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seccomp: JIT compile seccomp filter 

Take advantage of internal BPF JIT

05-sim-long_jumps.c of libseccomp was used as micro-benchmark:

 seccomp_rule_add_exact(ctx,...
 seccomp_rule_add_exact(ctx,...

 rc = seccomp_load(ctx);

 for (i = 0; i < 10000000; i++)
    syscall(...);

$ sudo sysctl net.core.bpf_jit_enable=1
$ time ./bench
real	0m2.769s
user	0m1.136s
sys	0m1.624s

$ sudo sysctl net.core.bpf_jit_enable=0
$ time ./bench
real	0m5.825s
user	0m1.268s
sys	0m4.548s

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov 2014-05-13 19:50:47 -07:00 committed by David S. Miller
parent 622582786c
commit 8f577cadf7
1 changed files with 20 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
kernel/seccomp.c
View File

@ -54,8 +54,7 @@
struct seccomp_filter {
atomic_t usage;
struct seccomp_filter *prev;
unsigned short len; /* Instruction count */
struct sock_filter_int insnsi[];
struct sk_filter *prog;
};
/* Limit any path through the tree to 256KB worth of instructions. */
@ -189,7 +188,8 @@ static u32 seccomp_run_filters(int syscall)
* value always takes priority (ignoring the DATA).
*/
for (f = current->seccomp.filter; f; f = f->prev) {
u32 cur_ret = sk_run_filter_int_seccomp(&sd, f->insnsi);
u32 cur_ret = SK_RUN_FILTER(f->prog, (void *)&sd);
if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION))
ret = cur_ret;
}
@ -215,7 +215,7 @@ static long seccomp_attach_filter(struct sock_fprog *fprog)
return -EINVAL;
for (filter = current->seccomp.filter; filter; filter = filter->prev)
total_insns += filter->len + 4; /* include a 4 instr penalty */
total_insns += filter->prog->len + 4; /* include a 4 instr penalty */
if (total_insns > MAX_INSNS_PER_PATH)
return -ENOMEM;
@ -256,19 +256,27 @@ static long seccomp_attach_filter(struct sock_fprog *fprog)
/* Allocate a new seccomp_filter */
ret = -ENOMEM;
filter = kzalloc(sizeof(struct seccomp_filter) +
sizeof(struct sock_filter_int) * new_len,
filter = kzalloc(sizeof(struct seccomp_filter),
GFP_KERNEL|__GFP_NOWARN);
if (!filter)
goto free_prog;
ret = sk_convert_filter(fp, fprog->len, filter->insnsi, &new_len);
if (ret)
filter->prog = kzalloc(sk_filter_size(new_len),
GFP_KERNEL|__GFP_NOWARN);
if (!filter->prog)
goto free_filter;
ret = sk_convert_filter(fp, fprog->len, filter->prog->insnsi, &new_len);
if (ret)
goto free_filter_prog;
kfree(fp);
atomic_set(&filter->usage, 1);
filter->len = new_len;
filter->prog->len = new_len;
filter->prog->bpf_func = (void *)sk_run_filter_int_seccomp;
/* JIT internal BPF into native HW instructions */
bpf_int_jit_compile(filter->prog);
/*
* If there is an existing filter, make it the prev and don't drop its
@ -278,6 +286,8 @@ static long seccomp_attach_filter(struct sock_fprog *fprog)
current->seccomp.filter = filter;
return 0;
free_filter_prog:
kfree(filter->prog);
free_filter:
kfree(filter);
free_prog:
@ -330,6 +340,7 @@ void put_seccomp_filter(struct task_struct *tsk)
while (orig && atomic_dec_and_test(&orig->usage)) {
struct seccomp_filter *freeme = orig;
orig = orig->prev;
bpf_jit_free(freeme->prog);
kfree(freeme);
}
}