[PATCH 10/15] bpf: Add trampolines to kallsyms

Jiri Olsa
2020-03-12T19:57:14Z

Adding trampolines to kallsyms. It's displayed as
bpf_trampoline_<ID> [bpf]

where ID is the BTF id of the trampoline function.

Adding bpf_image_ksym_add/del functions that setup
the start/end values and call KSYMBOL perf events
handlers.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
include/linux/bpf.h | 3 +++
kernel/bpf/trampoline.c | 28 ++++++++++++++++++++++++++++
2 files changed, 31 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 83920cbce24c..7edbf30cf2b2 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -513,6 +513,7 @@ struct bpf_trampoline {
/* Executable image of trampoline */
void *image;
u64 selector;
+ struct bpf_ksym ksym;
};

#define BPF_DISPATCHER_MAX 48 /* Fits in 2048B */
@@ -585,6 +586,8 @@ struct bpf_image {
bool is_bpf_image_address(unsigned long address);
void *bpf_image_alloc(void);
/* Called only from JIT-enabled code, so there's no need for stubs. */
+void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym);
+void bpf_image_ksym_del(struct bpf_ksym *ksym);
void bpf_ksym_add(struct bpf_ksym *ksym);
void bpf_ksym_del(struct bpf_ksym *ksym);
#else
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 221a17af1f81..36549c9afec4 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -5,6 +5,7 @@
#include <linux/filter.h>
#include <linux/ftrace.h>
#include <linux/rbtree_latch.h>
+#include <linux/perf_event.h>

/* dummy _ops. The verifier will operate on target program's ops. */
const struct bpf_verifier_ops bpf_extension_verifier_ops = {
@@ -96,6 +97,30 @@ bool is_bpf_image_address(unsigned long addr)
return ret;
}

+void bpf_image_ksym_add(void *data, struct bpf_ksym *ksym)
+{
+ ksym->start = (unsigned long) data;
+ ksym->end = ksym->start + BPF_IMAGE_SIZE;
+ bpf_ksym_add(ksym);
+ perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
+ BPF_IMAGE_SIZE, false, ksym->name);
+}
+
+void bpf_image_ksym_del(struct bpf_ksym *ksym)
+{
+ bpf_ksym_del(ksym);
+ perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, ksym->start,
+ BPF_IMAGE_SIZE, true, ksym->name);
+}
+
+static void bpf_trampoline_ksym_add(struct bpf_trampoline *tr)
+{
+ struct bpf_ksym *ksym = &tr->ksym;
+
+ snprintf(ksym->name, KSYM_NAME_LEN, "bpf_trampoline_%llu", tr->key);
+ bpf_image_ksym_add(tr->image, ksym);
+}
+
struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
{
struct bpf_trampoline *tr;
@@ -131,6 +156,8 @@ struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
for (i = 0; i < BPF_TRAMP_MAX; i++)
INIT_HLIST_HEAD(&tr->progs_hlist[i]);
tr->image = image;
+ INIT_LIST_HEAD_RCU(&tr->ksym.lnode);
+ bpf_trampoline_ksym_add(tr);
out:
mutex_unlock(&trampoline_mutex);
return tr;
@@ -368,6 +395,7 @@ void bpf_trampoline_put(struct bpf_trampoline *tr)
goto out;
if (WARN_ON_ONCE(!hlist_empty(&tr->progs_hlist[BPF_TRAMP_FEXIT])))
goto out;
+ bpf_image_ksym_del(&tr->ksym);
image = container_of(tr->image, struct bpf_image, data);
latch_tree_erase(&image->tnode, &image_tree, &image_tree_ops);
/* wait for tasks to get out of trampoline before freeing it */
--
2.24.1