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bpftool: Use a local bpf_perf_event_value to fix accessing its fields

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Fix the following error when building bpftool:

  CLANG   profiler.bpf.o
  CLANG   pid_iter.bpf.o
skeleton/profiler.bpf.c:18:21: error: invalid application of 'sizeof' to an incomplete type 'struct bpf_perf_event_value'
        __uint(value_size, sizeof(struct bpf_perf_event_value));
                           ^     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helpers.h:13:39: note: expanded from macro '__uint'
tools/bpf/bpftool/bootstrap/libbpf/include/bpf/bpf_helper_defs.h:7:8: note: forward declaration of 'struct bpf_perf_event_value'
struct bpf_perf_event_value;
       ^

struct bpf_perf_event_value is being used in the kernel only when
CONFIG_BPF_EVENTS is enabled, so it misses a BTF entry then.
Define struct bpf_perf_event_value___local with the
`preserve_access_index` attribute inside the pid_iter BPF prog to
allow compiling on any configs. It is a full mirror of a UAPI
structure, so is compatible both with and w/o CO-RE.
bpf_perf_event_read_value() requires a pointer of the original type,
so a cast is needed.

Fixes: 47c09d6a9f ("bpftool: Introduce "prog profile" command")
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230707095425.168126-5-quentin@isovalent.com
This commit is contained in:
Alexander Lobakin 2023-07-07 10:54:25 +01:00 • committed by Andrii Nakryiko
parent 44ba7b30e8
commit 658ac06801
1 changed files with 17 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

27
tools/bpf/bpftool/skeleton/profiler.bpf.c
View file

@ -4,6 +4,12 @@
#include <bpf/bpf_helpers.h> #include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.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 */ /* map of perf event fds, num_cpu * num_metric entries */
struct { struct {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY); __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
@ -15,14 +21,14 @@ struct {
struct { struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY); __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(key_size, sizeof(u32)); __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"); } fentry_readings SEC(".maps");
/* accumulated readings */ /* accumulated readings */
struct { struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY); __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(key_size, sizeof(u32)); __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"); } accum_readings SEC(".maps");
/* sample counts, one per cpu */ /* sample counts, one per cpu */
@ -39,7 +45,7 @@ const volatile __u32 num_metric = 1;
SEC("fentry/XXX") SEC("fentry/XXX")
int BPF_PROG(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 key = bpf_get_smp_processor_id();
u32 i; u32 i;
@ -53,10 +59,10 @@ int BPF_PROG(fentry_XXX)
} }
for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++) { 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; int err;
err = bpf_perf_event_read_value(&events, key, &reading, err = bpf_perf_event_read_value(&events, key, (void *)&reading,
sizeof(reading)); sizeof(reading));
if (err) if (err)
return 0; return 0;
@ -68,14 +74,14 @@ int BPF_PROG(fentry_XXX)
} }
static inline void 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); before = bpf_map_lookup_elem(&fentry_readings, &id);
/* only account samples with a valid fentry_reading */ /* only account samples with a valid fentry_reading */
if (before && before->counter) { if (before && before->counter) {
struct bpf_perf_event_value *accum; struct bpf_perf_event_value___local *accum;
diff.counter = after->counter - before->counter; diff.counter = after->counter - before->counter;
diff.enabled = after->enabled - before->enabled; diff.enabled = after->enabled - before->enabled;
@ -93,7 +99,7 @@ fexit_update_maps(u32 id, struct bpf_perf_event_value *after)
SEC("fexit/XXX") SEC("fexit/XXX")
int BPF_PROG(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 cpu = bpf_get_smp_processor_id();
u32 i, zero = 0; u32 i, zero = 0;
int err; int err;
@ -102,7 +108,8 @@ int BPF_PROG(fexit_XXX)
/* read all events before updating the maps, to reduce error */ /* read all events before updating the maps, to reduce error */
for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++) { for (i = 0; i < num_metric && i < MAX_NUM_MATRICS; i++) {
err = bpf_perf_event_read_value(&events, cpu + i * num_cpu, err = bpf_perf_event_read_value(&events, cpu + i * num_cpu,
readings + i, sizeof(*readings)); (void *)(readings + i),
sizeof(*readings));
if (err) if (err)
return 0; return 0;
} }