/*
* 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.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <pcap-types.h>
#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <string.h>
#include <errno.h>
#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 <intrin.h>
#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 <string.h>, 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 <strings.h> and declares ffs() there,
* or some other platform (UN*X conforming to a sufficient recent version
* of the Single UNIX Specification).
*/
#include <strings.h>
#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 {
/*
* 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] & (1 << ((unsigned)(a) % BITS_PER_WORD)))
/*
* Add 'a' to uset p.
*/
#define SET_INSERT(p, a) \
(p)[(unsigned)(a) / BITS_PER_WORD] |= (1 << ((unsigned)(a) % BITS_PER_WORD))
/*
* Delete 'a' from uset p.
*/
#define SET_DELETE(p, a) \
(p)[(unsigned)(a) / BITS_PER_WORD] &= ~(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 {
/*
* 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(compiler_state_t *, opt_state_t *, struct icode *);
static void opt_cleanup(opt_state_t *);
static void intern_blocks(opt_state_t *, struct icode *);
static void find_inedges(opt_state_t *, struct block *);
#ifdef BDEBUG
static void opt_dump(compiler_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(compiler_state_t *cstate, 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)
bpf_error(cstate, "division by zero");
a /= b;
break;
case BPF_MOD:
if (b == 0)
bpf_error(cstate, "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 <<= b;
break;
case BPF_RSH:
a >>= b;
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(compiler_state_t *cstate, 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;
s->k = -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) {
/* don't optimize away "sub #0"
* as it may be needed later to
* fixup the generated math code */
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 (opt_state->vmap[val[A_ATOM]].is_const) {
fold_op(cstate, 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(cstate, 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;
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(compiler_state_t *cstate, 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(cstate, 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 &=~ (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(compiler_state_t *cstate, 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(cstate, 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(compiler_state_t *cstate, 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(cstate, 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(cstate, 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(cstate, ic);
}
#endif
} while (!opt_state->done);
}
/*
* Optimize the filter code in its dag representation.
*/
void
bpf_optimize(compiler_state_t *cstate, struct icode *ic)
{
opt_state_t opt_state;
opt_init(cstate, &opt_state, ic);
opt_loop(cstate, &opt_state, ic, 0);
opt_loop(cstate, &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(cstate, ic);
}
#endif
opt_root(&ic->root);
#ifdef BDEBUG
if (pcap_optimizer_debug > 1 || pcap_print_dot_graph) {
printf("after opt_root()\n");
opt_dump(cstate, ic);
}
#endif
opt_cleanup(&opt_state);
}
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);
}
/*
* 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(compiler_state_t *cstate, 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)
bpf_error(cstate, "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)
bpf_error(cstate, "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)
bpf_error(cstate, "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)
bpf_error(cstate, "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));
opt_state->vnode_base = (struct valnode *)calloc(opt_state->maxval, sizeof(*opt_state->vnode_base));
if (opt_state->vmap == NULL || opt_state->vnode_base == NULL)
bpf_error(cstate, "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
/*
* 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(compiler_state_t *cstate, 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(cstate, conv_state, ic, JF(p)) == 0)
return (0);
if (convert_code_r(cstate, 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) {
bpf_error(cstate, "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) {
bpf_error(cstate, "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) {
bpf_error(cstate, ljerr, "no jmp destination", off);
/*NOTREACHED*/
}
jt = jf = 0;
for (i = 0; i < slen; i++) {
if (offset[i] == src->s.jt) {
if (jt) {
bpf_error(cstate, ljerr, "multiple matches", off);
/*NOTREACHED*/
}
if (i - off - 1 >= 256) {
bpf_error(cstate, ljerr, "out-of-range jump", off);
/*NOTREACHED*/
}
dst->jt = (u_char)(i - off - 1);
jt++;
}
if (offset[i] == src->s.jf) {
if (jf) {
bpf_error(cstate, ljerr, "multiple matches", off);
/*NOTREACHED*/
}
if (i - off - 1 >= 256) {
bpf_error(cstate, ljerr, "out-of-range jump", off);
/*NOTREACHED*/
}
dst->jf = (u_char)(i - off - 1);
jf++;
}
}
if (!jt || !jf) {
bpf_error(cstate, 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) {
bpf_error(cstate, "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) {
bpf_error(cstate, "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(compiler_state_t *cstate, struct icode *ic,
struct block *root, u_int *lenp)
{
u_int n;
struct bpf_insn *fp;
conv_state_t conv_state;
/*
* 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)
bpf_error(cstate, "malloc");
memset((char *)fp, 0, sizeof(*fp) * n);
conv_state.fstart = fp;
conv_state.ftail = fp + n;
unMarkAll(ic);
if (convert_code_r(cstate, &conv_state, ic, root))
break;
free(fp);
}
return fp;
}
/*
* 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 void
dot_dump(compiler_state_t *cstate, struct icode *ic)
{
struct bpf_program f;
FILE *out = stdout;
memset(bids, 0, sizeof bids);
f.bf_insns = icode_to_fcode(cstate, ic, ic->root, &f.bf_len);
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);
}
static void
plain_dump(compiler_state_t *cstate, struct icode *ic)
{
struct bpf_program f;
memset(bids, 0, sizeof bids);
f.bf_insns = icode_to_fcode(cstate, ic, ic->root, &f.bf_len);
bpf_dump(&f, 1);
putchar('\n');
free((char *)f.bf_insns);
}
static void
opt_dump(compiler_state_t *cstate, struct icode *ic)
{
/*
* 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)
dot_dump(cstate, ic);
else
plain_dump(cstate, ic);
}
#endif