/* * 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 2007 Sun Microsystems, Inc. All rights reserved. * Use is subject to license terms. */ #pragma ident "%Z%%M% %I% %E% SMI" #include #include #include #include #include #include #include #include #include #include #include /* * Lossless User-Land Tracing on SPARC * ----------------------------------- * * The Basic Idea * * The most important design constraint is, of course, correct execution of * the user thread above all else. The next most important goal is rapid * execution. We combine execution of instructions in user-land with * emulation of certain instructions in the kernel to aim for complete * correctness and maximal performance. * * We take advantage of the split PC/NPC architecture to speed up logical * single-stepping; when we copy an instruction out to the scratch space in * the ulwp_t structure (held in the %g7 register on SPARC), we can * effectively single step by setting the PC to our scratch space and leaving * the NPC alone. This executes the replaced instruction and then continues * on without having to reenter the kernel as with single- stepping. The * obvious caveat is for instructions whose execution is PC dependant -- * branches, call and link instructions (call and jmpl), and the rdpc * instruction. These instructions cannot be executed in the manner described * so they must be emulated in the kernel. * * Emulation for this small set of instructions if fairly simple; the most * difficult part being emulating branch conditions. * * * A Cache Heavy Portfolio * * It's important to note at this time that copying an instruction out to the * ulwp_t scratch space in user-land is rather complicated. SPARC has * separate data and instruction caches so any writes to the D$ (using a * store instruction for example) aren't necessarily reflected in the I$. * The flush instruction can be used to synchronize the two and must be used * for any self-modifying code, but the flush instruction only applies to the * primary address space (the absence of a flusha analogue to the flush * instruction that accepts an ASI argument is an obvious omission from SPARC * v9 where the notion of the alternate address space was introduced on * SPARC). To correctly copy out the instruction we must use a block store * that doesn't allocate in the D$ and ensures synchronization with the I$; * see dtrace_blksuword32() for the implementation (this function uses * ASI_BLK_COMMIT_S to write a block through the secondary ASI in the manner * described). Refer to the UltraSPARC I/II manual for details on the * ASI_BLK_COMMIT_S ASI. * * * Return Subtleties * * When we're firing a return probe we need to expose the value returned by * the function being traced. Since the function can set the return value * in its last instruction, we need to fire the return probe only _after_ * the effects of the instruction are apparent. For instructions that we * emulate, we can call dtrace_probe() after we've performed the emulation; * for instructions that we execute after we return to user-land, we set * %pc to the instruction we copied out (as described above) and set %npc * to a trap instruction stashed in the ulwp_t structure. After the traced * instruction is executed, the trap instruction returns control to the * kernel where we can fire the return probe. * * This need for a second trap in cases where we execute the traced * instruction makes it all the more important to emulate the most common * instructions to avoid the second trip in and out of the kernel. * * * Making it Fast * * Since copying out an instruction is neither simple nor inexpensive for the * CPU, we should attempt to avoid doing it in as many cases as possible. * Since function entry and return are usually the most interesting probe * sites, we attempt to tune the performance of the fasttrap provider around * instructions typically in those places. * * Looking at a bunch of functions in libraries and executables reveals that * most functions begin with either a save or a sethi (to setup a larger * argument to the save) and end with a restore or an or (in the case of leaf * functions). To try to improve performance, we emulate all of these * instructions in the kernel. * * The save and restore instructions are a little tricky since they perform * register window maniplulation. Rather than trying to tinker with the * register windows from the kernel, we emulate the implicit add that takes * place as part of those instructions and set the %pc to point to a simple * save or restore we've hidden in the ulwp_t structure. If we're in a return * probe so want to make it seem as though the tracepoint has been completely * executed we need to remember that we've pulled this trick with restore and * pull registers from the previous window (the one that we'll switch to once * the simple store instruction is executed) rather than the current one. This * is why in the case of emulating a restore we set the DTrace CPU flag * CPU_DTRACE_FAKERESTORE before calling dtrace_probe() for the return probes * (see fasttrap_return_common()). */ #define OP(x) ((x) >> 30) #define OP2(x) (((x) >> 22) & 0x07) #define OP3(x) (((x) >> 19) & 0x3f) #define RCOND(x) (((x) >> 25) & 0x07) #define COND(x) (((x) >> 25) & 0x0f) #define A(x) (((x) >> 29) & 0x01) #define I(x) (((x) >> 13) & 0x01) #define RD(x) (((x) >> 25) & 0x1f) #define RS1(x) (((x) >> 14) & 0x1f) #define RS2(x) (((x) >> 0) & 0x1f) #define CC(x) (((x) >> 20) & 0x03) #define DISP16(x) ((((x) >> 6) & 0xc000) | ((x) & 0x3fff)) #define DISP22(x) ((x) & 0x3fffff) #define DISP19(x) ((x) & 0x7ffff) #define DISP30(x) ((x) & 0x3fffffff) #define SW_TRAP(x) ((x) & 0x7f) #define OP3_OR 0x02 #define OP3_RD 0x28 #define OP3_JMPL 0x38 #define OP3_RETURN 0x39 #define OP3_TCC 0x3a #define OP3_SAVE 0x3c #define OP3_RESTORE 0x3d #define OP3_PREFETCH 0x2d #define OP3_CASA 0x3c #define OP3_PREFETCHA 0x3d #define OP3_CASXA 0x3e #define OP2_ILLTRAP 0x0 #define OP2_BPcc 0x1 #define OP2_Bicc 0x2 #define OP2_BPr 0x3 #define OP2_SETHI 0x4 #define OP2_FBPfcc 0x5 #define OP2_FBfcc 0x6 #define R_G0 0 #define R_O0 8 #define R_SP 14 #define R_I0 24 #define R_I1 25 #define R_I2 26 #define R_I3 27 /* * Check the comment in fasttrap.h when changing these offsets or adding * new instructions. */ #define FASTTRAP_OFF_SAVE 64 #define FASTTRAP_OFF_RESTORE 68 #define FASTTRAP_OFF_FTRET 72 #define FASTTRAP_OFF_RETURN 76 #define BREAKPOINT_INSTR 0x91d02001 /* ta 1 */ /* * Tunable to let users turn off the fancy save instruction optimization. * If a program is non-ABI compliant, there's a possibility that the save * instruction optimization could cause an error. */ int fasttrap_optimize_save = 1; static uint64_t fasttrap_anarg(struct regs *rp, int argno) { uint64_t value; if (argno < 6) return ((&rp->r_o0)[argno]); if (curproc->p_model == DATAMODEL_NATIVE) { struct frame *fr = (struct frame *)(rp->r_sp + STACK_BIAS); DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT); value = dtrace_fulword(&fr->fr_argd[argno]); DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT | CPU_DTRACE_BADADDR | CPU_DTRACE_BADALIGN); } else { struct frame32 *fr = (struct frame32 *)rp->r_sp; DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT); value = dtrace_fuword32(&fr->fr_argd[argno]); DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT | CPU_DTRACE_BADADDR | CPU_DTRACE_BADALIGN); } return (value); } static ulong_t fasttrap_getreg(struct regs *, uint_t); static void fasttrap_putreg(struct regs *, uint_t, ulong_t); static void fasttrap_usdt_args(fasttrap_probe_t *probe, struct regs *rp, int argc, uintptr_t *argv) { int i, x, cap = MIN(argc, probe->ftp_nargs); if (curproc->p_model == DATAMODEL_NATIVE) { struct frame *fr = (struct frame *)(rp->r_sp + STACK_BIAS); uintptr_t v; for (i = 0; i < cap; i++) { x = probe->ftp_argmap[i]; if (x < 6) argv[i] = (&rp->r_o0)[x]; else if (fasttrap_fulword(&fr->fr_argd[x], &v) != 0) argv[i] = 0; } } else { struct frame32 *fr = (struct frame32 *)rp->r_sp; uint32_t v; for (i = 0; i < cap; i++) { x = probe->ftp_argmap[i]; if (x < 6) argv[i] = (&rp->r_o0)[x]; else if (fasttrap_fuword32(&fr->fr_argd[x], &v) != 0) argv[i] = 0; } } for (; i < argc; i++) { argv[i] = 0; } } static void fasttrap_return_common(struct regs *rp, uintptr_t pc, pid_t pid, uint_t fake_restore) { fasttrap_tracepoint_t *tp; fasttrap_bucket_t *bucket; fasttrap_id_t *id; kmutex_t *pid_mtx; dtrace_icookie_t cookie; pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock; mutex_enter(pid_mtx); 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_defunct) 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 || tp->ftt_retids == NULL) { mutex_exit(pid_mtx); return; } for (id = tp->ftt_retids; id != NULL; id = id->fti_next) { fasttrap_probe_t *probe = id->fti_probe; if (id->fti_ptype == DTFTP_POST_OFFSETS) { if (probe->ftp_argmap == NULL) { dtrace_probe(probe->ftp_id, rp->r_o0, rp->r_o1, rp->r_o2, rp->r_o3, rp->r_o4); } else { uintptr_t t[5]; fasttrap_usdt_args(probe, rp, sizeof (t) / sizeof (t[0]), t); dtrace_probe(probe->ftp_id, t[0], t[1], t[2], t[3], t[4]); } continue; } /* * If this is only a possible return point, we must * be looking at a potential tail call in leaf context. * If the %npc is still within this function, then we * must have misidentified a jmpl as a tail-call when it * is, in fact, part of a jump table. It would be nice to * remove this tracepoint, but this is neither the time * nor the place. */ if ((tp->ftt_flags & FASTTRAP_F_RETMAYBE) && rp->r_npc - probe->ftp_faddr < probe->ftp_fsize) continue; /* * It's possible for a function to branch to the delay slot * of an instruction that we've identified as a return site. * We can dectect this spurious return probe activation by * observing that in this case %npc will be %pc + 4 and %npc * will be inside the current function (unless the user is * doing _crazy_ instruction picking in which case there's * very little we can do). The second check is important * in case the last instructions of a function make a tail- * call to the function located immediately subsequent. */ if (rp->r_npc == rp->r_pc + 4 && rp->r_npc - probe->ftp_faddr < probe->ftp_fsize) continue; /* * The first argument is the offset of return tracepoint * in the function; the remaining arguments are the return * values. * * If fake_restore is set, we need to pull the return values * out of the %i's rather than the %o's -- a little trickier. */ if (!fake_restore) { dtrace_probe(probe->ftp_id, pc - probe->ftp_faddr, rp->r_o0, rp->r_o1, rp->r_o2, rp->r_o3); } else { uintptr_t arg0 = fasttrap_getreg(rp, R_I0); uintptr_t arg1 = fasttrap_getreg(rp, R_I1); uintptr_t arg2 = fasttrap_getreg(rp, R_I2); uintptr_t arg3 = fasttrap_getreg(rp, R_I3); cookie = dtrace_interrupt_disable(); DTRACE_CPUFLAG_SET(CPU_DTRACE_FAKERESTORE); dtrace_probe(probe->ftp_id, pc - probe->ftp_faddr, arg0, arg1, arg2, arg3); DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_FAKERESTORE); dtrace_interrupt_enable(cookie); } } mutex_exit(pid_mtx); } int fasttrap_pid_probe(struct regs *rp) { proc_t *p = curproc; fasttrap_tracepoint_t *tp, tp_local; fasttrap_id_t *id; pid_t pid; uintptr_t pc = rp->r_pc; uintptr_t npc = rp->r_npc; uintptr_t orig_pc = pc; fasttrap_bucket_t *bucket; kmutex_t *pid_mtx; uint_t fake_restore = 0, is_enabled = 0; dtrace_icookie_t cookie; /* * 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; /* * 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; } pid = p->p_pid; pid_mtx = &cpu_core[CPU->cpu_id].cpuc_pid_lock; mutex_enter(pid_mtx); 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_defunct) break; } /* * If we couldn't find a matching tracepoint, either a tracepoint has * been inserted without using the pid ioctl interface (see * fasttrap_ioctl), or somehow we have mislaid this tracepoint. */ if (tp == NULL) { mutex_exit(pid_mtx); return (-1); } for (id = tp->ftt_ids; id != NULL; id = id->fti_next) { fasttrap_probe_t *probe = id->fti_probe; int isentry = (id->fti_ptype == DTFTP_ENTRY); if (id->fti_ptype == DTFTP_IS_ENABLED) { is_enabled = 1; continue; } /* * We note that this was an entry probe to help ustack() find * the first caller. */ if (isentry) { cookie = dtrace_interrupt_disable(); DTRACE_CPUFLAG_SET(CPU_DTRACE_ENTRY); } dtrace_probe(probe->ftp_id, rp->r_o0, rp->r_o1, rp->r_o2, rp->r_o3, rp->r_o4); if (isentry) { DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_ENTRY); dtrace_interrupt_enable(cookie); } } /* * 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; mutex_exit(pid_mtx); tp = &tp_local; /* * If there's an is-enabled probe conntected to this tracepoint it * means that there was a 'mov %g0, %o0' 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 %o0. 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_o0 = 1; pc = rp->r_npc; npc = pc + 4; 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_SAVE: { int32_t imm; /* * This an optimization to let us handle function entry * probes more efficiently. Many functions begin with a save * instruction that follows the pattern: * save %sp, , %sp * * Meanwhile, we've stashed the instruction: * save %g1, %g0, %sp * * off of %g7, so all we have to do is stick the right value * into %g1 and reset %pc to point to the instruction we've * cleverly hidden (%npc should not be touched). */ imm = tp->ftt_instr << 19; imm >>= 19; rp->r_g1 = rp->r_sp + imm; pc = rp->r_g7 + FASTTRAP_OFF_SAVE; break; } case FASTTRAP_T_RESTORE: { ulong_t value; uint_t rd; /* * This is an optimization to let us handle function * return probes more efficiently. Most non-leaf functions * end with the sequence: * ret * restore , , %oX * * We've stashed the instruction: * restore %g0, %g0, %g0 * * off of %g7 so we just need to place the correct value * in the right %i register (since after our fake-o * restore, the %i's will become the %o's) and set the %pc * to point to our hidden restore. We also set fake_restore to * let fasttrap_return_common() know that it will find the * return values in the %i's rather than the %o's. */ if (I(tp->ftt_instr)) { int32_t imm; imm = tp->ftt_instr << 19; imm >>= 19; value = fasttrap_getreg(rp, RS1(tp->ftt_instr)) + imm; } else { value = fasttrap_getreg(rp, RS1(tp->ftt_instr)) + fasttrap_getreg(rp, RS2(tp->ftt_instr)); } /* * Convert %o's to %i's; leave %g's as they are. */ rd = RD(tp->ftt_instr); fasttrap_putreg(rp, ((rd & 0x18) == 0x8) ? rd + 16 : rd, value); pc = rp->r_g7 + FASTTRAP_OFF_RESTORE; fake_restore = 1; break; } case FASTTRAP_T_RETURN: { uintptr_t target; /* * A return instruction is like a jmpl (without the link * part) that executes an implicit restore. We've stashed * the instruction: * return %o0 * * off of %g7 so we just need to place the target in %o0 * and set the %pc to point to the stashed return instruction. * We use %o0 since that register disappears after the return * executes, erasing any evidence of this tampering. */ if (I(tp->ftt_instr)) { int32_t imm; imm = tp->ftt_instr << 19; imm >>= 19; target = fasttrap_getreg(rp, RS1(tp->ftt_instr)) + imm; } else { target = fasttrap_getreg(rp, RS1(tp->ftt_instr)) + fasttrap_getreg(rp, RS2(tp->ftt_instr)); } fasttrap_putreg(rp, R_O0, target); pc = rp->r_g7 + FASTTRAP_OFF_RETURN; fake_restore = 1; break; } case FASTTRAP_T_OR: { ulong_t value; if (I(tp->ftt_instr)) { int32_t imm; imm = tp->ftt_instr << 19; imm >>= 19; value = fasttrap_getreg(rp, RS1(tp->ftt_instr)) | imm; } else { value = fasttrap_getreg(rp, RS1(tp->ftt_instr)) | fasttrap_getreg(rp, RS2(tp->ftt_instr)); } fasttrap_putreg(rp, RD(tp->ftt_instr), value); pc = rp->r_npc; npc = pc + 4; break; } case FASTTRAP_T_SETHI: if (RD(tp->ftt_instr) != R_G0) { uint32_t imm32 = tp->ftt_instr << 10; fasttrap_putreg(rp, RD(tp->ftt_instr), (ulong_t)imm32); } pc = rp->r_npc; npc = pc + 4; break; case FASTTRAP_T_CCR: { uint_t c, v, z, n, taken; uint_t ccr = rp->r_tstate >> TSTATE_CCR_SHIFT; if (tp->ftt_cc != 0) ccr >>= 4; c = (ccr >> 0) & 1; v = (ccr >> 1) & 1; z = (ccr >> 2) & 1; n = (ccr >> 3) & 1; switch (tp->ftt_code) { case 0x0: /* BN */ taken = 0; break; case 0x1: /* BE */ taken = z; break; case 0x2: /* BLE */ taken = z | (n ^ v); break; case 0x3: /* BL */ taken = n ^ v; break; case 0x4: /* BLEU */ taken = c | z; break; case 0x5: /* BCS (BLU) */ taken = c; break; case 0x6: /* BNEG */ taken = n; break; case 0x7: /* BVS */ taken = v; break; case 0x8: /* BA */ /* * We handle the BA case differently since the annul * bit means something slightly different. */ panic("fasttrap: mishandled a branch"); taken = 1; break; case 0x9: /* BNE */ taken = ~z; break; case 0xa: /* BG */ taken = ~(z | (n ^ v)); break; case 0xb: /* BGE */ taken = ~(n ^ v); break; case 0xc: /* BGU */ taken = ~(c | z); break; case 0xd: /* BCC (BGEU) */ taken = ~c; break; case 0xe: /* BPOS */ taken = ~n; break; case 0xf: /* BVC */ taken = ~v; break; } if (taken & 1) { pc = rp->r_npc; npc = tp->ftt_dest; } else if (tp->ftt_flags & FASTTRAP_F_ANNUL) { /* * Untaken annulled branches don't execute the * instruction in the delay slot. */ pc = rp->r_npc + 4; npc = pc + 4; } else { pc = rp->r_npc; npc = pc + 4; } break; } case FASTTRAP_T_FCC: { uint_t fcc; uint_t taken; uint64_t fsr; dtrace_getfsr(&fsr); if (tp->ftt_cc == 0) { fcc = (fsr >> 10) & 0x3; } else { uint_t shift; ASSERT(tp->ftt_cc <= 3); shift = 30 + tp->ftt_cc * 2; fcc = (fsr >> shift) & 0x3; } switch (tp->ftt_code) { case 0x0: /* FBN */ taken = (1 << fcc) & (0|0|0|0); break; case 0x1: /* FBNE */ taken = (1 << fcc) & (8|4|2|0); break; case 0x2: /* FBLG */ taken = (1 << fcc) & (0|4|2|0); break; case 0x3: /* FBUL */ taken = (1 << fcc) & (8|0|2|0); break; case 0x4: /* FBL */ taken = (1 << fcc) & (0|0|2|0); break; case 0x5: /* FBUG */ taken = (1 << fcc) & (8|4|0|0); break; case 0x6: /* FBG */ taken = (1 << fcc) & (0|4|0|0); break; case 0x7: /* FBU */ taken = (1 << fcc) & (8|0|0|0); break; case 0x8: /* FBA */ /* * We handle the FBA case differently since the annul * bit means something slightly different. */ panic("fasttrap: mishandled a branch"); taken = (1 << fcc) & (8|4|2|1); break; case 0x9: /* FBE */ taken = (1 << fcc) & (0|0|0|1); break; case 0xa: /* FBUE */ taken = (1 << fcc) & (8|0|0|1); break; case 0xb: /* FBGE */ taken = (1 << fcc) & (0|4|0|1); break; case 0xc: /* FBUGE */ taken = (1 << fcc) & (8|4|0|1); break; case 0xd: /* FBLE */ taken = (1 << fcc) & (0|0|2|1); break; case 0xe: /* FBULE */ taken = (1 << fcc) & (8|0|2|1); break; case 0xf: /* FBO */ taken = (1 << fcc) & (0|4|2|1); break; } if (taken) { pc = rp->r_npc; npc = tp->ftt_dest; } else if (tp->ftt_flags & FASTTRAP_F_ANNUL) { /* * Untaken annulled branches don't execute the * instruction in the delay slot. */ pc = rp->r_npc + 4; npc = pc + 4; } else { pc = rp->r_npc; npc = pc + 4; } break; } case FASTTRAP_T_REG: { int64_t value; uint_t taken; uint_t reg = RS1(tp->ftt_instr); /* * An ILP32 process shouldn't be using a branch predicated on * an %i or an %l since it would violate the ABI. It's a * violation of the ABI because we can't ensure deterministic * behavior. We should have identified this case when we * enabled the probe. */ ASSERT(p->p_model == DATAMODEL_LP64 || reg < 16); value = (int64_t)fasttrap_getreg(rp, reg); switch (tp->ftt_code) { case 0x1: /* BRZ */ taken = (value == 0); break; case 0x2: /* BRLEZ */ taken = (value <= 0); break; case 0x3: /* BRLZ */ taken = (value < 0); break; case 0x5: /* BRNZ */ taken = (value != 0); break; case 0x6: /* BRGZ */ taken = (value > 0); break; case 0x7: /* BRGEZ */ taken = (value >= 0); break; default: case 0x0: case 0x4: panic("fasttrap: mishandled a branch"); } if (taken) { pc = rp->r_npc; npc = tp->ftt_dest; } else if (tp->ftt_flags & FASTTRAP_F_ANNUL) { /* * Untaken annulled branches don't execute the * instruction in the delay slot. */ pc = rp->r_npc + 4; npc = pc + 4; } else { pc = rp->r_npc; npc = pc + 4; } break; } case FASTTRAP_T_ALWAYS: /* * BAs, BA,As... */ if (tp->ftt_flags & FASTTRAP_F_ANNUL) { /* * Annulled branch always instructions never execute * the instruction in the delay slot. */ pc = tp->ftt_dest; npc = tp->ftt_dest + 4; } else { pc = rp->r_npc; npc = tp->ftt_dest; } break; case FASTTRAP_T_RDPC: fasttrap_putreg(rp, RD(tp->ftt_instr), rp->r_pc); pc = rp->r_npc; npc = pc + 4; break; case FASTTRAP_T_CALL: /* * It's a call _and_ link remember... */ rp->r_o7 = rp->r_pc; pc = rp->r_npc; npc = tp->ftt_dest; break; case FASTTRAP_T_JMPL: pc = rp->r_npc; if (I(tp->ftt_instr)) { uint_t rs1 = RS1(tp->ftt_instr); int32_t imm; imm = tp->ftt_instr << 19; imm >>= 19; npc = fasttrap_getreg(rp, rs1) + imm; } else { uint_t rs1 = RS1(tp->ftt_instr); uint_t rs2 = RS2(tp->ftt_instr); npc = fasttrap_getreg(rp, rs1) + fasttrap_getreg(rp, rs2); } /* * Do the link part of the jump-and-link instruction. */ fasttrap_putreg(rp, RD(tp->ftt_instr), rp->r_pc); break; case FASTTRAP_T_COMMON: { curthread->t_dtrace_scrpc = rp->r_g7; curthread->t_dtrace_astpc = rp->r_g7 + FASTTRAP_OFF_FTRET; /* * Copy the instruction to a reserved location in the * user-land thread structure, then set the PC to that * location and leave the NPC alone. We take pains to ensure * consistency in the instruction stream (See SPARC * Architecture Manual Version 9, sections 8.4.7, A.20, and * H.1.6; UltraSPARC I/II User's Manual, sections 3.1.1.1, * and 13.6.4) by using the ASI ASI_BLK_COMMIT_S to copy the * instruction into the user's address space without * bypassing the I$. There's no AS_USER version of this ASI * (as exist for other ASIs) so we use the lofault * mechanism to catch faults. */ if (dtrace_blksuword32(rp->r_g7, &tp->ftt_instr, 1) == -1) { /* * If the copyout fails, then the process's state * is not consistent (the effects of the traced * instruction will never be seen). This process * cannot be allowed to continue execution. */ fasttrap_sigtrap(curproc, curthread, pc); return (0); } curthread->t_dtrace_pc = pc; curthread->t_dtrace_npc = npc; curthread->t_dtrace_on = 1; pc = curthread->t_dtrace_scrpc; if (tp->ftt_retids != NULL) { curthread->t_dtrace_step = 1; curthread->t_dtrace_ret = 1; npc = curthread->t_dtrace_astpc; } break; } default: panic("fasttrap: mishandled an instruction"); } /* * This bit me in the ass a couple of times, so lets toss this * in as a cursory sanity check. */ ASSERT(pc != rp->r_g7 + 4); ASSERT(pc != rp->r_g7 + 8); 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 we return to the kernel. */ if (tp->ftt_type != FASTTRAP_T_COMMON) { fasttrap_return_common(rp, orig_pc, pid, fake_restore); } else { ASSERT(curthread->t_dtrace_ret != 0); ASSERT(curthread->t_dtrace_pc == orig_pc); ASSERT(curthread->t_dtrace_scrpc == rp->r_g7); ASSERT(npc == curthread->t_dtrace_astpc); } } ASSERT(pc != 0); rp->r_pc = pc; rp->r_npc = npc; return (0); } int fasttrap_return_probe(struct regs *rp) { proc_t *p = ttoproc(curthread); pid_t pid; 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; /* * Treat a child created by a call to vfork(2) as if it were its * parent. We know there's only one thread of control in such a * process: this one. */ while (p->p_flag & SVFORK) { p = p->p_parent; } /* * We set the %pc and %npc to their values when the traced * instruction was initially executed 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 and %npc * after we return. */ rp->r_pc = pc; rp->r_npc = npc; pid = p->p_pid; fasttrap_return_common(rp, pc, pid, 0); return (0); } int fasttrap_tracepoint_install(proc_t *p, fasttrap_tracepoint_t *tp) { fasttrap_instr_t instr = FASTTRAP_INSTR; if (uwrite(p, &instr, 4, tp->ftt_pc) != 0) return (-1); return (0); } int fasttrap_tracepoint_remove(proc_t *p, fasttrap_tracepoint_t *tp) { fasttrap_instr_t instr; /* * Distinguish between read or write failures and a changed * instruction. */ if (uread(p, &instr, 4, tp->ftt_pc) != 0) return (0); if (instr != FASTTRAP_INSTR && instr != BREAKPOINT_INSTR) return (0); if (uwrite(p, &tp->ftt_instr, 4, tp->ftt_pc) != 0) return (-1); return (0); } int fasttrap_tracepoint_init(proc_t *p, fasttrap_tracepoint_t *tp, uintptr_t pc, fasttrap_probe_type_t type) { uint32_t instr; int32_t disp; /* * 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. */ if (uread(p, &instr, 4, pc) != 0) return (-1); /* * Decode the instruction to fill in the probe flags. We can have * the process execute most instructions on its own using a pc/npc * trick, but pc-relative control transfer present a problem since * we're relocating the instruction. We emulate these instructions * in the kernel. We assume a default type and over-write that as * needed. * * pc-relative instructions must be emulated for correctness; * other instructions (which represent a large set of commonly traced * instructions) are emulated or otherwise optimized for performance. */ tp->ftt_type = FASTTRAP_T_COMMON; if (OP(instr) == 1) { /* * Call instructions. */ tp->ftt_type = FASTTRAP_T_CALL; disp = DISP30(instr) << 2; tp->ftt_dest = pc + (intptr_t)disp; } else if (OP(instr) == 0) { /* * Branch instructions. * * Unconditional branches need careful attention when they're * annulled: annulled unconditional branches never execute * the instruction in the delay slot. */ switch (OP2(instr)) { case OP2_ILLTRAP: case 0x7: /* * The compiler may place an illtrap after a call to * a function that returns a structure. In the case of * a returned structure, the compiler places an illtrap * whose const22 field is the size of the returned * structure immediately following the delay slot of * the call. To stay out of the way, we refuse to * place tracepoints on top of illtrap instructions. * * This is one of the dumbest architectural decisions * I've ever had to work around. * * We also identify the only illegal op2 value (See * SPARC Architecture Manual Version 9, E.2 table 31). */ return (-1); case OP2_BPcc: if (COND(instr) == 8) { tp->ftt_type = FASTTRAP_T_ALWAYS; } else { /* * Check for an illegal instruction. */ if (CC(instr) & 1) return (-1); tp->ftt_type = FASTTRAP_T_CCR; tp->ftt_cc = CC(instr); tp->ftt_code = COND(instr); } if (A(instr) != 0) tp->ftt_flags |= FASTTRAP_F_ANNUL; disp = DISP19(instr); disp <<= 13; disp >>= 11; tp->ftt_dest = pc + (intptr_t)disp; break; case OP2_Bicc: if (COND(instr) == 8) { tp->ftt_type = FASTTRAP_T_ALWAYS; } else { tp->ftt_type = FASTTRAP_T_CCR; tp->ftt_cc = 0; tp->ftt_code = COND(instr); } if (A(instr) != 0) tp->ftt_flags |= FASTTRAP_F_ANNUL; disp = DISP22(instr); disp <<= 10; disp >>= 8; tp->ftt_dest = pc + (intptr_t)disp; break; case OP2_BPr: /* * Check for an illegal instruction. */ if ((RCOND(instr) & 3) == 0) return (-1); /* * It's a violation of the v8plus ABI to use a * register-predicated branch in a 32-bit app if * the register used is an %l or an %i (%gs and %os * are legit because they're not saved to the stack * in 32-bit words when we take a trap). */ if (p->p_model == DATAMODEL_ILP32 && RS1(instr) >= 16) return (-1); tp->ftt_type = FASTTRAP_T_REG; if (A(instr) != 0) tp->ftt_flags |= FASTTRAP_F_ANNUL; disp = DISP16(instr); disp <<= 16; disp >>= 14; tp->ftt_dest = pc + (intptr_t)disp; tp->ftt_code = RCOND(instr); break; case OP2_SETHI: tp->ftt_type = FASTTRAP_T_SETHI; break; case OP2_FBPfcc: if (COND(instr) == 8) { tp->ftt_type = FASTTRAP_T_ALWAYS; } else { tp->ftt_type = FASTTRAP_T_FCC; tp->ftt_cc = CC(instr); tp->ftt_code = COND(instr); } if (A(instr) != 0) tp->ftt_flags |= FASTTRAP_F_ANNUL; disp = DISP19(instr); disp <<= 13; disp >>= 11; tp->ftt_dest = pc + (intptr_t)disp; break; case OP2_FBfcc: if (COND(instr) == 8) { tp->ftt_type = FASTTRAP_T_ALWAYS; } else { tp->ftt_type = FASTTRAP_T_FCC; tp->ftt_cc = 0; tp->ftt_code = COND(instr); } if (A(instr) != 0) tp->ftt_flags |= FASTTRAP_F_ANNUL; disp = DISP22(instr); disp <<= 10; disp >>= 8; tp->ftt_dest = pc + (intptr_t)disp; break; } } else if (OP(instr) == 2) { switch (OP3(instr)) { case OP3_RETURN: tp->ftt_type = FASTTRAP_T_RETURN; break; case OP3_JMPL: tp->ftt_type = FASTTRAP_T_JMPL; break; case OP3_RD: if (RS1(instr) == 5) tp->ftt_type = FASTTRAP_T_RDPC; break; case OP3_SAVE: /* * We optimize for save instructions at function * entry; see the comment in fasttrap_pid_probe() * (near FASTTRAP_T_SAVE) for details. */ if (fasttrap_optimize_save != 0 && type == DTFTP_ENTRY && I(instr) == 1 && RD(instr) == R_SP) tp->ftt_type = FASTTRAP_T_SAVE; break; case OP3_RESTORE: /* * We optimize restore instructions at function * return; see the comment in fasttrap_pid_probe() * (near FASTTRAP_T_RESTORE) for details. * * rd must be an %o or %g register. */ if ((RD(instr) & 0x10) == 0) tp->ftt_type = FASTTRAP_T_RESTORE; break; case OP3_OR: /* * A large proportion of instructions in the delay * slot of retl instructions are or's so we emulate * these downstairs as an optimization. */ tp->ftt_type = FASTTRAP_T_OR; break; case OP3_TCC: /* * Breakpoint instructions are effectively position- * dependent since the debugger uses the %pc value * to lookup which breakpoint was executed. As a * result, we can't actually instrument breakpoints. */ if (SW_TRAP(instr) == ST_BREAKPOINT) return (-1); break; case 0x19: case 0x1d: case 0x29: case 0x33: case 0x3f: /* * Identify illegal instructions (See SPARC * Architecture Manual Version 9, E.2 table 32). */ return (-1); } } else if (OP(instr) == 3) { uint32_t op3 = OP3(instr); /* * Identify illegal instructions (See SPARC Architecture * Manual Version 9, E.2 table 33). */ if ((op3 & 0x28) == 0x28) { if (op3 != OP3_PREFETCH && op3 != OP3_CASA && op3 != OP3_PREFETCHA && op3 != OP3_CASXA) return (-1); } else { if ((op3 & 0x0f) == 0x0c || (op3 & 0x3b) == 0x31) return (-1); } } tp->ftt_instr = instr; /* * We don't know how this tracepoint is going to be used, but in case * it's used as part of a function return probe, we need to indicate * whether it's always a return site or only potentially a return * site. If it's part of a return probe, it's always going to be a * return from that function if it's a restore instruction or if * the previous instruction was a return. If we could reliably * distinguish jump tables from return sites, this wouldn't be * necessary. */ if (tp->ftt_type != FASTTRAP_T_RESTORE && (uread(p, &instr, 4, pc - sizeof (instr)) != 0 || !(OP(instr) == 2 && OP3(instr) == OP3_RETURN))) tp->ftt_flags |= FASTTRAP_F_RETMAYBE; return (0); } /*ARGSUSED*/ uint64_t fasttrap_pid_getarg(void *arg, dtrace_id_t id, void *parg, int argno, int aframes) { return (fasttrap_anarg(ttolwp(curthread)->lwp_regs, argno)); } /*ARGSUSED*/ uint64_t fasttrap_usdt_getarg(void *arg, dtrace_id_t id, void *parg, int argno, int aframes) { return (fasttrap_anarg(ttolwp(curthread)->lwp_regs, argno)); } static uint64_t fasttrap_getreg_fast_cnt; static uint64_t fasttrap_getreg_mpcb_cnt; static uint64_t fasttrap_getreg_slow_cnt; static ulong_t fasttrap_getreg(struct regs *rp, uint_t reg) { ulong_t value; dtrace_icookie_t cookie; struct machpcb *mpcb; extern ulong_t dtrace_getreg_win(uint_t, uint_t); /* * We have the %os and %gs in our struct regs, but if we need to * snag a %l or %i we need to go scrounging around in the process's * address space. */ if (reg == 0) return (0); if (reg < 16) return ((&rp->r_g1)[reg - 1]); /* * Before we look at the user's stack, we'll check the register * windows to see if the information we want is in there. */ cookie = dtrace_interrupt_disable(); if (dtrace_getotherwin() > 0) { value = dtrace_getreg_win(reg, 1); dtrace_interrupt_enable(cookie); atomic_add_64(&fasttrap_getreg_fast_cnt, 1); return (value); } dtrace_interrupt_enable(cookie); /* * First check the machpcb structure to see if we've already read * in the register window we're looking for; if we haven't, (and * we probably haven't) try to copy in the value of the register. */ /* LINTED - alignment */ mpcb = (struct machpcb *)((caddr_t)rp - REGOFF); if (get_udatamodel() == DATAMODEL_NATIVE) { struct frame *fr = (struct frame *)(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) continue; atomic_add_64(&fasttrap_getreg_mpcb_cnt, 1); return (rwin[i].rw_local[reg - 16]); } while (i > 0); } if (fasttrap_fulword(&fr->fr_local[reg - 16], &value) != 0) goto err; } else { struct frame32 *fr = (struct frame32 *)(uintptr_t)(caddr32_t)rp->r_sp; uint32_t *v32 = (uint32_t *)&value; 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) continue; atomic_add_64(&fasttrap_getreg_mpcb_cnt, 1); return (rwin[i].rw_local[reg - 16]); } while (i > 0); } if (fasttrap_fuword32(&fr->fr_local[reg - 16], &v32[1]) != 0) goto err; v32[0] = 0; } atomic_add_64(&fasttrap_getreg_slow_cnt, 1); return (value); err: /* * If the copy in failed, the process will be in a irrecoverable * state, and we have no choice but to kill it. */ psignal(ttoproc(curthread), SIGILL); return (0); } static uint64_t fasttrap_putreg_fast_cnt; static uint64_t fasttrap_putreg_mpcb_cnt; static uint64_t fasttrap_putreg_slow_cnt; static void fasttrap_putreg(struct regs *rp, uint_t reg, ulong_t value) { dtrace_icookie_t cookie; struct machpcb *mpcb; extern void dtrace_putreg_win(uint_t, ulong_t); if (reg == 0) return; if (reg < 16) { (&rp->r_g1)[reg - 1] = value; return; } /* * If the user process is still using some register windows, we * can just place the value in the correct window. */ cookie = dtrace_interrupt_disable(); if (dtrace_getotherwin() > 0) { dtrace_putreg_win(reg, value); dtrace_interrupt_enable(cookie); atomic_add_64(&fasttrap_putreg_fast_cnt, 1); return; } dtrace_interrupt_enable(cookie); /* * First see if there's a copy of the register window in the * machpcb structure that we can modify; if there isn't try to * copy out the value. If that fails, we try to create a new * register window in the machpcb structure. While this isn't * _precisely_ the intended use of the machpcb structure, it * can't cause any problems since we know at this point in the * code that all of the user's data have been flushed out of the * register file (since %otherwin is 0). */ /* LINTED - alignment */ mpcb = (struct machpcb *)((caddr_t)rp - REGOFF); if (get_udatamodel() == DATAMODEL_NATIVE) { struct frame *fr = (struct frame *)(rp->r_sp + STACK_BIAS); /* LINTED - alignment */ struct rwindow *rwin = (struct rwindow *)mpcb->mpcb_wbuf; if (mpcb->mpcb_wbcnt > 0) { int i = mpcb->mpcb_wbcnt; do { i--; if ((long)mpcb->mpcb_spbuf[i] != rp->r_sp) continue; rwin[i].rw_local[reg - 16] = value; atomic_add_64(&fasttrap_putreg_mpcb_cnt, 1); return; } while (i > 0); } if (fasttrap_sulword(&fr->fr_local[reg - 16], value) != 0) { if (mpcb->mpcb_wbcnt >= MAXWIN || copyin(fr, &rwin[mpcb->mpcb_wbcnt], sizeof (*rwin)) != 0) goto err; rwin[mpcb->mpcb_wbcnt].rw_local[reg - 16] = value; mpcb->mpcb_spbuf[mpcb->mpcb_wbcnt] = (caddr_t)rp->r_sp; mpcb->mpcb_wbcnt++; atomic_add_64(&fasttrap_putreg_mpcb_cnt, 1); return; } } else { struct frame32 *fr = (struct frame32 *)(uintptr_t)(caddr32_t)rp->r_sp; /* LINTED - alignment */ struct rwindow32 *rwin = (struct rwindow32 *)mpcb->mpcb_wbuf; uint32_t v32 = (uint32_t)value; if (mpcb->mpcb_wbcnt > 0) { int i = mpcb->mpcb_wbcnt; do { i--; if ((long)mpcb->mpcb_spbuf[i] != rp->r_sp) continue; rwin[i].rw_local[reg - 16] = v32; atomic_add_64(&fasttrap_putreg_mpcb_cnt, 1); return; } while (i > 0); } if (fasttrap_suword32(&fr->fr_local[reg - 16], v32) != 0) { if (mpcb->mpcb_wbcnt >= MAXWIN || copyin(fr, &rwin[mpcb->mpcb_wbcnt], sizeof (*rwin)) != 0) goto err; rwin[mpcb->mpcb_wbcnt].rw_local[reg - 16] = v32; mpcb->mpcb_spbuf[mpcb->mpcb_wbcnt] = (caddr_t)rp->r_sp; mpcb->mpcb_wbcnt++; atomic_add_64(&fasttrap_putreg_mpcb_cnt, 1); return; } } atomic_add_64(&fasttrap_putreg_slow_cnt, 1); return; err: /* * If we couldn't record this register's value, the process is in an * irrecoverable state and we have no choice but to euthanize it. */ psignal(ttoproc(curthread), SIGILL); }