[RFC PATCH net-next 2/6] x86: bpf_jit_comp: support BPF_S_ANC_SECCOMP_LD_W instruction

Xi Wang
2013-04-26T07:51:42Z

This patch implements the seccomp BPF_S_ANC_SECCOMP_LD_W instruction
in x86 JIT.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
---
arch/x86/net/bpf_jit_comp.c | 38 ++++++++++++++++++++++++++------------
1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index f66b540..03c9c81 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -8,10 +8,11 @@
* of the License.
*/
#include <linux/moduleloader.h>
-#include <asm/cacheflush.h>
#include <linux/netdevice.h>
#include <linux/filter.h>
#include <linux/if_vlan.h>
+#include <asm/cacheflush.h>
+#include <asm/syscall.h>

/*
* Conventions :
@@ -144,7 +145,7 @@ static int pkt_type_offset(void)
return -1;
}

-void bpf_jit_compile(struct sk_filter *fp)
+bpf_func_t bpf_jit_compile(struct sock_filter *filter, unsigned int flen)
{
u8 temp[64];
u8 *prog;
@@ -157,15 +158,14 @@ void bpf_jit_compile(struct sk_filter *fp)
int pc_ret0 = -1; /* bpf index of first RET #0 instruction (if any) */
unsigned int cleanup_addr; /* epilogue code offset */
unsigned int *addrs;
- const struct sock_filter *filter = fp->insns;
- int flen = fp->len;
+ bpf_func_t bpf_func = sk_run_filter;

if (!bpf_jit_enable)
- return;
+ return bpf_func;

addrs = kmalloc(flen * sizeof(*addrs), GFP_KERNEL);
if (addrs == NULL)
- return;
+ return bpf_func;

/* Before first pass, make a rough estimation of addrs[]
* each bpf instruction is translated to less than 64 bytes
@@ -684,6 +684,20 @@ cond_branch: f_offset = addrs[i + filter[i].jf] - addrs[i];
}
EMIT_COND_JMP(f_op, f_offset);
break;
+#ifdef CONFIG_SECCOMP_FILTER
+ case BPF_S_ANC_SECCOMP_LD_W:
+ if (K == offsetof(struct seccomp_data, arch)) {
+ int arch = syscall_get_arch(current, NULL);
+
+ EMIT1_off32(0xb8, arch); /* mov arch,%eax */
+ break;
+ }
+ func = (u8 *)seccomp_bpf_load;
+ t_offset = func - (image + addrs[i]);
+ EMIT1_off32(0xbf, K); /* mov imm32,%edi */
+ EMIT1_off32(0xe8, t_offset); /* call seccomp_bpf_load */
+ break;
+#endif
default:
/* hmm, too complex filter, give up with jit compiler */
goto out;
@@ -694,7 +708,7 @@ cond_branch: f_offset = addrs[i + filter[i].jf] - addrs[i];
pr_err("bpb_jit_compile fatal error\n");
kfree(addrs);
module_free(NULL, image);
- return;
+ return bpf_func;
}
memcpy(image + proglen, temp, ilen);
}
@@ -731,11 +745,11 @@ cond_branch: f_offset = addrs[i + filter[i].jf] - addrs[i];

if (image) {
bpf_flush_icache(image, image + proglen);
- fp->bpf_func = (void *)image;
+ bpf_func = (void *)image;
}
out:
kfree(addrs);
- return;
+ return bpf_func;
}

static void jit_free_defer(struct work_struct *arg)
@@ -746,10 +760,10 @@ static void jit_free_defer(struct work_struct *arg)
/* run from softirq, we must use a work_struct to call
* module_free() from process context
*/
-void bpf_jit_free(struct sk_filter *fp)
+void bpf_jit_free(bpf_func_t bpf_func)
{
- if (fp->bpf_func != sk_run_filter) {
- struct work_struct *work = (struct work_struct *)fp->bpf_func;
+ if (bpf_func != sk_run_filter) {
+ struct work_struct *work = (struct work_struct *)bpf_func;

INIT_WORK(work, jit_free_defer);
schedule_work(work);
--
1.8.1.2