From 4d56a76ead2fcd856e677cdc9445ad331a409b8c Mon Sep 17 00:00:00 2001 From: Sandipan Das Date: Thu, 24 May 2018 12:26:51 +0530 Subject: [PATCH] bpf: fix multi-function JITed dump obtained via syscall Currently, for multi-function programs, we cannot get the JITed instructions using the bpf system call's BPF_OBJ_GET_INFO_BY_FD command. Because of this, userspace tools such as bpftool fail to identify a multi-function program as being JITed or not. With the JIT enabled and the test program running, this can be verified as follows: # cat /proc/sys/net/core/bpf_jit_enable 1 Before applying this patch: # bpftool prog list 1: kprobe name foo tag b811aab41a39ad3d gpl loaded_at 2018-05-16T11:43:38+0530 uid 0 xlated 216B not jited memlock 65536B ... # bpftool prog dump jited id 1 no instructions returned After applying this patch: # bpftool prog list 1: kprobe name foo tag b811aab41a39ad3d gpl loaded_at 2018-05-16T12:13:01+0530 uid 0 xlated 216B jited 308B memlock 65536B ... # bpftool prog dump jited id 1 0: nop 4: nop 8: mflr r0 c: std r0,16(r1) 10: stdu r1,-112(r1) 14: std r31,104(r1) 18: addi r31,r1,48 1c: li r3,10 ... Signed-off-by: Sandipan Das Signed-off-by: Daniel Borkmann --- kernel/bpf/syscall.c | 37 ++++++++++++++++++++++++++++++++++--- 1 file changed, 34 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 068a4fc79ddb..c8e987a612b5 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1970,13 +1970,44 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog, * for offload. */ ulen = info.jited_prog_len; - info.jited_prog_len = prog->jited_len; + if (prog->aux->func_cnt) { + u32 i; + + info.jited_prog_len = 0; + for (i = 0; i < prog->aux->func_cnt; i++) + info.jited_prog_len += prog->aux->func[i]->jited_len; + } else { + info.jited_prog_len = prog->jited_len; + } + if (info.jited_prog_len && ulen) { if (bpf_dump_raw_ok()) { uinsns = u64_to_user_ptr(info.jited_prog_insns); ulen = min_t(u32, info.jited_prog_len, ulen); - if (copy_to_user(uinsns, prog->bpf_func, ulen)) - return -EFAULT; + + /* for multi-function programs, copy the JITed + * instructions for all the functions + */ + if (prog->aux->func_cnt) { + u32 len, free, i; + u8 *img; + + free = ulen; + for (i = 0; i < prog->aux->func_cnt; i++) { + len = prog->aux->func[i]->jited_len; + len = min_t(u32, len, free); + img = (u8 *) prog->aux->func[i]->bpf_func; + if (copy_to_user(uinsns, img, len)) + return -EFAULT; + uinsns += len; + free -= len; + if (!free) + break; + } + } else { + if (copy_to_user(uinsns, prog->bpf_func, ulen)) + return -EFAULT; + } } else { info.jited_prog_insns = 0; } -- 2.11.0