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authorAlexei Starovoitov <ast@plumgrid.com>2015-05-19 16:59:05 -0700
committerDavid S. Miller <davem@davemloft.net>2015-05-21 17:07:59 -0400
commit5bacd7805ab4f07a69c7ef4b1d45ce553d2b1c3a (patch)
tree6e2b12a280e4431e2a5c3d971a8d3ebad4c0b5bc /samples/bpf/bpf_load.c
parentb52f00e6a7154308a08d0a2edab621f277801a2c (diff)
downloadlinux-5bacd7805ab4f07a69c7ef4b1d45ce553d2b1c3a.tar.gz
samples/bpf: bpf_tail_call example for tracing
kprobe example that demonstrates how future seccomp programs may look like. It attaches to seccomp_phase1() function and tail-calls other BPF programs depending on syscall number. Existing optimized classic BPF seccomp programs generated by Chrome look like: if (sd.nr < 121) { if (sd.nr < 57) { if (sd.nr < 22) { if (sd.nr < 7) { if (sd.nr < 4) { if (sd.nr < 1) { check sys_read } else { if (sd.nr < 3) { check sys_write and sys_open } else { check sys_close } } } else { } else { } else { } else { } else { } the future seccomp using native eBPF may look like: bpf_tail_call(&sd, &syscall_jmp_table, sd.nr); which is simpler, faster and leaves more room for per-syscall checks. Usage: $ sudo ./tracex5 <...>-366 [001] d... 4.870033: : read(fd=1, buf=00007f6d5bebf000, size=771) <...>-369 [003] d... 4.870066: : mmap <...>-369 [003] d... 4.870077: : syscall=110 (one of get/set uid/pid/gid) <...>-369 [003] d... 4.870089: : syscall=107 (one of get/set uid/pid/gid) sh-369 [000] d... 4.891740: : read(fd=0, buf=00000000023d1000, size=512) sh-369 [000] d... 4.891747: : write(fd=1, buf=00000000023d3000, size=512) sh-369 [000] d... 4.891747: : read(fd=1, buf=00000000023d3000, size=512) Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'samples/bpf/bpf_load.c')
-rw-r--r--samples/bpf/bpf_load.c57
1 files changed, 45 insertions, 12 deletions
diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
index 38dac5a53b51..da86a8e0a95a 100644
--- a/samples/bpf/bpf_load.c
+++ b/samples/bpf/bpf_load.c
@@ -16,6 +16,7 @@
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <poll.h>
+#include <ctype.h>
#include "libbpf.h"
#include "bpf_helpers.h"
#include "bpf_load.h"
@@ -29,6 +30,19 @@ int map_fd[MAX_MAPS];
int prog_fd[MAX_PROGS];
int event_fd[MAX_PROGS];
int prog_cnt;
+int prog_array_fd = -1;
+
+static int populate_prog_array(const char *event, int prog_fd)
+{
+ int ind = atoi(event), err;
+
+ err = bpf_update_elem(prog_array_fd, &ind, &prog_fd, BPF_ANY);
+ if (err < 0) {
+ printf("failed to store prog_fd in prog_array\n");
+ return -1;
+ }
+ return 0;
+}
static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
{
@@ -54,12 +68,40 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
return -1;
}
+ fd = bpf_prog_load(prog_type, prog, size, license, kern_version);
+ if (fd < 0) {
+ printf("bpf_prog_load() err=%d\n%s", errno, bpf_log_buf);
+ return -1;
+ }
+
+ prog_fd[prog_cnt++] = fd;
+
+ if (is_socket) {
+ event += 6;
+ if (*event != '/')
+ return 0;
+ event++;
+ if (!isdigit(*event)) {
+ printf("invalid prog number\n");
+ return -1;
+ }
+ return populate_prog_array(event, fd);
+ }
+
if (is_kprobe || is_kretprobe) {
if (is_kprobe)
event += 7;
else
event += 10;
+ if (*event == 0) {
+ printf("event name cannot be empty\n");
+ return -1;
+ }
+
+ if (isdigit(*event))
+ return populate_prog_array(event, fd);
+
snprintf(buf, sizeof(buf),
"echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
is_kprobe ? 'p' : 'r', event, event);
@@ -71,18 +113,6 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
}
}
- fd = bpf_prog_load(prog_type, prog, size, license, kern_version);
-
- if (fd < 0) {
- printf("bpf_prog_load() err=%d\n%s", errno, bpf_log_buf);
- return -1;
- }
-
- prog_fd[prog_cnt++] = fd;
-
- if (is_socket)
- return 0;
-
strcpy(buf, DEBUGFS);
strcat(buf, "events/kprobes/");
strcat(buf, event);
@@ -130,6 +160,9 @@ static int load_maps(struct bpf_map_def *maps, int len)
maps[i].max_entries);
if (map_fd[i] < 0)
return 1;
+
+ if (maps[i].type == BPF_MAP_TYPE_PROG_ARRAY)
+ prog_array_fd = map_fd[i];
}
return 0;
}