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Diffstat (limited to '')
| -rw-r--r-- | tools/bpf/bpf_dbg.c | 1398 |
1 files changed, 1398 insertions, 0 deletions
diff --git a/tools/bpf/bpf_dbg.c b/tools/bpf/bpf_dbg.c new file mode 100644 index 000000000..a0ebcdf59 --- /dev/null +++ b/tools/bpf/bpf_dbg.c @@ -0,0 +1,1398 @@ +// 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 <borkmann@redhat.com> + */ + +#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); +} |