On 6 May 2020, at 3:45, Alexei Starovoitov wrote:
On Wed, Apr 29, 2020 at 4:51 AM Eelco Chaudron <echaudro@xxxxxxxxxx> wrote:Hi Alexie at al. I was trying to attach a fentry/fexit trace to BPF_PROG_TYPE_EXT BPF program but I'm getting a verifier error, and not sure why. Is this supported?The intent was to make it possible. The verifier comment says:/* Cannot fentry/fexit another fentry/fexit program. * Cannot attach program extension to another extension. * It's ok to attach fentry/fexit to extension program.*/
I tried it with the freplace in the fexit_bpf2bpf.c test, and here it works fine.
This is the error: libbpf: -- BEGIN DUMP LOG --- libbpf: arg#0 type is not a struct Unrecognized arg#0 type PTRlooks like verifier got confused here. It should have detected correct btf_id from freplace prog. not sure what's going on.
This is an EXT BPF program using the, struct xdp_md *xdp, so not sure how to connect.
So I did try both: - int BPF_PROG(trace_on_entry, struct xdp_md *xdp) - int BPF_PROG(trace_on_entry, struct xdp_buff *xdp) This is the information from bpftool: ./bpftool prog show id 46 46: ext name xdp_test_I tag b5a46c6e9935298c gpl loaded_at 2020-05-13T08:54:53+0000 uid 0 xlated 136B jited 108B memlock 4096B btf_id 16 ./bpftool btf dump id 16 [1] PTR '(anon)' type_id=2 [2] STRUCT 'xdp_md' size=20 vlen=5 'data' type_id=3 bits_offset=0 'data_end' type_id=3 bits_offset=32 'data_meta' type_id=3 bits_offset=64 'ingress_ifindex' type_id=3 bits_offset=96 'rx_queue_index' type_id=3 bits_offset=128 [3] TYPEDEF '__u32' type_id=4 [4] INT 'unsigned int' size=4 bits_offset=0 nr_bits=32 encoding=(none) [5] FUNC_PROTO '(anon)' ret_type_id=6 vlen=1 'ctx' type_id=1 [6] INT 'int' size=4 bits_offset=0 nr_bits=32 encoding=SIGNED [7] FUNC 'xdp_test_I' type_id=5 linkage=global [8] INT 'char' size=1 bits_offset=0 nr_bits=8 encoding=SIGNED [9] ARRAY '(anon)' type_id=8 index_type_id=10 nr_elems=4[10] INT '__ARRAY_SIZE_TYPE__' size=4 bits_offset=0 nr_bits=32 encoding=(none)
[11] VAR '_license' type_id=9, linkage=global-alloc
[12] DATASEC 'license' size=4 vlen=1
type_id=11 offset=0 size=4
./bpftool prog dump xlated id 46
int xdp_test_I(struct xdp_md * ctx):
; int xdp_test_I(struct xdp_md *ctx)
0: (b7) r2 = 10
; bpf_debug("PASS[1]: prog %u\n", ctx->ingress_ifindex);
1: (6b) *(u16 *)(r10 -8) = r2
2: (18) r2 = 0x752520676f727020
4: (7b) *(u64 *)(r10 -16) = r2
5: (18) r2 = 0x3a5d315b53534150
7: (7b) *(u64 *)(r10 -24) = r2
8: (79) r3 = *(u64 *)(r1 +40)
9: (79) r3 = *(u64 *)(r3 +0)
10: (61) r3 = *(u32 *)(r3 +256)
11: (bf) r1 = r10
;
12: (07) r1 += -24
; bpf_debug("PASS[1]: prog %u\n", ctx->ingress_ifindex);
13: (b7) r2 = 18
14: (85) call bpf_trace_printk#-56048
; return XDP_PASS;
15: (b7) r0 = 2
16: (95) exit
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <xdp/xdp_helpers.h>
#define bpf_debug(fmt, ...) \
{ \
char __fmt[] = fmt; \
bpf_trace_printk(__fmt, sizeof(__fmt), \
##__VA_ARGS__); \
}
SEC("xdp_test_prog_I")
int xdp_test_I(struct xdp_md *ctx)
{
bpf_debug("PASS[1]: prog %u\n", ctx->ingress_ifindex);
return XDP_PASS;
}
Any idea??
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