| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Daniel Borkmann | 6438 | 99.80% | 3 | 60.00% |
| John Fastabend | 12 | 0.19% | 1 | 20.00% |
| Brendan Hickey | 1 | 0.02% | 1 | 20.00% |
| Total | 6451 | 5 |
/* * 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.txt * 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 <borkmann@redhat.com> * Licensed under the GNU General Public License, version 2.0 (GPLv2) */ #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 == false && stop == false) { 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 || (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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