Commit a108f7dc authored by Jiri Olsa's avatar Jiri Olsa Committed by Alexei Starovoitov
Browse files

bpf: Add trampolines to kallsyms 



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: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200312195610.346362-11-jolsa@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent dba122fb

include/linux/bpf.h

+3 −0
Original line number Diff line number Diff line
@@ -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

kernel/bpf/trampoline.c

+28 −0
Original line number Diff line number Diff line
@@ -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 */

CRA Git | Maintained and supported by SUSTech CRA and CCSE