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Fix tracing tc-bpf with --filter-track-skb-by-stackid #452

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merged 1 commit into from
Nov 28, 2024
+24 −8
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Fix tracing tc-bpf with --filter-track-skb-by-stackid #452

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32 changes: 24 additions & 8 deletions bpf/kprobe_pwru.c
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Original file line number Diff line number Diff line change
Expand Up @@ -391,9 +391,25 @@ set_shinfo_btf(struct sk_buff *skb, u64 *event_id) {
}

static __always_inline u64
get_stackid(struct pt_regs *ctx) {
get_tracing_fp(void)
{
u64 fp;

/* get frame pointer */
asm volatile ("%[fp] = r10" : [fp] "+r"(fp) :);
return fp;
}

static __always_inline u64
get_kprobe_fp(struct pt_regs *ctx)
{
return PT_REGS_FP(ctx);
}

static __always_inline u64
get_stackid(void *ctx, const bool is_kprobe) {
u64 caller_fp;
u64 fp = PT_REGS_FP(ctx);
u64 fp = is_kprobe ? get_kprobe_fp(ctx) : get_tracing_fp();
for (int depth = 0; depth < MAX_STACK_DEPTH; depth++) {
if (bpf_probe_read_kernel(&caller_fp, sizeof(caller_fp), (void *)fp) < 0)
break;
Expand Down Expand Up @@ -436,8 +452,8 @@ handle_everything(struct sk_buff *skb, void *ctx, struct event_t *event, u64 *_s
u64 skb_head = (u64) BPF_CORE_READ(skb, head);
u64 stackid;

if (cfg->track_skb_by_stackid && is_kprobe)
stackid = _stackid ? *_stackid : get_stackid(ctx);
if (cfg->track_skb_by_stackid)
stackid = _stackid ? *_stackid : get_stackid(ctx, is_kprobe);

if (cfg->is_set) {
if (cfg->track_xdp && cfg->track_skb) {
Expand All @@ -453,7 +469,7 @@ handle_everything(struct sk_buff *skb, void *ctx, struct event_t *event, u64 *_s
goto cont;
}

if (cfg->track_skb_by_stackid && is_kprobe && bpf_map_lookup_elem(&stackid_skb, &stackid)) {
if (cfg->track_skb_by_stackid && bpf_map_lookup_elem(&stackid_skb, &stackid)) {
tracked_by = TRACKED_BY_STACKID;
goto cont;
}
Expand All @@ -475,7 +491,7 @@ handle_everything(struct sk_buff *skb, void *ctx, struct event_t *event, u64 *_s
bpf_map_update_elem(&xdp_dhs_skb_heads, &skb_head, &skb_addr, BPF_ANY);
}

if (cfg->track_skb_by_stackid && is_kprobe && tracked_by != TRACKED_BY_STACKID) {
if (cfg->track_skb_by_stackid && tracked_by != TRACKED_BY_STACKID) {
u64 *old_stackid = bpf_map_lookup_elem(&skb_stackid, &skb);
if (old_stackid && *old_stackid != stackid) {
bpf_map_delete_elem(&stackid_skb, old_stackid);
Expand Down Expand Up @@ -533,7 +549,7 @@ PWRU_ADD_KPROBE(5)

SEC("kprobe/skb_by_stackid")
int kprobe_skb_by_stackid(struct pt_regs *ctx) {
u64 stackid = get_stackid(ctx);
u64 stackid = get_stackid(ctx, true);

struct sk_buff **skb = bpf_map_lookup_elem(&stackid_skb, &stackid);
if (skb && *skb)
Expand All @@ -550,7 +566,7 @@ int kprobe_skb_lifetime_termination(struct pt_regs *ctx) {
bpf_map_delete_elem(&skb_addresses, &skb_addr);

if (cfg->track_skb_by_stackid) {
u64 stackid = get_stackid(ctx);
u64 stackid = get_stackid(ctx, true);
bpf_map_delete_elem(&stackid_skb, &stackid);
bpf_map_delete_elem(&skb_stackid, &skb_addr);
}
Expand Down
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