// SPDX-License-Identifier: GPL-2.0-only
/*
* Minimal BPF debugger
*
* Minimal BPF debugger that mimics the kernel's engine (w/o extensions)
* and allows for single stepping through selected packets from a pcap
* with a provided user filter in order to facilitate verification of a
* BPF program. Besides others, this is useful to verify BPF programs
* before attaching to a live system, and can be used in socket filters,
* cls_bpf, xt_bpf, team driver and e.g. PTP code; in particular when a
* single more complex BPF program is being used. Reasons for a more
* complex BPF program are likely primarily to optimize execution time
* for making a verdict when multiple simple BPF programs are combined
* into one in order to prevent parsing same headers multiple times.
*
* More on how to debug BPF opcodes see Documentation/networking/filter.rst
* which is the main document on BPF. Mini howto for getting started:
*
* 1) `./bpf_dbg` to enter the shell (shell cmds denoted with '>'):
* 2) > load bpf 6,40 0 0 12,21 0 3 20... (output from `bpf_asm` or
* `tcpdump -iem1 -ddd port 22 | tr '\n' ','` to load as filter)
* 3) > load pcap foo.pcap
* 4) > run <n>/disassemble/dump/quit (self-explanatory)
* 5) > breakpoint 2 (sets bp at loaded BPF insns 2, do `run` then;
* multiple bps can be set, of course, a call to `breakpoint`
* w/o args shows currently loaded bps, `breakpoint reset` for
* resetting all breakpoints)
* 6) > select 3 (`run` etc will start from the 3rd packet in the pcap)
* 7) > step [-<n>, +<n>] (performs single stepping through the BPF)
*
* Copyright 2013 Daniel Borkmann <[email protected]>
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <ctype.h>
#include <stdbool.h>
#include <stdarg.h>
#include <setjmp.h>
#include <linux/filter.h>
#include <linux/if_packet.h>
#include <readline/readline.h>
#include <readline/history.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <errno.h>
#include <signal.h>
#include <arpa/inet.h>
#include <net/ethernet.h>
#define TCPDUMP_MAGIC 0xa1b2c3d4
#define BPF_LDX_B (BPF_LDX | BPF_B)
#define BPF_LDX_W (BPF_LDX | BPF_W)
#define BPF_JMP_JA (BPF_JMP | BPF_JA)
#define BPF_JMP_JEQ (BPF_JMP | BPF_JEQ)
#define BPF_JMP_JGT (BPF_JMP | BPF_JGT)
#define BPF_JMP_JGE (BPF_JMP | BPF_JGE)
#define BPF_JMP_JSET (BPF_JMP | BPF_JSET)
#define BPF_ALU_ADD (BPF_ALU | BPF_ADD)
#define BPF_ALU_SUB (BPF_ALU | BPF_SUB)
#define BPF_ALU_MUL (BPF_ALU | BPF_MUL)
#define BPF_ALU_DIV (BPF_ALU | BPF_DIV)
#define BPF_ALU_MOD (BPF_ALU | BPF_MOD)
#define BPF_ALU_NEG (BPF_ALU | BPF_NEG)
#define BPF_ALU_AND (BPF_ALU | BPF_AND)
#define BPF_ALU_OR (BPF_ALU | BPF_OR)
#define BPF_ALU_XOR (BPF_ALU | BPF_XOR)
#define BPF_ALU_LSH (BPF_ALU | BPF_LSH)
#define BPF_ALU_RSH (BPF_ALU | BPF_RSH)
#define BPF_MISC_TAX (BPF_MISC | BPF_TAX)
#define BPF_MISC_TXA (BPF_MISC | BPF_TXA)
#define BPF_LD_B (BPF_LD | BPF_B)
#define BPF_LD_H (BPF_LD | BPF_H)
#define BPF_LD_W (BPF_LD | BPF_W)
#ifndef array_size
# define array_size(x) (sizeof(x) / sizeof((x)[0]))
#endif
#ifndef __check_format_printf
# define __check_format_printf(pos_fmtstr, pos_fmtargs) \
__attribute__ ((format (printf, (pos_fmtstr), (pos_fmtargs))))
#endif
enum {
CMD_OK,
CMD_ERR,
CMD_EX,
};
struct shell_cmd {
const char *name;
int (*func)(char *args);
};
struct pcap_filehdr {
uint32_t magic;
uint16_t version_major;
uint16_t version_minor;
int32_t thiszone;
uint32_t sigfigs;
uint32_t snaplen;
uint32_t linktype;
};
struct pcap_timeval {
int32_t tv_sec;
int32_t tv_usec;
};
struct pcap_pkthdr {
struct pcap_timeval ts;
uint32_t caplen;
uint32_t len;
};
struct bpf_regs {
uint32_t A;
uint32_t X;
uint32_t M[BPF_MEMWORDS];
uint32_t R;
bool Rs;
uint16_t Pc;
};
static struct sock_filter bpf_image[BPF_MAXINSNS + 1];
static unsigned int bpf_prog_len;
static int bpf_breakpoints[64];
static struct bpf_regs bpf_regs[BPF_MAXINSNS + 1];
static struct bpf_regs bpf_curr;
static unsigned int bpf_regs_len;
static int pcap_fd = -1;
static unsigned int pcap_packet;
static size_t pcap_map_size;
static char *pcap_ptr_va_start, *pcap_ptr_va_curr;
static const char * const op_table[] = {
[BPF_ST] = "st",
[BPF_STX] = "stx",
[BPF_LD_B] = "ldb",
[BPF_LD_H] = "ldh",
[BPF_LD_W] = "ld",
[BPF_LDX] = "ldx",
[BPF_LDX_B] = "ldxb",
[BPF_JMP_JA] = "ja",
[BPF_JMP_JEQ] = "jeq",
[BPF_JMP_JGT] = "jgt",
[BPF_JMP_JGE] = "jge",
[BPF_JMP_JSET] = "jset",
[BPF_ALU_ADD] = "add",
[BPF_ALU_SUB] = "sub",
[BPF_ALU_MUL] = "mul",
[BPF_ALU_DIV] = "div",
[BPF_ALU_MOD] = "mod",
[BPF_ALU_NEG] = "neg",
[BPF_ALU_AND] = "and",
[BPF_ALU_OR] = "or",
[BPF_ALU_XOR] = "xor",
[BPF_ALU_LSH] = "lsh",
[BPF_ALU_RSH] = "rsh",
[BPF_MISC_TAX] = "tax",
[BPF_MISC_TXA] = "txa",
[BPF_RET] = "ret",
};
static __check_format_printf(1, 2) int rl_printf(const char *fmt, ...)
{
int ret;
va_list vl;
va_start(vl, fmt);
ret = vfprintf(rl_outstream, fmt, vl);
va_end(vl);
return ret;
}
static int matches(const char *cmd, const char *pattern)
{
int len = strlen(cmd);
if (len > strlen(pattern))
return -1;
return memcmp(pattern, cmd, len);
}
static void hex_dump(const uint8_t *buf, size_t len)
{
int i;
rl_printf("%3u: ", 0);
for (i = 0; i < len; i++) {
if (i && !(i % 16))
rl_printf("\n%3u: ", i);
rl_printf("%02x ", buf[i]);
}
rl_printf("\n");
}
static bool bpf_prog_loaded(void)
{
if (bpf_prog_len == 0)
rl_printf("no bpf program loaded!\n");
return bpf_prog_len > 0;
}
static void bpf_disasm(const struct sock_filter f, unsigned int i)
{
const char *op, *fmt;
int val = f.k;
char buf[256];
switch (f.code) {
case BPF_RET | BPF_K:
op = op_table[BPF_RET];
fmt = "#%#x";
break;
case BPF_RET | BPF_A:
op = op_table[BPF_RET];
fmt = "a";
break;
case BPF_RET | BPF_X:
op = op_table[BPF_RET];
fmt = "x";
break;
case BPF_MISC_TAX:
op = op_table[BPF_MISC_TAX];
fmt = "";
break;
case BPF_MISC_TXA:
op = op_table[BPF_MISC_TXA];
fmt = "";
break;
case BPF_ST:
op = op_table[BPF_ST];
fmt = "M[%d]";
break;
case BPF_STX:
op = op_table[BPF_STX];
fmt = "M[%d]";
break;
case BPF_LD_W | BPF_ABS:
op = op_table[BPF_LD_W];
fmt = "[%d]";
break;
case BPF_LD_H | BPF_ABS:
op = op_table[BPF_LD_H];
fmt = "[%d]";
break;
case BPF_LD_B | BPF_ABS:
op = op_table[BPF_LD_B];
fmt = "[%d]";
break;
case BPF_LD_W | BPF_LEN:
op = op_table[BPF_LD_W];
fmt = "#len";
break;
case BPF_LD_W | BPF_IND:
op = op_table[BPF_LD_W];
fmt = "[x+%d]";
break;
case BPF_LD_H | BPF_IND:
op = op_table[BPF_LD_H];
fmt = "[x+%d]";
break;
case BPF_LD_B | BPF_IND:
op = op_table[BPF_LD_B];
fmt = "[x+%d]";
break;
case BPF_LD | BPF_IMM:
op = op_table[BPF_LD_W];
fmt = "#%#x";
break;
case BPF_LDX | BPF_IMM:
op = op_table[BPF_LDX];
fmt = "#%#x";
break;
case BPF_LDX_B | BPF_MSH:
op = op_table[BPF_LDX_B];
fmt = "4*([%d]&0xf)";
break;
case BPF_LD | BPF_MEM:
op = op_table[BPF_LD_W];
fmt = "M[%d]";
break;
case BPF_LDX | BPF_MEM:
op = op_table[BPF_LDX];
fmt = "M[%d]";
break;
case BPF_JMP_JA:
op = op_table[BPF_JMP_JA];
fmt = "%d";
val = i + 1 + f.k;
break;
case BPF_JMP_JGT | BPF_X:
op = op_table[BPF_JMP_JGT];
fmt = "x";
break;
case BPF_JMP_JGT | BPF_K:
op = op_table[BPF_JMP_JGT];
fmt = "#%#x";
break;
case BPF_JMP_JGE | BPF_X:
op = op_table[BPF_JMP_JGE];
fmt = "x";
break;
case BPF_JMP_JGE | BPF_K:
op = op_table[BPF_JMP_JGE];
fmt = "#%#x";
break;
case BPF_JMP_JEQ | BPF_X:
op = op_table[BPF_JMP_JEQ];
fmt = "x";
break;
case BPF_JMP_JEQ | BPF_K:
op = op_table[BPF_JMP_JEQ];
fmt = "#%#x";
break;
case BPF_JMP_JSET | BPF_X:
op = op_table[BPF_JMP_JSET];
fmt = "x";
break;
case BPF_JMP_JSET | BPF_K:
op = op_table[BPF_JMP_JSET];
fmt = "#%#x";
break;
case BPF_ALU_NEG:
op = op_table[BPF_ALU_NEG];
fmt = "";
break;
case BPF_ALU_LSH | BPF_X:
op = op_table[BPF_ALU_LSH];
fmt = "x";
break;
case BPF_ALU_LSH | BPF_K:
op = op_table[BPF_ALU_LSH];
fmt = "#%d";
break;
case BPF_ALU_RSH | BPF_X:
op = op_table[BPF_ALU_RSH];
fmt = "x";
break;
case BPF_ALU_RSH | BPF_K:
op = op_table[BPF_ALU_RSH];
fmt = "#%d";
break;
case BPF_ALU_ADD | BPF_X:
op = op_table[BPF_ALU_ADD];
fmt = "x";
break;
case BPF_ALU_ADD | BPF_K:
op = op_table[BPF_ALU_ADD];
fmt = "#%d";
break;
case BPF_ALU_SUB | BPF_X:
op = op_table[BPF_ALU_SUB];
fmt = "x";
break;
case BPF_ALU_SUB | BPF_K:
op = op_table[BPF_ALU_SUB];
fmt = "#%d";
break;
case BPF_ALU_MUL | BPF_X:
op = op_table[BPF_ALU_MUL];
fmt = "x";
break;
case BPF_ALU_MUL | BPF_K:
op = op_table[BPF_ALU_MUL];
fmt = "#%d";
break;
case BPF_ALU_DIV | BPF_X:
op = op_table[BPF_ALU_DIV];
fmt = "x";
break;
case BPF_ALU_DIV | BPF_K:
op = op_table[BPF_ALU_DIV];
fmt = "#%d";
break;
case BPF_ALU_MOD | BPF_X:
op = op_table[BPF_ALU_MOD];
fmt = "x";
break;
case BPF_ALU_MOD | BPF_K:
op = op_table[BPF_ALU_MOD];
fmt = "#%d";
break;
case BPF_ALU_AND | BPF_X:
op = op_table[BPF_ALU_AND];
fmt = "x";
break;
case BPF_ALU_AND | BPF_K:
op = op_table[BPF_ALU_AND];
fmt = "#%#x";
break;
case BPF_ALU_OR | BPF_X:
op = op_table[BPF_ALU_OR];
fmt = "x";
break;
case BPF_ALU_OR | BPF_K:
op = op_table[BPF_ALU_OR];
fmt = "#%#x";
break;
case BPF_ALU_XOR | BPF_X:
op = op_table[BPF_ALU_XOR];
fmt = "x";
break;
case BPF_ALU_XOR | BPF_K:
op = op_table[BPF_ALU_XOR];
fmt = "#%#x";
break;
default:
op = "nosup";
fmt = "%#x";
val = f.code;
break;
}
memset(buf, 0, sizeof(buf));
snprintf(buf, sizeof(buf), fmt, val);
buf[sizeof(buf) - 1] = 0;
if ((BPF_CLASS(f.code) == BPF_JMP && BPF_OP(f.code) != BPF_JA))
rl_printf("l%d:\t%s %s, l%d, l%d\n", i, op, buf,
i + 1 + f.jt, i + 1 + f.jf);
else
rl_printf("l%d:\t%s %s\n", i, op, buf);
}
static void bpf_dump_curr(struct bpf_regs *r, struct sock_filter *f)
{
int i, m = 0;
rl_printf("pc: [%u]\n", r->Pc);
rl_printf("code: [%u] jt[%u] jf[%u] k[%u]\n",
f->code, f->jt, f->jf, f->k);
rl_printf("curr: ");
bpf_disasm(*f, r->Pc);
if (f->jt || f->jf) {
rl_printf("jt: ");
bpf_disasm(*(f + f->jt + 1), r->Pc + f->jt + 1);
rl_printf("jf: ");
bpf_disasm(*(f + f->jf + 1), r->Pc + f->jf + 1);
}
rl_printf("A: [%#08x][%u]\n", r->A, r->A);
rl_printf("X: [%#08x][%u]\n", r->X, r->X);
if (r->Rs)
rl_printf("ret: [%#08x][%u]!\n", r->R, r->R);
for (i = 0; i < BPF_MEMWORDS; i++) {
if (r->M[i]) {
m++;
rl_printf("M[%d]: [%#08x][%u]\n", i, r->M[i], r->M[i]);
}
}
if (m == 0)
rl_printf("M[0,%d]: [%#08x][%u]\n", BPF_MEMWORDS - 1, 0, 0);
}
static void bpf_dump_pkt(uint8_t *pkt, uint32_t pkt_caplen, uint32_t pkt_len)
{
if (pkt_caplen != pkt_len)
rl_printf("cap: %u, len: %u\n", pkt_caplen, pkt_len);
else
rl_printf("len: %u\n", pkt_len);
hex_dump(pkt, pkt_caplen);
}
static void bpf_disasm_all(const struct sock_filter *f, unsigned int len)
{
unsigned int i;
for (i = 0; i < len; i++)
bpf_disasm(f[i], i);
}
static void bpf_dump_all(const struct sock_filter *f, unsigned int len)
{
unsigned int i;
rl_printf("/* { op, jt, jf, k }, */\n");
for (i = 0; i < len; i++)
rl_printf("{ %#04x, %2u, %2u, %#010x },\n",
f[i].code, f[i].jt, f[i].jf, f[i].k);
}
static bool bpf_runnable(struct sock_filter *f, unsigned int len)
{
int sock, ret, i;
struct sock_fprog bpf = {
.filter = f,
.len = len,
};
sock = socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0) {
rl_printf("cannot open socket!\n");
return false;
}
ret = setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &bpf, sizeof(bpf));
close(sock);
if (ret < 0) {
rl_printf("program not allowed to run by kernel!\n");
return false;
}
for (i = 0; i < len; i++) {
if (BPF_CLASS(f[i].code) == BPF_LD &&
f[i].k > SKF_AD_OFF) {
rl_printf("extensions currently not supported!\n");
return false;
}
}
return true;
}
static void bpf_reset_breakpoints(void)
{
int i;
for (i = 0; i < array_size(bpf_breakpoints); i++)
bpf_breakpoints[i] = -1;
}
static void bpf_set_breakpoints(unsigned int where)
{
int i;
bool set = false;
for (i = 0; i < array_size(bpf_breakpoints); i++) {
if (bpf_breakpoints[i] == (int) where) {
rl_printf("breakpoint already set!\n");
set = true;
break;
}
if (bpf_breakpoints[i] == -1 && set == false) {
bpf_breakpoints[i] = where;
set = true;
}
}
if (!set)
rl_printf("too many breakpoints set, reset first!\n");
}
static void bpf_dump_breakpoints(void)
{
int i;
rl_printf("breakpoints: ");
for (i = 0; i < array_size(bpf_breakpoints); i++) {
if (bpf_breakpoints[i] < 0)
continue;
rl_printf("%d ", bpf_breakpoints[i]);
}
rl_printf("\n");
}
static void bpf_reset(void)
{
bpf_regs_len = 0;
memset(bpf_regs, 0, sizeof(bpf_regs));
memset(&bpf_curr, 0, sizeof(bpf_curr));
}
static void bpf_safe_regs(void)
{
memcpy(&bpf_regs[bpf_regs_len++], &bpf_curr, sizeof(bpf_curr));
}
static bool bpf_restore_regs(int off)
{
unsigned int index = bpf_regs_len - 1 + off;
if (index == 0) {
bpf_reset();
return true;
} else if (index < bpf_regs_len) {
memcpy(&bpf_curr, &bpf_regs[index], sizeof(bpf_curr));
bpf_regs_len = index;
return true;
} else {
rl_printf("reached bottom of register history stack!\n");
return false;
}
}
static uint32_t extract_u32(uint8_t *pkt, uint32_t off)
{
uint32_t r;
memcpy(&r, &pkt[off], sizeof(r));
return ntohl(r);
}
static uint16_t extract_u16(uint8_t *pkt, uint32_t off)
{
uint16_t r;
memcpy(&r, &pkt[off], sizeof(r));
return ntohs(r);
}
static uint8_t extract_u8(uint8_t *pkt, uint32_t off)
{
return pkt[off];
}
static void set_return(struct bpf_regs *r)
{
r->R = 0;
r->Rs = true;
}
static void bpf_single_step(struct bpf_regs *r, struct sock_filter *f,
uint8_t *pkt, uint32_t pkt_caplen,
uint32_t pkt_len)
{
uint32_t K = f->k;
int d;
switch (f->code) {
case BPF_RET | BPF_K:
r->R = K;
r->Rs = true;
break;
case BPF_RET | BPF_A:
r->R = r->A;
r->Rs = true;
break;
case BPF_RET | BPF_X:
r->R = r->X;
r->Rs = true;
break;
case BPF_MISC_TAX:
r->X = r->A;
break;
case BPF_MISC_TXA:
r->A = r->X;
break;
case BPF_ST:
r->M[K] = r->A;
break;
case BPF_STX:
r->M[K] = r->X;
break;
case BPF_LD_W | BPF_ABS:
d = pkt_caplen - K;
if (d >= sizeof(uint32_t))
r->A = extract_u32(pkt, K);
else
set_return(r);
break;
case BPF_LD_H | BPF_ABS:
d = pkt_caplen - K;
if (d >= sizeof(uint16_t))
r->A = extract_u16(pkt, K);
else
set_return(r);
break;
case BPF_LD_B | BPF_ABS:
d = pkt_caplen - K;
if (d >= sizeof(uint8_t))
r->A = extract_u8(pkt, K);
else
set_return(r);
break;
case BPF_LD_W | BPF_IND:
d = pkt_caplen - (r->X + K);
if (d >= sizeof(uint32_t))
r->A = extract_u32(pkt, r->X + K);
break;
case BPF_LD_H | BPF_IND:
d = pkt_caplen - (r->X + K);
if (d >= sizeof(uint16_t))
r->A = extract_u16(pkt, r->X + K);
else
set_return(r);
break;
case BPF_LD_B | BPF_IND:
d = pkt_caplen - (r->X + K);
if (d >= sizeof(uint8_t))
r->A = extract_u8(pkt, r->X + K);
else
set_return(r);
break;
case BPF_LDX_B | BPF_MSH:
d = pkt_caplen - K;
if (d >= sizeof(uint8_t)) {
r->X = extract_u8(pkt, K);
r->X = (r->X & 0xf) << 2;
} else
set_return(r);
break;
case BPF_LD_W | BPF_LEN:
r->A = pkt_len;
break;
case BPF_LDX_W | BPF_LEN:
r->A = pkt_len;
break;
case BPF_LD | BPF_IMM:
r->A = K;
break;
case BPF_LDX | BPF_IMM:
r->X = K;
break;
case BPF_LD | BPF_MEM:
r->A = r->M[K];
break;
case BPF_LDX | BPF_MEM:
r->X = r->M[K];
break;
case BPF_JMP_JA:
r->Pc += K;
break;
case BPF_JMP_JGT | BPF_X:
r->Pc += r->A > r->X ? f->jt : f->jf;
break;
case BPF_JMP_JGT | BPF_K:
r->Pc += r->A > K ? f->jt : f->jf;
break;
case BPF_JMP_JGE | BPF_X:
r->Pc += r->A >= r->X ? f->jt : f->jf;
break;
case BPF_JMP_JGE | BPF_K:
r->Pc += r->A >= K ? f->jt : f->jf;
break;
case BPF_JMP_JEQ | BPF_X:
r->Pc += r->A == r->X ? f->jt : f->jf;
break;
case BPF_JMP_JEQ | BPF_K:
r->Pc += r->A == K ? f->jt : f->jf;
break;
case BPF_JMP_JSET | BPF_X:
r->Pc += r->A & r->X ? f->jt : f->jf;
break;
case BPF_JMP_JSET | BPF_K:
r->Pc += r->A & K ? f->jt : f->jf;
break;
case BPF_ALU_NEG:
r->A = -r->A;
break;
case BPF_ALU_LSH | BPF_X:
r->A <<= r->X;
break;
case BPF_ALU_LSH | BPF_K:
r->A <<= K;
break;
case BPF_ALU_RSH | BPF_X:
r->A >>= r->X;
break;
case BPF_ALU_RSH | BPF_K:
r->A >>= K;
break;
case BPF_ALU_ADD | BPF_X:
r->A += r->X;
break;
case BPF_ALU_ADD | BPF_K:
r->A += K;
break;
case BPF_ALU_SUB | BPF_X:
r->A -= r->X;
break;
case BPF_ALU_SUB | BPF_K:
r->A -= K;
break;
case BPF_ALU_MUL | BPF_X:
r->A *= r->X;
break;
case BPF_ALU_MUL | BPF_K:
r->A *= K;
break;
case BPF_ALU_DIV | BPF_X:
case BPF_ALU_MOD | BPF_X:
if (r->X == 0) {
set_return(r);
break;
}
goto do_div;
case BPF_ALU_DIV | BPF_K:
case BPF_ALU_MOD | BPF_K:
if (K == 0) {
set_return(r);
break;
}
do_div:
switch (f->code) {
case BPF_ALU_DIV | BPF_X:
r->A /= r->X;
break;
case BPF_ALU_DIV | BPF_K:
r->A /= K;
break;
case BPF_ALU_MOD | BPF_X:
r->A %= r->X;
break;
case BPF_ALU_MOD | BPF_K:
r->A %= K;
break;
}
break;
case BPF_ALU_AND | BPF_X:
r->A &= r->X;
break;
case BPF_ALU_AND | BPF_K:
r->A &= K;
break;
case BPF_ALU_OR | BPF_X:
r->A |= r->X;
break;
case BPF_ALU_OR | BPF_K:
r->A |= K;
break;
case BPF_ALU_XOR | BPF_X:
r->A ^= r->X;
break;
case BPF_ALU_XOR | BPF_K:
r->A ^= K;
break;
}
}
static bool bpf_pc_has_breakpoint(uint16_t pc)
{
int i;
for (i = 0; i < array_size(bpf_breakpoints); i++) {
if (bpf_breakpoints[i] < 0)
continue;
if (bpf_breakpoints[i] == pc)
return true;
}
return false;
}
static bool bpf_handle_breakpoint(struct bpf_regs *r, struct sock_filter *f,
uint8_t *pkt, uint32_t pkt_caplen,
uint32_t pkt_len)
{
rl_printf("-- register dump --\n");
bpf_dump_curr(r, &f[r->Pc]);
rl_printf("-- packet dump --\n");
bpf_dump_pkt(pkt, pkt_caplen, pkt_len);
rl_printf("(breakpoint)\n");
return true;
}
static int bpf_run_all(struct sock_filter *f, uint16_t bpf_len, uint8_t *pkt,
uint32_t pkt_caplen, uint32_t pkt_len)
{
bool stop = false;
while (bpf_curr.Rs == false && stop == false) {
bpf_safe_regs();
if (bpf_pc_has_breakpoint(bpf_curr.Pc))
stop = bpf_handle_breakpoint(&bpf_curr, f, pkt,
pkt_caplen, pkt_len);
bpf_single_step(&bpf_curr, &f[bpf_curr.Pc], pkt, pkt_caplen,
pkt_len);
bpf_curr.Pc++;
}
return stop ? -1 : bpf_curr.R;
}
static int bpf_run_stepping(struct sock_filter *f, uint16_t bpf_len,
uint8_t *pkt, uint32_t pkt_caplen,
uint32_t pkt_len, int next)
{
bool stop = false;
int i = 1;
while (!bpf_curr.Rs && !stop) {
bpf_safe_regs();
if (i++ == next)
stop = bpf_handle_breakpoint(&bpf_curr, f, pkt,
pkt_caplen, pkt_len);
bpf_single_step(&bpf_curr, &f[bpf_curr.Pc], pkt, pkt_caplen,
pkt_len);
bpf_curr.Pc++;
}
return stop ? -1 : bpf_curr.R;
}
static bool pcap_loaded(void)
{
if (pcap_fd < 0)
rl_printf("no pcap file loaded!\n");
return pcap_fd >= 0;
}
static struct pcap_pkthdr *pcap_curr_pkt(void)
{
return (void *) pcap_ptr_va_curr;
}
static bool pcap_next_pkt(void)
{
struct pcap_pkthdr *hdr = pcap_curr_pkt();
if (pcap_ptr_va_curr + sizeof(*hdr) -
pcap_ptr_va_start >= pcap_map_size)
return false;
if (hdr->caplen == 0 || hdr->len == 0 || hdr->caplen > hdr->len)
return false;
if (pcap_ptr_va_curr + sizeof(*hdr) + hdr->caplen -
pcap_ptr_va_start >= pcap_map_size)
return false;
pcap_ptr_va_curr += (sizeof(*hdr) + hdr->caplen);
return true;
}
static void pcap_reset_pkt(void)
{
pcap_ptr_va_curr = pcap_ptr_va_start + sizeof(struct pcap_filehdr);
}
static int try_load_pcap(const char *file)
{
struct pcap_filehdr *hdr;
struct stat sb;
int ret;
pcap_fd = open(file, O_RDONLY);
if (pcap_fd < 0) {
rl_printf("cannot open pcap [%s]!\n", strerror(errno));
return CMD_ERR;
}
ret = fstat(pcap_fd, &sb);
if (ret < 0) {
rl_printf("cannot fstat pcap file!\n");
return CMD_ERR;
}
if (!S_ISREG(sb.st_mode)) {
rl_printf("not a regular pcap file, duh!\n");
return CMD_ERR;
}
pcap_map_size = sb.st_size;
if (pcap_map_size <= sizeof(struct pcap_filehdr)) {
rl_printf("pcap file too small!\n");
return CMD_ERR;
}
pcap_ptr_va_start = mmap(NULL, pcap_map_size, PROT_READ,
MAP_SHARED | MAP_LOCKED, pcap_fd, 0);
if (pcap_ptr_va_start == MAP_FAILED) {
rl_printf("mmap of file failed!");
return CMD_ERR;
}
hdr = (void *) pcap_ptr_va_start;
if (hdr->magic != TCPDUMP_MAGIC) {
rl_printf("wrong pcap magic!\n");
return CMD_ERR;
}
pcap_reset_pkt();
return CMD_OK;
}
static void try_close_pcap(void)
{
if (pcap_fd >= 0) {
munmap(pcap_ptr_va_start, pcap_map_size);
close(pcap_fd);
pcap_ptr_va_start = pcap_ptr_va_curr = NULL;
pcap_map_size = 0;
pcap_packet = 0;
pcap_fd = -1;
}
}
static int cmd_load_bpf(char *bpf_string)
{
char sp, *token, separator = ',';
unsigned short bpf_len, i = 0;
struct sock_filter tmp;
bpf_prog_len = 0;
memset(bpf_image, 0, sizeof(bpf_image));
if (sscanf(bpf_string, "%hu%c", &bpf_len, &sp) != 2 ||
sp != separator || bpf_len > BPF_MAXINSNS || bpf_len == 0) {
rl_printf("syntax error in head length encoding!\n");
return CMD_ERR;
}
token = bpf_string;
while ((token = strchr(token, separator)) && (++token)[0]) {
if (i >= bpf_len) {
rl_printf("program exceeds encoded length!\n");
return CMD_ERR;
}
if (sscanf(token, "%hu %hhu %hhu %u,",
&tmp.code, &tmp.jt, &tmp.jf, &tmp.k) != 4) {
rl_printf("syntax error at instruction %d!\n", i);
return CMD_ERR;
}
bpf_image[i].code = tmp.code;
bpf_image[i].jt = tmp.jt;
bpf_image[i].jf = tmp.jf;
bpf_image[i].k = tmp.k;
i++;
}
if (i != bpf_len) {
rl_printf("syntax error exceeding encoded length!\n");
return CMD_ERR;
} else
bpf_prog_len = bpf_len;
if (!bpf_runnable(bpf_image, bpf_prog_len))
bpf_prog_len = 0;
return CMD_OK;
}
static int cmd_load_pcap(char *file)
{
char *file_trim, *tmp;
file_trim = strtok_r(file, " ", &tmp);
if (file_trim == NULL)
return CMD_ERR;
try_close_pcap();
return try_load_pcap(file_trim);
}
static int cmd_load(char *arg)
{
char *subcmd, *cont = NULL, *tmp = strdup(arg);
int ret = CMD_OK;
subcmd = strtok_r(tmp, " ", &cont);
if (subcmd == NULL)
goto out;
if (matches(subcmd, "bpf") == 0) {
bpf_reset();
bpf_reset_breakpoints();
if (!cont)
ret = CMD_ERR;
else
ret = cmd_load_bpf(cont);
} else if (matches(subcmd, "pcap") == 0) {
ret = cmd_load_pcap(cont);
} else {
out:
rl_printf("bpf <code>: load bpf code\n");
rl_printf("pcap <file>: load pcap file\n");
ret = CMD_ERR;
}
free(tmp);
return ret;
}
static int cmd_step(char *num)
{
struct pcap_pkthdr *hdr;
int steps, ret;
if (!bpf_prog_loaded() || !pcap_loaded())
return CMD_ERR;
steps = strtol(num, NULL, 10);
if (steps == 0 || strlen(num) == 0)
steps = 1;
if (steps < 0) {
if (!bpf_restore_regs(steps))
return CMD_ERR;
steps = 1;
}
hdr = pcap_curr_pkt();
ret = bpf_run_stepping(bpf_image, bpf_prog_len,
(uint8_t *) hdr + sizeof(*hdr),
hdr->caplen, hdr->len, steps);
if (ret >= 0 || bpf_curr.Rs) {
bpf_reset();
if (!pcap_next_pkt()) {
rl_printf("(going back to first packet)\n");
pcap_reset_pkt();
} else {
rl_printf("(next packet)\n");
}
}
return CMD_OK;
}
static int cmd_select(char *num)
{
unsigned int which, i;
bool have_next = true;
if (!pcap_loaded() || strlen(num) == 0)
return CMD_ERR;
which = strtoul(num, NULL, 10);
if (which == 0) {
rl_printf("packet count starts with 1, clamping!\n");
which = 1;
}
pcap_reset_pkt();
bpf_reset();
for (i = 0; i < which && (have_next = pcap_next_pkt()); i++)
/* noop */;
if (!have_next || pcap_curr_pkt() == NULL) {
rl_printf("no packet #%u available!\n", which);
pcap_reset_pkt();
return CMD_ERR;
}
return CMD_OK;
}
static int cmd_breakpoint(char *subcmd)
{
if (!bpf_prog_loaded())
return CMD_ERR;
if (strlen(subcmd) == 0)
bpf_dump_breakpoints();
else if (matches(subcmd, "reset") == 0)
bpf_reset_breakpoints();
else {
unsigned int where = strtoul(subcmd, NULL, 10);
if (where < bpf_prog_len) {
bpf_set_breakpoints(where);
rl_printf("breakpoint at: ");
bpf_disasm(bpf_image[where], where);
}
}
return CMD_OK;
}
static int cmd_run(char *num)
{
static uint32_t pass, fail;
bool has_limit = true;
int pkts = 0, i = 0;
if (!bpf_prog_loaded() || !pcap_loaded())
return CMD_ERR;
pkts = strtol(num, NULL, 10);
if (pkts == 0 || strlen(num) == 0)
has_limit = false;
do {
struct pcap_pkthdr *hdr = pcap_curr_pkt();
int ret = bpf_run_all(bpf_image, bpf_prog_len,
(uint8_t *) hdr + sizeof(*hdr),
hdr->caplen, hdr->len);
if (ret > 0)
pass++;
else if (ret == 0)
fail++;
else
return CMD_OK;
bpf_reset();
} while (pcap_next_pkt() && (!has_limit || (++i < pkts)));
rl_printf("bpf passes:%u fails:%u\n", pass, fail);
pcap_reset_pkt();
bpf_reset();
pass = fail = 0;
return CMD_OK;
}
static int cmd_disassemble(char *line_string)
{
bool single_line = false;
unsigned long line;
if (!bpf_prog_loaded())
return CMD_ERR;
if (strlen(line_string) > 0 &&
(line = strtoul(line_string, NULL, 10)) < bpf_prog_len)
single_line = true;
if (single_line)
bpf_disasm(bpf_image[line], line);
else
bpf_disasm_all(bpf_image, bpf_prog_len);
return CMD_OK;
}
static int cmd_dump(char *dontcare)
{
if (!bpf_prog_loaded())
return CMD_ERR;
bpf_dump_all(bpf_image, bpf_prog_len);
return CMD_OK;
}
static int cmd_quit(char *dontcare)
{
return CMD_EX;
}
static const struct shell_cmd cmds[] = {
{ .name = "load", .func = cmd_load },
{ .name = "select", .func = cmd_select },
{ .name = "step", .func = cmd_step },
{ .name = "run", .func = cmd_run },
{ .name = "breakpoint", .func = cmd_breakpoint },
{ .name = "disassemble", .func = cmd_disassemble },
{ .name = "dump", .func = cmd_dump },
{ .name = "quit", .func = cmd_quit },
};
static int execf(char *arg)
{
char *cmd, *cont, *tmp = strdup(arg);
int i, ret = 0, len;
cmd = strtok_r(tmp, " ", &cont);
if (cmd == NULL)
goto out;
len = strlen(cmd);
for (i = 0; i < array_size(cmds); i++) {
if (len != strlen(cmds[i].name))
continue;
if (strncmp(cmds[i].name, cmd, len) == 0) {
ret = cmds[i].func(cont);
break;
}
}
out:
free(tmp);
return ret;
}
static char *shell_comp_gen(const char *buf, int state)
{
static int list_index, len;
if (!state) {
list_index = 0;
len = strlen(buf);
}
for (; list_index < array_size(cmds); ) {
const char *name = cmds[list_index].name;
list_index++;
if (strncmp(name, buf, len) == 0)
return strdup(name);
}
return NULL;
}
static char **shell_completion(const char *buf, int start, int end)
{
char **matches = NULL;
if (start == 0)
matches = rl_completion_matches(buf, shell_comp_gen);
return matches;
}
static void intr_shell(int sig)
{
if (rl_end)
rl_kill_line(-1, 0);
rl_crlf();
rl_refresh_line(0, 0);
rl_free_line_state();
}
static void init_shell(FILE *fin, FILE *fout)
{
char file[128];
snprintf(file, sizeof(file), "%s/.bpf_dbg_history", getenv("HOME"));
read_history(file);
rl_instream = fin;
rl_outstream = fout;
rl_readline_name = "bpf_dbg";
rl_terminal_name = getenv("TERM");
rl_catch_signals = 0;
rl_catch_sigwinch = 1;
rl_attempted_completion_function = shell_completion;
rl_bind_key('\t', rl_complete);
rl_bind_key_in_map('\t', rl_complete, emacs_meta_keymap);
rl_bind_key_in_map('\033', rl_complete, emacs_meta_keymap);
snprintf(file, sizeof(file), "%s/.bpf_dbg_init", getenv("HOME"));
rl_read_init_file(file);
rl_prep_terminal(0);
rl_set_signals();
signal(SIGINT, intr_shell);
}
static void exit_shell(FILE *fin, FILE *fout)
{
char file[128];
snprintf(file, sizeof(file), "%s/.bpf_dbg_history", getenv("HOME"));
write_history(file);
clear_history();
rl_deprep_terminal();
try_close_pcap();
if (fin != stdin)
fclose(fin);
if (fout != stdout)
fclose(fout);
}
static int run_shell_loop(FILE *fin, FILE *fout)
{
char *buf;
init_shell(fin, fout);
while ((buf = readline("> ")) != NULL) {
int ret = execf(buf);
if (ret == CMD_EX)
break;
if (ret == CMD_OK && strlen(buf) > 0)
add_history(buf);
free(buf);
}
exit_shell(fin, fout);
return 0;
}
int main(int argc, char **argv)
{
FILE *fin = NULL, *fout = NULL;
if (argc >= 2)
fin = fopen(argv[1], "r");
if (argc >= 3)
fout = fopen(argv[2], "w");
return run_shell_loop(fin ? : stdin, fout ? : stdout);
}
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