* [PATCHv3 bpf-next 1/2] perf tools: Register fallback libbpf section handler
2022-06-03 9:21 [PATCHv3 bpf-next 0/3] perf tools: Fix prologue generation Jiri Olsa
@ 2022-06-03 9:21 ` Jiri Olsa
2022-06-03 9:21 ` [PATCHv3 bpf-next 2/2] perf tools: Rework prologue generation code Jiri Olsa
1 sibling, 0 replies; 5+ messages in thread
From: Jiri Olsa @ 2022-06-03 9:21 UTC (permalink / raw)
To: Arnaldo Carvalho de Melo, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko
Cc: linux-perf-users, netdev, bpf, Ingo Molnar, Namhyung Kim,
Alexander Shishkin, Peter Zijlstra, Martin KaFai Lau, Song Liu,
Yonghong Song, John Fastabend, Ian Rogers
Perf is using section name to declare special kprobe arguments,
which no longer works with current libbpf, that either requires
certain form of the section name or allows to register custom
handler.
Adding perf support to register 'fallback' section handler to take
care of perf kprobe programs. The fallback means that it handles
any section definition besides the ones that libbpf handles.
The handler serves two purposes:
- allows perf programs to have special arguments in section name
- allows perf to use pre-load callback where we can attach init
code (zeroing all argument registers) to each perf program
The second is essential part of new prologue generation code,
that's coming in following patch.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/perf/util/bpf-loader.c | 45 ++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index f8ad581ea247..e7992a0eb477 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -86,6 +86,7 @@ bpf_perf_object__next(struct bpf_perf_object *prev)
(perf_obj) = (tmp), (tmp) = bpf_perf_object__next(tmp))
static bool libbpf_initialized;
+static int libbpf_sec_handler;
static int bpf_perf_object__add(struct bpf_object *obj)
{
@@ -99,12 +100,56 @@ static int bpf_perf_object__add(struct bpf_object *obj)
return perf_obj ? 0 : -ENOMEM;
}
+static struct bpf_insn prologue_init_insn[] = {
+ BPF_MOV64_IMM(BPF_REG_2, 0),
+ BPF_MOV64_IMM(BPF_REG_3, 0),
+ BPF_MOV64_IMM(BPF_REG_4, 0),
+ BPF_MOV64_IMM(BPF_REG_5, 0),
+};
+
+static int libbpf_prog_prepare_load_fn(struct bpf_program *prog,
+ struct bpf_prog_load_opts *opts __maybe_unused,
+ long cookie __maybe_unused)
+{
+ size_t init_size_cnt = ARRAY_SIZE(prologue_init_insn);
+ size_t orig_insn_cnt, insn_cnt, init_size, orig_size;
+ const struct bpf_insn *orig_insn;
+ struct bpf_insn *insn;
+
+ /* prepend initialization code to program instructions */
+ orig_insn = bpf_program__insns(prog);
+ orig_insn_cnt = bpf_program__insn_cnt(prog);
+ init_size = init_size_cnt * sizeof(*insn);
+ orig_size = orig_insn_cnt * sizeof(*insn);
+
+ insn_cnt = orig_insn_cnt + init_size_cnt;
+ insn = malloc(insn_cnt * sizeof(*insn));
+ if (!insn)
+ return -ENOMEM;
+
+ memcpy(insn, prologue_init_insn, init_size);
+ memcpy((char *) insn + init_size, orig_insn, orig_size);
+ bpf_program__set_insns(prog, insn, insn_cnt);
+ return 0;
+}
+
static int libbpf_init(void)
{
+ LIBBPF_OPTS(libbpf_prog_handler_opts, handler_opts,
+ .prog_prepare_load_fn = libbpf_prog_prepare_load_fn,
+ );
+
if (libbpf_initialized)
return 0;
libbpf_set_print(libbpf_perf_print);
+ libbpf_sec_handler = libbpf_register_prog_handler(NULL, BPF_PROG_TYPE_KPROBE,
+ 0, &handler_opts);
+ if (libbpf_sec_handler < 0) {
+ pr_debug("bpf: failed to register libbpf section handler: %d\n",
+ libbpf_sec_handler);
+ return -BPF_LOADER_ERRNO__INTERNAL;
+ }
libbpf_initialized = true;
return 0;
}
--
2.35.3
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCHv3 bpf-next 2/2] perf tools: Rework prologue generation code
2022-06-03 9:21 [PATCHv3 bpf-next 0/3] perf tools: Fix prologue generation Jiri Olsa
2022-06-03 9:21 ` [PATCHv3 bpf-next 1/2] perf tools: Register fallback libbpf section handler Jiri Olsa
@ 2022-06-03 9:21 ` Jiri Olsa
2022-06-03 18:46 ` Andrii Nakryiko
1 sibling, 1 reply; 5+ messages in thread
From: Jiri Olsa @ 2022-06-03 9:21 UTC (permalink / raw)
To: Arnaldo Carvalho de Melo, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko
Cc: linux-perf-users, netdev, bpf, Ingo Molnar, Namhyung Kim,
Alexander Shishkin, Peter Zijlstra, Martin KaFai Lau, Song Liu,
Yonghong Song, John Fastabend, Ian Rogers
Some functions we use for bpf prologue generation are going to be
deprecated. This change reworks current code not to use them.
We need to replace following functions/struct:
bpf_program__set_prep
bpf_program__nth_fd
struct bpf_prog_prep_result
Currently we use bpf_program__set_prep to hook perf callback before
program is loaded and provide new instructions with the prologue.
We replace this function/ality by taking instructions for specific
program, attaching prologue to them and load such new ebpf programs
with prologue using separate bpf_prog_load calls (outside libbpf
load machinery).
Before we can take and use program instructions, we need libbpf to
actually load it. This way we get the final shape of its instructions
with all relocations and verifier adjustments).
There's one glitch though.. perf kprobe program already assumes
generated prologue code with proper values in argument registers,
so loading such program directly will fail in the verifier.
That's where the fallback pre-load handler fits in and prepends
the initialization code to the program. Once such program is loaded
we take its instructions, cut off the initialization code and prepend
the prologue.
I know.. sorry ;-)
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
tools/perf/util/bpf-loader.c | 128 ++++++++++++++++++++++++++++++-----
1 file changed, 110 insertions(+), 18 deletions(-)
diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index e7992a0eb477..2ce5f9684863 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -9,6 +9,7 @@
#include <linux/bpf.h>
#include <bpf/libbpf.h>
#include <bpf/bpf.h>
+#include <linux/filter.h>
#include <linux/err.h>
#include <linux/kernel.h>
#include <linux/string.h>
@@ -49,6 +50,7 @@ struct bpf_prog_priv {
struct bpf_insn *insns_buf;
int nr_types;
int *type_mapping;
+ int *proglogue_fds;
};
struct bpf_perf_object {
@@ -56,6 +58,11 @@ struct bpf_perf_object {
struct bpf_object *obj;
};
+struct bpf_preproc_result {
+ struct bpf_insn *new_insn_ptr;
+ int new_insn_cnt;
+};
+
static LIST_HEAD(bpf_objects_list);
static struct hashmap *bpf_program_hash;
static struct hashmap *bpf_map_hash;
@@ -233,14 +240,31 @@ struct bpf_object *bpf__prepare_load(const char *filename, bool source)
return obj;
}
+static void close_prologue_programs(struct bpf_prog_priv *priv)
+{
+ struct perf_probe_event *pev;
+ int i, fd;
+
+ if (!priv->need_prologue)
+ return;
+ pev = &priv->pev;
+ for (i = 0; i < pev->ntevs; i++) {
+ fd = priv->proglogue_fds[i];
+ if (fd != -1)
+ close(fd);
+ }
+}
+
static void
clear_prog_priv(const struct bpf_program *prog __maybe_unused,
void *_priv)
{
struct bpf_prog_priv *priv = _priv;
+ close_prologue_programs(priv);
cleanup_perf_probe_events(&priv->pev, 1);
zfree(&priv->insns_buf);
+ zfree(&priv->proglogue_fds);
zfree(&priv->type_mapping);
zfree(&priv->sys_name);
zfree(&priv->evt_name);
@@ -603,8 +627,8 @@ static int bpf__prepare_probe(void)
static int
preproc_gen_prologue(struct bpf_program *prog, int n,
- struct bpf_insn *orig_insns, int orig_insns_cnt,
- struct bpf_prog_prep_result *res)
+ const struct bpf_insn *orig_insns, int orig_insns_cnt,
+ struct bpf_preproc_result *res)
{
struct bpf_prog_priv *priv = program_priv(prog);
struct probe_trace_event *tev;
@@ -652,7 +676,6 @@ preproc_gen_prologue(struct bpf_program *prog, int n,
res->new_insn_ptr = buf;
res->new_insn_cnt = prologue_cnt + orig_insns_cnt;
- res->pfd = NULL;
return 0;
errout:
@@ -760,7 +783,7 @@ static int hook_load_preprocessor(struct bpf_program *prog)
struct bpf_prog_priv *priv = program_priv(prog);
struct perf_probe_event *pev;
bool need_prologue = false;
- int err, i;
+ int i;
if (IS_ERR_OR_NULL(priv)) {
pr_debug("Internal error when hook preprocessor\n");
@@ -798,6 +821,13 @@ static int hook_load_preprocessor(struct bpf_program *prog)
return -ENOMEM;
}
+ priv->proglogue_fds = malloc(sizeof(int) * pev->ntevs);
+ if (!priv->proglogue_fds) {
+ pr_debug("Not enough memory: alloc prologue fds failed\n");
+ return -ENOMEM;
+ }
+ memset(priv->proglogue_fds, -1, sizeof(int) * pev->ntevs);
+
priv->type_mapping = malloc(sizeof(int) * pev->ntevs);
if (!priv->type_mapping) {
pr_debug("Not enough memory: alloc type_mapping failed\n");
@@ -806,13 +836,7 @@ static int hook_load_preprocessor(struct bpf_program *prog)
memset(priv->type_mapping, -1,
sizeof(int) * pev->ntevs);
- err = map_prologue(pev, priv->type_mapping, &priv->nr_types);
- if (err)
- return err;
-
- err = bpf_program__set_prep(prog, priv->nr_types,
- preproc_gen_prologue);
- return err;
+ return map_prologue(pev, priv->type_mapping, &priv->nr_types);
}
int bpf__probe(struct bpf_object *obj)
@@ -919,6 +943,77 @@ int bpf__unprobe(struct bpf_object *obj)
return ret;
}
+static int bpf_object__load_prologue(struct bpf_object *obj)
+{
+ int init_cnt = ARRAY_SIZE(prologue_init_insn);
+ const struct bpf_insn *orig_insns;
+ struct bpf_preproc_result res;
+ struct perf_probe_event *pev;
+ struct bpf_program *prog;
+ int orig_insns_cnt;
+
+ bpf_object__for_each_program(prog, obj) {
+ struct bpf_prog_priv *priv = program_priv(prog);
+ int err, i, fd;
+
+ if (IS_ERR_OR_NULL(priv)) {
+ pr_debug("bpf: failed to get private field\n");
+ return -BPF_LOADER_ERRNO__INTERNAL;
+ }
+
+ if (!priv->need_prologue)
+ continue;
+
+ /*
+ * For each program that needs prologue we do following:
+ *
+ * - take its current instructions and use them
+ * to generate the new code with prologue
+ * - load new instructions with bpf_prog_load
+ * and keep the fd in proglogue_fds
+ * - new fd will be used in bpf__foreach_event
+ * to connect this program with perf evsel
+ */
+ orig_insns = bpf_program__insns(prog);
+ orig_insns_cnt = bpf_program__insn_cnt(prog);
+
+ pev = &priv->pev;
+ for (i = 0; i < pev->ntevs; i++) {
+ /*
+ * Skipping artificall prologue_init_insn instructions
+ * (init_cnt), so the prologue can be generated instead
+ * of them.
+ */
+ err = preproc_gen_prologue(prog, i,
+ orig_insns + init_cnt,
+ orig_insns_cnt - init_cnt,
+ &res);
+ if (err)
+ return err;
+
+ fd = bpf_prog_load(bpf_program__get_type(prog),
+ bpf_program__name(prog), "GPL",
+ res.new_insn_ptr,
+ res.new_insn_cnt, NULL);
+ if (fd < 0) {
+ char bf[128];
+
+ libbpf_strerror(-errno, bf, sizeof(bf));
+ pr_debug("bpf: load objects with prologue failed: err=%d: (%s)\n",
+ -errno, bf);
+ return -errno;
+ }
+ priv->proglogue_fds[i] = fd;
+ }
+ /*
+ * We no longer need the original program,
+ * we can unload it.
+ */
+ bpf_program__unload(prog);
+ }
+ return 0;
+}
+
int bpf__load(struct bpf_object *obj)
{
int err;
@@ -930,7 +1025,7 @@ int bpf__load(struct bpf_object *obj)
pr_debug("bpf: load objects failed: err=%d: (%s)\n", err, bf);
return err;
}
- return 0;
+ return bpf_object__load_prologue(obj);
}
int bpf__foreach_event(struct bpf_object *obj,
@@ -965,13 +1060,10 @@ int bpf__foreach_event(struct bpf_object *obj,
for (i = 0; i < pev->ntevs; i++) {
tev = &pev->tevs[i];
- if (priv->need_prologue) {
- int type = priv->type_mapping[i];
-
- fd = bpf_program__nth_fd(prog, type);
- } else {
+ if (priv->need_prologue)
+ fd = priv->proglogue_fds[i];
+ else
fd = bpf_program__fd(prog);
- }
if (fd < 0) {
pr_debug("bpf: failed to get file descriptor\n");
--
2.35.3
^ permalink raw reply related [flat|nested] 5+ messages in thread