xref: /illumos-gate/usr/src/cmd/mdb/intel/mdb/proc_amd64dep.c (revision 0a47c91c)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (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 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */
/*
 * Copyright (c) 2012, Joyent, Inc.  All rights reserved.
 */

/*
 * User Process Target Intel 32-bit component
 *
 * This file provides the ISA-dependent portion of the user process target.
 * For more details on the implementation refer to mdb_proc.c.
 */

#include <mdb/mdb_proc.h>
#include <mdb/mdb_kreg.h>
#include <mdb/mdb_err.h>
#include <mdb/mdb_amd64util.h>
#include <mdb/mdb.h>

#include <sys/frame.h>
#include <libproc.h>
#include <sys/fp.h>
#include <ieeefp.h>

const mdb_tgt_regdesc_t pt_regdesc[] = {
	{ "r15",	REG_R15,	MDB_TGT_R_EXPORT },
	{ "r15d",	REG_R15,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "r15w",	REG_R15,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "r15l",	REG_R15,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "r14",	REG_R14,	MDB_TGT_R_EXPORT },
	{ "r14d",	REG_R14,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "r14w",	REG_R14,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "r14l",	REG_R14,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "r13",	REG_R13,	MDB_TGT_R_EXPORT },
	{ "r13d",	REG_R13,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "r13w",	REG_R13,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "r13l",	REG_R13,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "r12",	REG_R12,	MDB_TGT_R_EXPORT },
	{ "r12d",	REG_R12,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "r12w",	REG_R12,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "r12l",	REG_R12,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "r11",	REG_R11,	MDB_TGT_R_EXPORT },
	{ "r11d",	REG_R11,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "r11w",	REG_R11,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "r11l",	REG_R11,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "r10",	REG_R10,	MDB_TGT_R_EXPORT },
	{ "r10d",	REG_R10,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "r10w",	REG_R10,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "r10l",	REG_R10,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "r9",		REG_R9,		MDB_TGT_R_EXPORT },
	{ "r9d",	REG_R8,		MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "r9w",	REG_R8,		MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "r9l",	REG_R8,		MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "r8",		REG_R8,		MDB_TGT_R_EXPORT },
	{ "r8d",	REG_R8,		MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "r8w",	REG_R8,		MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "r8l",	REG_R8,		MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "rdi",	REG_RDI,	MDB_TGT_R_EXPORT },
	{ "edi",	REG_RDI,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "di",		REG_RDI,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "dil",	REG_RDI,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "rsi",	REG_RSI,	MDB_TGT_R_EXPORT },
	{ "esi",	REG_RSI,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "si",		REG_RSI,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "sil",	REG_RSI,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "rbp",	REG_RBP,	MDB_TGT_R_EXPORT },
	{ "ebp",	REG_RBP,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "bp",		REG_RBP,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "bpl",	REG_RBP,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "rbx",	REG_RBX,	MDB_TGT_R_EXPORT },
	{ "ebx",	REG_RBX,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "bx",		REG_RBX,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "bh",		REG_RBX,	MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
	{ "bl",		REG_RBX,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "rdx",	REG_RDX,	MDB_TGT_R_EXPORT },
	{ "edx",	REG_RDX,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "dx",		REG_RDX,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "dh",		REG_RDX,	MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
	{ "dl",		REG_RDX,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "rcx",	REG_RCX,	MDB_TGT_R_EXPORT },
	{ "ecx",	REG_RCX,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "cx",		REG_RCX,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "ch",		REG_RCX,	MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
	{ "cl",		REG_RCX,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "rax",	REG_RAX,	MDB_TGT_R_EXPORT },
	{ "eax",	REG_RAX,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "ax",		REG_RAX,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "ah",		REG_RAX,	MDB_TGT_R_EXPORT | MDB_TGT_R_8H },
	{ "al",		REG_RAX,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "trapno",	REG_TRAPNO,	MDB_TGT_R_EXPORT },
	{ "err",	REG_ERR,	MDB_TGT_R_EXPORT },
	{ "rip",	REG_RIP,	MDB_TGT_R_EXPORT },
	{ "cs",		REG_CS,		MDB_TGT_R_EXPORT },
	{ "rflags",	REG_RFL,	MDB_TGT_R_EXPORT },
	{ "eflags",	REG_RFL,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "rsp",	REG_RSP,	MDB_TGT_R_EXPORT },
	{ "esp",	REG_RSP,	MDB_TGT_R_EXPORT | MDB_TGT_R_32 },
	{ "sp",		REG_RSP,	MDB_TGT_R_EXPORT | MDB_TGT_R_16 },
	{ "spl",	REG_RSP,	MDB_TGT_R_EXPORT | MDB_TGT_R_8L },
	{ "ss",		REG_SS,		MDB_TGT_R_EXPORT },
	{ "fs",		REG_FS,		MDB_TGT_R_EXPORT },
	{ "gs",		REG_GS,		MDB_TGT_R_EXPORT },
	{ "es",		REG_ES,		MDB_TGT_R_EXPORT },
	{ "ds",		REG_DS,		MDB_TGT_R_EXPORT },
	{ "fsbase",	REG_FSBASE,	MDB_TGT_R_EXPORT },
	{ "gsbase",	REG_GSBASE,	MDB_TGT_R_EXPORT },
	{ NULL, 0, 0 }
};

/*
 * We cannot rely on pr_instr, because if we hit a breakpoint or the user has
 * artifically modified memory, it will no longer be correct.
 */
static uint8_t
pt_read_instr(mdb_tgt_t *t)
{
	const lwpstatus_t *psp = &Pstatus(t->t_pshandle)->pr_lwp;
	uint8_t ret = 0;

	(void) mdb_tgt_vread(t, &ret, sizeof (ret), psp->pr_reg[REG_RIP]);

	return (ret);
}

/*ARGSUSED*/
int
pt_regs(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
	mdb_tgt_t *t = mdb.m_target;
	mdb_tgt_tid_t tid;
	prgregset_t grs;
	prgreg_t rflags;

	if (argc != 0)
		return (DCMD_USAGE);

	if (t->t_pshandle == NULL || Pstate(t->t_pshandle) == PS_UNDEAD) {
		mdb_warn("no process active\n");
		return (DCMD_ERR);
	}

	if (Pstate(t->t_pshandle) == PS_LOST) {
		mdb_warn("debugger has lost control of process\n");
		return (DCMD_ERR);
	}

	if (flags & DCMD_ADDRSPEC)
		tid = (mdb_tgt_tid_t)addr;
	else
		tid = PTL_TID(t);

	if (PTL_GETREGS(t, tid, grs) != 0) {
		mdb_warn("failed to get current register set");
		return (DCMD_ERR);
	}

	rflags = grs[REG_RFL];

	mdb_printf("%%rax = 0x%0?p\t%%r8  = 0x%0?p\n",
	    grs[REG_RAX], grs[REG_R8]);
	mdb_printf("%%rbx = 0x%0?p\t%%r9  = 0x%0?p\n",
	    grs[REG_RBX], grs[REG_R9]);
	mdb_printf("%%rcx = 0x%0?p\t%%r10 = 0x%0?p\n",
	    grs[REG_RCX], grs[REG_R10]);
	mdb_printf("%%rdx = 0x%0?p\t%%r11 = 0x%0?p\n",
	    grs[REG_RDX], grs[REG_R11]);
	mdb_printf("%%rsi = 0x%0?p\t%%r12 = 0x%0?p\n",
	    grs[REG_RSI], grs[REG_R12]);
	mdb_printf("%%rdi = 0x%0?p\t%%r13 = 0x%0?p\n",
	    grs[REG_RDI], grs[REG_R13]);
	mdb_printf("         %?s\t%%r14 = 0x%0?p\n",
	    "", grs[REG_R14]);
	mdb_printf("         %?s\t%%r15 = 0x%0?p\n",
	    "", grs[REG_R15]);

	mdb_printf("\n");

	mdb_printf("%%cs = 0x%04x\t%%fs = 0x%04x\t%%gs = 0x%04x\n",
	    grs[REG_CS], grs[REG_FS], grs[REG_GS]);
	mdb_printf("%%ds = 0x%04x\t%%es = 0x%04x\t%%ss = 0x%04x\n",
	    grs[REG_DS], grs[REG_ES], grs[REG_SS]);

	mdb_printf("\n");

	mdb_printf("%%rip = 0x%0?p %A\n", grs[REG_RIP], grs[REG_RIP]);
	mdb_printf("%%rbp = 0x%0?p\n", grs[REG_RBP], grs[REG_RBP]);
	mdb_printf("%%rsp = 0x%0?p\n", grs[REG_RSP], grs[REG_RSP]);

	mdb_printf("\n");

	mdb_printf("%%rflags = 0x%08x\n", rflags);

	mdb_printf("  id=%u vip=%u vif=%u ac=%u vm=%u rf=%u nt=%u iopl=0x%x\n",
	    (rflags & KREG_EFLAGS_ID_MASK) >> KREG_EFLAGS_ID_SHIFT,
	    (rflags & KREG_EFLAGS_VIP_MASK) >> KREG_EFLAGS_VIP_SHIFT,
	    (rflags & KREG_EFLAGS_VIF_MASK) >> KREG_EFLAGS_VIF_SHIFT,
	    (rflags & KREG_EFLAGS_AC_MASK) >> KREG_EFLAGS_AC_SHIFT,
	    (rflags & KREG_EFLAGS_VM_MASK) >> KREG_EFLAGS_VM_SHIFT,
	    (rflags & KREG_EFLAGS_RF_MASK) >> KREG_EFLAGS_RF_SHIFT,
	    (rflags & KREG_EFLAGS_NT_MASK) >> KREG_EFLAGS_NT_SHIFT,
	    (rflags & KREG_EFLAGS_IOPL_MASK) >> KREG_EFLAGS_IOPL_SHIFT);

	mdb_printf("  status=<%s,%s,%s,%s,%s,%s,%s,%s,%s>\n",
	    (rflags & KREG_EFLAGS_OF_MASK) ? "OF" : "of",
	    (rflags & KREG_EFLAGS_DF_MASK) ? "DF" : "df",
	    (rflags & KREG_EFLAGS_IF_MASK) ? "IF" : "if",
	    (rflags & KREG_EFLAGS_TF_MASK) ? "TF" : "tf",
	    (rflags & KREG_EFLAGS_SF_MASK) ? "SF" : "sf",
	    (rflags & KREG_EFLAGS_ZF_MASK) ? "ZF" : "zf",
	    (rflags & KREG_EFLAGS_AF_MASK) ? "AF" : "af",
	    (rflags & KREG_EFLAGS_PF_MASK) ? "PF" : "pf",
	    (rflags & KREG_EFLAGS_CF_MASK) ? "CF" : "cf");

	mdb_printf("\n");

	mdb_printf("%%gsbase = 0x%0?p\n", grs[REG_GSBASE]);
	mdb_printf("%%fsbase = 0x%0?p\n", grs[REG_FSBASE]);
	mdb_printf("%%trapno = 0x%x\n", grs[REG_TRAPNO]);
	mdb_printf("   %%err = 0x%x\n", grs[REG_ERR]);

	return (set_errno(ENOTSUP));
}

static const char *
fpcw2str(uint32_t cw, char *buf, size_t nbytes)
{
	char *end = buf + nbytes;
	char *p = buf;

	buf[0] = '\0';

	/*
	 * Decode all masks in the 80387 control word.
	 */
	if (cw & FPIM)
		p += mdb_snprintf(p, (size_t)(end - p), "|IM");
	if (cw & FPDM)
		p += mdb_snprintf(p, (size_t)(end - p), "|DM");
	if (cw & FPZM)
		p += mdb_snprintf(p, (size_t)(end - p), "|ZM");
	if (cw & FPOM)
		p += mdb_snprintf(p, (size_t)(end - p), "|OM");
	if (cw & FPUM)
		p += mdb_snprintf(p, (size_t)(end - p), "|UM");
	if (cw & FPPM)
		p += mdb_snprintf(p, (size_t)(end - p), "|PM");
	if (cw & FPPC)
		p += mdb_snprintf(p, (size_t)(end - p), "|PC");
	if (cw & FPRC)
		p += mdb_snprintf(p, (size_t)(end - p), "|RC");
	if (cw & FPIC)
		p += mdb_snprintf(p, (size_t)(end - p), "|IC");

	/*
	 * Decode precision, rounding, and infinity options in control word.
	 */
	if (cw & FPSIG24)
		p += mdb_snprintf(p, (size_t)(end - p), "|SIG24");
	if (cw & FPSIG53)
		p += mdb_snprintf(p, (size_t)(end - p), "|SIG53");
	if (cw & FPSIG64)
		p += mdb_snprintf(p, (size_t)(end - p), "|SIG64");

	if ((cw & FPRC) == (FPRD|FPRU))
		p += mdb_snprintf(p, (size_t)(end - p), "|RTZ");
	else if (cw & FPRD)
		p += mdb_snprintf(p, (size_t)(end - p), "|RD");
	else if (cw & FPRU)
		p += mdb_snprintf(p, (size_t)(end - p), "|RU");
	else
		p += mdb_snprintf(p, (size_t)(end - p), "|RTN");

	if (cw & FPA)
		p += mdb_snprintf(p, (size_t)(end - p), "|A");
	else
		p += mdb_snprintf(p, (size_t)(end - p), "|P");
	if (cw & WFPB17)
		p += mdb_snprintf(p, (size_t)(end - p), "|WFPB17");
	if (cw & WFPB24)
		p += mdb_snprintf(p, (size_t)(end - p), "|WFPB24");

	if (buf[0] == '|')
		return (buf + 1);

	return ("0");
}

static const char *
fpsw2str(uint32_t cw, char *buf, size_t nbytes)
{
	char *end = buf + nbytes;
	char *p = buf;

	buf[0] = '\0';

	/*
	 * Decode all masks in the 80387 status word.
	 */
	if (cw & FPS_IE)
		p += mdb_snprintf(p, (size_t)(end - p), "|IE");
	if (cw & FPS_DE)
		p += mdb_snprintf(p, (size_t)(end - p), "|DE");
	if (cw & FPS_ZE)
		p += mdb_snprintf(p, (size_t)(end - p), "|ZE");
	if (cw & FPS_OE)
		p += mdb_snprintf(p, (size_t)(end - p), "|OE");
	if (cw & FPS_UE)
		p += mdb_snprintf(p, (size_t)(end - p), "|UE");
	if (cw & FPS_PE)
		p += mdb_snprintf(p, (size_t)(end - p), "|PE");
	if (cw & FPS_SF)
		p += mdb_snprintf(p, (size_t)(end - p), "|SF");
	if (cw & FPS_ES)
		p += mdb_snprintf(p, (size_t)(end - p), "|ES");
	if (cw & FPS_C0)
		p += mdb_snprintf(p, (size_t)(end - p), "|C0");
	if (cw & FPS_C1)
		p += mdb_snprintf(p, (size_t)(end - p), "|C1");
	if (cw & FPS_C2)
		p += mdb_snprintf(p, (size_t)(end - p), "|C2");
	if (cw & FPS_C3)
		p += mdb_snprintf(p, (size_t)(end - p), "|C3");
	if (cw & FPS_B)
		p += mdb_snprintf(p, (size_t)(end - p), "|B");

	if (buf[0] == '|')
		return (buf + 1);

	return ("0");
}

static const char *
fpmxcsr2str(uint32_t mxcsr, char *buf, size_t nbytes)
{
	char *end = buf + nbytes;
	char *p = buf;

	buf[0] = '\0';

	/*
	 * Decode the MXCSR word
	 */
	if (mxcsr & SSE_IE)
		p += mdb_snprintf(p, (size_t)(end - p), "|IE");
	if (mxcsr & SSE_DE)
		p += mdb_snprintf(p, (size_t)(end - p), "|DE");
	if (mxcsr & SSE_ZE)
		p += mdb_snprintf(p, (size_t)(end - p), "|ZE");
	if (mxcsr & SSE_OE)
		p += mdb_snprintf(p, (size_t)(end - p), "|OE");
	if (mxcsr & SSE_UE)
		p += mdb_snprintf(p, (size_t)(end - p), "|UE");
	if (mxcsr & SSE_PE)
		p += mdb_snprintf(p, (size_t)(end - p), "|PE");

	if (mxcsr & SSE_DAZ)
		p += mdb_snprintf(p, (size_t)(end - p), "|DAZ");

	if (mxcsr & SSE_IM)
		p += mdb_snprintf(p, (size_t)(end - p), "|IM");
	if (mxcsr & SSE_DM)
		p += mdb_snprintf(p, (size_t)(end - p), "|DM");
	if (mxcsr & SSE_ZM)
		p += mdb_snprintf(p, (size_t)(end - p), "|ZM");
	if (mxcsr & SSE_OM)
		p += mdb_snprintf(p, (size_t)(end - p), "|OM");
	if (mxcsr & SSE_UM)
		p += mdb_snprintf(p, (size_t)(end - p), "|UM");
	if (mxcsr & SSE_PM)
		p += mdb_snprintf(p, (size_t)(end - p), "|PM");

	if ((mxcsr & SSE_RC) == (SSE_RD|SSE_RU))
		p += mdb_snprintf(p, (size_t)(end - p), "|RTZ");
	else if (mxcsr & SSE_RD)
		p += mdb_snprintf(p, (size_t)(end - p), "|RD");
	else if (mxcsr & SSE_RU)
		p += mdb_snprintf(p, (size_t)(end - p), "|RU");
	else
		p += mdb_snprintf(p, (size_t)(end - p), "|RTN");

	if (mxcsr & SSE_FZ)
		p += mdb_snprintf(p, (size_t)(end - p), "|FZ");

	if (buf[0] == '|')
		return (buf + 1);
	return ("0");
}

/*ARGSUSED*/
int
pt_fpregs(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
{
	mdb_tgt_t *t = mdb.m_target;
	mdb_tgt_tid_t tid;
	prfpregset_t fprs;
	struct fpchip_state fps;
	char buf[256];
	uint_t top;
	int i;

	/*
	 * Union for overlaying _fpreg structure on to quad-precision
	 * floating-point value (long double).
	 */
	union {
		struct _fpreg reg;
		long double ld;
	} fpru;

	/*
	 * Array of strings corresponding to FPU tag word values (see
	 * section 7.3.6 of the Intel Programmer's Reference Manual).
	 */
	const char *tag_strings[] = { "valid", "zero", "special", "empty" };

	if (argc != 0)
		return (DCMD_USAGE);

	if (t->t_pshandle == NULL || Pstate(t->t_pshandle) == PS_UNDEAD) {
		mdb_warn("no process active\n");
		return (DCMD_ERR);
	}

	if (Pstate(t->t_pshandle) == PS_LOST) {
		mdb_warn("debugger has lost control of process\n");
		return (DCMD_ERR);
	}

	if (flags & DCMD_ADDRSPEC)
		tid = (mdb_tgt_tid_t)addr;
	else
		tid = PTL_TID(t);

	mdb_printf("AMD64 (80486 chip with SSE)\n");

	if (PTL_GETFPREGS(t, tid, &fprs) != 0) {
		mdb_warn("failed to get floating point registers");
		return (DCMD_ERR);
	}

	bcopy(&fprs.fp_reg_set.fpchip_state, &fps, sizeof (fps));

	fps.status &= 0xffff;	/* saved status word is really 16 bits */

	mdb_printf("cw     0x%04x (%s)\n", fps.cw,
	    fpcw2str(fps.cw, buf, sizeof (buf)));

	top = (fps.sw & FPS_TOP) >> 11;
	mdb_printf("sw     0x%04x (TOP=0t%u) (%s)\n", fps.sw,
	    top, fpsw2str(fps.sw, buf, sizeof (buf)));

	mdb_printf("xcp sw 0x%04x (%s)\n\n", fps.status,
	    fpsw2str(fps.status, buf, sizeof (buf)));

	mdb_printf("fop    0x%x\n", fps.fop);
	mdb_printf("rip    0x%x\n", fps.rip);
	mdb_printf("rdp    0x%x\n\n", fps.rdp);

	for (i = 0; i < 8; i++) {
		/*
		 * Recall that we need to use the current TOP-of-stack value to
		 * associate the _st[] index back to a physical register number,
		 * since tag word indices are physical register numbers.  Then
		 * to get the tag value, we shift over two bits for each tag
		 * index, and then grab the bottom two bits.
		 */
		uint_t tag_index = (i + top) & 7;
		uint_t tag_fctw = (fps.fctw >> tag_index) & 1;
		uint_t tag_value;
		uint_t exp;

		/*
		 * AMD64 stores the tag in a compressed form. It is
		 * necessary to extract the original 2-bit tag value.
		 * See AMD64 Architecture Programmer's Manual Volume 2:
		 * System Programming, Chapter 11.
		 */

		fpru.ld = fps.st[i].__fpr_pad._q;
		exp = fpru.reg.exponent & 0x7fff;

		if (tag_fctw == 0) {
			tag_value = 3; /* empty */
		} else if (exp == 0) {
			if (fpru.reg.significand[0] == 0 &&
			    fpru.reg.significand[1] == 0 &&
			    fpru.reg.significand[2] == 0 &&
			    fpru.reg.significand[3] == 0)
				tag_value = 1; /* zero */
			else
				tag_value = 2; /* special: denormal */
		} else if (exp == 0x7fff) {
			tag_value = 2; /* special: infinity or NaN */
		} else if (fpru.reg.significand[3] & 0x8000) {
			tag_value = 0; /* valid */
		} else {
			tag_value = 2; /* special: unnormal */
		}

		mdb_printf("%%st%d   0x%04x.%04x%04x%04x%04x = %lg %s\n",
		    i, fpru.reg.exponent,
		    fpru.reg.significand[3], fpru.reg.significand[2],
		    fpru.reg.significand[1], fpru.reg.significand[0],
		    fpru.ld, tag_strings[tag_value]);
	}

	mdb_printf("\nmxcsr  0x%04x (%s)\n", fps.mxcsr,
	    fpmxcsr2str(fps.mxcsr, buf, sizeof (buf)));
	mdb_printf("xcp    0x%04x (%s)\n\n", fps.xstatus,
	    fpmxcsr2str(fps.xstatus, buf, sizeof (buf)));

	for (i = 0; i < 8; i++)
		mdb_printf("%%xmm%d  0x%08x%08x%08x%08x\n", i,
		    fps.xmm[i]._l[3], fps.xmm[i]._l[2],
		    fps.xmm[i]._l[1], fps.xmm[i]._l[0]);

	return (DCMD_OK);
}

/*ARGSUSED*/
int
pt_getfpreg(mdb_tgt_t *t, mdb_tgt_tid_t tid, ushort_t rd_num,
    ushort_t rd_flags, mdb_tgt_reg_t *rp)
{
	return (set_errno(ENOTSUP));
}

/*ARGSUSED*/
int
pt_putfpreg(mdb_tgt_t *t, mdb_tgt_tid_t tid, ushort_t rd_num,
    ushort_t rd_flags, mdb_tgt_reg_t rval)
{
	return (set_errno(ENOTSUP));
}

/*ARGSUSED*/
void
pt_addfpregs(mdb_tgt_t *t)
{
	/* not implemented */
}

/*ARGSUSED*/
int
pt_frameregs(void *arglim, uintptr_t pc, uint_t argc, const long *argv,
    const mdb_tgt_gregset_t *gregs, boolean_t pc_faked)
{
	return (set_errno(ENOTSUP));
}

/*ARGSUSED*/
const char *
pt_disasm(const GElf_Ehdr *ehp)
{
	return ("amd64");
}

/*
 * Determine the return address for the current frame.
 */
int
pt_step_out(mdb_tgt_t *t, uintptr_t *p)
{
	const lwpstatus_t *psp = &Pstatus(t->t_pshandle)->pr_lwp;

	if (Pstate(t->t_pshandle) != PS_STOP)
		return (set_errno(EMDB_TGTBUSY));

	return (mdb_amd64_step_out(t, p, psp->pr_reg[EIP], psp->pr_reg[EBP],
	    psp->pr_reg[UESP], psp->pr_instr));
}

/*
 * Return the address of the next instruction following a call, or return -1
 * and set errno to EAGAIN if the target should just single-step.
 */
int
pt_next(mdb_tgt_t *t, uintptr_t *p)
{
	const lwpstatus_t *psp = &Pstatus(t->t_pshandle)->pr_lwp;

	if (Pstate(t->t_pshandle) != PS_STOP)
		return (set_errno(EMDB_TGTBUSY));

	return (mdb_amd64_next(t, p, psp->pr_reg[REG_RIP], pt_read_instr(t)));
}