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| author | Alexei Starovoitov <ast@plumgrid.com> | 2015-05-20 01:59:05 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-05-21 23:07:59 +0200 |
| commit | 5bacd7805ab4f07a69c7ef4b1d45ce553d2b1c3a (patch) | |
| tree | 6e2b12a280e4431e2a5c3d971a8d3ebad4c0b5bc /samples/bpf/bpf_helpers.h | |
| parent | x86: bpf_jit: implement bpf_tail_call() helper (diff) | |
| download | linux-5bacd7805ab4f07a69c7ef4b1d45ce553d2b1c3a.tar.xz linux-5bacd7805ab4f07a69c7ef4b1d45ce553d2b1c3a.zip | |
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_helpers.h')
| -rw-r--r-- | samples/bpf/bpf_helpers.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/samples/bpf/bpf_helpers.h b/samples/bpf/bpf_helpers.h index f960b5fb3ed8..699ed8dbdd64 100644 --- a/samples/bpf/bpf_helpers.h +++ b/samples/bpf/bpf_helpers.h @@ -21,6 +21,8 @@ static unsigned long long (*bpf_ktime_get_ns)(void) = (void *) BPF_FUNC_ktime_get_ns; static int (*bpf_trace_printk)(const char *fmt, int fmt_size, ...) = (void *) BPF_FUNC_trace_printk; +static void (*bpf_tail_call)(void *ctx, void *map, int index) = + (void *) BPF_FUNC_tail_call; /* llvm builtin functions that eBPF C program may use to * emit BPF_LD_ABS and BPF_LD_IND instructions |