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Linux/samples/bpf/bpf_load.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 #include <stdio.h>
  3 #include <sys/types.h>
  4 #include <sys/stat.h>
  5 #include <fcntl.h>
  6 #include <libelf.h>
  7 #include <gelf.h>
  8 #include <errno.h>
  9 #include <unistd.h>
 10 #include <string.h>
 11 #include <stdbool.h>
 12 #include <stdlib.h>
 13 #include <linux/bpf.h>
 14 #include <linux/filter.h>
 15 #include <linux/perf_event.h>
 16 #include <linux/netlink.h>
 17 #include <linux/rtnetlink.h>
 18 #include <linux/types.h>
 19 #include <sys/types.h>
 20 #include <sys/socket.h>
 21 #include <sys/syscall.h>
 22 #include <sys/ioctl.h>
 23 #include <sys/mman.h>
 24 #include <poll.h>
 25 #include <ctype.h>
 26 #include <assert.h>
 27 #include <bpf/bpf.h>
 28 #include "bpf_load.h"
 29 #include "perf-sys.h"
 30 
 31 #define DEBUGFS "/sys/kernel/debug/tracing/"
 32 
 33 static char license[128];
 34 static int kern_version;
 35 static bool processed_sec[128];
 36 char bpf_log_buf[BPF_LOG_BUF_SIZE];
 37 int map_fd[MAX_MAPS];
 38 int prog_fd[MAX_PROGS];
 39 int event_fd[MAX_PROGS];
 40 int prog_cnt;
 41 int prog_array_fd = -1;
 42 
 43 struct bpf_map_data map_data[MAX_MAPS];
 44 int map_data_count = 0;
 45 
 46 static int populate_prog_array(const char *event, int prog_fd)
 47 {
 48         int ind = atoi(event), err;
 49 
 50         err = bpf_map_update_elem(prog_array_fd, &ind, &prog_fd, BPF_ANY);
 51         if (err < 0) {
 52                 printf("failed to store prog_fd in prog_array\n");
 53                 return -1;
 54         }
 55         return 0;
 56 }
 57 
 58 static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
 59 {
 60         bool is_socket = strncmp(event, "socket", 6) == 0;
 61         bool is_kprobe = strncmp(event, "kprobe/", 7) == 0;
 62         bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0;
 63         bool is_tracepoint = strncmp(event, "tracepoint/", 11) == 0;
 64         bool is_raw_tracepoint = strncmp(event, "raw_tracepoint/", 15) == 0;
 65         bool is_xdp = strncmp(event, "xdp", 3) == 0;
 66         bool is_perf_event = strncmp(event, "perf_event", 10) == 0;
 67         bool is_cgroup_skb = strncmp(event, "cgroup/skb", 10) == 0;
 68         bool is_cgroup_sk = strncmp(event, "cgroup/sock", 11) == 0;
 69         bool is_sockops = strncmp(event, "sockops", 7) == 0;
 70         bool is_sk_skb = strncmp(event, "sk_skb", 6) == 0;
 71         bool is_sk_msg = strncmp(event, "sk_msg", 6) == 0;
 72         size_t insns_cnt = size / sizeof(struct bpf_insn);
 73         enum bpf_prog_type prog_type;
 74         char buf[256];
 75         int fd, efd, err, id;
 76         struct perf_event_attr attr = {};
 77 
 78         attr.type = PERF_TYPE_TRACEPOINT;
 79         attr.sample_type = PERF_SAMPLE_RAW;
 80         attr.sample_period = 1;
 81         attr.wakeup_events = 1;
 82 
 83         if (is_socket) {
 84                 prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
 85         } else if (is_kprobe || is_kretprobe) {
 86                 prog_type = BPF_PROG_TYPE_KPROBE;
 87         } else if (is_tracepoint) {
 88                 prog_type = BPF_PROG_TYPE_TRACEPOINT;
 89         } else if (is_raw_tracepoint) {
 90                 prog_type = BPF_PROG_TYPE_RAW_TRACEPOINT;
 91         } else if (is_xdp) {
 92                 prog_type = BPF_PROG_TYPE_XDP;
 93         } else if (is_perf_event) {
 94                 prog_type = BPF_PROG_TYPE_PERF_EVENT;
 95         } else if (is_cgroup_skb) {
 96                 prog_type = BPF_PROG_TYPE_CGROUP_SKB;
 97         } else if (is_cgroup_sk) {
 98                 prog_type = BPF_PROG_TYPE_CGROUP_SOCK;
 99         } else if (is_sockops) {
100                 prog_type = BPF_PROG_TYPE_SOCK_OPS;
101         } else if (is_sk_skb) {
102                 prog_type = BPF_PROG_TYPE_SK_SKB;
103         } else if (is_sk_msg) {
104                 prog_type = BPF_PROG_TYPE_SK_MSG;
105         } else {
106                 printf("Unknown event '%s'\n", event);
107                 return -1;
108         }
109 
110         fd = bpf_load_program(prog_type, prog, insns_cnt, license, kern_version,
111                               bpf_log_buf, BPF_LOG_BUF_SIZE);
112         if (fd < 0) {
113                 printf("bpf_load_program() err=%d\n%s", errno, bpf_log_buf);
114                 return -1;
115         }
116 
117         prog_fd[prog_cnt++] = fd;
118 
119         if (is_xdp || is_perf_event || is_cgroup_skb || is_cgroup_sk)
120                 return 0;
121 
122         if (is_socket || is_sockops || is_sk_skb || is_sk_msg) {
123                 if (is_socket)
124                         event += 6;
125                 else
126                         event += 7;
127                 if (*event != '/')
128                         return 0;
129                 event++;
130                 if (!isdigit(*event)) {
131                         printf("invalid prog number\n");
132                         return -1;
133                 }
134                 return populate_prog_array(event, fd);
135         }
136 
137         if (is_raw_tracepoint) {
138                 efd = bpf_raw_tracepoint_open(event + 15, fd);
139                 if (efd < 0) {
140                         printf("tracepoint %s %s\n", event + 15, strerror(errno));
141                         return -1;
142                 }
143                 event_fd[prog_cnt - 1] = efd;
144                 return 0;
145         }
146 
147         if (is_kprobe || is_kretprobe) {
148                 bool need_normal_check = true;
149                 const char *event_prefix = "";
150 
151                 if (is_kprobe)
152                         event += 7;
153                 else
154                         event += 10;
155 
156                 if (*event == 0) {
157                         printf("event name cannot be empty\n");
158                         return -1;
159                 }
160 
161                 if (isdigit(*event))
162                         return populate_prog_array(event, fd);
163 
164 #ifdef __x86_64__
165                 if (strncmp(event, "sys_", 4) == 0) {
166                         snprintf(buf, sizeof(buf),
167                                  "echo '%c:__x64_%s __x64_%s' >> /sys/kernel/debug/tracing/kprobe_events",
168                                  is_kprobe ? 'p' : 'r', event, event);
169                         err = system(buf);
170                         if (err >= 0) {
171                                 need_normal_check = false;
172                                 event_prefix = "__x64_";
173                         }
174                 }
175 #endif
176                 if (need_normal_check) {
177                         snprintf(buf, sizeof(buf),
178                                  "echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
179                                  is_kprobe ? 'p' : 'r', event, event);
180                         err = system(buf);
181                         if (err < 0) {
182                                 printf("failed to create kprobe '%s' error '%s'\n",
183                                        event, strerror(errno));
184                                 return -1;
185                         }
186                 }
187 
188                 strcpy(buf, DEBUGFS);
189                 strcat(buf, "events/kprobes/");
190                 strcat(buf, event_prefix);
191                 strcat(buf, event);
192                 strcat(buf, "/id");
193         } else if (is_tracepoint) {
194                 event += 11;
195 
196                 if (*event == 0) {
197                         printf("event name cannot be empty\n");
198                         return -1;
199                 }
200                 strcpy(buf, DEBUGFS);
201                 strcat(buf, "events/");
202                 strcat(buf, event);
203                 strcat(buf, "/id");
204         }
205 
206         efd = open(buf, O_RDONLY, 0);
207         if (efd < 0) {
208                 printf("failed to open event %s\n", event);
209                 return -1;
210         }
211 
212         err = read(efd, buf, sizeof(buf));
213         if (err < 0 || err >= sizeof(buf)) {
214                 printf("read from '%s' failed '%s'\n", event, strerror(errno));
215                 return -1;
216         }
217 
218         close(efd);
219 
220         buf[err] = 0;
221         id = atoi(buf);
222         attr.config = id;
223 
224         efd = sys_perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
225         if (efd < 0) {
226                 printf("event %d fd %d err %s\n", id, efd, strerror(errno));
227                 return -1;
228         }
229         event_fd[prog_cnt - 1] = efd;
230         err = ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
231         if (err < 0) {
232                 printf("ioctl PERF_EVENT_IOC_ENABLE failed err %s\n",
233                        strerror(errno));
234                 return -1;
235         }
236         err = ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd);
237         if (err < 0) {
238                 printf("ioctl PERF_EVENT_IOC_SET_BPF failed err %s\n",
239                        strerror(errno));
240                 return -1;
241         }
242 
243         return 0;
244 }
245 
246 static int load_maps(struct bpf_map_data *maps, int nr_maps,
247                      fixup_map_cb fixup_map)
248 {
249         int i, numa_node;
250 
251         for (i = 0; i < nr_maps; i++) {
252                 if (fixup_map) {
253                         fixup_map(&maps[i], i);
254                         /* Allow userspace to assign map FD prior to creation */
255                         if (maps[i].fd != -1) {
256                                 map_fd[i] = maps[i].fd;
257                                 continue;
258                         }
259                 }
260 
261                 numa_node = maps[i].def.map_flags & BPF_F_NUMA_NODE ?
262                         maps[i].def.numa_node : -1;
263 
264                 if (maps[i].def.type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
265                     maps[i].def.type == BPF_MAP_TYPE_HASH_OF_MAPS) {
266                         int inner_map_fd = map_fd[maps[i].def.inner_map_idx];
267 
268                         map_fd[i] = bpf_create_map_in_map_node(maps[i].def.type,
269                                                         maps[i].name,
270                                                         maps[i].def.key_size,
271                                                         inner_map_fd,
272                                                         maps[i].def.max_entries,
273                                                         maps[i].def.map_flags,
274                                                         numa_node);
275                 } else {
276                         map_fd[i] = bpf_create_map_node(maps[i].def.type,
277                                                         maps[i].name,
278                                                         maps[i].def.key_size,
279                                                         maps[i].def.value_size,
280                                                         maps[i].def.max_entries,
281                                                         maps[i].def.map_flags,
282                                                         numa_node);
283                 }
284                 if (map_fd[i] < 0) {
285                         printf("failed to create a map: %d %s\n",
286                                errno, strerror(errno));
287                         return 1;
288                 }
289                 maps[i].fd = map_fd[i];
290 
291                 if (maps[i].def.type == BPF_MAP_TYPE_PROG_ARRAY)
292                         prog_array_fd = map_fd[i];
293         }
294         return 0;
295 }
296 
297 static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname,
298                    GElf_Shdr *shdr, Elf_Data **data)
299 {
300         Elf_Scn *scn;
301 
302         scn = elf_getscn(elf, i);
303         if (!scn)
304                 return 1;
305 
306         if (gelf_getshdr(scn, shdr) != shdr)
307                 return 2;
308 
309         *shname = elf_strptr(elf, ehdr->e_shstrndx, shdr->sh_name);
310         if (!*shname || !shdr->sh_size)
311                 return 3;
312 
313         *data = elf_getdata(scn, 0);
314         if (!*data || elf_getdata(scn, *data) != NULL)
315                 return 4;
316 
317         return 0;
318 }
319 
320 static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
321                                 GElf_Shdr *shdr, struct bpf_insn *insn,
322                                 struct bpf_map_data *maps, int nr_maps)
323 {
324         int i, nrels;
325 
326         nrels = shdr->sh_size / shdr->sh_entsize;
327 
328         for (i = 0; i < nrels; i++) {
329                 GElf_Sym sym;
330                 GElf_Rel rel;
331                 unsigned int insn_idx;
332                 bool match = false;
333                 int j, map_idx;
334 
335                 gelf_getrel(data, i, &rel);
336 
337                 insn_idx = rel.r_offset / sizeof(struct bpf_insn);
338 
339                 gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym);
340 
341                 if (insn[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
342                         printf("invalid relo for insn[%d].code 0x%x\n",
343                                insn_idx, insn[insn_idx].code);
344                         return 1;
345                 }
346                 insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
347 
348                 /* Match FD relocation against recorded map_data[] offset */
349                 for (map_idx = 0; map_idx < nr_maps; map_idx++) {
350                         if (maps[map_idx].elf_offset == sym.st_value) {
351                                 match = true;
352                                 break;
353                         }
354                 }
355                 if (match) {
356                         insn[insn_idx].imm = maps[map_idx].fd;
357                 } else {
358                         printf("invalid relo for insn[%d] no map_data match\n",
359                                insn_idx);
360                         return 1;
361                 }
362         }
363 
364         return 0;
365 }
366 
367 static int cmp_symbols(const void *l, const void *r)
368 {
369         const GElf_Sym *lsym = (const GElf_Sym *)l;
370         const GElf_Sym *rsym = (const GElf_Sym *)r;
371 
372         if (lsym->st_value < rsym->st_value)
373                 return -1;
374         else if (lsym->st_value > rsym->st_value)
375                 return 1;
376         else
377                 return 0;
378 }
379 
380 static int load_elf_maps_section(struct bpf_map_data *maps, int maps_shndx,
381                                  Elf *elf, Elf_Data *symbols, int strtabidx)
382 {
383         int map_sz_elf, map_sz_copy;
384         bool validate_zero = false;
385         Elf_Data *data_maps;
386         int i, nr_maps;
387         GElf_Sym *sym;
388         Elf_Scn *scn;
389         int copy_sz;
390 
391         if (maps_shndx < 0)
392                 return -EINVAL;
393         if (!symbols)
394                 return -EINVAL;
395 
396         /* Get data for maps section via elf index */
397         scn = elf_getscn(elf, maps_shndx);
398         if (scn)
399                 data_maps = elf_getdata(scn, NULL);
400         if (!scn || !data_maps) {
401                 printf("Failed to get Elf_Data from maps section %d\n",
402                        maps_shndx);
403                 return -EINVAL;
404         }
405 
406         /* For each map get corrosponding symbol table entry */
407         sym = calloc(MAX_MAPS+1, sizeof(GElf_Sym));
408         for (i = 0, nr_maps = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) {
409                 assert(nr_maps < MAX_MAPS+1);
410                 if (!gelf_getsym(symbols, i, &sym[nr_maps]))
411                         continue;
412                 if (sym[nr_maps].st_shndx != maps_shndx)
413                         continue;
414                 /* Only increment iif maps section */
415                 nr_maps++;
416         }
417 
418         /* Align to map_fd[] order, via sort on offset in sym.st_value */
419         qsort(sym, nr_maps, sizeof(GElf_Sym), cmp_symbols);
420 
421         /* Keeping compatible with ELF maps section changes
422          * ------------------------------------------------
423          * The program size of struct bpf_load_map_def is known by loader
424          * code, but struct stored in ELF file can be different.
425          *
426          * Unfortunately sym[i].st_size is zero.  To calculate the
427          * struct size stored in the ELF file, assume all struct have
428          * the same size, and simply divide with number of map
429          * symbols.
430          */
431         map_sz_elf = data_maps->d_size / nr_maps;
432         map_sz_copy = sizeof(struct bpf_load_map_def);
433         if (map_sz_elf < map_sz_copy) {
434                 /*
435                  * Backward compat, loading older ELF file with
436                  * smaller struct, keeping remaining bytes zero.
437                  */
438                 map_sz_copy = map_sz_elf;
439         } else if (map_sz_elf > map_sz_copy) {
440                 /*
441                  * Forward compat, loading newer ELF file with larger
442                  * struct with unknown features. Assume zero means
443                  * feature not used.  Thus, validate rest of struct
444                  * data is zero.
445                  */
446                 validate_zero = true;
447         }
448 
449         /* Memcpy relevant part of ELF maps data to loader maps */
450         for (i = 0; i < nr_maps; i++) {
451                 struct bpf_load_map_def *def;
452                 unsigned char *addr, *end;
453                 const char *map_name;
454                 size_t offset;
455 
456                 map_name = elf_strptr(elf, strtabidx, sym[i].st_name);
457                 maps[i].name = strdup(map_name);
458                 if (!maps[i].name) {
459                         printf("strdup(%s): %s(%d)\n", map_name,
460                                strerror(errno), errno);
461                         free(sym);
462                         return -errno;
463                 }
464 
465                 /* Symbol value is offset into ELF maps section data area */
466                 offset = sym[i].st_value;
467                 def = (struct bpf_load_map_def *)(data_maps->d_buf + offset);
468                 maps[i].elf_offset = offset;
469                 memset(&maps[i].def, 0, sizeof(struct bpf_load_map_def));
470                 memcpy(&maps[i].def, def, map_sz_copy);
471 
472                 /* Verify no newer features were requested */
473                 if (validate_zero) {
474                         addr = (unsigned char*) def + map_sz_copy;
475                         end  = (unsigned char*) def + map_sz_elf;
476                         for (; addr < end; addr++) {
477                                 if (*addr != 0) {
478                                         free(sym);
479                                         return -EFBIG;
480                                 }
481                         }
482                 }
483         }
484 
485         free(sym);
486         return nr_maps;
487 }
488 
489 static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map)
490 {
491         int fd, i, ret, maps_shndx = -1, strtabidx = -1;
492         Elf *elf;
493         GElf_Ehdr ehdr;
494         GElf_Shdr shdr, shdr_prog;
495         Elf_Data *data, *data_prog, *data_maps = NULL, *symbols = NULL;
496         char *shname, *shname_prog;
497         int nr_maps = 0;
498 
499         /* reset global variables */
500         kern_version = 0;
501         memset(license, 0, sizeof(license));
502         memset(processed_sec, 0, sizeof(processed_sec));
503 
504         if (elf_version(EV_CURRENT) == EV_NONE)
505                 return 1;
506 
507         fd = open(path, O_RDONLY, 0);
508         if (fd < 0)
509                 return 1;
510 
511         elf = elf_begin(fd, ELF_C_READ, NULL);
512 
513         if (!elf)
514                 return 1;
515 
516         if (gelf_getehdr(elf, &ehdr) != &ehdr)
517                 return 1;
518 
519         /* clear all kprobes */
520         i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");
521 
522         /* scan over all elf sections to get license and map info */
523         for (i = 1; i < ehdr.e_shnum; i++) {
524 
525                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
526                         continue;
527 
528                 if (0) /* helpful for llvm debugging */
529                         printf("section %d:%s data %p size %zd link %d flags %d\n",
530                                i, shname, data->d_buf, data->d_size,
531                                shdr.sh_link, (int) shdr.sh_flags);
532 
533                 if (strcmp(shname, "license") == 0) {
534                         processed_sec[i] = true;
535                         memcpy(license, data->d_buf, data->d_size);
536                 } else if (strcmp(shname, "version") == 0) {
537                         processed_sec[i] = true;
538                         if (data->d_size != sizeof(int)) {
539                                 printf("invalid size of version section %zd\n",
540                                        data->d_size);
541                                 return 1;
542                         }
543                         memcpy(&kern_version, data->d_buf, sizeof(int));
544                 } else if (strcmp(shname, "maps") == 0) {
545                         int j;
546 
547                         maps_shndx = i;
548                         data_maps = data;
549                         for (j = 0; j < MAX_MAPS; j++)
550                                 map_data[j].fd = -1;
551                 } else if (shdr.sh_type == SHT_SYMTAB) {
552                         strtabidx = shdr.sh_link;
553                         symbols = data;
554                 }
555         }
556 
557         ret = 1;
558 
559         if (!symbols) {
560                 printf("missing SHT_SYMTAB section\n");
561                 goto done;
562         }
563 
564         if (data_maps) {
565                 nr_maps = load_elf_maps_section(map_data, maps_shndx,
566                                                 elf, symbols, strtabidx);
567                 if (nr_maps < 0) {
568                         printf("Error: Failed loading ELF maps (errno:%d):%s\n",
569                                nr_maps, strerror(-nr_maps));
570                         goto done;
571                 }
572                 if (load_maps(map_data, nr_maps, fixup_map))
573                         goto done;
574                 map_data_count = nr_maps;
575 
576                 processed_sec[maps_shndx] = true;
577         }
578 
579         /* process all relo sections, and rewrite bpf insns for maps */
580         for (i = 1; i < ehdr.e_shnum; i++) {
581                 if (processed_sec[i])
582                         continue;
583 
584                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
585                         continue;
586 
587                 if (shdr.sh_type == SHT_REL) {
588                         struct bpf_insn *insns;
589 
590                         /* locate prog sec that need map fixup (relocations) */
591                         if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
592                                     &shdr_prog, &data_prog))
593                                 continue;
594 
595                         if (shdr_prog.sh_type != SHT_PROGBITS ||
596                             !(shdr_prog.sh_flags & SHF_EXECINSTR))
597                                 continue;
598 
599                         insns = (struct bpf_insn *) data_prog->d_buf;
600                         processed_sec[i] = true; /* relo section */
601 
602                         if (parse_relo_and_apply(data, symbols, &shdr, insns,
603                                                  map_data, nr_maps))
604                                 continue;
605                 }
606         }
607 
608         /* load programs */
609         for (i = 1; i < ehdr.e_shnum; i++) {
610 
611                 if (processed_sec[i])
612                         continue;
613 
614                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
615                         continue;
616 
617                 if (memcmp(shname, "kprobe/", 7) == 0 ||
618                     memcmp(shname, "kretprobe/", 10) == 0 ||
619                     memcmp(shname, "tracepoint/", 11) == 0 ||
620                     memcmp(shname, "raw_tracepoint/", 15) == 0 ||
621                     memcmp(shname, "xdp", 3) == 0 ||
622                     memcmp(shname, "perf_event", 10) == 0 ||
623                     memcmp(shname, "socket", 6) == 0 ||
624                     memcmp(shname, "cgroup/", 7) == 0 ||
625                     memcmp(shname, "sockops", 7) == 0 ||
626                     memcmp(shname, "sk_skb", 6) == 0 ||
627                     memcmp(shname, "sk_msg", 6) == 0) {
628                         ret = load_and_attach(shname, data->d_buf,
629                                               data->d_size);
630                         if (ret != 0)
631                                 goto done;
632                 }
633         }
634 
635 done:
636         close(fd);
637         return ret;
638 }
639 
640 int load_bpf_file(char *path)
641 {
642         return do_load_bpf_file(path, NULL);
643 }
644 
645 int load_bpf_file_fixup_map(const char *path, fixup_map_cb fixup_map)
646 {
647         return do_load_bpf_file(path, fixup_map);
648 }
649 
650 void read_trace_pipe(void)
651 {
652         int trace_fd;
653 
654         trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
655         if (trace_fd < 0)
656                 return;
657 
658         while (1) {
659                 static char buf[4096];
660                 ssize_t sz;
661 
662                 sz = read(trace_fd, buf, sizeof(buf));
663                 if (sz > 0) {
664                         buf[sz] = 0;
665                         puts(buf);
666                 }
667         }
668 }
669 

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