From cbd357008604925355ae7b54a09137dabb81b580 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Fri, 26 Sep 2014 00:17:03 -0700 Subject: bpf: verifier (add ability to receive verification log) add optional attributes for BPF_PROG_LOAD syscall: union bpf_attr { struct { ... __u32 log_level; /* verbosity level of eBPF verifier */ __u32 log_size; /* size of user buffer */ __aligned_u64 log_buf; /* user supplied 'char *buffer' */ }; }; when log_level > 0 the verifier will return its verification log in the user supplied buffer 'log_buf' which can be used by program author to analyze why verifier rejected given program. 'Understanding eBPF verifier messages' section of Documentation/networking/filter.txt provides several examples of these messages, like the program: BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0), BPF_MOV64_REG(BPF_REG_2, BPF_REG_10), BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8), BPF_LD_MAP_FD(BPF_REG_1, 0), BPF_CALL_FUNC(BPF_FUNC_map_lookup_elem), BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1), BPF_ST_MEM(BPF_DW, BPF_REG_0, 4, 0), BPF_EXIT_INSN(), will be rejected with the following multi-line message in log_buf: 0: (7a) *(u64 *)(r10 -8) = 0 1: (bf) r2 = r10 2: (07) r2 += -8 3: (b7) r1 = 0 4: (85) call 1 5: (15) if r0 == 0x0 goto pc+1 R0=map_ptr R10=fp 6: (7a) *(u64 *)(r0 +4) = 0 misaligned access off 4 size 8 The format of the output can change at any time as verifier evolves. Signed-off-by: Alexei Starovoitov Signed-off-by: David S. Miller --- include/uapi/linux/bpf.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include') diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 424f442016e7..31b0ac208a52 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -138,6 +138,9 @@ union bpf_attr { __u32 insn_cnt; __aligned_u64 insns; __aligned_u64 license; + __u32 log_level; /* verbosity level of verifier */ + __u32 log_size; /* size of user buffer */ + __aligned_u64 log_buf; /* user supplied buffer */ }; } __attribute__((aligned(8))); -- cgit v1.2.3