dt_isadep.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) 2012 by Delphix. All rights reserved.
 */

#include <stdlib.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <libgen.h>

#include <dt_impl.h>
#include <dt_pid.h>

#include <dis_tables.h>

#ifdef __FreeBSD__
#include <libproc.h>
#include <libproc_compat.h>
#endif

#define	DT_POPL_EBP	0x5d
#define	DT_RET		0xc3
#define	DT_RET16	0xc2
#define	DT_LEAVE	0xc9
#define	DT_JMP32	0xe9
#define	DT_JMP8		0xeb
#define	DT_REP		0xf3

#define	DT_MOVL_EBP_ESP	0xe58b

#define	DT_ISJ32(op16)	(((op16) & 0xfff0) == 0x0f80)
#define	DT_ISJ8(op8)	(((op8) & 0xf0) == 0x70)

#define	DT_MODRM_REG(modrm)	(((modrm) >> 3) & 0x7)

static int dt_instr_size(uchar_t *, dtrace_hdl_t *, pid_t, uintptr_t, char);

/*ARGSUSED*/
int
dt_pid_create_entry_probe(struct ps_prochandle *P, dtrace_hdl_t *dtp,
    fasttrap_probe_spec_t *ftp, const GElf_Sym *symp)
{
	ftp->ftps_type = DTFTP_ENTRY;
	ftp->ftps_pc = (uintptr_t)symp->st_value;
	ftp->ftps_size = (size_t)symp->st_size;
	ftp->ftps_noffs = 1;
	ftp->ftps_offs[0] = 0;

	if (ioctl(dtp->dt_ftfd, FASTTRAPIOC_MAKEPROBE, ftp) != 0) {
		dt_dprintf("fasttrap probe creation ioctl failed: %s\n",
		    strerror(errno));
		return (dt_set_errno(dtp, errno));
	}

	return (1);
}

static int
dt_pid_has_jump_table(struct ps_prochandle *P, dtrace_hdl_t *dtp,
    uint8_t *text, fasttrap_probe_spec_t *ftp, const GElf_Sym *symp)
{
	ulong_t i;
	int size;
#ifdef illumos
	pid_t pid = Pstatus(P)->pr_pid;
	char dmodel = Pstatus(P)->pr_dmodel;
#else
	pid_t pid = proc_getpid(P);
	char dmodel = proc_getmodel(P);
#endif

	/*
	 * Take a pass through the function looking for a register-dependant
	 * jmp instruction. This could be a jump table so we have to be
	 * ultra conservative.
	 */
	for (i = 0; i < ftp->ftps_size; i += size) {
		size = dt_instr_size(&text[i], dtp, pid, symp->st_value + i,
		    dmodel);

		/*
		 * Assume the worst if we hit an illegal instruction.
		 */
		if (size <= 0) {
			dt_dprintf("error at %#lx (assuming jump table)\n", i);
			return (1);
		}

#ifdef notyet
		/*
		 * Register-dependant jmp instructions start with a 0xff byte
		 * and have the modrm.reg field set to 4. They can have an
		 * optional REX prefix on the 64-bit ISA.
		 */
		if ((text[i] == 0xff && DT_MODRM_REG(text[i + 1]) == 4) ||
		    (dmodel == PR_MODEL_LP64 && (text[i] & 0xf0) == 0x40 &&
		    text[i + 1] == 0xff && DT_MODRM_REG(text[i + 2]) == 4)) {
			dt_dprintf("found a suspected jump table at %s:%lx\n",
			    ftp->ftps_func, i);
			return (1);
		}
#endif
	}

	return (0);
}

/*ARGSUSED*/
int
dt_pid_create_return_probe(struct ps_prochandle *P, dtrace_hdl_t *dtp,
    fasttrap_probe_spec_t *ftp, const GElf_Sym *symp, uint64_t *stret)
{
	uint8_t *text;
	ulong_t i, end;
	int size;
#ifdef illumos
	pid_t pid = Pstatus(P)->pr_pid;
	char dmodel = Pstatus(P)->pr_dmodel;
#else
	pid_t pid = proc_getpid(P);
	char dmodel = proc_getmodel(P);
#endif

	/*
	 * We allocate a few extra bytes at the end so we don't have to check
	 * for overrunning the buffer.
	 */
	if ((text = calloc(1, symp->st_size + 4)) == NULL) {
		dt_dprintf("mr sparkle: malloc() failed\n");
		return (DT_PROC_ERR);
	}

	if (Pread(P, text, symp->st_size, symp->st_value) != symp->st_size) {
		dt_dprintf("mr sparkle: Pread() failed\n");
		free(text);
		return (DT_PROC_ERR);
	}

	ftp->ftps_type = DTFTP_RETURN;
	ftp->ftps_pc = (uintptr_t)symp->st_value;
	ftp->ftps_size = (size_t)symp->st_size;
	ftp->ftps_noffs = 0;

	/*
	 * If there's a jump table in the function we're only willing to
	 * instrument these specific (and equivalent) instruction sequences:
	 *	leave
	 *	[rep] ret
	 * and
	 *	movl	%ebp,%esp
	 *	popl	%ebp
	 *	[rep] ret
	 *
	 * We do this to avoid accidentally interpreting jump table
	 * offsets as actual instructions.
	 */
	if (dt_pid_has_jump_table(P, dtp, text, ftp, symp)) {
		for (i = 0, end = ftp->ftps_size; i < end; i += size) {
			size = dt_instr_size(&text[i], dtp, pid,
			    symp->st_value + i, dmodel);

			/* bail if we hit an invalid opcode */
			if (size <= 0)
				break;

			if (text[i] == DT_LEAVE && text[i + 1] == DT_RET) {
				dt_dprintf("leave/ret at %lx\n", i + 1);
				ftp->ftps_offs[ftp->ftps_noffs++] = i + 1;
				size = 2;
			} else if (text[i] == DT_LEAVE &&
			    text[i + 1] == DT_REP && text[i + 2] == DT_RET) {
				dt_dprintf("leave/rep ret at %lx\n", i + 1);
				ftp->ftps_offs[ftp->ftps_noffs++] = i + 1;
				size = 3;
			} else if (*(uint16_t *)&text[i] == DT_MOVL_EBP_ESP &&
			    text[i + 2] == DT_POPL_EBP &&
			    text[i + 3] == DT_RET) {
				dt_dprintf("movl/popl/ret at %lx\n", i + 3);
				ftp->ftps_offs[ftp->ftps_noffs++] = i + 3;
				size = 4;
			} else if (*(uint16_t *)&text[i] == DT_MOVL_EBP_ESP &&
			    text[i + 2] == DT_POPL_EBP &&
			    text[i + 3] == DT_REP &&
			    text[i + 4] == DT_RET) {
				dt_dprintf("movl/popl/rep ret at %lx\n", i + 3);
				ftp->ftps_offs[ftp->ftps_noffs++] = i + 3;
				size = 5;
			}
		}
	} else {
		for (i = 0, end = ftp->ftps_size; i < end; i += size) {
			size = dt_instr_size(&text[i], dtp, pid,
			    symp->st_value + i, dmodel);

			/* bail if we hit an invalid opcode */
			if (size <= 0)
				break;

			/* ordinary ret */
			if (size == 1 && text[i] == DT_RET)
				goto is_ret;

			/* two-byte ret */
			if (size == 2 && text[i] == DT_REP &&
			    text[i + 1] == DT_RET)
				goto is_ret;

			/* ret <imm16> */
			if (size == 3 && text[i] == DT_RET16)
				goto is_ret;

			/* two-byte ret <imm16> */
			if (size == 4 && text[i] == DT_REP &&
			    text[i + 1] == DT_RET16)
				goto is_ret;

			/* 32-bit displacement jmp outside of the function */
			if (size == 5 && text[i] == DT_JMP32 && symp->st_size <=
			    (uintptr_t)(i + size + *(int32_t *)&text[i + 1]))
				goto is_ret;

			/* 8-bit displacement jmp outside of the function */
			if (size == 2 && text[i] == DT_JMP8 && symp->st_size <=
			    (uintptr_t)(i + size + *(int8_t *)&text[i + 1]))
				goto is_ret;

			/* 32-bit disp. conditional jmp outside of the func. */
			if (size == 6 && DT_ISJ32(*(uint16_t *)&text[i]) &&
			    symp->st_size <=
			    (uintptr_t)(i + size + *(int32_t *)&text[i + 2]))
				goto is_ret;

			/* 8-bit disp. conditional jmp outside of the func. */
			if (size == 2 && DT_ISJ8(text[i]) && symp->st_size <=
			    (uintptr_t)(i + size + *(int8_t *)&text[i + 1]))
				goto is_ret;

			continue;
is_ret:
			dt_dprintf("return at offset %lx\n", i);
			ftp->ftps_offs[ftp->ftps_noffs++] = i;
		}
	}

	free(text);
	if (ftp->ftps_noffs > 0) {
		if (ioctl(dtp->dt_ftfd, FASTTRAPIOC_MAKEPROBE, ftp) != 0) {
			dt_dprintf("fasttrap probe creation ioctl failed: %s\n",
			    strerror(errno));
			return (dt_set_errno(dtp, errno));
		}
	}

	return (ftp->ftps_noffs);
}

/*ARGSUSED*/
int
dt_pid_create_offset_probe(struct ps_prochandle *P, dtrace_hdl_t *dtp,
    fasttrap_probe_spec_t *ftp, const GElf_Sym *symp, ulong_t off)
{
	ftp->ftps_type = DTFTP_OFFSETS;
	ftp->ftps_pc = (uintptr_t)symp->st_value;
	ftp->ftps_size = (size_t)symp->st_size;
	ftp->ftps_noffs = 1;

	if (strcmp("-", ftp->ftps_func) == 0) {
		ftp->ftps_offs[0] = off;
	} else {
		uint8_t *text;
		ulong_t i;
		int size;
#ifdef illumos
		pid_t pid = Pstatus(P)->pr_pid;
		char dmodel = Pstatus(P)->pr_dmodel;
#else
		pid_t pid = proc_getpid(P);
		char dmodel = proc_getmodel(P);
#endif

		if ((text = malloc(symp->st_size)) == NULL) {
			dt_dprintf("mr sparkle: malloc() failed\n");
			return (DT_PROC_ERR);
		}

		if (Pread(P, text, symp->st_size, symp->st_value) !=
		    symp->st_size) {
			dt_dprintf("mr sparkle: Pread() failed\n");
			free(text);
			return (DT_PROC_ERR);
		}

		/*
		 * We can't instrument offsets in functions with jump tables
		 * as we might interpret a jump table offset as an
		 * instruction.
		 */
		if (dt_pid_has_jump_table(P, dtp, text, ftp, symp)) {
			free(text);
			return (0);
		}

		for (i = 0; i < symp->st_size; i += size) {
			if (i == off) {
				ftp->ftps_offs[0] = i;
				break;
			}

			/*
			 * If we've passed the desired offset without a
			 * match, then the given offset must not lie on a
			 * instruction boundary.
			 */
			if (i > off) {
				free(text);
				return (DT_PROC_ALIGN);
			}

			size = dt_instr_size(&text[i], dtp, pid,
			    symp->st_value + i, dmodel);

			/*
			 * If we hit an invalid instruction, bail as if we
			 * couldn't find the offset.
			 */
			if (size <= 0) {
				free(text);
				return (DT_PROC_ALIGN);
			}
		}

		free(text);
	}

	if (ioctl(dtp->dt_ftfd, FASTTRAPIOC_MAKEPROBE, ftp) != 0) {
		dt_dprintf("fasttrap probe creation ioctl failed: %s\n",
		    strerror(errno));
		return (dt_set_errno(dtp, errno));
	}

	return (ftp->ftps_noffs);
}

/*ARGSUSED*/
int
dt_pid_create_glob_offset_probes(struct ps_prochandle *P, dtrace_hdl_t *dtp,
    fasttrap_probe_spec_t *ftp, const GElf_Sym *symp, const char *pattern)
{
	uint8_t *text;
	int size;
	ulong_t i, end = symp->st_size;
#ifdef illumos
	pid_t pid = Pstatus(P)->pr_pid;
	char dmodel = Pstatus(P)->pr_dmodel;
#else
	pid_t pid = proc_getpid(P);
	char dmodel = proc_getmodel(P);
#endif

	ftp->ftps_type = DTFTP_OFFSETS;
	ftp->ftps_pc = (uintptr_t)symp->st_value;
	ftp->ftps_size = (size_t)symp->st_size;
	ftp->ftps_noffs = 0;

	if ((text = malloc(symp->st_size)) == NULL) {
		dt_dprintf("mr sparkle: malloc() failed\n");
		return (DT_PROC_ERR);
	}

	if (Pread(P, text, symp->st_size, symp->st_value) != symp->st_size) {
		dt_dprintf("mr sparkle: Pread() failed\n");
		free(text);
		return (DT_PROC_ERR);
	}

	/*
	 * We can't instrument offsets in functions with jump tables as
	 * we might interpret a jump table offset as an instruction.
	 */
	if (dt_pid_has_jump_table(P, dtp, text, ftp, symp)) {
		free(text);
		return (0);
	}

	if (strcmp("*", pattern) == 0) {
		for (i = 0; i < end; i += size) {
			ftp->ftps_offs[ftp->ftps_noffs++] = i;

			size = dt_instr_size(&text[i], dtp, pid,
			    symp->st_value + i, dmodel);

			/* bail if we hit an invalid opcode */
			if (size <= 0)
				break;
		}
	} else {
		char name[sizeof (i) * 2 + 1];

		for (i = 0; i < end; i += size) {
			(void) snprintf(name, sizeof (name), "%lx", i);
			if (gmatch(name, pattern))
				ftp->ftps_offs[ftp->ftps_noffs++] = i;

			size = dt_instr_size(&text[i], dtp, pid,
			    symp->st_value + i, dmodel);

			/* bail if we hit an invalid opcode */
			if (size <= 0)
				break;
		}
	}

	free(text);
	if (ftp->ftps_noffs > 0) {
		if (ioctl(dtp->dt_ftfd, FASTTRAPIOC_MAKEPROBE, ftp) != 0) {
			dt_dprintf("fasttrap probe creation ioctl failed: %s\n",
			    strerror(errno));
			return (dt_set_errno(dtp, errno));
		}
	}

	return (ftp->ftps_noffs);
}

typedef struct dtrace_dis {
	uchar_t	*instr;
	dtrace_hdl_t *dtp;
	pid_t pid;
	uintptr_t addr;
} dtrace_dis_t;

static int
dt_getbyte(void *data)
{
	dtrace_dis_t	*dis = data;
	int ret = *dis->instr;

	if (ret == FASTTRAP_INSTR) {
		fasttrap_instr_query_t instr;

		instr.ftiq_pid = dis->pid;
		instr.ftiq_pc = dis->addr;

		/*
		 * If we hit a byte that looks like the fasttrap provider's
		 * trap instruction (which doubles as the breakpoint
		 * instruction for debuggers) we need to query the kernel
		 * for the real value. This may just be part of an immediate
		 * value so there's no need to return an error if the
		 * kernel doesn't know about this address.
		 */
		if (ioctl(dis->dtp->dt_ftfd, FASTTRAPIOC_GETINSTR, &instr) == 0)
			ret = instr.ftiq_instr;
	}

	dis->addr++;
	dis->instr++;

	return (ret);
}

static int
dt_instr_size(uchar_t *instr, dtrace_hdl_t *dtp, pid_t pid, uintptr_t addr,
    char dmodel)
{
	dtrace_dis_t data;
	dis86_t x86dis;
	uint_t cpu_mode;

	data.instr = instr;
	data.dtp = dtp;
	data.pid = pid;
	data.addr = addr;

	x86dis.d86_data = &data;
	x86dis.d86_get_byte = dt_getbyte;
	x86dis.d86_check_func = NULL;

	cpu_mode = (dmodel == PR_MODEL_ILP32) ? SIZE32 : SIZE64;

	if (dtrace_disx86(&x86dis, cpu_mode) != 0)
		return (-1);

	/*
	 * If the instruction was a single-byte breakpoint, there may be
	 * another debugger attached to this process. The original instruction
	 * can't be recovered so this must fail.
	 */
	if (x86dis.d86_len == 1 &&
	    (uchar_t)x86dis.d86_bytes[0] == FASTTRAP_INSTR)
		return (-1);

	return (x86dis.d86_len);
}