Aren/NetBSD
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
6ffefad6ef
NetBSD/dist/libpcap/optimize.c
drochner 65f32e5703 Make the optimizer use unsigned numbers as the kernel does. 
While it is not agreed on that purely unsigned arithmetics is nice,
different behaviour of optimized and unoptimized code is less desirable.
2006-05-17 17:48:36 +00:00

2296 lines
47 KiB
C
Raw Blame History

/*
* 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 tcpdump intermediate representation.
*/
#ifndef lint
static const char rcsid[] _U_ =
"@(#) $Header: /cvsroot/src/dist/libpcap/Attic/optimize.c,v 1.4 2006/05/17 17:48:36 drochner Exp $ (LBL)";
#endif
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <string.h>
#include <errno.h>
#include "pcap-int.h"
#include "gencode.h"
#ifdef HAVE_OS_PROTO_H
#include "os-proto.h"
#endif
#ifdef BDEBUG
extern int dflag;
#endif
#if defined(MSDOS) && !defined(__DJGPP__)
extern int _w32_ffs (int mask);
#define ffs _w32_ffs
#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
/*
* A flag to indicate that further optimization is needed.
* Iterative passes are continued until a given pass yields no
* branch movement.
*/
static int done;
/*
* A block is marked if only if its mark equals the current mark.
* Rather than traverse the code array, marking each item, 'cur_mark' is
* incremented. This automatically makes each element unmarked.
*/
static int cur_mark;
#define isMarked(p) ((p)->mark == cur_mark)
#define unMarkAll() cur_mark += 1
#define Mark(p) ((p)->mark = cur_mark)
static void opt_init(struct block *);
static void opt_cleanup(void);
static void make_marks(struct block *);
static void mark_code(struct block *);
static void intern_blocks(struct block *);
static int eq_slist(struct slist *, struct slist *);
static void find_levels_r(struct block *);
static void find_levels(struct block *);
static void find_dom(struct block *);
static void propedom(struct edge *);
static void find_edom(struct block *);
static void find_closure(struct block *);
static int atomuse(struct stmt *);
static int atomdef(struct stmt *);
static void compute_local_ud(struct block *);
static void find_ud(struct block *);
static void init_val(void);
static int F(int, int, int);
static inline void vstore(struct stmt *, int *, int, int);
static void opt_blk(struct block *, int);
static int use_conflict(struct block *, struct block *);
static void opt_j(struct edge *);
static void or_pullup(struct block *);
static void and_pullup(struct block *);
static void opt_blks(struct block *, int);
static inline void link_inedge(struct edge *, struct block *);
static void find_inedges(struct block *);
static void opt_root(struct block **);
static void opt_loop(struct block *, int);
static void fold_op(struct stmt *, int, int);
static inline struct slist *this_op(struct slist *);
static void opt_not(struct block *);
static void opt_peep(struct block *);
static void opt_stmt(struct stmt *, int[], int);
static void deadstmt(struct stmt *, struct stmt *[]);
static void opt_deadstores(struct block *);
static struct block *fold_edge(struct block *, struct edge *);
static inline int eq_blk(struct block *, struct block *);
static int slength(struct slist *);
static int count_blocks(struct block *);
static void number_blks_r(struct block *);
static int count_stmts(struct block *);
static int convert_code_r(struct block *);
#ifdef BDEBUG
static void opt_dump(struct block *);
#endif
static int n_blocks;
struct block **blocks;
static 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.
*/
static int nodewords;
static 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++;\
}
static uset all_dom_sets;
static uset all_closure_sets;
static uset all_edge_sets;
#ifndef MAX
#define MAX(a,b) ((a)>(b)?(a):(b))
#endif
static void
find_levels_r(b)
struct block *b;
{
int level;
if (isMarked(b))
return;
Mark(b);
b->link = 0;
if (JT(b)) {
find_levels_r(JT(b));
find_levels_r(JF(b));
level = MAX(JT(b)->level, JF(b)->level) + 1;
} else
level = 0;
b->level = level;
b->link = levels[level];
levels[level] = b;
}
/*
* Level graph. The levels go from 0 at the leaves to
* N_LEVELS at the root. The 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(root)
struct block *root;
{
memset((char *)levels, 0, n_blocks * sizeof(*levels));
unMarkAll();
find_levels_r(root);
}
/*
* Find dominator relationships.
* Assumes graph has been leveled.
*/
static void
find_dom(root)
struct block *root;
{
int i;
struct block *b;
bpf_u_int32 *x;
/*
* Initialize sets to contain all nodes.
*/
x = all_dom_sets;
i = n_blocks * nodewords;
while (--i >= 0)
*x++ = ~0;
/* Root starts off empty. */
for (i = nodewords; --i >= 0;)
root->dom[i] = 0;
/* root->level is the highest level no found. */
for (i = root->level; i >= 0; --i) {
for (b = levels[i]; b; b = b->link) {
SET_INSERT(b->dom, b->id);
if (JT(b) == 0)
continue;
SET_INTERSECT(JT(b)->dom, b->dom, nodewords);
SET_INTERSECT(JF(b)->dom, b->dom, nodewords);
}
}
}
static void
propedom(ep)
struct edge *ep;
{
SET_INSERT(ep->edom, ep->id);
if (ep->succ) {
SET_INTERSECT(ep->succ->et.edom, ep->edom, edgewords);
SET_INTERSECT(ep->succ->ef.edom, ep->edom, edgewords);
}
}
/*
* Compute edge dominators.
* Assumes graph has been leveled and predecessors established.
*/
static void
find_edom(root)
struct block *root;
{
int i;
uset x;
struct block *b;
x = all_edge_sets;
for (i = n_edges * edgewords; --i >= 0; )
x[i] = ~0;
/* root->level is the highest level no found. */
memset(root->et.edom, 0, edgewords * sizeof(*(uset)0));
memset(root->ef.edom, 0, edgewords * sizeof(*(uset)0));
for (i = root->level; i >= 0; --i) {
for (b = levels[i]; b != 0; b = b->link) {
propedom(&b->et);
propedom(&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(root)
struct block *root;
{
int i;
struct block *b;
/*
* Initialize sets to contain no nodes.
*/
memset((char *)all_closure_sets, 0,
n_blocks * nodewords * sizeof(*all_closure_sets));
/* root->level is the highest level no found. */
for (i = root->level; i >= 0; --i) {
for (b = levels[i]; b; b = b->link) {
SET_INSERT(b->closure, b->id);
if (JT(b) == 0)
continue;
SET_UNION(JT(b)->closure, b->closure, nodewords);
SET_UNION(JF(b)->closure, b->closure, 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(s)
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(s)
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(b)
struct block *b;
{
struct slist *s;
atomset def = 0, use = 0, kill = 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))
kill |= 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 = kill;
b->in_use = use;
}
/*
* Assume graph is already leveled.
*/
static void
find_ud(root)
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 = levels[i]; p; p = p->link) {
compute_local_ud(p);
p->out_use = 0;
}
for (i = 1; i <= maxlevel; ++i) {
for (p = 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;
}
}
}
/*
* 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;
};
#define MODULUS 213
static struct valnode *hashtbl[MODULUS];
static int curval;
static int maxval;
/* Integer constants mapped with the load immediate opcode. */
#define K(i) F(BPF_LD|BPF_IMM|BPF_W, i, 0L)
struct vmapinfo {
int is_const;
bpf_int32 const_val;
};
struct vmapinfo *vmap;
struct valnode *vnode_base;
struct valnode *next_vnode;
static void
init_val()
{
curval = 0;
next_vnode = vnode_base;
memset((char *)vmap, 0, maxval * sizeof(*vmap));
memset((char *)hashtbl, 0, sizeof hashtbl);
}
/* Because we really don't have an IR, this stuff is a little messy. */
static int
F(code, v0, v1)
int code;
int v0, v1;
{
u_int hash;
int val;
struct valnode *p;
hash = (u_int)code ^ (v0 << 4) ^ (v1 << 8);
hash %= MODULUS;
for (p = hashtbl[hash]; p; p = p->next)
if (p->code == code && p->v0 == v0 && p->v1 == v1)
return p->val;
val = ++curval;
if (BPF_MODE(code) == BPF_IMM &&
(BPF_CLASS(code) == BPF_LD || BPF_CLASS(code) == BPF_LDX)) {
vmap[val].const_val = v0;
vmap[val].is_const = 1;
}
p = next_vnode++;
p->val = val;
p->code = code;
p->v0 = v0;
p->v1 = v1;
p->next = hashtbl[hash];
hashtbl[hash] = p;
return val;
}
static inline void
vstore(s, valp, newval, alter)
struct stmt *s;
int *valp;
int newval;
int alter;
{
if (alter && *valp == newval)
s->code = NOP;
else
*valp = newval;
}
static void
fold_op(s, v0, v1)
struct stmt *s;
int v0, v1;
{
bpf_u_int32 a, b;
a = vmap[v0].const_val;
b = 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("division by zero");
a /= b;
break;
case BPF_AND:
a &= b;
break;
case BPF_OR:
a |= b;
break;
case BPF_LSH:
a <<= b;
break;
case BPF_RSH:
a >>= b;
break;
case BPF_NEG:
a = -a;
break;
default:
abort();
}
s->k = a;
s->code = BPF_LD|BPF_IMM;
done = 0;
}
static inline struct slist *
this_op(s)
struct slist *s;
{
while (s != 0 && s->s.code == NOP)
s = s->next;
return s;
}
static void
opt_not(b)
struct block *b;
{
struct block *tmp = JT(b);
JT(b) = JF(b);
JF(b) = tmp;
}
static void
opt_peep(b)
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) {
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;
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;
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 (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 += vmap[val].const_val;
last->s.code = NOP;
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;
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;
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;
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 (b->s.k == 0xffffffff)
JF(b) = JT(b);
}
/*
* If the accumulator is a known constant, we can compute the
* comparison result.
*/
val = b->val[A_ATOM];
if (vmap[val].is_const && BPF_SRC(b->s.code) == BPF_K) {
bpf_int32 v = 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 > b->s.k;
break;
case BPF_JGE:
v = (unsigned)v >= b->s.k;
break;
case BPF_JSET:
v &= b->s.k;
break;
default:
abort();
}
if (JF(b) != JT(b))
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(s, val, alter)
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(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 && vmap[v].is_const) {
s->code = BPF_LD|BPF_ABS|BPF_SIZE(s->code);
s->k += vmap[v].const_val;
v = F(s->code, s->k, 0L);
done = 0;
}
else
v = F(s->code, s->k, v);
vstore(s, &val[A_ATOM], v, alter);
break;
case BPF_LD|BPF_LEN:
v = F(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(s->code, s->k, 0L);
vstore(s, &val[X_ATOM], v, alter);
break;
case BPF_ALU|BPF_NEG:
if (alter && vmap[val[A_ATOM]].is_const) {
s->code = BPF_LD|BPF_IMM;
s->k = -vmap[val[A_ATOM]].const_val;
val[A_ATOM] = K(s->k);
}
else
val[A_ATOM] = F(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_AND|BPF_K:
case BPF_ALU|BPF_OR|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) {
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 (vmap[val[A_ATOM]].is_const) {
fold_op(s, val[A_ATOM], K(s->k));
val[A_ATOM] = K(s->k);
break;
}
}
val[A_ATOM] = F(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_AND|BPF_X:
case BPF_ALU|BPF_OR|BPF_X:
case BPF_ALU|BPF_LSH|BPF_X:
case BPF_ALU|BPF_RSH|BPF_X:
op = BPF_OP(s->code);
if (alter && vmap[val[X_ATOM]].is_const) {
if (vmap[val[A_ATOM]].is_const) {
fold_op(s, val[A_ATOM], val[X_ATOM]);
val[A_ATOM] = K(s->k);
}
else {
s->code = BPF_ALU|BPF_K|op;
s->k = vmap[val[X_ATOM]].const_val;
done = 0;
val[A_ATOM] =
F(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 && vmap[val[A_ATOM]].is_const
&& vmap[val[A_ATOM]].const_val == 0) {
if (op == BPF_ADD || op == BPF_OR) {
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_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(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 && vmap[v].is_const) {
s->code = BPF_LD|BPF_IMM;
s->k = vmap[v].const_val;
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 && vmap[v].is_const) {
s->code = BPF_LDX|BPF_IMM;
s->k = vmap[v].const_val;
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(s, last)
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]) {
done = 0;
last[atom]->code = NOP;
}
last[atom] = s;
}
}
static void
opt_deadstores(b)
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(&s->s, last);
deadstmt(&b->s, last);
for (atom = 0; atom < N_ATOMS; ++atom)
if (last[atom] && !ATOMELEM(b->out_use, atom)) {
last[atom]->code = NOP;
done = 0;
}
}
static void
opt_blk(b, do_stmts)
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(&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 != 0 && b->val[A_ATOM] == aval &&
xval != 0 && b->val[X_ATOM] == xval) ||
BPF_CLASS(b->s.code) == BPF_RET)) {
if (b->stmts != 0) {
b->stmts = 0;
done = 0;
}
} else {
opt_peep(b);
opt_deadstores(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(b, succ)
struct block *b, *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(child, ep)
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(ep)
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)) {
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 < edgewords; ++i) {
register bpf_u_int32 x = ep->edom[i];
while (x != 0) {
k = ffs(x) - 1;
x &=~ (1 << k);
k += i * BITS_PER_WORD;
target = fold_edge(ep->succ, 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)) {
done = 0;
ep->succ = target;
if (JT(target) != 0)
/*
* Start over unless we hit a leaf.
*/
goto top;
return;
}
}
}
}
static void
or_pullup(b)
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;
while (1) {
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);
while (1) {
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;
done = 0;
}
static void
and_pullup(b)
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;
while (1) {
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);
while (1) {
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;
done = 0;
}
static void
opt_blks(root, do_stmts)
struct block *root;
int do_stmts;
{
int i, maxlevel;
struct block *p;
init_val();
maxlevel = root->level;
find_inedges(root);
for (i = maxlevel; i >= 0; --i)
for (p = levels[i]; p; p = p->link)
opt_blk(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 = levels[i]; p; p = p->link) {
opt_j(&p->et);
opt_j(&p->ef);
}
}
find_inedges(root);
for (i = 1; i <= maxlevel; ++i) {
for (p = levels[i]; p; p = p->link) {
or_pullup(p);
and_pullup(p);
}
}
}
static inline void
link_inedge(parent, child)
struct edge *parent;
struct block *child;
{
parent->next = child->in_edges;
child->in_edges = parent;
}
static void
find_inedges(root)
struct block *root;
{
int i;
struct block *b;
for (i = 0; i < n_blocks; ++i)
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 = levels[i]; b != 0; b = b->link) {
link_inedge(&b->et, JT(b));
link_inedge(&b->ef, JF(b));
}
}
}
static void
opt_root(b)
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(root, do_stmts)
struct block *root;
int do_stmts;
{
#ifdef BDEBUG
if (dflag > 1) {
printf("opt_loop(root, %d) begin\n", do_stmts);
opt_dump(root);
}
#endif
do {
done = 1;
find_levels(root);
find_dom(root);
find_closure(root);
find_ud(root);
find_edom(root);
opt_blks(root, do_stmts);
#ifdef BDEBUG
if (dflag > 1) {
printf("opt_loop(root, %d) bottom, done=%d\n", do_stmts, done);
opt_dump(root);
}
#endif
} while (!done);
}
/*
* Optimize the filter code in its dag representation.
*/
void
bpf_optimize(rootp)
struct block **rootp;
{
struct block *root;
root = *rootp;
opt_init(root);
opt_loop(root, 0);
opt_loop(root, 1);
intern_blocks(root);
#ifdef BDEBUG
if (dflag > 1) {
printf("after intern_blocks()\n");
opt_dump(root);
}
#endif
opt_root(rootp);
#ifdef BDEBUG
if (dflag > 1) {
printf("after opt_root()\n");
opt_dump(root);
}
#endif
opt_cleanup();
}
static void
make_marks(p)
struct block *p;
{
if (!isMarked(p)) {
Mark(p);
if (BPF_CLASS(p->s.code) != BPF_RET) {
make_marks(JT(p));
make_marks(JF(p));
}
}
}
/*
* Mark code array such that isMarked(i) is true
* only for nodes that are alive.
*/
static void
mark_code(p)
struct block *p;
{
cur_mark += 1;
make_marks(p);
}
/*
* True iff the two stmt lists load the same value from the packet into
* the accumulator.
*/
static int
eq_slist(x, y)
struct slist *x, *y;
{
while (1) {
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(b0, b1)
struct block *b0, *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(root)
struct block *root;
{
struct block *p;
int i, j;
int done1; /* don't shadow global */
top:
done1 = 1;
for (i = 0; i < n_blocks; ++i)
blocks[i]->link = 0;
mark_code(root);
for (i = n_blocks - 1; --i >= 0; ) {
if (!isMarked(blocks[i]))
continue;
for (j = i + 1; j < n_blocks; ++j) {
if (!isMarked(blocks[j]))
continue;
if (eq_blk(blocks[i], blocks[j])) {
blocks[i]->link = blocks[j]->link ?
blocks[j]->link : blocks[j];
break;
}
}
}
for (i = 0; i < n_blocks; ++i) {
p = 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()
{
free((void *)vnode_base);
free((void *)vmap);
free((void *)edges);
free((void *)space);
free((void *)levels);
free((void *)blocks);
}
/*
* Return the number of stmts in 's'.
*/
static int
slength(s)
struct slist *s;
{
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(p)
struct block *p;
{
if (p == 0 || isMarked(p))
return 0;
Mark(p);
return count_blocks(JT(p)) + count_blocks(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(p)
struct block *p;
{
int n;
if (p == 0 || isMarked(p))
return;
Mark(p);
n = n_blocks++;
p->id = n;
blocks[n] = p;
number_blks_r(JT(p));
number_blks_r(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 int
count_stmts(p)
struct block *p;
{
int n;
if (p == 0 || isMarked(p))
return 0;
Mark(p);
n = count_stmts(JT(p)) + count_stmts(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(root)
struct block *root;
{
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();
n = count_blocks(root);
blocks = (struct block **)malloc(n * sizeof(*blocks));
if (blocks == NULL)
bpf_error("malloc");
unMarkAll();
n_blocks = 0;
number_blks_r(root);
n_edges = 2 * n_blocks;
edges = (struct edge **)malloc(n_edges * sizeof(*edges));
if (edges == NULL)
bpf_error("malloc");
/*
* The number of levels is bounded by the number of nodes.
*/
levels = (struct block **)malloc(n_blocks * sizeof(*levels));
if (levels == NULL)
bpf_error("malloc");
edgewords = n_edges / (8 * sizeof(bpf_u_int32)) + 1;
nodewords = n_blocks / (8 * sizeof(bpf_u_int32)) + 1;
/* XXX */
space = (bpf_u_int32 *)malloc(2 * n_blocks * nodewords * sizeof(*space)
+ n_edges * edgewords * sizeof(*space));
if (space == NULL)
bpf_error("malloc");
p = space;
all_dom_sets = p;
for (i = 0; i < n; ++i) {
blocks[i]->dom = p;
p += nodewords;
}
all_closure_sets = p;
for (i = 0; i < n; ++i) {
blocks[i]->closure = p;
p += nodewords;
}
all_edge_sets = p;
for (i = 0; i < n; ++i) {
register struct block *b = blocks[i];
b->et.edom = p;
p += edgewords;
b->ef.edom = p;
p += edgewords;
b->et.id = i;
edges[i] = &b->et;
b->ef.id = n_blocks + i;
edges[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(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.
*/
maxval = 3 * max_stmts;
vmap = (struct vmapinfo *)malloc(maxval * sizeof(*vmap));
vnode_base = (struct valnode *)malloc(maxval * sizeof(*vnode_base));
if (vmap == NULL || vnode_base == NULL)
bpf_error("malloc");
}
/*
* 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.
*/
static struct bpf_insn *fstart;
static struct bpf_insn *ftail;
#ifdef BDEBUG
int bids[1000];
#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(p)
struct block *p;
{
struct bpf_insn *dst;
struct slist *src;
int slen;
u_int off;
int extrajmps; /* number of extra jumps inserted */
struct slist **offset = NULL;
if (p == 0 || isMarked(p))
return (1);
Mark(p);
if (convert_code_r(JF(p)) == 0)
return (0);
if (convert_code_r(JT(p)) == 0)
return (0);
slen = slength(p->stmts);
dst = ftail -= (slen + 1 + p->longjt + p->longjf);
/* inflate length by any extra jumps */
p->offset = dst - fstart;
/* generate offset[] for convenience */
if (slen) {
offset = (struct slist **)calloc(slen, sizeof(struct slist *));
if (!offset) {
bpf_error("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("illegal jmp destination");
/*NOTREACHED*/
}
#endif
goto filled;
}
if (off == slen - 2) /*???*/
goto filled;
{
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(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(ljerr, "multiple matches", off);
/*NOTREACHED*/
}
dst->jt = i - off - 1;
jt++;
}
if (offset[i] == src->s.jf) {
if (jf) {
bpf_error(ljerr, "multiple matches", off);
/*NOTREACHED*/
}
dst->jf = i - off - 1;
jf++;
}
}
if (!jt || !jf) {
bpf_error(ljerr, "no destination found", off);
/*NOTREACHED*/
}
}
filled:
++dst;
++off;
}
if (offset)
free(offset);
#ifdef BDEBUG
bids[dst - 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 */
dst->jt = extrajmps;
extrajmps++;
dst[extrajmps].code = BPF_JMP|BPF_JA;
dst[extrajmps].k = off - extrajmps;
}
else
dst->jt = 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 */
dst->jf = extrajmps;
extrajmps++;
dst[extrajmps].code = BPF_JMP|BPF_JA;
dst[extrajmps].k = off - extrajmps;
}
else
dst->jf = off;
}
return (1);
}
/*
* Convert flowgraph intermediate representation to the
* BPF array representation. Set *lenp to the number of instructions.
*/
struct bpf_insn *
icode_to_fcode(root, lenp)
struct block *root;
int *lenp;
{
int n;
struct bpf_insn *fp;
/*
* Loop doing convert_code_r() until no branches remain
* with too-large offsets.
*/
while (1) {
unMarkAll();
n = *lenp = count_stmts(root);
fp = (struct bpf_insn *)malloc(sizeof(*fp) * n);
if (fp == NULL)
bpf_error("malloc");
memset((char *)fp, 0, sizeof(*fp) * n);
fstart = fp;
ftail = fp + n;
unMarkAll();
if (convert_code_r(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;
/*
* 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) {
snprintf(p->errbuf, sizeof(p->errbuf),
"malloc: %s", pcap_strerror(errno));
return (-1);
}
memcpy(p->fcode.bf_insns, fp->bf_insns, prog_size);
return (0);
}
#ifdef BDEBUG
static void
opt_dump(root)
struct block *root;
{
struct bpf_program f;
memset(bids, 0, sizeof bids);
f.bf_insns = icode_to_fcode(root, &f.bf_len);
bpf_dump(&f, 1);
putchar('\n');
free((char *)f.bf_insns);
}
#endif
Reference in New Issue View Git Blame Copy Permalink