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Test for bpf_perf_link #88

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Test for bpf_perf_link #88

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03d18d6
bpftool: use a local copy of perf_event to fix accessing ::bpf_cookie
solbjorn Apr 21, 2022
53b62e9
bpftool: define a local bpf_perf_link to fix accessing its fields
solbjorn Apr 21, 2022
fa7db6b
bpftool: use a local bpf_perf_event_value to fix accessing its fields
solbjorn Apr 21, 2022
661d7c1
bpbtool: define BPF_LINK_TYPE_PERF_EVENT for kernels before 5.15
hramrach May 5, 2023
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21 changes: 17 additions & 4 deletions src/skeleton/pid_iter.bpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,19 @@ enum bpf_obj_type {
BPF_OBJ_BTF,
};

struct bpf_perf_link___local {
struct bpf_link link;
struct file *perf_file;
} __attribute__((preserve_access_index));

struct perf_event___local {
u64 bpf_cookie;
} __attribute__((preserve_access_index));

enum bpf_link_type___local {
BPF_LINK_TYPE_PERF_EVENT___local = 7,
};

extern const void bpf_link_fops __ksym;
extern const void bpf_map_fops __ksym;
extern const void bpf_prog_fops __ksym;
Expand All @@ -41,10 +54,10 @@ static __always_inline __u32 get_obj_id(void *ent, enum bpf_obj_type type)
/* could be used only with BPF_LINK_TYPE_PERF_EVENT links */
static __u64 get_bpf_cookie(struct bpf_link *link)
{
struct bpf_perf_link *perf_link;
struct perf_event *event;
struct bpf_perf_link___local *perf_link;
struct perf_event___local *event;

perf_link = container_of(link, struct bpf_perf_link, link);
perf_link = container_of(link, struct bpf_perf_link___local, link);
event = BPF_CORE_READ(perf_link, perf_file, private_data);
return BPF_CORE_READ(event, bpf_cookie);
}
Expand Down Expand Up @@ -87,7 +100,7 @@ int iter(struct bpf_iter__task_file *ctx)
if (obj_type == BPF_OBJ_LINK) {
struct bpf_link *link = (struct bpf_link *) file->private_data;

if (BPF_CORE_READ(link, type) == BPF_LINK_TYPE_PERF_EVENT) {
if (BPF_CORE_READ(link, type) == BPF_LINK_TYPE_PERF_EVENT___local) {
e.has_bpf_cookie = true;
e.bpf_cookie = get_bpf_cookie(link);
}
Expand Down
27 changes: 17 additions & 10 deletions src/skeleton/profiler.bpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,12 @@
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>

struct bpf_perf_event_value___local {
__u64 counter;
__u64 enabled;
__u64 running;
} __attribute__((preserve_access_index));

/* map of perf event fds, num_cpu * num_metric entries */
struct {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
Expand All @@ -15,14 +21,14 @@ struct {
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(key_size, sizeof(u32));
__uint(value_size, sizeof(struct bpf_perf_event_value));
__uint(value_size, sizeof(struct bpf_perf_event_value___local));
} fentry_readings SEC(".maps");

/* accumulated readings */
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(key_size, sizeof(u32));
__uint(value_size, sizeof(struct bpf_perf_event_value));
__uint(value_size, sizeof(struct bpf_perf_event_value___local));
} accum_readings SEC(".maps");

/* sample counts, one per cpu */
Expand All @@ -39,7 +45,7 @@ const volatile __u32 num_metric = 1;
SEC("fentry/XXX")
int BPF_PROG(fentry_XXX)
{
struct bpf_perf_event_value *ptrs[MAX_NUM_MATRICS];
struct bpf_perf_event_value___local *ptrs[MAX_NUM_MATRICS];
u32 key = bpf_get_smp_processor_id();
u32 i;

Expand All @@ -53,10 +59,10 @@ int BPF_PROG(fentry_XXX)
}

for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++) {
struct bpf_perf_event_value reading;
struct bpf_perf_event_value___local reading;
int err;

err = bpf_perf_event_read_value(&events, key, &reading,
err = bpf_perf_event_read_value(&events, key, (void *)&reading,
sizeof(reading));
if (err)
return 0;
Expand All @@ -68,14 +74,14 @@ int BPF_PROG(fentry_XXX)
}

static inline void
fexit_update_maps(u32 id, struct bpf_perf_event_value *after)
fexit_update_maps(u32 id, struct bpf_perf_event_value___local *after)
{
struct bpf_perf_event_value *before, diff;
struct bpf_perf_event_value___local *before, diff;

before = bpf_map_lookup_elem(&fentry_readings, &id);
/* only account samples with a valid fentry_reading */
if (before && before->counter) {
struct bpf_perf_event_value *accum;
struct bpf_perf_event_value___local *accum;

diff.counter = after->counter - before->counter;
diff.enabled = after->enabled - before->enabled;
Expand All @@ -93,7 +99,7 @@ fexit_update_maps(u32 id, struct bpf_perf_event_value *after)
SEC("fexit/XXX")
int BPF_PROG(fexit_XXX)
{
struct bpf_perf_event_value readings[MAX_NUM_MATRICS];
struct bpf_perf_event_value___local readings[MAX_NUM_MATRICS];
u32 cpu = bpf_get_smp_processor_id();
u32 i, zero = 0;
int err;
Expand All @@ -102,7 +108,8 @@ int BPF_PROG(fexit_XXX)
/* read all events before updating the maps, to reduce error */
for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++) {
err = bpf_perf_event_read_value(&events, cpu + i * num_cpu,
readings + i, sizeof(*readings));
(void *)(readings + i),
sizeof(*readings));
if (err)
return 0;
}
Expand Down