/*
* 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
*
* Portions Copyright 2010 The FreeBSD Foundation
*
* $FreeBSD$
*/
/*
* Copyright 2008 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#ifdef illumos
#pragma ident "%Z%%M% %I% %E% SMI"
#endif
#include <sys/fasttrap_isa.h>
#include <sys/fasttrap_impl.h>
#include <sys/dtrace.h>
#include <sys/dtrace_impl.h>
#include <sys/cmn_err.h>
#ifdef illumos
#include <sys/regset.h>
#include <sys/privregs.h>
#include <sys/segments.h>
#include <sys/x86_archext.h>
#else
#include <sys/types.h>
#include <sys/dtrace_bsd.h>
#include <sys/proc.h>
#include <sys/rmlock.h>
#include <cddl/dev/dtrace/dtrace_cddl.h>
#include <cddl/dev/dtrace/x86/regset.h>
#include <machine/segments.h>
#include <machine/reg.h>
#include <machine/pcb.h>
#endif
#include <sys/sysmacros.h>
#ifdef illumos
#include <sys/trap.h>
#include <sys/archsystm.h>
#else
#include <sys/ptrace.h>
#endif /* illumos */
#ifdef __i386__
#define r_rax r_eax
#define r_rbx r_ebx
#define r_rip r_eip
#define r_rflags r_eflags
#define r_rsp r_esp
#define r_rbp r_ebp
#endif
/*
* Lossless User-Land Tracing on x86
* ---------------------------------
*
* The execution of most instructions is not dependent on the address; for
* these instructions it is sufficient to copy them into the user process's
* address space and execute them. To effectively single-step an instruction
* in user-land, we copy out the following sequence of instructions to scratch
* space in the user thread's ulwp_t structure.
*
* We then set the program counter (%eip or %rip) to point to this scratch
* space. Once execution resumes, the original instruction is executed and
* then control flow is redirected to what was originally the subsequent
* instruction. If the kernel attemps to deliver a signal while single-
* stepping, the signal is deferred and the program counter is moved into the
* second sequence of instructions. The second sequence ends in a trap into
* the kernel where the deferred signal is then properly handled and delivered.
*
* For instructions whose execute is position dependent, we perform simple
* emulation. These instructions are limited to control transfer
* instructions in 32-bit mode, but in 64-bit mode there's the added wrinkle
* of %rip-relative addressing that means that almost any instruction can be
* position dependent. For all the details on how we emulate generic
* instructions included %rip-relative instructions, see the code in
* fasttrap_pid_probe() below where we handle instructions of type
* FASTTRAP_T_COMMON (under the header: Generic Instruction Tracing).
*/
#define FASTTRAP_MODRM_MOD(modrm) (((modrm) >> 6) & 0x3)
#define FASTTRAP_MODRM_REG(modrm) (((modrm) >> 3) & 0x7)
#define FASTTRAP_MODRM_RM(modrm) ((modrm) & 0x7)
#define FASTTRAP_MODRM(mod, reg, rm) (((mod) << 6) | ((reg) << 3) | (rm))
#define FASTTRAP_SIB_SCALE(sib) (((sib) >> 6) & 0x3)
#define FASTTRAP_SIB_INDEX(sib) (((sib) >> 3) & 0x7)
#define FASTTRAP_SIB_BASE(sib) ((sib) & 0x7)
#define FASTTRAP_REX_W(rex) (((rex) >> 3) & 1)
#define FASTTRAP_REX_R(rex) (((rex) >> 2) & 1)
#define FASTTRAP_REX_X(rex) (((rex) >> 1) & 1)
#define FASTTRAP_REX_B(rex) ((rex) & 1)
#define FASTTRAP_REX(w, r, x, b) \
(0x40 | ((w) << 3) | ((r) << 2) | ((x) << 1) | (b))
/*
* Single-byte op-codes.
*/
#define FASTTRAP_PUSHL_EBP 0x55
#define FASTTRAP_JO 0x70
#define FASTTRAP_JNO 0x71
#define FASTTRAP_JB 0x72
#define FASTTRAP_JAE 0x73
#define FASTTRAP_JE 0x74
#define FASTTRAP_JNE 0x75
#define FASTTRAP_JBE 0x76
#define FASTTRAP_JA 0x77
#define FASTTRAP_JS 0x78
#define FASTTRAP_JNS 0x79
#define FASTTRAP_JP 0x7a
#define FASTTRAP_JNP 0x7b
#define FASTTRAP_JL 0x7c
#define FASTTRAP_JGE 0x7d
#define FASTTRAP_JLE 0x7e
#define FASTTRAP_JG 0x7f
#define FASTTRAP_NOP 0x90
#define FASTTRAP_MOV_EAX 0xb8
#define FASTTRAP_MOV_ECX 0xb9
#define FASTTRAP_RET16 0xc2
#define FASTTRAP_RET 0xc3
#define FASTTRAP_LOOPNZ 0xe0
#define FASTTRAP_LOOPZ 0xe1
#define FASTTRAP_LOOP 0xe2
#define FASTTRAP_JCXZ 0xe3
#define FASTTRAP_CALL 0xe8
#define FASTTRAP_JMP32 0xe9
#define FASTTRAP_JMP8 0xeb
#define FASTTRAP_INT3 0xcc
#define FASTTRAP_INT 0xcd
#define FASTTRAP_2_BYTE_OP 0x0f
#define FASTTRAP_GROUP5_OP 0xff
/*
* Two-byte op-codes (second byte only).
*/
#define FASTTRAP_0F_JO 0x80
#define FASTTRAP_0F_JNO 0x81
#define FASTTRAP_0F_JB 0x82
#define FASTTRAP_0F_JAE 0x83
#define FASTTRAP_0F_JE 0x84
#define FASTTRAP_0F_JNE 0x85
#define FASTTRAP_0F_JBE 0x86
#define FASTTRAP_0F_JA 0x87
#define FASTTRAP_0F_JS 0x88
#define FASTTRAP_0F_JNS 0x89
#define FASTTRAP_0F_JP 0x8a
#define FASTTRAP_0F_JNP 0x8b
#define FASTTRAP_0F_JL 0x8c
#define FASTTRAP_0F_JGE 0x8d
#define FASTTRAP_0F_JLE 0x8e
#define FASTTRAP_0F_JG 0x8f
#define FASTTRAP_EFLAGS_OF 0x800
#define FASTTRAP_EFLAGS_DF 0x400
#define FASTTRAP_EFLAGS_SF 0x080
#define FASTTRAP_EFLAGS_ZF 0x040
#define FASTTRAP_EFLAGS_AF 0x010
#define FASTTRAP_EFLAGS_PF 0x004
#define FASTTRAP_EFLAGS_CF 0x001
/*
* Instruction prefixes.
*/
#define FASTTRAP_PREFIX_OPERAND 0x66
#define FASTTRAP_PREFIX_ADDRESS 0x67
#define FASTTRAP_PREFIX_CS 0x2E
#define FASTTRAP_PREFIX_DS 0x3E
#define FASTTRAP_PREFIX_ES 0x26
#define FASTTRAP_PREFIX_FS 0x64
#define FASTTRAP_PREFIX_GS 0x65
#define FASTTRAP_PREFIX_SS 0x36
#define FASTTRAP_PREFIX_LOCK 0xF0
#define FASTTRAP_PREFIX_REP 0xF3
#define FASTTRAP_PREFIX_REPNE 0xF2
#define FASTTRAP_NOREG 0xff
/*
* Map between instruction register encodings and the kernel constants which
* correspond to indicies into struct regs.
*/
#ifdef __amd64
static const uint8_t regmap[16] = {
REG_RAX, REG_RCX, REG_RDX, REG_RBX, REG_RSP, REG_RBP, REG_RSI, REG_RDI,
REG_R8, REG_R9, REG_R10, REG_R11, REG_R12, REG_R13, REG_R14, REG_R15,
};
#else
static const uint8_t regmap[8] = {
EAX, ECX, EDX, EBX, UESP, EBP, ESI, EDI
};
#endif
static ulong_t fasttrap_getreg(struct reg *, uint_t);
static uint64_t
fasttrap_anarg(struct reg *rp, int function_entry, int argno)
{
uint64_t value = 0;
int shift = function_entry ? 1 : 0;
#ifdef __amd64
if (curproc->p_model == DATAMODEL_LP64) {
uintptr_t *stack;
/*
* In 64-bit mode, the first six arguments are stored in
* registers.
*/
if (argno < 6)
switch (argno) {
case 0:
return (rp->r_rdi);
case 1:
return (rp->r_rsi);
case 2:
return (rp->r_rdx);
case 3:
return (rp->r_rcx);
case 4:
return (rp->r_r8);
case 5:
return (rp->r_r9);
}
stack = (uintptr_t *)rp->r_rsp;
DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
value = dtrace_fulword(&stack[argno - 6 + shift]);
DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT | CPU_DTRACE_BADADDR);
} else {
#endif
uint32_t *stack = (uint32_t *)rp->r_rsp;
DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
value = dtrace_fuword32(&stack[argno + shift]);
DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT | CPU_DTRACE_BADADDR);
#ifdef __amd64
}
#endif
return (value);
}
/*ARGSUSED*/
int
fasttrap_tracepoint_init(proc_t *p, fasttrap_tracepoint_t *tp, uintptr_t pc,
fasttrap_probe_type_t type)
{
uint8_t instr[FASTTRAP_MAX_INSTR_SIZE + 10];
size_t len = FASTTRAP_MAX_INSTR_SIZE;
size_t first = MIN(len, PAGESIZE - (pc & PAGEOFFSET));
uint_t start = 0;
int rmindex, size;
uint8_t seg, rex = 0;
/*
* Read the instruction at the given address out of the process's
* address space. We don't have to worry about a debugger
* changing this instruction before we overwrite it with our trap
* instruction since P_PR_LOCK is set. Since instructions can span
* pages, we potentially read the instruction in two parts. If the
* second part fails, we just zero out that part of the instruction.
*/
if (uread(p, &instr[0], first, pc) != 0)
return (-1);
if (len > first &&
uread(p, &instr[first], len - first, pc + first) != 0) {
bzero(&instr[first], len - first);
len = first;
}
/*
* If the disassembly fails, then we have a malformed instruction.
*/
if ((size = dtrace_instr_size_isa(instr, p->p_model, &rmindex)) <= 0)
return (-1);
/*
* Make sure the disassembler isn't completely broken.
*/
ASSERT(-1 <= rmindex && rmindex < size);
/*
* If the computed size is greater than the number of bytes read,
* then it was a malformed instruction possibly because it fell on a
* page boundary and the subsequent page was missing or because of
* some malicious user.
*/
if (size > len)
return (-1);
tp->ftt_size = (uint8_t)size;
tp->ftt_segment = FASTTRAP_SEG_NONE;
/*
* Find the start of the instruction's opcode by processing any
* legacy prefixes.
*/
for (;;) {
seg = 0;
switch (instr[start]) {
case FASTTRAP_PREFIX_SS:
seg++;
/*FALLTHRU*/
case FASTTRAP_PREFIX_GS:
seg++;
/*FALLTHRU*/
case FASTTRAP_PREFIX_FS:
seg++;
/*FALLTHRU*/
case FASTTRAP_PREFIX_ES:
seg++;
/*FALLTHRU*/
case FASTTRAP_PREFIX_DS:
seg++;
/*FALLTHRU*/
case FASTTRAP_PREFIX_CS:
seg++;
/*FALLTHRU*/
case FASTTRAP_PREFIX_OPERAND:
case FASTTRAP_PREFIX_ADDRESS:
case FASTTRAP_PREFIX_LOCK:
case FASTTRAP_PREFIX_REP:
case FASTTRAP_PREFIX_REPNE:
if (seg != 0) {
/*
* It's illegal for an instruction to specify
* two segment prefixes -- give up on this
* illegal instruction.
*/
if (tp->ftt_segment != FASTTRAP_SEG_NONE)
return (-1);
tp->ftt_segment = seg;
}
start++;
continue;
}
break;
}
#ifdef __amd64
/*
* Identify the REX prefix on 64-bit processes.
*/
if (p->p_model == DATAMODEL_LP64 && (instr[start] & 0xf0) == 0x40)
rex = instr[start++];
#endif
/*
* Now that we're pretty sure that the instruction is okay, copy the
* valid part to the tracepoint.
*/
bcopy(instr, tp->ftt_instr, FASTTRAP_MAX_INSTR_SIZE);
tp->ftt_type = FASTTRAP_T_COMMON;
if (instr[start] == FASTTRAP_2_BYTE_OP) {
switch (instr[start + 1]) {
case FASTTRAP_0F_JO:
case FASTTRAP_0F_JNO:
case FASTTRAP_0F_JB:
case FASTTRAP_0F_JAE:
case FASTTRAP_0F_JE:
case FASTTRAP_0F_JNE:
case FASTTRAP_0F_JBE:
case FASTTRAP_0F_JA:
case FASTTRAP_0F_JS:
case FASTTRAP_0F_JNS:
case FASTTRAP_0F_JP:
case FASTTRAP_0F_JNP:
case FASTTRAP_0F_JL:
case FASTTRAP_0F_JGE:
case FASTTRAP_0F_JLE:
case FASTTRAP_0F_JG:
tp->ftt_type = FASTTRAP_T_JCC;
tp->ftt_code = (instr[start + 1] & 0x0f) | FASTTRAP_JO;
tp->ftt_dest = pc + tp->ftt_size +
/* LINTED - alignment */
*(int32_t *)&instr[start + 2];
break;
}
} else if (instr[start] == FASTTRAP_GROUP5_OP) {
uint_t mod = FASTTRAP_MODRM_MOD(instr[start + 1]);
uint_t reg = FASTTRAP_MODRM_REG(instr[start + 1]);
uint_t rm = FASTTRAP_MODRM_RM(instr[start + 1]);
if (reg == 2 || reg == 4) {
uint_t i, sz;
if (reg == 2)
tp->ftt_type = FASTTRAP_T_CALL;
else
tp->ftt_type = FASTTRAP_T_JMP;
if (mod == 3)
tp->ftt_code = 2;
else
tp->ftt_code = 1;
ASSERT(p->p_model == DATAMODEL_LP64 || rex == 0);
/*
* See AMD x86-64 Architecture Programmer's Manual
* Volume 3, Section 1.2.7, Table 1-12, and
* Appendix A.3.1, Table A-15.
*/
if (mod != 3 && rm == 4) {
uint8_t sib = instr[start + 2];
uint_t index = FASTTRAP_SIB_INDEX(sib);
uint_t base = FASTTRAP_SIB_BASE(sib);
tp->ftt_scale = FASTTRAP_SIB_SCALE(sib);
tp->ftt_index = (index == 4) ?
FASTTRAP_NOREG :
regmap[index | (FASTTRAP_REX_X(rex) << 3)];
tp->ftt_base = (mod == 0 && base == 5) ?
FASTTRAP_NOREG :
regmap[base | (FASTTRAP_REX_B(rex) << 3)];
i = 3;
sz = mod == 1 ? 1 : 4;
} else {
/*
* In 64-bit mode, mod == 0 and r/m == 5
* denotes %rip-relative addressing; in 32-bit
* mode, the base register isn't used. In both
* modes, there is a 32-bit operand.
*/
if (mod == 0 && rm == 5) {
#ifdef __amd64
if (p->p_model == DATAMODEL_LP64)
tp->ftt_base = REG_RIP;
else
#endif
tp->ftt_base = FASTTRAP_NOREG;
sz = 4;
} else {
uint8_t base = rm |
(FASTTRAP_REX_B(rex) << 3);
tp->ftt_base = regmap[base];
sz = mod == 1 ? 1 : mod == 2 ? 4 : 0;
}
tp->ftt_index = FASTTRAP_NOREG;
i = 2;
}
if (sz == 1) {
tp->ftt_dest = *(int8_t *)&instr[start + i];
} else if (sz == 4) {
/* LINTED - alignment */
tp->ftt_dest = *(int32_t *)&instr[start + i];
} else {
tp->ftt_dest = 0;
}
}
} else {
switch (instr[start]) {
case FASTTRAP_RET:
tp->ftt_type = FASTTRAP_T_RET;
break;
case FASTTRAP_RET16:
tp->ftt_type = FASTTRAP_T_RET16;
/* LINTED - alignment */
tp->ftt_dest = *(uint16_t *)&instr[start + 1];
break;
case FASTTRAP_JO:
case FASTTRAP_JNO:
case FASTTRAP_JB:
case FASTTRAP_JAE:
case FASTTRAP_JE:
case FASTTRAP_JNE:
case FASTTRAP_JBE:
case FASTTRAP_JA:
case FASTTRAP_JS:
case FASTTRAP_JNS:
case FASTTRAP_JP:
case FASTTRAP_JNP:
case FASTTRAP_JL:
case FASTTRAP_JGE:
case FASTTRAP_JLE:
case FASTTRAP_JG:
tp->ftt_type = FASTTRAP_T_JCC;
tp->ftt_code = instr[start];
tp->ftt_dest = pc + tp->ftt_size +
(int8_t)instr[start + 1];
break;
case FASTTRAP_LOOPNZ:
case FASTTRAP_LOOPZ:
case FASTTRAP_LOOP:
tp->ftt_type = FASTTRAP_T_LOOP;
tp->ftt_code = instr[start];
tp->ftt_dest = pc + tp->ftt_size +
(int8_t)instr[start + 1];
break;
case FASTTRAP_JCXZ:
tp->ftt_type = FASTTRAP_T_JCXZ;
tp->ftt_dest = pc + tp->ftt_size +
(int8_t)instr[start + 1];
break;
case FASTTRAP_CALL:
tp->ftt_type = FASTTRAP_T_CALL;
tp->ftt_dest = pc + tp->ftt_size +
/* LINTED - alignment */
*(int32_t *)&instr[start + 1];
tp->ftt_code = 0;
break;
case FASTTRAP_JMP32:
tp->ftt_type = FASTTRAP_T_JMP;
tp->ftt_dest = pc + tp->ftt_size +
/* LINTED - alignment */
*(int32_t *)&instr[start + 1];
break;
case FASTTRAP_JMP8:
tp->ftt_type = FASTTRAP_T_JMP;
tp->ftt_dest = pc + tp->ftt_size +
(int8_t)instr[start + 1];
break;
case FASTTRAP_PUSHL_EBP:
if (start == 0)
tp->ftt_type = FASTTRAP_T_PUSHL_EBP;
break;
case FASTTRAP_NOP:
#ifdef __amd64
ASSERT(p->p_model == DATAMODEL_LP64 || rex == 0);
/*
* On amd64 we have to be careful not to confuse a nop
* (actually xchgl %eax, %eax) with an instruction using
* the same opcode, but that does something different
* (e.g. xchgl %r8d, %eax or xcghq %r8, %rax).
*/
if (FASTTRAP_REX_B(rex) == 0)
#endif
tp->ftt_type = FASTTRAP_T_NOP;
break;
case FASTTRAP_INT3:
/*
* The pid provider shares the int3 trap with debugger
* breakpoints so we can't instrument them.
*/
ASSERT(instr[start] == FASTTRAP_INSTR);
return (-1);
case FASTTRAP_INT:
/*
* Interrupts seem like they could be traced with
* no negative implications, but it's possible that
* a thread could be redirected by the trap handling
* code which would eventually return to the
* instruction after the interrupt. If the interrupt
* were in our scratch space, the subsequent
* instruction might be overwritten before we return.
* Accordingly we refuse to instrument any interrupt.
*/
return (-1);
}
}
#ifdef __amd64
if (p->p_model == DATAMODEL_LP64 && tp->ftt_type == FASTTRAP_T_COMMON) {
/*
* If the process is 64-bit and the instruction type is still
* FASTTRAP_T_COMMON -- meaning we're going to copy it out an
* execute it -- we need to watch for %rip-relative
* addressing mode. See the portion of fasttrap_pid_probe()
* below where we handle tracepoints with type
* FASTTRAP_T_COMMON for how we emulate instructions that
* employ %rip-relative addressing.
*/
if (rmindex != -1) {
uint_t mod = FASTTRAP_MODRM_MOD(instr[rmindex]);
uint_t reg = FASTTRAP_MODRM_REG(instr[rmindex]);
uint_t rm = FASTTRAP_MODRM_RM(instr[rmindex]);
ASSERT(rmindex > start);
if (mod == 0 && rm == 5) {
/*
* We need to be sure to avoid other
* registers used by this instruction. While
* the reg field may determine the op code
* rather than denoting a register, assuming
* that it denotes a register is always safe.
* We leave the REX field intact and use
* whatever value's there for simplicity.
*/
if (reg != 0) {
tp->ftt_ripmode = FASTTRAP_RIP_1 |
(FASTTRAP_RIP_X *
FASTTRAP_REX_B(rex));
rm = 0;
} else {
tp->ftt_ripmode = FASTTRAP_RIP_2 |
(FASTTRAP_RIP_X *
FASTTRAP_REX_B(rex));
rm = 1;
}
tp->ftt_modrm = tp->ftt_instr[rmindex];
tp->ftt_instr[rmindex] =
FASTTRAP_MODRM(2, reg, rm);
}
}
}
#endif
return (0);
}
int
fasttrap_tracepoint_install(proc_t *p, fasttrap_tracepoint_t *tp)
{
fasttrap_instr_t instr = FASTTRAP_INSTR;
if (uwrite(p, &instr, 1, tp->ftt_pc) != 0)
return (-1);
return (0);
}
int
fasttrap_tracepoint_remove(proc_t *p, fasttrap_tracepoint_t *tp)
{
uint8_t instr;
/*
* Distinguish between read or write failures and a changed
* instruction.
*/
if (uread(p, &instr, 1, tp->ftt_pc) != 0)
return (0);
if (instr != FASTTRAP_INSTR)
return (0);
if (uwrite(p, &tp->ftt_instr[0], 1, tp->ftt_pc) != 0)
return (-1);
return (0);
}
#ifdef __amd64
static uintptr_t
fasttrap_fulword_noerr(const void *uaddr)
{
uintptr_t ret;
if ((ret = fasttrap_fulword(uaddr)) != -1)
return (ret);
return (0);
}
#endif
static uint32_t
fasttrap_fuword32_noerr(const void *uaddr)
{
uint32_t ret;
if ((ret = fasttrap_fuword32(uaddr)) != -1)
return (ret);
return (0);
}
static void
fasttrap_return_common(struct reg *rp, uintptr_t pc, pid_t pid,
uintptr_t new_pc)
{
fasttrap_tracepoint_t *tp;
fasttrap_bucket_t *bucket;
fasttrap_id_t *id;
#ifdef illumos
kmutex_t *pid_mtx;
pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock;
mutex_enter(pid_mtx);
#else
struct rm_priotracker tracker;
rm_rlock(&fasttrap_tp_lock, &tracker);
#endif
bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
for (tp = bucket->ftb_data; tp != NULL; tp = tp->ftt_next) {
if (pid == tp->ftt_pid && pc == tp->ftt_pc &&
tp->ftt_proc->ftpc_acount != 0)
break;
}
/*
* Don't sweat it if we can't find the tracepoint again; unlike
* when we're in fasttrap_pid_probe(), finding the tracepoint here
* is not essential to the correct execution of the process.
*/
if (tp == NULL) {
#ifdef illumos
mutex_exit(pid_mtx);
#else
rm_runlock(&fasttrap_tp_lock, &tracker);
#endif
return;
}
for (id = tp->ftt_retids; id != NULL; id = id->fti_next) {
/*
* If there's a branch that could act as a return site, we
* need to trace it, and check here if the program counter is
* external to the function.
*/
if (tp->ftt_type != FASTTRAP_T_RET &&
tp->ftt_type != FASTTRAP_T_RET16 &&
new_pc - id->fti_probe->ftp_faddr <
id->fti_probe->ftp_fsize)
continue;
dtrace_probe(id->fti_probe->ftp_id,
pc - id->fti_probe->ftp_faddr,
rp->r_rax, rp->r_rbx, 0, 0);
}
#ifdef illumos
mutex_exit(pid_mtx);
#else
rm_runlock(&fasttrap_tp_lock, &tracker);
#endif
}
static void
fasttrap_sigsegv(proc_t *p, kthread_t *t, uintptr_t addr)
{
#ifdef illumos
sigqueue_t *sqp = kmem_zalloc(sizeof (sigqueue_t), KM_SLEEP);
sqp->sq_info.si_signo = SIGSEGV;
sqp->sq_info.si_code = SEGV_MAPERR;
sqp->sq_info.si_addr = (caddr_t)addr;
mutex_enter(&p->p_lock);
sigaddqa(p, t, sqp);
mutex_exit(&p->p_lock);
if (t != NULL)
aston(t);
#else
ksiginfo_t *ksi = kmem_zalloc(sizeof (ksiginfo_t), KM_SLEEP);
ksiginfo_init(ksi);
ksi->ksi_signo = SIGSEGV;
ksi->ksi_code = SEGV_MAPERR;
ksi->ksi_addr = (caddr_t)addr;
(void) tdksignal(t, SIGSEGV, ksi);
#endif
}
#ifdef __amd64
static void
fasttrap_usdt_args64(fasttrap_probe_t *probe, struct reg *rp, int argc,
uintptr_t *argv)
{
int i, x, cap = MIN(argc, probe->ftp_nargs);
uintptr_t *stack = (uintptr_t *)rp->r_rsp;
for (i = 0; i < cap; i++) {
x = probe->ftp_argmap[i];
if (x < 6)
argv[i] = (&rp->r_rdi)[x];
else
argv[i] = fasttrap_fulword_noerr(&stack[x]);
}
for (; i < argc; i++) {
argv[i] = 0;
}
}
#endif
static void
fasttrap_usdt_args32(fasttrap_probe_t *probe, struct reg *rp, int argc,
uint32_t *argv)
{
int i, x, cap = MIN(argc, probe->ftp_nargs);
uint32_t *stack = (uint32_t *)rp->r_rsp;
for (i = 0; i < cap; i++) {
x = probe->ftp_argmap[i];
argv[i] = fasttrap_fuword32_noerr(&stack[x]);
}
for (; i < argc; i++) {
argv[i] = 0;
}
}
static int
fasttrap_do_seg(fasttrap_tracepoint_t *tp, struct reg *rp, uintptr_t *addr)
{
proc_t *p = curproc;
#ifdef __i386__
struct segment_descriptor *desc;
#else
struct user_segment_descriptor *desc;
#endif
uint16_t sel = 0, ndx, type;
uintptr_t limit;
switch (tp->ftt_segment) {
case FASTTRAP_SEG_CS:
sel = rp->r_cs;
break;
case FASTTRAP_SEG_DS:
sel = rp->r_ds;
break;
case FASTTRAP_SEG_ES:
sel = rp->r_es;
break;
case FASTTRAP_SEG_FS:
sel = rp->r_fs;
break;
case FASTTRAP_SEG_GS:
sel = rp->r_gs;
break;
case FASTTRAP_SEG_SS:
sel = rp->r_ss;
break;
}
/*
* Make sure the given segment register specifies a user priority
* selector rather than a kernel selector.
*/
if (ISPL(sel) != SEL_UPL)
return (-1);
ndx = IDXSEL(sel);
/*
* Check the bounds and grab the descriptor out of the specified
* descriptor table.
*/
if (ISLDT(sel)) {
#ifdef __i386__
if (ndx > p->p_md.md_ldt->ldt_len)
return (-1);
desc = (struct segment_descriptor *)
p->p_md.md_ldt[ndx].ldt_base;
#else
if (ndx > max_ldt_segment)
return (-1);
desc = (struct user_segment_descriptor *)
p->p_md.md_ldt[ndx].ldt_base;
#endif
} else {
if (ndx >= NGDT)
return (-1);
#ifdef __i386__
desc = &gdt[ndx].sd;
#else
desc = &gdt[ndx];
#endif
}
/*
* The descriptor must have user privilege level and it must be
* present in memory.
*/
if (desc->sd_dpl != SEL_UPL || desc->sd_p != 1)
return (-1);
type = desc->sd_type;
/*
* If the S bit in the type field is not set, this descriptor can
* only be used in system context.
*/
if ((type & 0x10) != 0x10)
return (-1);
limit = USD_GETLIMIT(desc) * (desc->sd_gran ? PAGESIZE : 1);
if (tp->ftt_segment == FASTTRAP_SEG_CS) {
/*
* The code/data bit and readable bit must both be set.
*/
if ((type & 0xa) != 0xa)
return (-1);
if (*addr > limit)
return (-1);
} else {
/*
* The code/data bit must be clear.
*/
if ((type & 0x8) != 0)
return (-1);
/*
* If the expand-down bit is clear, we just check the limit as
* it would naturally be applied. Otherwise, we need to check
* that the address is the range [limit + 1 .. 0xffff] or
* [limit + 1 ... 0xffffffff] depending on if the default
* operand size bit is set.
*/
if ((type & 0x4) == 0) {
if (*addr > limit)
return (-1);
} else if (desc->sd_def32) {
if (*addr < limit + 1 || 0xffff < *addr)
return (-1);
} else {
if (*addr < limit + 1 || 0xffffffff < *addr)
return (-1);
}
}
*addr += USD_GETBASE(desc);
return (0);
}
int
fasttrap_pid_probe(struct reg *rp)
{
proc_t *p = curproc;
#ifndef illumos
struct rm_priotracker tracker;
proc_t *pp;
#endif
uintptr_t pc = rp->r_rip - 1;
uintptr_t new_pc = 0;
fasttrap_bucket_t *bucket;
#ifdef illumos
kmutex_t *pid_mtx;
#endif
fasttrap_tracepoint_t *tp, tp_local;
pid_t pid;
dtrace_icookie_t cookie;
uint_t is_enabled = 0;
/*
* It's possible that a user (in a veritable orgy of bad planning)
* could redirect this thread's flow of control before it reached the
* return probe fasttrap. In this case we need to kill the process
* since it's in a unrecoverable state.
*/
if (curthread->t_dtrace_step) {
ASSERT(curthread->t_dtrace_on);
fasttrap_sigtrap(p, curthread, pc);
return (0);
}
/*
* Clear all user tracing flags.
*/
curthread->t_dtrace_ft = 0;
curthread->t_dtrace_pc = 0;
curthread->t_dtrace_npc = 0;
curthread->t_dtrace_scrpc = 0;
curthread->t_dtrace_astpc = 0;
#ifdef __amd64
curthread->t_dtrace_regv = 0;
#endif
/*
* Treat a child created by a call to vfork(2) as if it were its
* parent. We know that there's only one thread of control in such a
* process: this one.
*/
#ifdef illumos
while (p->p_flag & SVFORK) {
p = p->p_parent;
}
pid = p->p_pid;
pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock;
mutex_enter(pid_mtx);
#else
pp = p;
sx_slock(&proctree_lock);
while (pp->p_vmspace == pp->p_pptr->p_vmspace)
pp = pp->p_pptr;
pid = pp->p_pid;
sx_sunlock(&proctree_lock);
pp = NULL;
rm_rlock(&fasttrap_tp_lock, &tracker);
#endif
bucket = &fasttrap_tpoints.fth_table[FASTTRAP_TPOINTS_INDEX(pid, pc)];
/*
* Lookup the tracepoint that the process just hit.
*/
for (tp = bucket->ftb_data; tp != NULL; tp = tp->ftt_next) {
if (pid == tp->ftt_pid && pc == tp->ftt_pc &&
tp->ftt_proc->ftpc_acount != 0)
break;
}
/*
* If we couldn't find a matching tracepoint, either a tracepoint has
* been inserted without using the pid<pid> ioctl interface (see
* fasttrap_ioctl), or somehow we have mislaid this tracepoint.
*/
if (tp == NULL) {
#ifdef illumos
mutex_exit(pid_mtx);
#else
rm_runlock(&fasttrap_tp_lock, &tracker);
#endif
return (-1);
}
/*
* Set the program counter to the address of the traced instruction
* so that it looks right in ustack() output.
*/
rp->r_rip = pc;
if (tp->ftt_ids != NULL) {
fasttrap_id_t *id;
#ifdef __amd64
if (p->p_model == DATAMODEL_LP64) {
for (id = tp->ftt_ids; id != NULL; id = id->fti_next) {
fasttrap_probe_t *probe = id->fti_probe;
if (id->fti_ptype == DTFTP_ENTRY) {
/*
* We note that this was an entry
* probe to help ustack() find the
* first caller.
*/
cookie = dtrace_interrupt_disable();
DTRACE_CPUFLAG_SET(CPU_DTRACE_ENTRY);
dtrace_probe(probe->ftp_id, rp->r_rdi,
rp->r_rsi, rp->r_rdx, rp->r_rcx,
rp->r_r8);
DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_ENTRY);
dtrace_interrupt_enable(cookie);
} else if (id->fti_ptype == DTFTP_IS_ENABLED) {
/*
* Note that in this case, we don't
* call dtrace_probe() since it's only
* an artificial probe meant to change
* the flow of control so that it
* encounters the true probe.
*/
is_enabled = 1;
} else if (probe->ftp_argmap == NULL) {
dtrace_probe(probe->ftp_id, rp->r_rdi,
rp->r_rsi, rp->r_rdx, rp->r_rcx,
rp->r_r8);
} else {
uintptr_t t[5];
fasttrap_usdt_args64(probe, rp,
sizeof (t) / sizeof (t[0]), t);
dtrace_probe(probe->ftp_id, t[0], t[1],
t[2], t[3], t[4]);
}
}
} else {
#endif
uintptr_t s0, s1, s2, s3, s4, s5;
uint32_t *stack = (uint32_t *)rp->r_rsp;
/*
* In 32-bit mode, all arguments are passed on the
* stack. If this is a function entry probe, we need
* to skip the first entry on the stack as it
* represents the return address rather than a
* parameter to the function.
*/
s0 = fasttrap_fuword32_noerr(&stack[0]);
s1 = fasttrap_fuword32_noerr(&stack[1]);
s2 = fasttrap_fuword32_noerr(&stack[2]);
s3 = fasttrap_fuword32_noerr(&stack[3]);
s4 = fasttrap_fuword32_noerr(&stack[4]);
s5 = fasttrap_fuword32_noerr(&stack[5]);
for (id = tp->ftt_ids; id != NULL; id = id->fti_next) {
fasttrap_probe_t *probe = id->fti_probe;
if (id->fti_ptype == DTFTP_ENTRY) {
/*
* We note that this was an entry
* probe to help ustack() find the
* first caller.
*/
cookie = dtrace_interrupt_disable();
DTRACE_CPUFLAG_SET(CPU_DTRACE_ENTRY);
dtrace_probe(probe->ftp_id, s1, s2,
s3, s4, s5);
DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_ENTRY);
dtrace_interrupt_enable(cookie);
} else if (id->fti_ptype == DTFTP_IS_ENABLED) {
/*
* Note that in this case, we don't
* call dtrace_probe() since it's only
* an artificial probe meant to change
* the flow of control so that it
* encounters the true probe.
*/
is_enabled = 1;
} else if (probe->ftp_argmap == NULL) {
dtrace_probe(probe->ftp_id, s0, s1,
s2, s3, s4);
} else {
uint32_t t[5];
fasttrap_usdt_args32(probe, rp,
sizeof (t) / sizeof (t[0]), t);
dtrace_probe(probe->ftp_id, t[0], t[1],
t[2], t[3], t[4]);
}
}
#ifdef __amd64
}
#endif
}
/*
* We're about to do a bunch of work so we cache a local copy of
* the tracepoint to emulate the instruction, and then find the
* tracepoint again later if we need to light up any return probes.
*/
tp_local = *tp;
#ifdef illumos
mutex_exit(pid_mtx);
#else
rm_runlock(&fasttrap_tp_lock, &tracker);
#endif
tp = &tp_local;
/*
* Set the program counter to appear as though the traced instruction
* had completely executed. This ensures that fasttrap_getreg() will
* report the expected value for REG_RIP.
*/
rp->r_rip = pc + tp->ftt_size;
/*
* If there's an is-enabled probe connected to this tracepoint it
* means that there was a 'xorl %eax, %eax' or 'xorq %rax, %rax'
* instruction that was placed there by DTrace when the binary was
* linked. As this probe is, in fact, enabled, we need to stuff 1
* into %eax or %rax. Accordingly, we can bypass all the instruction
* emulation logic since we know the inevitable result. It's possible
* that a user could construct a scenario where the 'is-enabled'
* probe was on some other instruction, but that would be a rather
* exotic way to shoot oneself in the foot.
*/
if (is_enabled) {
rp->r_rax = 1;
new_pc = rp->r_rip;
goto done;
}
/*
* We emulate certain types of instructions to ensure correctness
* (in the case of position dependent instructions) or optimize
* common cases. The rest we have the thread execute back in user-
* land.
*/
switch (tp->ftt_type) {
case FASTTRAP_T_RET:
case FASTTRAP_T_RET16:
{
uintptr_t dst = 0;
uintptr_t addr = 0;
int ret = 0;
/*
* We have to emulate _every_ facet of the behavior of a ret
* instruction including what happens if the load from %esp
* fails; in that case, we send a SIGSEGV.
*/
#ifdef __amd64
if (p->p_model == DATAMODEL_NATIVE) {
ret = dst = fasttrap_fulword((void *)rp->r_rsp);
addr = rp->r_rsp + sizeof (uintptr_t);
} else {
#endif
uint32_t dst32;
ret = dst32 = fasttrap_fuword32((void *)rp->r_rsp);
dst = dst32;
addr = rp->r_rsp + sizeof (uint32_t);
#ifdef __amd64
}
#endif
if (ret == -1) {
fasttrap_sigsegv(p, curthread, rp->r_rsp);
new_pc = pc;
break;
}
if (tp->ftt_type == FASTTRAP_T_RET16)
addr += tp->ftt_dest;
rp->r_rsp = addr;
new_pc = dst;
break;
}
case FASTTRAP_T_JCC:
{
uint_t taken = 0;
switch (tp->ftt_code) {
case FASTTRAP_JO:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_OF) != 0;
break;
case FASTTRAP_JNO:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0;
break;
case FASTTRAP_JB:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) != 0;
break;
case FASTTRAP_JAE:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) == 0;
break;
case FASTTRAP_JE:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0;
break;
case FASTTRAP_JNE:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0;
break;
case FASTTRAP_JBE:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) != 0 ||
(rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0;
break;
case FASTTRAP_JA:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_CF) == 0 &&
(rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0;
break;
case FASTTRAP_JS:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_SF) != 0;
break;
case FASTTRAP_JNS:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0;
break;
case FASTTRAP_JP:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_PF) != 0;
break;
case FASTTRAP_JNP:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_PF) == 0;
break;
case FASTTRAP_JL:
taken = ((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) !=
((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
break;
case FASTTRAP_JGE:
taken = ((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) ==
((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
break;
case FASTTRAP_JLE:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0 ||
((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) !=
((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
break;
case FASTTRAP_JG:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0 &&
((rp->r_rflags & FASTTRAP_EFLAGS_SF) == 0) ==
((rp->r_rflags & FASTTRAP_EFLAGS_OF) == 0);
break;
}
if (taken)
new_pc = tp->ftt_dest;
else
new_pc = pc + tp->ftt_size;
break;
}
case FASTTRAP_T_LOOP:
{
uint_t taken = 0;
#ifdef __amd64
greg_t cx = rp->r_rcx--;
#else
greg_t cx = rp->r_ecx--;
#endif
switch (tp->ftt_code) {
case FASTTRAP_LOOPNZ:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) == 0 &&
cx != 0;
break;
case FASTTRAP_LOOPZ:
taken = (rp->r_rflags & FASTTRAP_EFLAGS_ZF) != 0 &&
cx != 0;
break;
case FASTTRAP_LOOP:
taken = (cx != 0);
break;
}
if (taken)
new_pc = tp->ftt_dest;
else
new_pc = pc + tp->ftt_size;
break;
}
case FASTTRAP_T_JCXZ:
{
#ifdef __amd64
greg_t cx = rp->r_rcx;
#else
greg_t cx = rp->r_ecx;
#endif
if (cx == 0)
new_pc = tp->ftt_dest;
else
new_pc = pc + tp->ftt_size;
break;
}
case FASTTRAP_T_PUSHL_EBP:
{
int ret = 0;
#ifdef __amd64
if (p->p_model == DATAMODEL_NATIVE) {
rp->r_rsp -= sizeof (uintptr_t);
ret = fasttrap_sulword((void *)rp->r_rsp, rp->r_rbp);
} else {
#endif
rp->r_rsp -= sizeof (uint32_t);
ret = fasttrap_suword32((void *)rp->r_rsp, rp->r_rbp);
#ifdef __amd64
}
#endif
if (ret == -1) {
fasttrap_sigsegv(p, curthread, rp->r_rsp);
new_pc = pc;
break;
}
new_pc = pc + tp->ftt_size;
break;
}
case FASTTRAP_T_NOP:
new_pc = pc + tp->ftt_size;
break;
case FASTTRAP_T_JMP:
case FASTTRAP_T_CALL:
if (tp->ftt_code == 0) {
new_pc = tp->ftt_dest;
} else {
uintptr_t value, addr = tp->ftt_dest;
if (tp->ftt_base != FASTTRAP_NOREG)
addr += fasttrap_getreg(rp, tp->ftt_base);
if (tp->ftt_index != FASTTRAP_NOREG)
addr += fasttrap_getreg(rp, tp->ftt_index) <<
tp->ftt_scale;
if (tp->ftt_code == 1) {
/*
* If there's a segment prefix for this
* instruction, we'll need to check permissions
* and bounds on the given selector, and adjust
* the address accordingly.
*/
if (tp->ftt_segment != FASTTRAP_SEG_NONE &&
fasttrap_do_seg(tp, rp, &addr) != 0) {
fasttrap_sigsegv(p, curthread, addr);
new_pc = pc;
break;
}
#ifdef __amd64
if (p->p_model == DATAMODEL_NATIVE) {
#endif
if ((value = fasttrap_fulword((void *)addr))
== -1) {
fasttrap_sigsegv(p, curthread,
addr);
new_pc = pc;
break;
}
new_pc = value;
#ifdef __amd64
} else {
uint32_t value32;
addr = (uintptr_t)(uint32_t)addr;
if ((value32 = fasttrap_fuword32((void *)addr))
== -1) {
fasttrap_sigsegv(p, curthread,
addr);
new_pc = pc;
break;
}
new_pc = value32;
}
#endif
} else {
new_pc = addr;
}
}
/*
* If this is a call instruction, we need to push the return
* address onto the stack. If this fails, we send the process
* a SIGSEGV and reset the pc to emulate what would happen if
* this instruction weren't traced.
*/
if (tp->ftt_type == FASTTRAP_T_CALL) {
int ret = 0;
uintptr_t addr = 0, pcps;
#ifdef __amd64
if (p->p_model == DATAMODEL_NATIVE) {
addr = rp->r_rsp - sizeof (uintptr_t);
pcps = pc + tp->ftt_size;
ret = fasttrap_sulword((void *)addr, pcps);
} else {
#endif
addr = rp->r_rsp - sizeof (uint32_t);
pcps = (uint32_t)(pc + tp->ftt_size);
ret = fasttrap_suword32((void *)addr, pcps);
#ifdef __amd64
}
#endif
if (ret == -1) {
fasttrap_sigsegv(p, curthread, addr);
new_pc = pc;
break;
}
rp->r_rsp = addr;
}
break;
case FASTTRAP_T_COMMON:
{
uintptr_t addr;
#if defined(__amd64)
uint8_t scratch[2 * FASTTRAP_MAX_INSTR_SIZE + 22];
#else
uint8_t scratch[2 * FASTTRAP_MAX_INSTR_SIZE + 7];
#endif
uint_t i = 0;
#ifdef illumos
klwp_t *lwp = ttolwp(curthread);
/*
* Compute the address of the ulwp_t and step over the
* ul_self pointer. The method used to store the user-land
* thread pointer is very different on 32- and 64-bit
* kernels.
*/
#if defined(__amd64)
if (p->p_model == DATAMODEL_LP64) {
addr = lwp->lwp_pcb.pcb_fsbase;
addr += sizeof (void *);
} else {
addr = lwp->lwp_pcb.pcb_gsbase;
addr += sizeof (caddr32_t);
}
#else
addr = USD_GETBASE(&lwp->lwp_pcb.pcb_gsdesc);
addr += sizeof (void *);
#endif
#else /* !illumos */
fasttrap_scrspace_t *scrspace;
scrspace = fasttrap_scraddr(curthread, tp->ftt_proc);
if (scrspace == NULL) {
/*
* We failed to allocate scratch space for this thread.
* Try to write the original instruction back out and
* reset the pc.
*/
if (fasttrap_copyout(tp->ftt_instr, (void *)pc,
tp->ftt_size))
fasttrap_sigtrap(p, curthread, pc);
new_pc = pc;
break;
}
addr = scrspace->ftss_addr;
#endif /* illumos */
/*
* Generic Instruction Tracing
* ---------------------------
*
* This is the layout of the scratch space in the user-land
* thread structure for our generated instructions.
*
* 32-bit mode bytes
* ------------------------ -----
* a: <original instruction> <= 15
* jmp <pc + tp->ftt_size> 5
* b: <original instruction> <= 15
* int T_DTRACE_RET 2
* -----
* <= 37
*
* 64-bit mode bytes
* ------------------------ -----
* a: <original instruction> <= 15
* jmp 0(%rip) 6
* <pc + tp->ftt_size> 8
* b: <original instruction> <= 15
* int T_DTRACE_RET 2
* -----
* <= 46
*
* The %pc is set to a, and curthread->t_dtrace_astpc is set
* to b. If we encounter a signal on the way out of the
* kernel, trap() will set %pc to curthread->t_dtrace_astpc
* so that we execute the original instruction and re-enter
* the kernel rather than redirecting to the next instruction.
*
* If there are return probes (so we know that we're going to
* need to reenter the kernel after executing the original
* instruction), the scratch space will just contain the
* original instruction followed by an interrupt -- the same
* data as at b.
*
* %rip-relative Addressing
* ------------------------
*
* There's a further complication in 64-bit mode due to %rip-
* relative addressing. While this is clearly a beneficial
* architectural decision for position independent code, it's
* hard not to see it as a personal attack against the pid
* provider since before there was a relatively small set of
* instructions to emulate; with %rip-relative addressing,
* almost every instruction can potentially depend on the
* address at which it's executed. Rather than emulating
* the broad spectrum of instructions that can now be
* position dependent, we emulate jumps and others as in
* 32-bit mode, and take a different tack for instructions
* using %rip-relative addressing.
*
* For every instruction that uses the ModRM byte, the
* in-kernel disassembler reports its location. We use the
* ModRM byte to identify that an instruction uses
* %rip-relative addressing and to see what other registers
* the instruction uses. To emulate those instructions,
* we modify the instruction to be %rax-relative rather than
* %rip-relative (or %rcx-relative if the instruction uses
* %rax; or %r8- or %r9-relative if the REX.B is present so
* we don't have to rewrite the REX prefix). We then load
* the value that %rip would have been into the scratch
* register and generate an instruction to reset the scratch
* register back to its original value. The instruction
* sequence looks like this:
*
* 64-mode %rip-relative bytes
* ------------------------ -----
* a: <modified instruction> <= 15
* movq $<value>, %<scratch> 6
* jmp 0(%rip) 6
* <pc + tp->ftt_size> 8
* b: <modified instruction> <= 15
* int T_DTRACE_RET 2
* -----
* 52
*
* We set curthread->t_dtrace_regv so that upon receiving
* a signal we can reset the value of the scratch register.
*/
ASSERT(tp->ftt_size <= FASTTRAP_MAX_INSTR_SIZE);
curthread->t_dtrace_scrpc = addr;
bcopy(tp->ftt_instr, &scratch[i], tp->ftt_size);
i += tp->ftt_size;
#ifdef __amd64
if (tp->ftt_ripmode != 0) {
greg_t *reg = NULL;
ASSERT(p->p_model == DATAMODEL_LP64);
ASSERT(tp->ftt_ripmode &
(FASTTRAP_RIP_1 | FASTTRAP_RIP_2));
/*
* If this was a %rip-relative instruction, we change
* it to be either a %rax- or %rcx-relative
* instruction (depending on whether those registers
* are used as another operand; or %r8- or %r9-
* relative depending on the value of REX.B). We then
* set that register and generate a movq instruction
* to reset the value.
*/
if (tp->ftt_ripmode & FASTTRAP_RIP_X)
scratch[i++] = FASTTRAP_REX(1, 0, 0, 1);
else
scratch[i++] = FASTTRAP_REX(1, 0, 0, 0);
if (tp->ftt_ripmode & FASTTRAP_RIP_1)
scratch[i++] = FASTTRAP_MOV_EAX;
else
scratch[i++] = FASTTRAP_MOV_ECX;
switch (tp->ftt_ripmode) {
case FASTTRAP_RIP_1:
reg = &rp->r_rax;
curthread->t_dtrace_reg = REG_RAX;
break;
case FASTTRAP_RIP_2:
reg = &rp->r_rcx;
curthread->t_dtrace_reg = REG_RCX;
break;
case FASTTRAP_RIP_1 | FASTTRAP_RIP_X:
reg = &rp->r_r8;
curthread->t_dtrace_reg = REG_R8;
break;
case FASTTRAP_RIP_2 | FASTTRAP_RIP_X:
reg = &rp->r_r9;
curthread->t_dtrace_reg = REG_R9;
break;
}
/* LINTED - alignment */
*(uint64_t *)&scratch[i] = *reg;
curthread->t_dtrace_regv = *reg;
*reg = pc + tp->ftt_size;
i += sizeof (uint64_t);
}
#endif
/*
* Generate the branch instruction to what would have
* normally been the subsequent instruction. In 32-bit mode,
* this is just a relative branch; in 64-bit mode this is a
* %rip-relative branch that loads the 64-bit pc value
* immediately after the jmp instruction.
*/
#ifdef __amd64
if (p->p_model == DATAMODEL_LP64) {
scratch[i++] = FASTTRAP_GROUP5_OP;
scratch[i++] = FASTTRAP_MODRM(0, 4, 5);
/* LINTED - alignment */
*(uint32_t *)&scratch[i] = 0;
i += sizeof (uint32_t);
/* LINTED - alignment */
*(uint64_t *)&scratch[i] = pc + tp->ftt_size;
i += sizeof (uint64_t);
} else {
#endif
/*
* Set up the jmp to the next instruction; note that
* the size of the traced instruction cancels out.
*/
scratch[i++] = FASTTRAP_JMP32;
/* LINTED - alignment */
*(uint32_t *)&scratch[i] = pc - addr - 5;
i += sizeof (uint32_t);
#ifdef __amd64
}
#endif
curthread->t_dtrace_astpc = addr + i;
bcopy(tp->ftt_instr, &scratch[i], tp->ftt_size);
i += tp->ftt_size;
scratch[i++] = FASTTRAP_INT;
scratch[i++] = T_DTRACE_RET;
ASSERT(i <= sizeof (scratch));
#ifdef illumos
if (fasttrap_copyout(scratch, (char *)addr, i)) {
#else
if (uwrite(p, scratch, i, addr)) {
#endif
fasttrap_sigtrap(p, curthread, pc);
new_pc = pc;
break;
}
if (tp->ftt_retids != NULL) {
curthread->t_dtrace_step = 1;
curthread->t_dtrace_ret = 1;
new_pc = curthread->t_dtrace_astpc;
} else {
new_pc = curthread->t_dtrace_scrpc;
}
curthread->t_dtrace_pc = pc;
curthread->t_dtrace_npc = pc + tp->ftt_size;
curthread->t_dtrace_on = 1;
break;
}
default:
panic("fasttrap: mishandled an instruction");
}
done:
/*
* If there were no return probes when we first found the tracepoint,
* we should feel no obligation to honor any return probes that were
* subsequently enabled -- they'll just have to wait until the next
* time around.
*/
if (tp->ftt_retids != NULL) {
/*
* We need to wait until the results of the instruction are
* apparent before invoking any return probes. If this
* instruction was emulated we can just call
* fasttrap_return_common(); if it needs to be executed, we
* need to wait until the user thread returns to the kernel.
*/
if (tp->ftt_type != FASTTRAP_T_COMMON) {
/*
* Set the program counter to the address of the traced
* instruction so that it looks right in ustack()
* output. We had previously set it to the end of the
* instruction to simplify %rip-relative addressing.
*/
rp->r_rip = pc;
fasttrap_return_common(rp, pc, pid, new_pc);
} else {
ASSERT(curthread->t_dtrace_ret != 0);
ASSERT(curthread->t_dtrace_pc == pc);
ASSERT(curthread->t_dtrace_scrpc != 0);
ASSERT(new_pc == curthread->t_dtrace_astpc);
}
}
rp->r_rip = new_pc;
#ifndef illumos
PROC_LOCK(p);
proc_write_regs(curthread, rp);
PROC_UNLOCK(p);
#endif
return (0);
}
int
fasttrap_return_probe(struct reg *rp)
{
proc_t *p = curproc;
uintptr_t pc = curthread->t_dtrace_pc;
uintptr_t npc = curthread->t_dtrace_npc;
curthread->t_dtrace_pc = 0;
curthread->t_dtrace_npc = 0;
curthread->t_dtrace_scrpc = 0;
curthread->t_dtrace_astpc = 0;
#ifdef illumos
/*
* Treat a child created by a call to vfork(2) as if it were its
* parent. We know that there's only one thread of control in such a
* process: this one.
*/
while (p->p_flag & SVFORK) {
p = p->p_parent;
}
#endif
/*
* We set rp->r_rip to the address of the traced instruction so
* that it appears to dtrace_probe() that we're on the original
* instruction, and so that the user can't easily detect our
* complex web of lies. dtrace_return_probe() (our caller)
* will correctly set %pc after we return.
*/
rp->r_rip = pc;
fasttrap_return_common(rp, pc, p->p_pid, npc);
return (0);
}
/*ARGSUSED*/
uint64_t
fasttrap_pid_getarg(void *arg, dtrace_id_t id, void *parg, int argno,
int aframes)
{
struct reg r;
fill_regs(curthread, &r);
return (fasttrap_anarg(&r, 1, argno));
}
/*ARGSUSED*/
uint64_t
fasttrap_usdt_getarg(void *arg, dtrace_id_t id, void *parg, int argno,
int aframes)
{
struct reg r;
fill_regs(curthread, &r);
return (fasttrap_anarg(&r, 0, argno));
}
static ulong_t
fasttrap_getreg(struct reg *rp, uint_t reg)
{
#ifdef __amd64
switch (reg) {
case REG_R15: return (rp->r_r15);
case REG_R14: return (rp->r_r14);
case REG_R13: return (rp->r_r13);
case REG_R12: return (rp->r_r12);
case REG_R11: return (rp->r_r11);
case REG_R10: return (rp->r_r10);
case REG_R9: return (rp->r_r9);
case REG_R8: return (rp->r_r8);
case REG_RDI: return (rp->r_rdi);
case REG_RSI: return (rp->r_rsi);
case REG_RBP: return (rp->r_rbp);
case REG_RBX: return (rp->r_rbx);
case REG_RDX: return (rp->r_rdx);
case REG_RCX: return (rp->r_rcx);
case REG_RAX: return (rp->r_rax);
case REG_TRAPNO: return (rp->r_trapno);
case REG_ERR: return (rp->r_err);
case REG_RIP: return (rp->r_rip);
case REG_CS: return (rp->r_cs);
case REG_RFL: return (rp->r_rflags);
case REG_RSP: return (rp->r_rsp);
case REG_SS: return (rp->r_ss);
case REG_FS: return (rp->r_fs);
case REG_GS: return (rp->r_gs);
case REG_DS: return (rp->r_ds);
case REG_ES: return (rp->r_es);
case REG_FSBASE: return (rdmsr(MSR_FSBASE));
case REG_GSBASE: return (rdmsr(MSR_GSBASE));
}
panic("dtrace: illegal register constant");
/*NOTREACHED*/
#else
#define _NGREG 19
if (reg >= _NGREG)
panic("dtrace: illegal register constant");
return (((greg_t *)&rp->r_gs)[reg]);
#endif
}