Fix broken --filter-trace-xdp caused by go-ebpf v0.17.1

There're two issue: One is `BPF_PROG_ADDR` must be set via `spec.Variable`. Another one is `.bss` map flag must be updated because go-ebpf v0.17.1 set `BPF_F_MMAPABLE` flag to created `.bss` map. As a result, we can reuse `.bss` map. Here's the test result: ```bash 2025/01/15 15:14:26 Attaching tc-bpf progs... 2025/01/15 15:14:26 Attaching xdp progs... 2025/01/15 15:14:26 Attaching kprobes (via kprobe)... 29 / 29 [--------------------------------------------------------------------------------------------------------------------------------------] 100.00% ? p/s 2025/01/15 15:14:26 Attached (ignored 0) 2025/01/15 15:14:26 Listening for events.. SKB CPU PROCESS NETNS MARK/x IFACE PROTO MTU LEN __sk_buff->cb[] TUPLE FUNC 0xffffb5dd40600b00 6 <empty>:0 4026531840 0 ens33:2 0x0000 1500 98 [0x00000000,0x00000000,0x00000000,0x00000000,0x00000000] 192.168.241.1:0->192.168.241.133:0(icmp) bpf_prog_3b185187f1855c4c_dummy[bpf](xdp) 0xffff995b7756d400 6 <empty>:0 4026531840 0 ens33:2 0x0800 1500 98 [0x00000000,0x00000000,0x00000000,0x00000000,0x00000000] 192.168.241.1:0->192.168.241.133:0(icmp) bpf_prog_e20a685998fd41c8_entry1[bpf](tc) 0xffff995b7756d400 6 <empty>:0 4026531840 0 ens33:2 0x0800 65536 64 [0x00000000,0x00000000,0x00000000,0x00000000,0x00000000] 192.168.241.1:0->192.168.241.133:0(icmp) icmp_rcv 0xffff995b7756d400 6 <empty>:0 4026531840 0 ens33:2 0x0800 65536 56 [0x00000000,0x00000000,0x00000000,0x00000000,0x00000000] 192.168.241.1:0->192.168.241.133:0(icmp) icmp_echo 0xffff995b7756d400 6 <empty>:0 4026531840 0 ens33:2 0x0800 65536 56 [0x00000000,0x00000000,0x00000000,0x00000000,0x00000000] 192.168.241.1:0->192.168.241.133:0(icmp) icmp_reply ^C2025/01/15 15:14:30 Received signal, exiting program.. 2025/01/15 15:14:30 Detaching kprobes... 29 / 29 [------------------------------------------------------------------------------------------------------------------------------------] 100.00% 132 p/s ``` And there's only one `.bss` map: ```bash 1 ``` Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>
cilium · Jan 15, 2025 · 49628ea · 49628ea
1 parent f383413
commit 49628ea
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Showing 2 changed files with 7 additions and 5 deletions.
diff --git a/bpf/kprobe_pwru.c b/bpf/kprobe_pwru.c
@@ -30,7 +30,7 @@
 const static bool TRUE = true;
 const static u32 ZERO = 0;
 
-volatile const static __u64 BPF_PROG_ADDR = 0;
+volatile const __u64 BPF_PROG_ADDR = 0;
 
 enum {
 	TRACKED_BY_FILTER = (1 << 0),

diff --git a/internal/pwru/tracing.go b/internal/pwru/tracing.go
@@ -92,10 +92,8 @@ func (t *tracing) traceProg(spec *ebpf.CollectionSpec,
 	}
 
 	spec = spec.Copy()
-	if err := spec.RewriteConstants(map[string]any{
-		"BPF_PROG_ADDR": addr,
-	}); err != nil {
-		return fmt.Errorf("failed to rewrite bpf prog addr: %w", err)
+	if err := spec.Variables["BPF_PROG_ADDR"].Set(addr); err != nil {
+		return fmt.Errorf("failed to set bpf prog addr: %w", err)
 	}
 
 	spec.Programs[tracingName].AttachTarget = prog
@@ -136,6 +134,10 @@ func (t *tracing) trace(coll *ebpf.Collection, spec *ebpf.CollectionSpec,
 	delete(replacedMaps, ".rodata")
 	opts.MapReplacements = replacedMaps
 
+	if m, ok := coll.Maps[".bss"]; ok && spec.Maps[".bss"].Flags != m.Flags() {
+		spec.Maps[".bss"].Flags = m.Flags()
+	}
+
 	var errg errgroup.Group
 
 	for _, prog := range progs {