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authorAlexei Starovoitov <ast@fb.com>2017-12-14 17:55:15 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2017-12-17 20:34:36 +0100
commit1c2a088a6626d4f51d2f2c97b0cbedbfbf3637f6 (patch)
tree6c75f7e998315da2373f0953700c788f14807d69 /arch/x86/net
parent60b58afc96c9df71871df2dbad42037757ceef26 (diff)
bpf: x64: add JIT support for multi-function programs
Typical JIT does several passes over bpf instructions to compute total size and relative offsets of jumps and calls. With multitple bpf functions calling each other all relative calls will have invalid offsets intially therefore we need to additional last pass over the program to emit calls with correct offsets. For example in case of three bpf functions: main: call foo call bpf_map_lookup exit foo: call bar exit bar: exit We will call bpf_int_jit_compile() indepedently for main(), foo() and bar() x64 JIT typically does 4-5 passes to converge. After these initial passes the image for these 3 functions will be good except call targets, since start addresses of foo() and bar() are unknown when we were JITing main() (note that call bpf_map_lookup will be resolved properly during initial passes). Once start addresses of 3 functions are known we patch call_insn->imm to point to right functions and call bpf_int_jit_compile() again which needs only one pass. Additional safety checks are done to make sure this last pass doesn't produce image that is larger or smaller than previous pass. When constant blinding is on it's applied to all functions at the first pass, since doing it once again at the last pass can change size of the JITed code. Tested on x64 and arm64 hw with JIT on/off, blinding on/off. x64 jits bpf-to-bpf calls correctly while arm64 falls back to interpreter. All other JITs that support normal BPF_CALL will behave the same way since bpf-to-bpf call is equivalent to bpf-to-kernel call from JITs point of view. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'arch/x86/net')
-rw-r--r--arch/x86/net/bpf_jit_comp.c47
1 files changed, 44 insertions, 3 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 68859b58ab84..87f214fbe66e 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1109,13 +1109,23 @@ common_load:
return proglen;
}
+struct x64_jit_data {
+ struct bpf_binary_header *header;
+ int *addrs;
+ u8 *image;
+ int proglen;
+ struct jit_context ctx;
+};
+
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
{
struct bpf_binary_header *header = NULL;
struct bpf_prog *tmp, *orig_prog = prog;
+ struct x64_jit_data *jit_data;
int proglen, oldproglen = 0;
struct jit_context ctx = {};
bool tmp_blinded = false;
+ bool extra_pass = false;
u8 *image = NULL;
int *addrs;
int pass;
@@ -1135,10 +1145,28 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
prog = tmp;
}
+ jit_data = prog->aux->jit_data;
+ if (!jit_data) {
+ jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
+ if (!jit_data) {
+ prog = orig_prog;
+ goto out;
+ }
+ prog->aux->jit_data = jit_data;
+ }
+ addrs = jit_data->addrs;
+ if (addrs) {
+ ctx = jit_data->ctx;
+ oldproglen = jit_data->proglen;
+ image = jit_data->image;
+ header = jit_data->header;
+ extra_pass = true;
+ goto skip_init_addrs;
+ }
addrs = kmalloc(prog->len * sizeof(*addrs), GFP_KERNEL);
if (!addrs) {
prog = orig_prog;
- goto out;
+ goto out_addrs;
}
/* Before first pass, make a rough estimation of addrs[]
@@ -1149,6 +1177,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
addrs[i] = proglen;
}
ctx.cleanup_addr = proglen;
+skip_init_addrs:
/* JITed image shrinks with every pass and the loop iterates
* until the image stops shrinking. Very large bpf programs
@@ -1189,7 +1218,15 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
if (image) {
bpf_flush_icache(header, image + proglen);
- bpf_jit_binary_lock_ro(header);
+ if (!prog->is_func || extra_pass) {
+ bpf_jit_binary_lock_ro(header);
+ } else {
+ jit_data->addrs = addrs;
+ jit_data->ctx = ctx;
+ jit_data->proglen = proglen;
+ jit_data->image = image;
+ jit_data->header = header;
+ }
prog->bpf_func = (void *)image;
prog->jited = 1;
prog->jited_len = proglen;
@@ -1197,8 +1234,12 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
prog = orig_prog;
}
+ if (!prog->is_func || extra_pass) {
out_addrs:
- kfree(addrs);
+ kfree(addrs);
+ kfree(jit_data);
+ prog->aux->jit_data = NULL;
+ }
out:
if (tmp_blinded)
bpf_jit_prog_release_other(prog, prog == orig_prog ?