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bpf: Use percpu array to replace __sync_fetch_and_add #412

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Aug 8, 2024
Merged

bpf: Use percpu array to replace __sync_fetch_and_add #412

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78 changes: 39 additions & 39 deletions bpf/kprobe_pwru.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@


const static bool TRUE = true;
const static u32 ZERO = 0;

volatile const static __u64 BPF_PROG_ADDR = 0;

Expand Down Expand Up @@ -65,9 +66,6 @@ struct tuple {
u8 pad;
} __attribute__((packed));

u64 print_skb_id = 0;
u64 print_shinfo_id = 0;

enum event_type {
EVENT_TYPE_KPROBE = 0,
EVENT_TYPE_TC = 1,
Expand All @@ -81,8 +79,8 @@ struct event_t {
u64 caller_addr;
u64 skb_head;
u64 ts;
typeof(print_skb_id) print_skb_id;
typeof(print_shinfo_id) print_shinfo_id;
u64 print_skb_id;
u64 print_shinfo_id;
struct skb_meta meta;
struct tuple tuple;
s64 print_stack_id;
Expand Down Expand Up @@ -164,15 +162,27 @@ struct print_shinfo_value {
char str[PRINT_SHINFO_STR_SIZE];
};
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__uint(max_entries, 256);
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(max_entries, 1);
__type(key, u32);
__type(value, u32);
} print_skb_id_map SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 256);
__type(key, u64);
__type(value, struct print_skb_value);
} print_skb_map SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__uint(max_entries, 256);
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(max_entries, 1);
__type(key, u32);
__type(value, u32);
} print_shinfo_id_map SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 256);
__type(key, u64);
__type(value, struct print_shinfo_value);
} print_shinfo_map SEC(".maps");
#endif
Expand Down Expand Up @@ -312,45 +322,42 @@ set_tuple(struct sk_buff *skb, struct tuple *tpl) {
__set_tuple(tpl, skb_head, l3_off, is_ipv4);
}

static __always_inline u64
sync_fetch_and_add(void *id_map) {
u32 *id = bpf_map_lookup_elem(id_map, &ZERO);
if (id)
return ((*id)++) | ((u64)bpf_get_smp_processor_id() << 32);
return 0;
}

static __always_inline void
set_skb_btf(struct sk_buff *skb, typeof(print_skb_id) *event_id) {
set_skb_btf(struct sk_buff *skb, u64 *event_id) {
#ifdef OUTPUT_SKB
static struct btf_ptr p = {};
struct print_skb_value *v;
typeof(print_skb_id) id;
long n;
static struct print_skb_value v = {};
u64 id;

p.type_id = bpf_core_type_id_kernel(struct sk_buff);
p.ptr = skb;
id = __sync_fetch_and_add(&print_skb_id, 1) % 256;
*event_id = sync_fetch_and_add(&print_skb_id_map);

v = bpf_map_lookup_elem(&print_skb_map, (u32 *) &id);
if (!v) {
v.len = bpf_snprintf_btf(v.str, PRINT_SKB_STR_SIZE, &p, sizeof(p), 0);
if (v.len < 0) {
return;
}

n = bpf_snprintf_btf(v->str, PRINT_SKB_STR_SIZE, &p, sizeof(p), 0);
if (n < 0) {
return;
}

v->len = n;

*event_id = id;
bpf_map_update_elem(&print_skb_map, event_id, &v, BPF_ANY);
#endif
}

static __always_inline void
set_shinfo_btf(struct sk_buff *skb, typeof(print_shinfo_id) *event_id) {
set_shinfo_btf(struct sk_buff *skb, u64 *event_id) {
#ifdef OUTPUT_SKB
struct skb_shared_info *shinfo;
static struct btf_ptr p = {};
struct print_shinfo_value *v;
typeof(print_shinfo_id) id;
static struct print_shinfo_value v = {};
unsigned char *head;
unsigned int end;
long n;

/* skb_shared_info is located at the end of skb data.
* When CONFIG_NET_SKBUFF_DATA_USES_OFFSET is enabled, skb->end
Expand All @@ -366,21 +373,14 @@ set_shinfo_btf(struct sk_buff *skb, typeof(print_shinfo_id) *event_id) {
p.type_id = bpf_core_type_id_kernel(struct skb_shared_info);
p.ptr = shinfo;

id = __sync_fetch_and_add(&print_shinfo_id, 1) % 256;
*event_id = sync_fetch_and_add(&print_shinfo_id_map);

v = bpf_map_lookup_elem(&print_shinfo_map, (u32 *) &id);
if (!v) {
v.len = bpf_snprintf_btf(v.str, PRINT_SHINFO_STR_SIZE, &p, sizeof(p), 0);
if (v.len < 0) {
return;
}

n = bpf_snprintf_btf(v->str, PRINT_SHINFO_STR_SIZE, &p, sizeof(p), 0);
if (n < 0) {
return;
}

v->len = n;

*event_id = id;
bpf_map_update_elem(&print_shinfo_map, event_id, &v, BPF_ANY);
#endif
}

Expand Down
19 changes: 8 additions & 11 deletions internal/pwru/output.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@
package pwru

import (
"encoding/binary"
"encoding/json"
"errors"
"fmt"
Expand Down Expand Up @@ -287,39 +286,37 @@ func getStackData(event *Event, o *output) (stackData string) {
}

func getSkbData(event *Event, o *output) (skbData string) {
id := uint32(event.PrintSkbId)
id := uint64(event.PrintSkbId)

b, err := o.printSkbMap.LookupBytes(&id)
if err != nil {
return ""
}

length := binary.NativeEndian.Uint32(b[:4])
defer o.printSkbMap.Delete(&id)

// Bounds check
if int(length+4) > len(b) {
if len(b) < 4 {
return ""
}

return "\n" + string(b[4:4+length])
return "\n" + string(b[4:])
}

func getShinfoData(event *Event, o *output) (shinfoData string) {
id := uint32(event.PrintShinfoId)
id := uint64(event.PrintShinfoId)

b, err := o.printShinfoMap.LookupBytes(&id)
if err != nil {
return ""
}

length := binary.NativeEndian.Uint32(b[:4])
defer o.printShinfoMap.Delete(&id)

// Bounds check
if int(length+4) > len(b) {
if len(b) < 4 {
return ""
}

return "\n" + string(b[4:4+length])
return "\n" + string(b[4:])
}

func getMetaData(event *Event, o *output) (metaData string) {
Expand Down
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