/* $NetBSD: optimize.c,v 1.11 2019/10/01 16:02:11 christos Exp $ */ /* * Copyright (c) 1988, 1989, 1990, 1991, 1993, 1994, 1995, 1996 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that: (1) source code distributions * retain the above copyright notice and this paragraph in its entirety, (2) * distributions including binary code include the above copyright notice and * this paragraph in its entirety in the documentation or other materials * provided with the distribution, and (3) all advertising materials mentioning * features or use of this software display the following acknowledgement: * ``This product includes software developed by the University of California, * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of * the University nor the names of its contributors may be used to endorse * or promote products derived from this software without specific prior * written permission. * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. * * Optimization module for BPF code intermediate representation. */ #include __RCSID("$NetBSD: optimize.c,v 1.11 2019/10/01 16:02:11 christos Exp $"); #ifdef HAVE_CONFIG_H #include #endif #include #include #include #include #include #include #include #include "pcap-int.h" #include "gencode.h" #include "optimize.h" #ifdef HAVE_OS_PROTO_H #include "os-proto.h" #endif #ifdef BDEBUG /* * The internal "debug printout" flag for the filter expression optimizer. * The code to print that stuff is present only if BDEBUG is defined, so * the flag, and the routine to set it, are defined only if BDEBUG is * defined. */ static int pcap_optimizer_debug; /* * Routine to set that flag. * * This is intended for libpcap developers, not for general use. * If you want to set these in a program, you'll have to declare this * routine yourself, with the appropriate DLL import attribute on Windows; * it's not declared in any header file, and won't be declared in any * header file provided by libpcap. */ PCAP_API void pcap_set_optimizer_debug(int value); PCAP_API_DEF void pcap_set_optimizer_debug(int value) { pcap_optimizer_debug = value; } /* * The internal "print dot graph" flag for the filter expression optimizer. * The code to print that stuff is present only if BDEBUG is defined, so * the flag, and the routine to set it, are defined only if BDEBUG is * defined. */ static int pcap_print_dot_graph; /* * Routine to set that flag. * * This is intended for libpcap developers, not for general use. * If you want to set these in a program, you'll have to declare this * routine yourself, with the appropriate DLL import attribute on Windows; * it's not declared in any header file, and won't be declared in any * header file provided by libpcap. */ PCAP_API void pcap_set_print_dot_graph(int value); PCAP_API_DEF void pcap_set_print_dot_graph(int value) { pcap_print_dot_graph = value; } #endif /* * lowest_set_bit(). * * Takes a 32-bit integer as an argument. * * If handed a non-zero value, returns the index of the lowest set bit, * counting upwards fro zero. * * If handed zero, the results are platform- and compiler-dependent. * Keep it out of the light, don't give it any water, don't feed it * after midnight, and don't pass zero to it. * * This is the same as the count of trailing zeroes in the word. */ #if PCAP_IS_AT_LEAST_GNUC_VERSION(3,4) /* * GCC 3.4 and later; we have __builtin_ctz(). */ #define lowest_set_bit(mask) __builtin_ctz(mask) #elif defined(_MSC_VER) /* * Visual Studio; we support only 2005 and later, so use * _BitScanForward(). */ #include #ifndef __clang__ #pragma intrinsic(_BitScanForward) #endif static __forceinline int lowest_set_bit(int mask) { unsigned long bit; /* * Don't sign-extend mask if long is longer than int. * (It's currently not, in MSVC, even on 64-bit platforms, but....) */ if (_BitScanForward(&bit, (unsigned int)mask) == 0) return -1; /* mask is zero */ return (int)bit; } #elif defined(MSDOS) && defined(__DJGPP__) /* * MS-DOS with DJGPP, which declares ffs() in , which * we've already included. */ #define lowest_set_bit(mask) (ffs((mask)) - 1) #elif (defined(MSDOS) && defined(__WATCOMC__)) || defined(STRINGS_H_DECLARES_FFS) /* * MS-DOS with Watcom C, which has and declares ffs() there, * or some other platform (UN*X conforming to a sufficient recent version * of the Single UNIX Specification). */ #include #define lowest_set_bit(mask) (ffs((mask)) - 1) #else /* * None of the above. * Use a perfect-hash-function-based function. */ static int lowest_set_bit(int mask) { unsigned int v = (unsigned int)mask; static const int MultiplyDeBruijnBitPosition[32] = { 0, 1, 28, 2, 29, 14, 24, 3, 30, 22, 20, 15, 25, 17, 4, 8, 31, 27, 13, 23, 21, 19, 16, 7, 26, 12, 18, 6, 11, 5, 10, 9 }; /* * We strip off all but the lowermost set bit (v & ~v), * and perform a minimal perfect hash on it to look up the * number of low-order zero bits in a table. * * See: * * http://7ooo.mooo.com/text/ComputingTrailingZerosHOWTO.pdf * * http://supertech.csail.mit.edu/papers/debruijn.pdf */ return (MultiplyDeBruijnBitPosition[((v & -v) * 0x077CB531U) >> 27]); } #endif /* * Represents a deleted instruction. */ #define NOP -1 /* * Register numbers for use-def values. * 0 through BPF_MEMWORDS-1 represent the corresponding scratch memory * location. A_ATOM is the accumulator and X_ATOM is the index * register. */ #define A_ATOM BPF_MEMWORDS #define X_ATOM (BPF_MEMWORDS+1) /* * This define is used to represent *both* the accumulator and * x register in use-def computations. * Currently, the use-def code assumes only one definition per instruction. */ #define AX_ATOM N_ATOMS /* * These data structures are used in a Cocke and Shwarz style * value numbering scheme. Since the flowgraph is acyclic, * exit values can be propagated from a node's predecessors * provided it is uniquely defined. */ struct valnode { int code; int v0, v1; int val; struct valnode *next; }; /* Integer constants mapped with the load immediate opcode. */ #define K(i) F(opt_state, BPF_LD|BPF_IMM|BPF_W, i, 0L) struct vmapinfo { int is_const; bpf_int32 const_val; }; typedef struct { /* * Place to longjmp to on an error. */ jmp_buf top_ctx; /* * The buffer into which to put error message. */ char *errbuf; /* * A flag to indicate that further optimization is needed. * Iterative passes are continued until a given pass yields no * branch movement. */ int done; int n_blocks; struct block **blocks; int n_edges; struct edge **edges; /* * A bit vector set representation of the dominators. * We round up the set size to the next power of two. */ int nodewords; int edgewords; struct block **levels; bpf_u_int32 *space; #define BITS_PER_WORD (8*sizeof(bpf_u_int32)) /* * True if a is in uset {p} */ #define SET_MEMBER(p, a) \ ((p)[(unsigned)(a) / BITS_PER_WORD] & ((bpf_u_int32)1 << ((unsigned)(a) % BITS_PER_WORD))) /* * Add 'a' to uset p. */ #define SET_INSERT(p, a) \ (p)[(unsigned)(a) / BITS_PER_WORD] |= ((bpf_u_int32)1 << ((unsigned)(a) % BITS_PER_WORD)) /* * Delete 'a' from uset p. */ #define SET_DELETE(p, a) \ (p)[(unsigned)(a) / BITS_PER_WORD] &= ~((bpf_u_int32)1 << ((unsigned)(a) % BITS_PER_WORD)) /* * a := a intersect b */ #define SET_INTERSECT(a, b, n)\ {\ register bpf_u_int32 *_x = a, *_y = b;\ register int _n = n;\ while (--_n >= 0) *_x++ &= *_y++;\ } /* * a := a - b */ #define SET_SUBTRACT(a, b, n)\ {\ register bpf_u_int32 *_x = a, *_y = b;\ register int _n = n;\ while (--_n >= 0) *_x++ &=~ *_y++;\ } /* * a := a union b */ #define SET_UNION(a, b, n)\ {\ register bpf_u_int32 *_x = a, *_y = b;\ register int _n = n;\ while (--_n >= 0) *_x++ |= *_y++;\ } uset all_dom_sets; uset all_closure_sets; uset all_edge_sets; #define MODULUS 213 struct valnode *hashtbl[MODULUS]; int curval; int maxval; struct vmapinfo *vmap; struct valnode *vnode_base; struct valnode *next_vnode; } opt_state_t; typedef struct { /* * Place to longjmp to on an error. */ jmp_buf top_ctx; /* * The buffer into which to put error message. */ char *errbuf; /* * Some pointers used to convert the basic block form of the code, * into the array form that BPF requires. 'fstart' will point to * the malloc'd array while 'ftail' is used during the recursive * traversal. */ struct bpf_insn *fstart; struct bpf_insn *ftail; } conv_state_t; static void opt_init(opt_state_t *, struct icode *); static void opt_cleanup(opt_state_t *); static void PCAP_NORETURN opt_error(opt_state_t *, const char *, ...) PCAP_PRINTFLIKE(2, 3); static void intern_blocks(opt_state_t *, struct icode *); static void find_inedges(opt_state_t *, struct block *); #ifdef BDEBUG static void opt_dump(opt_state_t *, struct icode *); #endif #ifndef MAX #define MAX(a,b) ((a)>(b)?(a):(b)) #endif static void find_levels_r(opt_state_t *opt_state, struct icode *ic, struct block *b) { int level; if (isMarked(ic, b)) return; Mark(ic, b); b->link = 0; if (JT(b)) { find_levels_r(opt_state, ic, JT(b)); find_levels_r(opt_state, ic, JF(b)); level = MAX(JT(b)->level, JF(b)->level) + 1; } else level = 0; b->level = level; b->link = opt_state->levels[level]; opt_state->levels[level] = b; } /* * Level graph. The levels go from 0 at the leaves to * N_LEVELS at the root. The opt_state->levels[] array points to the * first node of the level list, whose elements are linked * with the 'link' field of the struct block. */ static void find_levels(opt_state_t *opt_state, struct icode *ic) { memset((char *)opt_state->levels, 0, opt_state->n_blocks * sizeof(*opt_state->levels)); unMarkAll(ic); find_levels_r(opt_state, ic, ic->root); } /* * Find dominator relationships. * Assumes graph has been leveled. */ static void find_dom(opt_state_t *opt_state, struct block *root) { int i; struct block *b; bpf_u_int32 *x; /* * Initialize sets to contain all nodes. */ x = opt_state->all_dom_sets; i = opt_state->n_blocks * opt_state->nodewords; while (--i >= 0) *x++ = 0xFFFFFFFFU; /* Root starts off empty. */ for (i = opt_state->nodewords; --i >= 0;) root->dom[i] = 0; /* root->level is the highest level no found. */ for (i = root->level; i >= 0; --i) { for (b = opt_state->levels[i]; b; b = b->link) { SET_INSERT(b->dom, b->id); if (JT(b) == 0) continue; SET_INTERSECT(JT(b)->dom, b->dom, opt_state->nodewords); SET_INTERSECT(JF(b)->dom, b->dom, opt_state->nodewords); } } } static void propedom(opt_state_t *opt_state, struct edge *ep) { SET_INSERT(ep->edom, ep->id); if (ep->succ) { SET_INTERSECT(ep->succ->et.edom, ep->edom, opt_state->edgewords); SET_INTERSECT(ep->succ->ef.edom, ep->edom, opt_state->edgewords); } } /* * Compute edge dominators. * Assumes graph has been leveled and predecessors established. */ static void find_edom(opt_state_t *opt_state, struct block *root) { int i; uset x; struct block *b; x = opt_state->all_edge_sets; for (i = opt_state->n_edges * opt_state->edgewords; --i >= 0; ) x[i] = 0xFFFFFFFFU; /* root->level is the highest level no found. */ memset(root->et.edom, 0, opt_state->edgewords * sizeof(*(uset)0)); memset(root->ef.edom, 0, opt_state->edgewords * sizeof(*(uset)0)); for (i = root->level; i >= 0; --i) { for (b = opt_state->levels[i]; b != 0; b = b->link) { propedom(opt_state, &b->et); propedom(opt_state, &b->ef); } } } /* * Find the backwards transitive closure of the flow graph. These sets * are backwards in the sense that we find the set of nodes that reach * a given node, not the set of nodes that can be reached by a node. * * Assumes graph has been leveled. */ static void find_closure(opt_state_t *opt_state, struct block *root) { int i; struct block *b; /* * Initialize sets to contain no nodes. */ memset((char *)opt_state->all_closure_sets, 0, opt_state->n_blocks * opt_state->nodewords * sizeof(*opt_state->all_closure_sets)); /* root->level is the highest level no found. */ for (i = root->level; i >= 0; --i) { for (b = opt_state->levels[i]; b; b = b->link) { SET_INSERT(b->closure, b->id); if (JT(b) == 0) continue; SET_UNION(JT(b)->closure, b->closure, opt_state->nodewords); SET_UNION(JF(b)->closure, b->closure, opt_state->nodewords); } } } /* * Return the register number that is used by s. If A and X are both * used, return AX_ATOM. If no register is used, return -1. * * The implementation should probably change to an array access. */ static int atomuse(struct stmt *s) { register int c = s->code; if (c == NOP) return -1; switch (BPF_CLASS(c)) { case BPF_RET: return (BPF_RVAL(c) == BPF_A) ? A_ATOM : (BPF_RVAL(c) == BPF_X) ? X_ATOM : -1; case BPF_LD: case BPF_LDX: return (BPF_MODE(c) == BPF_IND) ? X_ATOM : (BPF_MODE(c) == BPF_MEM) ? s->k : -1; case BPF_ST: return A_ATOM; case BPF_STX: return X_ATOM; case BPF_JMP: case BPF_ALU: if (BPF_SRC(c) == BPF_X) return AX_ATOM; return A_ATOM; case BPF_MISC: return BPF_MISCOP(c) == BPF_TXA ? X_ATOM : A_ATOM; } abort(); /* NOTREACHED */ } /* * Return the register number that is defined by 's'. We assume that * a single stmt cannot define more than one register. If no register * is defined, return -1. * * The implementation should probably change to an array access. */ static int atomdef(struct stmt *s) { if (s->code == NOP) return -1; switch (BPF_CLASS(s->code)) { case BPF_LD: case BPF_ALU: return A_ATOM; case BPF_LDX: return X_ATOM; case BPF_ST: case BPF_STX: return s->k; case BPF_MISC: return BPF_MISCOP(s->code) == BPF_TAX ? X_ATOM : A_ATOM; } return -1; } /* * Compute the sets of registers used, defined, and killed by 'b'. * * "Used" means that a statement in 'b' uses the register before any * statement in 'b' defines it, i.e. it uses the value left in * that register by a predecessor block of this block. * "Defined" means that a statement in 'b' defines it. * "Killed" means that a statement in 'b' defines it before any * statement in 'b' uses it, i.e. it kills the value left in that * register by a predecessor block of this block. */ static void compute_local_ud(struct block *b) { struct slist *s; atomset def = 0, use = 0, killed = 0; int atom; for (s = b->stmts; s; s = s->next) { if (s->s.code == NOP) continue; atom = atomuse(&s->s); if (atom >= 0) { if (atom == AX_ATOM) { if (!ATOMELEM(def, X_ATOM)) use |= ATOMMASK(X_ATOM); if (!ATOMELEM(def, A_ATOM)) use |= ATOMMASK(A_ATOM); } else if (atom < N_ATOMS) { if (!ATOMELEM(def, atom)) use |= ATOMMASK(atom); } else abort(); } atom = atomdef(&s->s); if (atom >= 0) { if (!ATOMELEM(use, atom)) killed |= ATOMMASK(atom); def |= ATOMMASK(atom); } } if (BPF_CLASS(b->s.code) == BPF_JMP) { /* * XXX - what about RET? */ atom = atomuse(&b->s); if (atom >= 0) { if (atom == AX_ATOM) { if (!ATOMELEM(def, X_ATOM)) use |= ATOMMASK(X_ATOM); if (!ATOMELEM(def, A_ATOM)) use |= ATOMMASK(A_ATOM); } else if (atom < N_ATOMS) { if (!ATOMELEM(def, atom)) use |= ATOMMASK(atom); } else abort(); } } b->def = def; b->kill = killed; b->in_use = use; } /* * Assume graph is already leveled. */ static void find_ud(opt_state_t *opt_state, struct block *root) { int i, maxlevel; struct block *p; /* * root->level is the highest level no found; * count down from there. */ maxlevel = root->level; for (i = maxlevel; i >= 0; --i) for (p = opt_state->levels[i]; p; p = p->link) { compute_local_ud(p); p->out_use = 0; } for (i = 1; i <= maxlevel; ++i) { for (p = opt_state->levels[i]; p; p = p->link) { p->out_use |= JT(p)->in_use | JF(p)->in_use; p->in_use |= p->out_use &~ p->kill; } } } static void init_val(opt_state_t *opt_state) { opt_state->curval = 0; opt_state->next_vnode = opt_state->vnode_base; memset((char *)opt_state->vmap, 0, opt_state->maxval * sizeof(*opt_state->vmap)); memset((char *)opt_state->hashtbl, 0, sizeof opt_state->hashtbl); } /* Because we really don't have an IR, this stuff is a little messy. */ static int F(opt_state_t *opt_state, int code, int v0, int v1) { u_int hash; int val; struct valnode *p; hash = (u_int)code ^ ((u_int)v0 << 4) ^ ((u_int)v1 << 8); hash %= MODULUS; for (p = opt_state->hashtbl[hash]; p; p = p->next) if (p->code == code && p->v0 == v0 && p->v1 == v1) return p->val; val = ++opt_state->curval; if (BPF_MODE(code) == BPF_IMM && (BPF_CLASS(code) == BPF_LD || BPF_CLASS(code) == BPF_LDX)) { opt_state->vmap[val].const_val = v0; opt_state->vmap[val].is_const = 1; } p = opt_state->next_vnode++; p->val = val; p->code = code; p->v0 = v0; p->v1 = v1; p->next = opt_state->hashtbl[hash]; opt_state->hashtbl[hash] = p; return val; } static inline void vstore(struct stmt *s, int *valp, int newval, int alter) { if (alter && newval != VAL_UNKNOWN && *valp == newval) s->code = NOP; else *valp = newval; } /* * Do constant-folding on binary operators. * (Unary operators are handled elsewhere.) */ static void fold_op(opt_state_t *opt_state, struct stmt *s, int v0, int v1) { bpf_u_int32 a, b; a = opt_state->vmap[v0].const_val; b = opt_state->vmap[v1].const_val; switch (BPF_OP(s->code)) { case BPF_ADD: a += b; break; case BPF_SUB: a -= b; break; case BPF_MUL: a *= b; break; case BPF_DIV: if (b == 0) opt_error(opt_state, "division by zero"); a /= b; break; case BPF_MOD: if (b == 0) opt_error(opt_state, "modulus by zero"); a %= b; break; case BPF_AND: a &= b; break; case BPF_OR: a |= b; break; case BPF_XOR: a ^= b; break; case BPF_LSH: /* * A left shift of more than the width of the type * is undefined in C; we'll just treat it as shifting * all the bits out. * * XXX - the BPF interpreter doesn't check for this, * so its behavior is dependent on the behavior of * the processor on which it's running. There are * processors on which it shifts all the bits out * and processors on which it does no shift. */ if (b < 32) a <<= b; else a = 0; break; case BPF_RSH: /* * A right shift of more than the width of the type * is undefined in C; we'll just treat it as shifting * all the bits out. * * XXX - the BPF interpreter doesn't check for this, * so its behavior is dependent on the behavior of * the processor on which it's running. There are * processors on which it shifts all the bits out * and processors on which it does no shift. */ if (b < 32) a >>= b; else a = 0; break; default: abort(); } s->k = a; s->code = BPF_LD|BPF_IMM; opt_state->done = 0; } static inline struct slist * this_op(struct slist *s) { while (s != 0 && s->s.code == NOP) s = s->next; return s; } static void opt_not(struct block *b) { struct block *tmp = JT(b); JT(b) = JF(b); JF(b) = tmp; } static void opt_peep(opt_state_t *opt_state, struct block *b) { struct slist *s; struct slist *next, *last; int val; s = b->stmts; if (s == 0) return; last = s; for (/*empty*/; /*empty*/; s = next) { /* * Skip over nops. */ s = this_op(s); if (s == 0) break; /* nothing left in the block */ /* * Find the next real instruction after that one * (skipping nops). */ next = this_op(s->next); if (next == 0) break; /* no next instruction */ last = next; /* * st M[k] --> st M[k] * ldx M[k] tax */ if (s->s.code == BPF_ST && next->s.code == (BPF_LDX|BPF_MEM) && s->s.k == next->s.k) { opt_state->done = 0; next->s.code = BPF_MISC|BPF_TAX; } /* * ld #k --> ldx #k * tax txa */ if (s->s.code == (BPF_LD|BPF_IMM) && next->s.code == (BPF_MISC|BPF_TAX)) { s->s.code = BPF_LDX|BPF_IMM; next->s.code = BPF_MISC|BPF_TXA; opt_state->done = 0; } /* * This is an ugly special case, but it happens * when you say tcp[k] or udp[k] where k is a constant. */ if (s->s.code == (BPF_LD|BPF_IMM)) { struct slist *add, *tax, *ild; /* * Check that X isn't used on exit from this * block (which the optimizer might cause). * We know the code generator won't generate * any local dependencies. */ if (ATOMELEM(b->out_use, X_ATOM)) continue; /* * Check that the instruction following the ldi * is an addx, or it's an ldxms with an addx * following it (with 0 or more nops between the * ldxms and addx). */ if (next->s.code != (BPF_LDX|BPF_MSH|BPF_B)) add = next; else add = this_op(next->next); if (add == 0 || add->s.code != (BPF_ALU|BPF_ADD|BPF_X)) continue; /* * Check that a tax follows that (with 0 or more * nops between them). */ tax = this_op(add->next); if (tax == 0 || tax->s.code != (BPF_MISC|BPF_TAX)) continue; /* * Check that an ild follows that (with 0 or more * nops between them). */ ild = this_op(tax->next); if (ild == 0 || BPF_CLASS(ild->s.code) != BPF_LD || BPF_MODE(ild->s.code) != BPF_IND) continue; /* * We want to turn this sequence: * * (004) ldi #0x2 {s} * (005) ldxms [14] {next} -- optional * (006) addx {add} * (007) tax {tax} * (008) ild [x+0] {ild} * * into this sequence: * * (004) nop * (005) ldxms [14] * (006) nop * (007) nop * (008) ild [x+2] * * XXX We need to check that X is not * subsequently used, because we want to change * what'll be in it after this sequence. * * We know we can eliminate the accumulator * modifications earlier in the sequence since * it is defined by the last stmt of this sequence * (i.e., the last statement of the sequence loads * a value into the accumulator, so we can eliminate * earlier operations on the accumulator). */ ild->s.k += s->s.k; s->s.code = NOP; add->s.code = NOP; tax->s.code = NOP; opt_state->done = 0; } } /* * If the comparison at the end of a block is an equality * comparison against a constant, and nobody uses the value * we leave in the A register at the end of a block, and * the operation preceding the comparison is an arithmetic * operation, we can sometime optimize it away. */ if (b->s.code == (BPF_JMP|BPF_JEQ|BPF_K) && !ATOMELEM(b->out_use, A_ATOM)) { /* * We can optimize away certain subtractions of the * X register. */ if (last->s.code == (BPF_ALU|BPF_SUB|BPF_X)) { val = b->val[X_ATOM]; if (opt_state->vmap[val].is_const) { /* * If we have a subtract to do a comparison, * and the X register is a known constant, * we can merge this value into the * comparison: * * sub x -> nop * jeq #y jeq #(x+y) */ b->s.k += opt_state->vmap[val].const_val; last->s.code = NOP; opt_state->done = 0; } else if (b->s.k == 0) { /* * If the X register isn't a constant, * and the comparison in the test is * against 0, we can compare with the * X register, instead: * * sub x -> nop * jeq #0 jeq x */ last->s.code = NOP; b->s.code = BPF_JMP|BPF_JEQ|BPF_X; opt_state->done = 0; } } /* * Likewise, a constant subtract can be simplified: * * sub #x -> nop * jeq #y -> jeq #(x+y) */ else if (last->s.code == (BPF_ALU|BPF_SUB|BPF_K)) { last->s.code = NOP; b->s.k += last->s.k; opt_state->done = 0; } /* * And, similarly, a constant AND can be simplified * if we're testing against 0, i.e.: * * and #k nop * jeq #0 -> jset #k */ else if (last->s.code == (BPF_ALU|BPF_AND|BPF_K) && b->s.k == 0) { b->s.k = last->s.k; b->s.code = BPF_JMP|BPF_K|BPF_JSET; last->s.code = NOP; opt_state->done = 0; opt_not(b); } } /* * jset #0 -> never * jset #ffffffff -> always */ if (b->s.code == (BPF_JMP|BPF_K|BPF_JSET)) { if (b->s.k == 0) JT(b) = JF(b); if ((u_int)b->s.k == 0xffffffffU) JF(b) = JT(b); } /* * If we're comparing against the index register, and the index * register is a known constant, we can just compare against that * constant. */ val = b->val[X_ATOM]; if (opt_state->vmap[val].is_const && BPF_SRC(b->s.code) == BPF_X) { bpf_int32 v = opt_state->vmap[val].const_val; b->s.code &= ~BPF_X; b->s.k = v; } /* * If the accumulator is a known constant, we can compute the * comparison result. */ val = b->val[A_ATOM]; if (opt_state->vmap[val].is_const && BPF_SRC(b->s.code) == BPF_K) { bpf_int32 v = opt_state->vmap[val].const_val; switch (BPF_OP(b->s.code)) { case BPF_JEQ: v = v == b->s.k; break; case BPF_JGT: v = (unsigned)v > (unsigned)b->s.k; break; case BPF_JGE: v = (unsigned)v >= (unsigned)b->s.k; break; case BPF_JSET: v &= b->s.k; break; default: abort(); } if (JF(b) != JT(b)) opt_state->done = 0; if (v) JF(b) = JT(b); else JT(b) = JF(b); } } /* * Compute the symbolic value of expression of 's', and update * anything it defines in the value table 'val'. If 'alter' is true, * do various optimizations. This code would be cleaner if symbolic * evaluation and code transformations weren't folded together. */ static void opt_stmt(opt_state_t *opt_state, struct stmt *s, int val[], int alter) { int op; int v; switch (s->code) { case BPF_LD|BPF_ABS|BPF_W: case BPF_LD|BPF_ABS|BPF_H: case BPF_LD|BPF_ABS|BPF_B: v = F(opt_state, s->code, s->k, 0L); vstore(s, &val[A_ATOM], v, alter); break; case BPF_LD|BPF_IND|BPF_W: case BPF_LD|BPF_IND|BPF_H: case BPF_LD|BPF_IND|BPF_B: v = val[X_ATOM]; if (alter && opt_state->vmap[v].is_const) { s->code = BPF_LD|BPF_ABS|BPF_SIZE(s->code); s->k += opt_state->vmap[v].const_val; v = F(opt_state, s->code, s->k, 0L); opt_state->done = 0; } else v = F(opt_state, s->code, s->k, v); vstore(s, &val[A_ATOM], v, alter); break; case BPF_LD|BPF_LEN: v = F(opt_state, s->code, 0L, 0L); vstore(s, &val[A_ATOM], v, alter); break; case BPF_LD|BPF_IMM: v = K(s->k); vstore(s, &val[A_ATOM], v, alter); break; case BPF_LDX|BPF_IMM: v = K(s->k); vstore(s, &val[X_ATOM], v, alter); break; case BPF_LDX|BPF_MSH|BPF_B: v = F(opt_state, s->code, s->k, 0L); vstore(s, &val[X_ATOM], v, alter); break; case BPF_ALU|BPF_NEG: if (alter && opt_state->vmap[val[A_ATOM]].is_const) { s->code = BPF_LD|BPF_IMM; /* * Do this negation as unsigned arithmetic; that's * what modern BPF engines do, and it guarantees * that all possible values can be negated. (Yeah, * negating 0x80000000, the minimum signed 32-bit * two's-complement value, results in 0x80000000, * so it's still negative, but we *should* be doing * all unsigned arithmetic here, to match what * modern BPF engines do.) * * Express it as 0U - (unsigned value) so that we * don't get compiler warnings about negating an * unsigned value and don't get UBSan warnings * about the result of negating 0x80000000 being * undefined. */ s->k = 0U - (bpf_u_int32)(opt_state->vmap[val[A_ATOM]].const_val); val[A_ATOM] = K(s->k); } else val[A_ATOM] = F(opt_state, s->code, val[A_ATOM], 0L); break; case BPF_ALU|BPF_ADD|BPF_K: case BPF_ALU|BPF_SUB|BPF_K: case BPF_ALU|BPF_MUL|BPF_K: case BPF_ALU|BPF_DIV|BPF_K: case BPF_ALU|BPF_MOD|BPF_K: case BPF_ALU|BPF_AND|BPF_K: case BPF_ALU|BPF_OR|BPF_K: case BPF_ALU|BPF_XOR|BPF_K: case BPF_ALU|BPF_LSH|BPF_K: case BPF_ALU|BPF_RSH|BPF_K: op = BPF_OP(s->code); if (alter) { if (s->k == 0) { /* * Optimize operations where the constant * is zero. * * Don't optimize away "sub #0" * as it may be needed later to * fixup the generated math code. * * Fail if we're dividing by zero or taking * a modulus by zero. */ if (op == BPF_ADD || op == BPF_LSH || op == BPF_RSH || op == BPF_OR || op == BPF_XOR) { s->code = NOP; break; } if (op == BPF_MUL || op == BPF_AND) { s->code = BPF_LD|BPF_IMM; val[A_ATOM] = K(s->k); break; } if (op == BPF_DIV) opt_error(opt_state, "division by zero"); if (op == BPF_MOD) opt_error(opt_state, "modulus by zero"); } if (opt_state->vmap[val[A_ATOM]].is_const) { fold_op(opt_state, s, val[A_ATOM], K(s->k)); val[A_ATOM] = K(s->k); break; } } val[A_ATOM] = F(opt_state, s->code, val[A_ATOM], K(s->k)); break; case BPF_ALU|BPF_ADD|BPF_X: case BPF_ALU|BPF_SUB|BPF_X: case BPF_ALU|BPF_MUL|BPF_X: case BPF_ALU|BPF_DIV|BPF_X: case BPF_ALU|BPF_MOD|BPF_X: case BPF_ALU|BPF_AND|BPF_X: case BPF_ALU|BPF_OR|BPF_X: case BPF_ALU|BPF_XOR|BPF_X: case BPF_ALU|BPF_LSH|BPF_X: case BPF_ALU|BPF_RSH|BPF_X: op = BPF_OP(s->code); if (alter && opt_state->vmap[val[X_ATOM]].is_const) { if (opt_state->vmap[val[A_ATOM]].is_const) { fold_op(opt_state, s, val[A_ATOM], val[X_ATOM]); val[A_ATOM] = K(s->k); } else { s->code = BPF_ALU|BPF_K|op; s->k = opt_state->vmap[val[X_ATOM]].const_val; /* * XXX - we need to make up our minds * as to what integers are signed and * what integers are unsigned in BPF * programs and in our IR. */ if ((op == BPF_LSH || op == BPF_RSH) && (s->k < 0 || s->k > 31)) opt_error(opt_state, "shift by more than 31 bits"); opt_state->done = 0; val[A_ATOM] = F(opt_state, s->code, val[A_ATOM], K(s->k)); } break; } /* * Check if we're doing something to an accumulator * that is 0, and simplify. This may not seem like * much of a simplification but it could open up further * optimizations. * XXX We could also check for mul by 1, etc. */ if (alter && opt_state->vmap[val[A_ATOM]].is_const && opt_state->vmap[val[A_ATOM]].const_val == 0) { if (op == BPF_ADD || op == BPF_OR || op == BPF_XOR) { s->code = BPF_MISC|BPF_TXA; vstore(s, &val[A_ATOM], val[X_ATOM], alter); break; } else if (op == BPF_MUL || op == BPF_DIV || op == BPF_MOD || op == BPF_AND || op == BPF_LSH || op == BPF_RSH) { s->code = BPF_LD|BPF_IMM; s->k = 0; vstore(s, &val[A_ATOM], K(s->k), alter); break; } else if (op == BPF_NEG) { s->code = NOP; break; } } val[A_ATOM] = F(opt_state, s->code, val[A_ATOM], val[X_ATOM]); break; case BPF_MISC|BPF_TXA: vstore(s, &val[A_ATOM], val[X_ATOM], alter); break; case BPF_LD|BPF_MEM: v = val[s->k]; if (alter && opt_state->vmap[v].is_const) { s->code = BPF_LD|BPF_IMM; s->k = opt_state->vmap[v].const_val; opt_state->done = 0; } vstore(s, &val[A_ATOM], v, alter); break; case BPF_MISC|BPF_TAX: vstore(s, &val[X_ATOM], val[A_ATOM], alter); break; case BPF_LDX|BPF_MEM: v = val[s->k]; if (alter && opt_state->vmap[v].is_const) { s->code = BPF_LDX|BPF_IMM; s->k = opt_state->vmap[v].const_val; opt_state->done = 0; } vstore(s, &val[X_ATOM], v, alter); break; case BPF_ST: vstore(s, &val[s->k], val[A_ATOM], alter); break; case BPF_STX: vstore(s, &val[s->k], val[X_ATOM], alter); break; } } static void deadstmt(opt_state_t *opt_state, register struct stmt *s, register struct stmt *last[]) { register int atom; atom = atomuse(s); if (atom >= 0) { if (atom == AX_ATOM) { last[X_ATOM] = 0; last[A_ATOM] = 0; } else last[atom] = 0; } atom = atomdef(s); if (atom >= 0) { if (last[atom]) { opt_state->done = 0; last[atom]->code = NOP; } last[atom] = s; } } static void opt_deadstores(opt_state_t *opt_state, register struct block *b) { register struct slist *s; register int atom; struct stmt *last[N_ATOMS]; memset((char *)last, 0, sizeof last); for (s = b->stmts; s != 0; s = s->next) deadstmt(opt_state, &s->s, last); deadstmt(opt_state, &b->s, last); for (atom = 0; atom < N_ATOMS; ++atom) if (last[atom] && !ATOMELEM(b->out_use, atom)) { last[atom]->code = NOP; opt_state->done = 0; } } static void opt_blk(opt_state_t *opt_state, struct block *b, int do_stmts) { struct slist *s; struct edge *p; int i; bpf_int32 aval, xval; #if 0 for (s = b->stmts; s && s->next; s = s->next) if (BPF_CLASS(s->s.code) == BPF_JMP) { do_stmts = 0; break; } #endif /* * Initialize the atom values. */ p = b->in_edges; if (p == 0) { /* * We have no predecessors, so everything is undefined * upon entry to this block. */ memset((char *)b->val, 0, sizeof(b->val)); } else { /* * Inherit values from our predecessors. * * First, get the values from the predecessor along the * first edge leading to this node. */ memcpy((char *)b->val, (char *)p->pred->val, sizeof(b->val)); /* * Now look at all the other nodes leading to this node. * If, for the predecessor along that edge, a register * has a different value from the one we have (i.e., * control paths are merging, and the merging paths * assign different values to that register), give the * register the undefined value of 0. */ while ((p = p->next) != NULL) { for (i = 0; i < N_ATOMS; ++i) if (b->val[i] != p->pred->val[i]) b->val[i] = 0; } } aval = b->val[A_ATOM]; xval = b->val[X_ATOM]; for (s = b->stmts; s; s = s->next) opt_stmt(opt_state, &s->s, b->val, do_stmts); /* * This is a special case: if we don't use anything from this * block, and we load the accumulator or index register with a * value that is already there, or if this block is a return, * eliminate all the statements. * * XXX - what if it does a store? * * XXX - why does it matter whether we use anything from this * block? If the accumulator or index register doesn't change * its value, isn't that OK even if we use that value? * * XXX - if we load the accumulator with a different value, * and the block ends with a conditional branch, we obviously * can't eliminate it, as the branch depends on that value. * For the index register, the conditional branch only depends * on the index register value if the test is against the index * register value rather than a constant; if nothing uses the * value we put into the index register, and we're not testing * against the index register's value, and there aren't any * other problems that would keep us from eliminating this * block, can we eliminate it? */ if (do_stmts && ((b->out_use == 0 && aval != VAL_UNKNOWN && b->val[A_ATOM] == aval && xval != VAL_UNKNOWN && b->val[X_ATOM] == xval) || BPF_CLASS(b->s.code) == BPF_RET)) { if (b->stmts != 0) { b->stmts = 0; opt_state->done = 0; } } else { opt_peep(opt_state, b); opt_deadstores(opt_state, b); } /* * Set up values for branch optimizer. */ if (BPF_SRC(b->s.code) == BPF_K) b->oval = K(b->s.k); else b->oval = b->val[X_ATOM]; b->et.code = b->s.code; b->ef.code = -b->s.code; } /* * Return true if any register that is used on exit from 'succ', has * an exit value that is different from the corresponding exit value * from 'b'. */ static int use_conflict(struct block *b, struct block *succ) { int atom; atomset use = succ->out_use; if (use == 0) return 0; for (atom = 0; atom < N_ATOMS; ++atom) if (ATOMELEM(use, atom)) if (b->val[atom] != succ->val[atom]) return 1; return 0; } static struct block * fold_edge(struct block *child, struct edge *ep) { int sense; int aval0, aval1, oval0, oval1; int code = ep->code; if (code < 0) { code = -code; sense = 0; } else sense = 1; if (child->s.code != code) return 0; aval0 = child->val[A_ATOM]; oval0 = child->oval; aval1 = ep->pred->val[A_ATOM]; oval1 = ep->pred->oval; if (aval0 != aval1) return 0; if (oval0 == oval1) /* * The operands of the branch instructions are * identical, so the result is true if a true * branch was taken to get here, otherwise false. */ return sense ? JT(child) : JF(child); if (sense && code == (BPF_JMP|BPF_JEQ|BPF_K)) /* * At this point, we only know the comparison if we * came down the true branch, and it was an equality * comparison with a constant. * * I.e., if we came down the true branch, and the branch * was an equality comparison with a constant, we know the * accumulator contains that constant. If we came down * the false branch, or the comparison wasn't with a * constant, we don't know what was in the accumulator. * * We rely on the fact that distinct constants have distinct * value numbers. */ return JF(child); return 0; } static void opt_j(opt_state_t *opt_state, struct edge *ep) { register int i, k; register struct block *target; if (JT(ep->succ) == 0) return; if (JT(ep->succ) == JF(ep->succ)) { /* * Common branch targets can be eliminated, provided * there is no data dependency. */ if (!use_conflict(ep->pred, ep->succ->et.succ)) { opt_state->done = 0; ep->succ = JT(ep->succ); } } /* * For each edge dominator that matches the successor of this * edge, promote the edge successor to the its grandchild. * * XXX We violate the set abstraction here in favor a reasonably * efficient loop. */ top: for (i = 0; i < opt_state->edgewords; ++i) { register bpf_u_int32 x = ep->edom[i]; while (x != 0) { k = lowest_set_bit(x); x &=~ ((bpf_u_int32)1 << k); k += i * BITS_PER_WORD; target = fold_edge(ep->succ, opt_state->edges[k]); /* * Check that there is no data dependency between * nodes that will be violated if we move the edge. */ if (target != 0 && !use_conflict(ep->pred, target)) { opt_state->done = 0; ep->succ = target; if (JT(target) != 0) /* * Start over unless we hit a leaf. */ goto top; return; } } } } static void or_pullup(opt_state_t *opt_state, struct block *b) { int val, at_top; struct block *pull; struct block **diffp, **samep; struct edge *ep; ep = b->in_edges; if (ep == 0) return; /* * Make sure each predecessor loads the same value. * XXX why? */ val = ep->pred->val[A_ATOM]; for (ep = ep->next; ep != 0; ep = ep->next) if (val != ep->pred->val[A_ATOM]) return; if (JT(b->in_edges->pred) == b) diffp = &JT(b->in_edges->pred); else diffp = &JF(b->in_edges->pred); at_top = 1; for (;;) { if (*diffp == 0) return; if (JT(*diffp) != JT(b)) return; if (!SET_MEMBER((*diffp)->dom, b->id)) return; if ((*diffp)->val[A_ATOM] != val) break; diffp = &JF(*diffp); at_top = 0; } samep = &JF(*diffp); for (;;) { if (*samep == 0) return; if (JT(*samep) != JT(b)) return; if (!SET_MEMBER((*samep)->dom, b->id)) return; if ((*samep)->val[A_ATOM] == val) break; /* XXX Need to check that there are no data dependencies between dp0 and dp1. Currently, the code generator will not produce such dependencies. */ samep = &JF(*samep); } #ifdef notdef /* XXX This doesn't cover everything. */ for (i = 0; i < N_ATOMS; ++i) if ((*samep)->val[i] != pred->val[i]) return; #endif /* Pull up the node. */ pull = *samep; *samep = JF(pull); JF(pull) = *diffp; /* * At the top of the chain, each predecessor needs to point at the * pulled up node. Inside the chain, there is only one predecessor * to worry about. */ if (at_top) { for (ep = b->in_edges; ep != 0; ep = ep->next) { if (JT(ep->pred) == b) JT(ep->pred) = pull; else JF(ep->pred) = pull; } } else *diffp = pull; opt_state->done = 0; } static void and_pullup(opt_state_t *opt_state, struct block *b) { int val, at_top; struct block *pull; struct block **diffp, **samep; struct edge *ep; ep = b->in_edges; if (ep == 0) return; /* * Make sure each predecessor loads the same value. */ val = ep->pred->val[A_ATOM]; for (ep = ep->next; ep != 0; ep = ep->next) if (val != ep->pred->val[A_ATOM]) return; if (JT(b->in_edges->pred) == b) diffp = &JT(b->in_edges->pred); else diffp = &JF(b->in_edges->pred); at_top = 1; for (;;) { if (*diffp == 0) return; if (JF(*diffp) != JF(b)) return; if (!SET_MEMBER((*diffp)->dom, b->id)) return; if ((*diffp)->val[A_ATOM] != val) break; diffp = &JT(*diffp); at_top = 0; } samep = &JT(*diffp); for (;;) { if (*samep == 0) return; if (JF(*samep) != JF(b)) return; if (!SET_MEMBER((*samep)->dom, b->id)) return; if ((*samep)->val[A_ATOM] == val) break; /* XXX Need to check that there are no data dependencies between diffp and samep. Currently, the code generator will not produce such dependencies. */ samep = &JT(*samep); } #ifdef notdef /* XXX This doesn't cover everything. */ for (i = 0; i < N_ATOMS; ++i) if ((*samep)->val[i] != pred->val[i]) return; #endif /* Pull up the node. */ pull = *samep; *samep = JT(pull); JT(pull) = *diffp; /* * At the top of the chain, each predecessor needs to point at the * pulled up node. Inside the chain, there is only one predecessor * to worry about. */ if (at_top) { for (ep = b->in_edges; ep != 0; ep = ep->next) { if (JT(ep->pred) == b) JT(ep->pred) = pull; else JF(ep->pred) = pull; } } else *diffp = pull; opt_state->done = 0; } static void opt_blks(opt_state_t *opt_state, struct icode *ic, int do_stmts) { int i, maxlevel; struct block *p; init_val(opt_state); maxlevel = ic->root->level; find_inedges(opt_state, ic->root); for (i = maxlevel; i >= 0; --i) for (p = opt_state->levels[i]; p; p = p->link) opt_blk(opt_state, p, do_stmts); if (do_stmts) /* * No point trying to move branches; it can't possibly * make a difference at this point. */ return; for (i = 1; i <= maxlevel; ++i) { for (p = opt_state->levels[i]; p; p = p->link) { opt_j(opt_state, &p->et); opt_j(opt_state, &p->ef); } } find_inedges(opt_state, ic->root); for (i = 1; i <= maxlevel; ++i) { for (p = opt_state->levels[i]; p; p = p->link) { or_pullup(opt_state, p); and_pullup(opt_state, p); } } } static inline void link_inedge(struct edge *parent, struct block *child) { parent->next = child->in_edges; child->in_edges = parent; } static void find_inedges(opt_state_t *opt_state, struct block *root) { int i; struct block *b; for (i = 0; i < opt_state->n_blocks; ++i) opt_state->blocks[i]->in_edges = 0; /* * Traverse the graph, adding each edge to the predecessor * list of its successors. Skip the leaves (i.e. level 0). */ for (i = root->level; i > 0; --i) { for (b = opt_state->levels[i]; b != 0; b = b->link) { link_inedge(&b->et, JT(b)); link_inedge(&b->ef, JF(b)); } } } static void opt_root(struct block **b) { struct slist *tmp, *s; s = (*b)->stmts; (*b)->stmts = 0; while (BPF_CLASS((*b)->s.code) == BPF_JMP && JT(*b) == JF(*b)) *b = JT(*b); tmp = (*b)->stmts; if (tmp != 0) sappend(s, tmp); (*b)->stmts = s; /* * If the root node is a return, then there is no * point executing any statements (since the bpf machine * has no side effects). */ if (BPF_CLASS((*b)->s.code) == BPF_RET) (*b)->stmts = 0; } static void opt_loop(opt_state_t *opt_state, struct icode *ic, int do_stmts) { #ifdef BDEBUG if (pcap_optimizer_debug > 1 || pcap_print_dot_graph) { printf("opt_loop(root, %d) begin\n", do_stmts); opt_dump(opt_state, ic); } #endif do { opt_state->done = 1; find_levels(opt_state, ic); find_dom(opt_state, ic->root); find_closure(opt_state, ic->root); find_ud(opt_state, ic->root); find_edom(opt_state, ic->root); opt_blks(opt_state, ic, do_stmts); #ifdef BDEBUG if (pcap_optimizer_debug > 1 || pcap_print_dot_graph) { printf("opt_loop(root, %d) bottom, done=%d\n", do_stmts, opt_state->done); opt_dump(opt_state, ic); } #endif } while (!opt_state->done); } /* * Optimize the filter code in its dag representation. * Return 0 on success, -1 on error. */ int bpf_optimize(struct icode *ic, char *errbuf) { opt_state_t opt_state; memset(&opt_state, 0, sizeof(opt_state)); opt_state.errbuf = errbuf; if (setjmp(opt_state.top_ctx)) { opt_cleanup(&opt_state); return -1; } opt_init(&opt_state, ic); opt_loop(&opt_state, ic, 0); opt_loop(&opt_state, ic, 1); intern_blocks(&opt_state, ic); #ifdef BDEBUG if (pcap_optimizer_debug > 1 || pcap_print_dot_graph) { printf("after intern_blocks()\n"); opt_dump(&opt_state, ic); } #endif opt_root(&ic->root); #ifdef BDEBUG if (pcap_optimizer_debug > 1 || pcap_print_dot_graph) { printf("after opt_root()\n"); opt_dump(&opt_state, ic); } #endif opt_cleanup(&opt_state); return 0; } static void make_marks(struct icode *ic, struct block *p) { if (!isMarked(ic, p)) { Mark(ic, p); if (BPF_CLASS(p->s.code) != BPF_RET) { make_marks(ic, JT(p)); make_marks(ic, JF(p)); } } } /* * Mark code array such that isMarked(ic->cur_mark, i) is true * only for nodes that are alive. */ static void mark_code(struct icode *ic) { ic->cur_mark += 1; make_marks(ic, ic->root); } /* * True iff the two stmt lists load the same value from the packet into * the accumulator. */ static int eq_slist(struct slist *x, struct slist *y) { for (;;) { while (x && x->s.code == NOP) x = x->next; while (y && y->s.code == NOP) y = y->next; if (x == 0) return y == 0; if (y == 0) return x == 0; if (x->s.code != y->s.code || x->s.k != y->s.k) return 0; x = x->next; y = y->next; } } static inline int eq_blk(struct block *b0, struct block *b1) { if (b0->s.code == b1->s.code && b0->s.k == b1->s.k && b0->et.succ == b1->et.succ && b0->ef.succ == b1->ef.succ) return eq_slist(b0->stmts, b1->stmts); return 0; } static void intern_blocks(opt_state_t *opt_state, struct icode *ic) { struct block *p; int i, j; int done1; /* don't shadow global */ top: done1 = 1; for (i = 0; i < opt_state->n_blocks; ++i) opt_state->blocks[i]->link = 0; mark_code(ic); for (i = opt_state->n_blocks - 1; --i >= 0; ) { if (!isMarked(ic, opt_state->blocks[i])) continue; for (j = i + 1; j < opt_state->n_blocks; ++j) { if (!isMarked(ic, opt_state->blocks[j])) continue; if (eq_blk(opt_state->blocks[i], opt_state->blocks[j])) { opt_state->blocks[i]->link = opt_state->blocks[j]->link ? opt_state->blocks[j]->link : opt_state->blocks[j]; break; } } } for (i = 0; i < opt_state->n_blocks; ++i) { p = opt_state->blocks[i]; if (JT(p) == 0) continue; if (JT(p)->link) { done1 = 0; JT(p) = JT(p)->link; } if (JF(p)->link) { done1 = 0; JF(p) = JF(p)->link; } } if (!done1) goto top; } static void opt_cleanup(opt_state_t *opt_state) { free((void *)opt_state->vnode_base); free((void *)opt_state->vmap); free((void *)opt_state->edges); free((void *)opt_state->space); free((void *)opt_state->levels); free((void *)opt_state->blocks); } /* * For optimizer errors. */ static void PCAP_NORETURN opt_error(opt_state_t *opt_state, const char *fmt, ...) { va_list ap; if (opt_state->errbuf != NULL) { va_start(ap, fmt); (void)pcap_vsnprintf(opt_state->errbuf, PCAP_ERRBUF_SIZE, fmt, ap); va_end(ap); } longjmp(opt_state->top_ctx, 1); /* NOTREACHED */ } /* * Return the number of stmts in 's'. */ static u_int slength(struct slist *s) { u_int n = 0; for (; s; s = s->next) if (s->s.code != NOP) ++n; return n; } /* * Return the number of nodes reachable by 'p'. * All nodes should be initially unmarked. */ static int count_blocks(struct icode *ic, struct block *p) { if (p == 0 || isMarked(ic, p)) return 0; Mark(ic, p); return count_blocks(ic, JT(p)) + count_blocks(ic, JF(p)) + 1; } /* * Do a depth first search on the flow graph, numbering the * the basic blocks, and entering them into the 'blocks' array.` */ static void number_blks_r(opt_state_t *opt_state, struct icode *ic, struct block *p) { int n; if (p == 0 || isMarked(ic, p)) return; Mark(ic, p); n = opt_state->n_blocks++; p->id = n; opt_state->blocks[n] = p; number_blks_r(opt_state, ic, JT(p)); number_blks_r(opt_state, ic, JF(p)); } /* * Return the number of stmts in the flowgraph reachable by 'p'. * The nodes should be unmarked before calling. * * Note that "stmts" means "instructions", and that this includes * * side-effect statements in 'p' (slength(p->stmts)); * * statements in the true branch from 'p' (count_stmts(JT(p))); * * statements in the false branch from 'p' (count_stmts(JF(p))); * * the conditional jump itself (1); * * an extra long jump if the true branch requires it (p->longjt); * * an extra long jump if the false branch requires it (p->longjf). */ static u_int count_stmts(struct icode *ic, struct block *p) { u_int n; if (p == 0 || isMarked(ic, p)) return 0; Mark(ic, p); n = count_stmts(ic, JT(p)) + count_stmts(ic, JF(p)); return slength(p->stmts) + n + 1 + p->longjt + p->longjf; } /* * Allocate memory. All allocation is done before optimization * is begun. A linear bound on the size of all data structures is computed * from the total number of blocks and/or statements. */ static void opt_init(opt_state_t *opt_state, struct icode *ic) { bpf_u_int32 *p; int i, n, max_stmts; /* * First, count the blocks, so we can malloc an array to map * block number to block. Then, put the blocks into the array. */ unMarkAll(ic); n = count_blocks(ic, ic->root); opt_state->blocks = (struct block **)calloc(n, sizeof(*opt_state->blocks)); if (opt_state->blocks == NULL) opt_error(opt_state, "malloc"); unMarkAll(ic); opt_state->n_blocks = 0; number_blks_r(opt_state, ic, ic->root); opt_state->n_edges = 2 * opt_state->n_blocks; opt_state->edges = (struct edge **)calloc(opt_state->n_edges, sizeof(*opt_state->edges)); if (opt_state->edges == NULL) { opt_error(opt_state, "malloc"); } /* * The number of levels is bounded by the number of nodes. */ opt_state->levels = (struct block **)calloc(opt_state->n_blocks, sizeof(*opt_state->levels)); if (opt_state->levels == NULL) { opt_error(opt_state, "malloc"); } opt_state->edgewords = opt_state->n_edges / (8 * sizeof(bpf_u_int32)) + 1; opt_state->nodewords = opt_state->n_blocks / (8 * sizeof(bpf_u_int32)) + 1; /* XXX */ opt_state->space = (bpf_u_int32 *)malloc(2 * opt_state->n_blocks * opt_state->nodewords * sizeof(*opt_state->space) + opt_state->n_edges * opt_state->edgewords * sizeof(*opt_state->space)); if (opt_state->space == NULL) { opt_error(opt_state, "malloc"); } p = opt_state->space; opt_state->all_dom_sets = p; for (i = 0; i < n; ++i) { opt_state->blocks[i]->dom = p; p += opt_state->nodewords; } opt_state->all_closure_sets = p; for (i = 0; i < n; ++i) { opt_state->blocks[i]->closure = p; p += opt_state->nodewords; } opt_state->all_edge_sets = p; for (i = 0; i < n; ++i) { register struct block *b = opt_state->blocks[i]; b->et.edom = p; p += opt_state->edgewords; b->ef.edom = p; p += opt_state->edgewords; b->et.id = i; opt_state->edges[i] = &b->et; b->ef.id = opt_state->n_blocks + i; opt_state->edges[opt_state->n_blocks + i] = &b->ef; b->et.pred = b; b->ef.pred = b; } max_stmts = 0; for (i = 0; i < n; ++i) max_stmts += slength(opt_state->blocks[i]->stmts) + 1; /* * We allocate at most 3 value numbers per statement, * so this is an upper bound on the number of valnodes * we'll need. */ opt_state->maxval = 3 * max_stmts; opt_state->vmap = (struct vmapinfo *)calloc(opt_state->maxval, sizeof(*opt_state->vmap)); if (opt_state->vmap == NULL) { opt_error(opt_state, "malloc"); } opt_state->vnode_base = (struct valnode *)calloc(opt_state->maxval, sizeof(*opt_state->vnode_base)); if (opt_state->vnode_base == NULL) { opt_error(opt_state, "malloc"); } } /* * This is only used when supporting optimizer debugging. It is * global state, so do *not* do more than one compile in parallel * and expect it to provide meaningful information. */ #ifdef BDEBUG int bids[NBIDS]; #endif static void PCAP_NORETURN conv_error(conv_state_t *, const char *, ...) PCAP_PRINTFLIKE(2, 3); /* * Returns true if successful. Returns false if a branch has * an offset that is too large. If so, we have marked that * branch so that on a subsequent iteration, it will be treated * properly. */ static int convert_code_r(conv_state_t *conv_state, struct icode *ic, struct block *p) { struct bpf_insn *dst; struct slist *src; u_int slen; u_int off; u_int extrajmps; /* number of extra jumps inserted */ struct slist **offset = NULL; if (p == 0 || isMarked(ic, p)) return (1); Mark(ic, p); if (convert_code_r(conv_state, ic, JF(p)) == 0) return (0); if (convert_code_r(conv_state, ic, JT(p)) == 0) return (0); slen = slength(p->stmts); dst = conv_state->ftail -= (slen + 1 + p->longjt + p->longjf); /* inflate length by any extra jumps */ p->offset = (int)(dst - conv_state->fstart); /* generate offset[] for convenience */ if (slen) { offset = (struct slist **)calloc(slen, sizeof(struct slist *)); if (!offset) { conv_error(conv_state, "not enough core"); /*NOTREACHED*/ } } src = p->stmts; for (off = 0; off < slen && src; off++) { #if 0 printf("off=%d src=%x\n", off, src); #endif offset[off] = src; src = src->next; } off = 0; for (src = p->stmts; src; src = src->next) { if (src->s.code == NOP) continue; dst->code = (u_short)src->s.code; dst->k = src->s.k; /* fill block-local relative jump */ if (BPF_CLASS(src->s.code) != BPF_JMP || src->s.code == (BPF_JMP|BPF_JA)) { #if 0 if (src->s.jt || src->s.jf) { free(offset); conv_error(conv_state, "illegal jmp destination"); /*NOTREACHED*/ } #endif goto filled; } if (off == slen - 2) /*???*/ goto filled; { u_int i; int jt, jf; const char ljerr[] = "%s for block-local relative jump: off=%d"; #if 0 printf("code=%x off=%d %x %x\n", src->s.code, off, src->s.jt, src->s.jf); #endif if (!src->s.jt || !src->s.jf) { free(offset); conv_error(conv_state, ljerr, "no jmp destination", off); /*NOTREACHED*/ } jt = jf = 0; for (i = 0; i < slen; i++) { if (offset[i] == src->s.jt) { if (jt) { free(offset); conv_error(conv_state, ljerr, "multiple matches", off); /*NOTREACHED*/ } if (i - off - 1 >= 256) { free(offset); conv_error(conv_state, ljerr, "out-of-range jump", off); /*NOTREACHED*/ } dst->jt = (u_char)(i - off - 1); jt++; } if (offset[i] == src->s.jf) { if (jf) { free(offset); conv_error(conv_state, ljerr, "multiple matches", off); /*NOTREACHED*/ } if (i - off - 1 >= 256) { free(offset); conv_error(conv_state, ljerr, "out-of-range jump", off); /*NOTREACHED*/ } dst->jf = (u_char)(i - off - 1); jf++; } } if (!jt || !jf) { free(offset); conv_error(conv_state, ljerr, "no destination found", off); /*NOTREACHED*/ } } filled: ++dst; ++off; } if (offset) free(offset); #ifdef BDEBUG if (dst - conv_state->fstart < NBIDS) bids[dst - conv_state->fstart] = p->id + 1; #endif dst->code = (u_short)p->s.code; dst->k = p->s.k; if (JT(p)) { extrajmps = 0; off = JT(p)->offset - (p->offset + slen) - 1; if (off >= 256) { /* offset too large for branch, must add a jump */ if (p->longjt == 0) { /* mark this instruction and retry */ p->longjt++; return(0); } /* branch if T to following jump */ if (extrajmps >= 256) { conv_error(conv_state, "too many extra jumps"); /*NOTREACHED*/ } dst->jt = (u_char)extrajmps; extrajmps++; dst[extrajmps].code = BPF_JMP|BPF_JA; dst[extrajmps].k = off - extrajmps; } else dst->jt = (u_char)off; off = JF(p)->offset - (p->offset + slen) - 1; if (off >= 256) { /* offset too large for branch, must add a jump */ if (p->longjf == 0) { /* mark this instruction and retry */ p->longjf++; return(0); } /* branch if F to following jump */ /* if two jumps are inserted, F goes to second one */ if (extrajmps >= 256) { conv_error(conv_state, "too many extra jumps"); /*NOTREACHED*/ } dst->jf = (u_char)extrajmps; extrajmps++; dst[extrajmps].code = BPF_JMP|BPF_JA; dst[extrajmps].k = off - extrajmps; } else dst->jf = (u_char)off; } return (1); } /* * Convert flowgraph intermediate representation to the * BPF array representation. Set *lenp to the number of instructions. * * This routine does *NOT* leak the memory pointed to by fp. It *must * not* do free(fp) before returning fp; doing so would make no sense, * as the BPF array pointed to by the return value of icode_to_fcode() * must be valid - it's being returned for use in a bpf_program structure. * * If it appears that icode_to_fcode() is leaking, the problem is that * the program using pcap_compile() is failing to free the memory in * the BPF program when it's done - the leak is in the program, not in * the routine that happens to be allocating the memory. (By analogy, if * a program calls fopen() without ever calling fclose() on the FILE *, * it will leak the FILE structure; the leak is not in fopen(), it's in * the program.) Change the program to use pcap_freecode() when it's * done with the filter program. See the pcap man page. */ struct bpf_insn * icode_to_fcode(struct icode *ic, struct block *root, u_int *lenp, char *errbuf) { u_int n; struct bpf_insn *fp; conv_state_t conv_state; conv_state.fstart = NULL; conv_state.errbuf = errbuf; if (setjmp(conv_state.top_ctx) != 0) { free(conv_state.fstart); return NULL; } /* * Loop doing convert_code_r() until no branches remain * with too-large offsets. */ for (;;) { unMarkAll(ic); n = *lenp = count_stmts(ic, root); fp = (struct bpf_insn *)malloc(sizeof(*fp) * n); if (fp == NULL) { (void)pcap_snprintf(errbuf, PCAP_ERRBUF_SIZE, "malloc"); free(fp); return NULL; } memset((char *)fp, 0, sizeof(*fp) * n); conv_state.fstart = fp; conv_state.ftail = fp + n; unMarkAll(ic); if (convert_code_r(&conv_state, ic, root)) break; free(fp); } return fp; } /* * For iconv_to_fconv() errors. */ static void PCAP_NORETURN conv_error(conv_state_t *conv_state, const char *fmt, ...) { va_list ap; va_start(ap, fmt); (void)pcap_vsnprintf(conv_state->errbuf, PCAP_ERRBUF_SIZE, fmt, ap); va_end(ap); longjmp(conv_state->top_ctx, 1); /* NOTREACHED */ } /* * Make a copy of a BPF program and put it in the "fcode" member of * a "pcap_t". * * If we fail to allocate memory for the copy, fill in the "errbuf" * member of the "pcap_t" with an error message, and return -1; * otherwise, return 0. */ int install_bpf_program(pcap_t *p, struct bpf_program *fp) { size_t prog_size; /* * Validate the program. */ if (!bpf_validate(fp->bf_insns, fp->bf_len)) { pcap_snprintf(p->errbuf, sizeof(p->errbuf), "BPF program is not valid"); return (-1); } /* * Free up any already installed program. */ pcap_freecode(&p->fcode); prog_size = sizeof(*fp->bf_insns) * fp->bf_len; p->fcode.bf_len = fp->bf_len; p->fcode.bf_insns = (struct bpf_insn *)malloc(prog_size); if (p->fcode.bf_insns == NULL) { pcap_fmt_errmsg_for_errno(p->errbuf, sizeof(p->errbuf), errno, "malloc"); return (-1); } memcpy(p->fcode.bf_insns, fp->bf_insns, prog_size); return (0); } #ifdef BDEBUG static void dot_dump_node(struct icode *ic, struct block *block, struct bpf_program *prog, FILE *out) { int icount, noffset; int i; if (block == NULL || isMarked(ic, block)) return; Mark(ic, block); icount = slength(block->stmts) + 1 + block->longjt + block->longjf; noffset = min(block->offset + icount, (int)prog->bf_len); fprintf(out, "\tblock%d [shape=ellipse, id=\"block-%d\" label=\"BLOCK%d\\n", block->id, block->id, block->id); for (i = block->offset; i < noffset; i++) { fprintf(out, "\\n%s", bpf_image(prog->bf_insns + i, i)); } fprintf(out, "\" tooltip=\""); for (i = 0; i < BPF_MEMWORDS; i++) if (block->val[i] != VAL_UNKNOWN) fprintf(out, "val[%d]=%d ", i, block->val[i]); fprintf(out, "val[A]=%d ", block->val[A_ATOM]); fprintf(out, "val[X]=%d", block->val[X_ATOM]); fprintf(out, "\""); if (JT(block) == NULL) fprintf(out, ", peripheries=2"); fprintf(out, "];\n"); dot_dump_node(ic, JT(block), prog, out); dot_dump_node(ic, JF(block), prog, out); } static void dot_dump_edge(struct icode *ic, struct block *block, FILE *out) { if (block == NULL || isMarked(ic, block)) return; Mark(ic, block); if (JT(block)) { fprintf(out, "\t\"block%d\":se -> \"block%d\":n [label=\"T\"]; \n", block->id, JT(block)->id); fprintf(out, "\t\"block%d\":sw -> \"block%d\":n [label=\"F\"]; \n", block->id, JF(block)->id); } dot_dump_edge(ic, JT(block), out); dot_dump_edge(ic, JF(block), out); } /* Output the block CFG using graphviz/DOT language * In the CFG, block's code, value index for each registers at EXIT, * and the jump relationship is show. * * example DOT for BPF `ip src host 1.1.1.1' is: digraph BPF { block0 [shape=ellipse, id="block-0" label="BLOCK0\n\n(000) ldh [12]\n(001) jeq #0x800 jt 2 jf 5" tooltip="val[A]=0 val[X]=0"]; block1 [shape=ellipse, id="block-1" label="BLOCK1\n\n(002) ld [26]\n(003) jeq #0x1010101 jt 4 jf 5" tooltip="val[A]=0 val[X]=0"]; block2 [shape=ellipse, id="block-2" label="BLOCK2\n\n(004) ret #68" tooltip="val[A]=0 val[X]=0", peripheries=2]; block3 [shape=ellipse, id="block-3" label="BLOCK3\n\n(005) ret #0" tooltip="val[A]=0 val[X]=0", peripheries=2]; "block0":se -> "block1":n [label="T"]; "block0":sw -> "block3":n [label="F"]; "block1":se -> "block2":n [label="T"]; "block1":sw -> "block3":n [label="F"]; } * * After install graphviz on http://www.graphviz.org/, save it as bpf.dot * and run `dot -Tpng -O bpf.dot' to draw the graph. */ static int dot_dump(struct icode *ic, char *errbuf) { struct bpf_program f; FILE *out = stdout; memset(bids, 0, sizeof bids); f.bf_insns = icode_to_fcode(ic, ic->root, &f.bf_len, errbuf); if (f.bf_insns == NULL) return -1; fprintf(out, "digraph BPF {\n"); unMarkAll(ic); dot_dump_node(ic, ic->root, &f, out); unMarkAll(ic); dot_dump_edge(ic, ic->root, out); fprintf(out, "}\n"); free((char *)f.bf_insns); return 0; } static int plain_dump(struct icode *ic, char *errbuf) { struct bpf_program f; memset(bids, 0, sizeof bids); f.bf_insns = icode_to_fcode(ic, ic->root, &f.bf_len, errbuf); if (f.bf_insns == NULL) return -1; bpf_dump(&f, 1); putchar('\n'); free((char *)f.bf_insns); return 0; } static void opt_dump(opt_state_t *opt_state, struct icode *ic) { int status; char errbuf[PCAP_ERRBUF_SIZE]; /* * If the CFG, in DOT format, is requested, output it rather than * the code that would be generated from that graph. */ if (pcap_print_dot_graph) status = dot_dump(ic, errbuf); else status = plain_dump(ic, errbuf); if (status == -1) opt_error(opt_state, "opt_dump: icode_to_fcode failed: %s", errbuf); } #endif