 0) {
                        struct rwindow32 *rwin = (void *)mpcb->mpcb_wbuf;
                        int i = mpcb->mpcb_wbcnt;
                        do {
                                i--;
                                if ((long)mpcb->mpcb_spbuf[i] == rp->r_sp)
                                        return (rwin[i].rw_local[reg - 16]);
                        } while (i > 0);
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                value = dtrace_fuword32(&fr->fr_local[reg - 16]);
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
        }

        return (value);

fake_restore:
        ASSERT(R_L0 <= reg && reg <= R_I7);

        /*
         * We first look two user windows down to see if we can dig out
         * the register we're looking for.
         */
        if (dtrace_getotherwin() > 1)
                return (dtrace_getreg_win(reg, 2));

        /*
         * First we need to get the frame pointer and then we perform
         * the same computation as in the non-fake-o-restore case.
         */

        mpcb = (struct machpcb *)((caddr_t)rp - REGOFF);

        if (dtrace_getotherwin() > 0) {
                fp = dtrace_getreg_win(R_FP, 1);
                goto got_fp;
        }

        if (curproc->p_model == DATAMODEL_NATIVE) {
                struct frame *fr = (void *)(rp->r_sp + STACK_BIAS);

                if (mpcb->mpcb_wbcnt > 0) {
                        struct rwindow *rwin = (void *)mpcb->mpcb_wbuf;
                        int i = mpcb->mpcb_wbcnt;
                        do {
                                i--;
                                if ((long)mpcb->mpcb_spbuf[i] == rp->r_sp) {
                                        fp = rwin[i].rw_fp;
                                        goto got_fp;
                                }
                        } while (i > 0);
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                fp = dtrace_fulword(&fr->fr_savfp);
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                if (cpu_core[CPU->cpu_id].cpuc_dtrace_flags & CPU_DTRACE_FAULT)
                        return (0);
        } else {
                struct frame32 *fr = (void *)(uintptr_t)(caddr32_t)rp->r_sp;

                if (mpcb->mpcb_wbcnt > 0) {
                        struct rwindow32 *rwin = (void *)mpcb->mpcb_wbuf;
                        int i = mpcb->mpcb_wbcnt;
                        do {
                                i--;
                                if ((long)mpcb->mpcb_spbuf[i] == rp->r_sp) {
                                        fp = rwin[i].rw_fp;
                                        goto got_fp;
                                }
                        } while (i > 0);
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                fp = dtrace_fuword32(&fr->fr_savfp);
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
                if (cpu_core[CPU->cpu_id].cpuc_dtrace_flags & CPU_DTRACE_FAULT)
                        return (0);
        }
got_fp:

        if (curproc->p_model == DATAMODEL_NATIVE) {
                struct frame *fr = (void *)(fp + STACK_BIAS);

                if (mpcb->mpcb_wbcnt > 0) {
                        struct rwindow *rwin = (void *)mpcb->mpcb_wbuf;
                        int i = mpcb->mpcb_wbcnt;
                        do {
                                i--;
                                if ((long)mpcb->mpcb_spbuf[i] == fp)
                                        return (rwin[i].rw_local[reg - 16]);
                        } while (i > 0);
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                value = dtrace_fulword(&fr->fr_local[reg - 16]);
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
        } else {
                struct frame32 *fr = (void *)(uintptr_t)(caddr32_t)fp;

                if (mpcb->mpcb_wbcnt > 0) {
                        struct rwindow32 *rwin = (void *)mpcb->mpcb_wbuf;
                        int i = mpcb->mpcb_wbcnt;
                        do {
                                i--;
                                if ((long)mpcb->mpcb_spbuf[i] == fp)
                                        return (rwin[i].rw_local[reg - 16]);
                        } while (i > 0);
                }

                DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
                value = dtrace_fuword32(&fr->fr_local[reg - 16]);
                DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
        }

        return (value);
}

/* ARGSUSED */
void
dtrace_setreg(struct regs *rp, uint_t reg, ulong_t val)
{
        /* Not supported at this time */
        DTRACE_CPUFLAG_SET(CPU_DTRACE_ILLOP);
}

/*ARGSUSED*/
uint64_t
dtrace_getvmreg(uint_t ndx, volatile uint16_t *flags)
{
        *flags |= CPU_DTRACE_ILLOP;

        return (0);
}