mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-23 10:08:17 +07:00
5bacd7805a
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>
47 lines
973 B
C
47 lines
973 B
C
#include <stdio.h>
|
|
#include <linux/bpf.h>
|
|
#include <unistd.h>
|
|
#include <linux/filter.h>
|
|
#include <linux/seccomp.h>
|
|
#include <sys/prctl.h>
|
|
#include "libbpf.h"
|
|
#include "bpf_load.h"
|
|
|
|
/* install fake seccomp program to enable seccomp code path inside the kernel,
|
|
* so that our kprobe attached to seccomp_phase1() can be triggered
|
|
*/
|
|
static void install_accept_all_seccomp(void)
|
|
{
|
|
struct sock_filter filter[] = {
|
|
BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW),
|
|
};
|
|
struct sock_fprog prog = {
|
|
.len = (unsigned short)(sizeof(filter)/sizeof(filter[0])),
|
|
.filter = filter,
|
|
};
|
|
if (prctl(PR_SET_SECCOMP, 2, &prog))
|
|
perror("prctl");
|
|
}
|
|
|
|
int main(int ac, char **argv)
|
|
{
|
|
FILE *f;
|
|
char filename[256];
|
|
|
|
snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
|
|
|
|
if (load_bpf_file(filename)) {
|
|
printf("%s", bpf_log_buf);
|
|
return 1;
|
|
}
|
|
|
|
install_accept_all_seccomp();
|
|
|
|
f = popen("dd if=/dev/zero of=/dev/null count=5", "r");
|
|
(void) f;
|
|
|
|
read_trace_pipe();
|
|
|
|
return 0;
|
|
}
|