Commit 911c0359 authored by Martin KaFai Lau's avatar Martin KaFai Lau
Browse files

Merge branch 'allow-struct_ops-to-create-map-id-to' 

Amery Hung says:

====================
This patchset allows struct_ops implementors to get map id from kdata in
reg(), unreg() and update() so that they create an id to struct_ops
instance mapping. This in turn allows struct_ops kfuncs to refer to the
calling instance without passing a pointer to the struct_ops. The selftest
provides an end-to-end example.

Some struct_ops users extend themselves with other bpf programs, which
also need to call struct_ops kfuncs. For example, scx_layered uses
syscall bpf programs as a scx_layered specific control plane and uses
tracing programs to get additional information for scheduling [0].
The kfuncs may need to refer to the struct_ops instance and perform
jobs accordingly. To allow calling struct_ops kfuncs referring to
specific instances from different program types and context (e.g.,
struct_ops, tracing, async callbacks), the traditional way is to pass
the struct_ops pointer to kfuncs.

This patchset provides an alternative way, through a combination of
bpf map id and global variable. First, a struct_ops implementor will
use the map id of the struct_ops map as the id of an instance. Then,
it needs to maintain an id to instance mapping: inserting a new mapping
during reg() and removing it during unreg(). The map id can be acquired
by calling bpf_struct_ops_id().

v1 -> v2
    Add bpf_struct_ops_id() instead of using bpf_struct_ops_get()

[0] https://github.com/sched-ext/scx/blob/main/scheds/rust/scx_layered/src/bpf/main.bpf.c
====================

Link: https://patch.msgid.link/20250806162540.681679-1-ameryhung@gmail.com


Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
parents f3af62b6 ba7000f1

include/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -1985,6 +1985,7 @@ static inline void bpf_module_put(const void *data, struct module *owner) 
		module_put(owner);

}

int bpf_struct_ops_link_create(union bpf_attr *attr);

u32 bpf_struct_ops_id(const void *kdata);



#ifdef CONFIG_NET

/* Define it here to avoid the use of forward declaration */

kernel/bpf/bpf_struct_ops.c

+12 −0
Original line number Diff line number Diff line
@@ -1174,6 +1174,18 @@ void bpf_struct_ops_put(const void *kdata) 
	bpf_map_put(&st_map->map);

}



u32 bpf_struct_ops_id(const void *kdata)

{

	struct bpf_struct_ops_value *kvalue;

	struct bpf_struct_ops_map *st_map;



	kvalue = container_of(kdata, struct bpf_struct_ops_value, data);

	st_map = container_of(kvalue, struct bpf_struct_ops_map, kvalue);



	return st_map->map.id;

}

EXPORT_SYMBOL_GPL(bpf_struct_ops_id);



static bool bpf_struct_ops_valid_to_reg(struct bpf_map *map)

{

	struct bpf_struct_ops_map *st_map = (struct bpf_struct_ops_map *)map;

tools/testing/selftests/bpf/prog_tests/test_struct_ops_id_ops_mapping.c

0 → 100644
+74 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include <test_progs.h>

#include "struct_ops_id_ops_mapping1.skel.h"

#include "struct_ops_id_ops_mapping2.skel.h"



static void test_st_ops_id_ops_mapping(void)

{

	struct struct_ops_id_ops_mapping1 *skel1 = NULL;

	struct struct_ops_id_ops_mapping2 *skel2 = NULL;

	struct bpf_map_info info = {};

	__u32 len = sizeof(info);

	int err, pid, prog1_fd, prog2_fd;



	skel1 = struct_ops_id_ops_mapping1__open_and_load();

	if (!ASSERT_OK_PTR(skel1, "struct_ops_id_ops_mapping1__open"))

		goto out;



	skel2 = struct_ops_id_ops_mapping2__open_and_load();

	if (!ASSERT_OK_PTR(skel2, "struct_ops_id_ops_mapping2__open"))

		goto out;



	err = bpf_map_get_info_by_fd(bpf_map__fd(skel1->maps.st_ops_map),

				     &info, &len);

	if (!ASSERT_OK(err, "bpf_map_get_info_by_fd"))

		goto out;



	skel1->bss->st_ops_id = info.id;



	err = bpf_map_get_info_by_fd(bpf_map__fd(skel2->maps.st_ops_map),

				     &info, &len);

	if (!ASSERT_OK(err, "bpf_map_get_info_by_fd"))

		goto out;



	skel2->bss->st_ops_id = info.id;



	err = struct_ops_id_ops_mapping1__attach(skel1);

	if (!ASSERT_OK(err, "struct_ops_id_ops_mapping1__attach"))

		goto out;



	err = struct_ops_id_ops_mapping2__attach(skel2);

	if (!ASSERT_OK(err, "struct_ops_id_ops_mapping2__attach"))

		goto out;



	/* run tracing prog that calls .test_1 and checks return */

	pid = getpid();

	skel1->bss->test_pid = pid;

	skel2->bss->test_pid = pid;

	sys_gettid();

	skel1->bss->test_pid = 0;

	skel2->bss->test_pid = 0;



	/* run syscall_prog that calls .test_1 and checks return */

	prog1_fd = bpf_program__fd(skel1->progs.syscall_prog);

	err = bpf_prog_test_run_opts(prog1_fd, NULL);

	ASSERT_OK(err, "bpf_prog_test_run_opts");



	prog2_fd = bpf_program__fd(skel2->progs.syscall_prog);

	err = bpf_prog_test_run_opts(prog2_fd, NULL);

	ASSERT_OK(err, "bpf_prog_test_run_opts");



	ASSERT_EQ(skel1->bss->test_err, 0, "skel1->bss->test_err");

	ASSERT_EQ(skel2->bss->test_err, 0, "skel2->bss->test_err");



out:

	struct_ops_id_ops_mapping1__destroy(skel1);

	struct_ops_id_ops_mapping2__destroy(skel2);

}



void test_struct_ops_id_ops_mapping(void)

{

	if (test__start_subtest("st_ops_id_ops_mapping"))

		test_st_ops_id_ops_mapping();

}

tools/testing/selftests/bpf/progs/struct_ops_id_ops_mapping1.c

0 → 100644
+59 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include <vmlinux.h>

#include <bpf/bpf_tracing.h>

#include "bpf_misc.h"

#include "../test_kmods/bpf_testmod.h"

#include "../test_kmods/bpf_testmod_kfunc.h"



char _license[] SEC("license") = "GPL";



#define bpf_kfunc_multi_st_ops_test_1(args) bpf_kfunc_multi_st_ops_test_1(args, st_ops_id)

int st_ops_id;



int test_pid;

int test_err;



#define MAP1_MAGIC 1234



SEC("struct_ops")

int BPF_PROG(test_1, struct st_ops_args *args)

{

	return MAP1_MAGIC;

}



SEC("tp_btf/sys_enter")

int BPF_PROG(sys_enter, struct pt_regs *regs, long id)

{

	struct st_ops_args args = {};

	struct task_struct *task;

	int ret;



	task = bpf_get_current_task_btf();

	if (!test_pid || task->pid != test_pid)

		return 0;



	ret = bpf_kfunc_multi_st_ops_test_1(&args);

	if (ret != MAP1_MAGIC)

		test_err++;



	return 0;

}



SEC("syscall")

int syscall_prog(void *ctx)

{

	struct st_ops_args args = {};

	int ret;



	ret = bpf_kfunc_multi_st_ops_test_1(&args);

	if (ret != MAP1_MAGIC)

		test_err++;



	return 0;

}



SEC(".struct_ops.link")

struct bpf_testmod_multi_st_ops st_ops_map = {

	.test_1 = (void *)test_1,

};

tools/testing/selftests/bpf/progs/struct_ops_id_ops_mapping2.c

0 → 100644
+59 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0



#include <vmlinux.h>

#include <bpf/bpf_tracing.h>

#include "bpf_misc.h"

#include "../test_kmods/bpf_testmod.h"

#include "../test_kmods/bpf_testmod_kfunc.h"



char _license[] SEC("license") = "GPL";



#define bpf_kfunc_multi_st_ops_test_1(args) bpf_kfunc_multi_st_ops_test_1(args, st_ops_id)

int st_ops_id;



int test_pid;

int test_err;



#define MAP2_MAGIC 4567



SEC("struct_ops")

int BPF_PROG(test_1, struct st_ops_args *args)

{

	return MAP2_MAGIC;

}



SEC("tp_btf/sys_enter")

int BPF_PROG(sys_enter, struct pt_regs *regs, long id)

{

	struct st_ops_args args = {};

	struct task_struct *task;

	int ret;



	task = bpf_get_current_task_btf();

	if (!test_pid || task->pid != test_pid)

		return 0;



	ret = bpf_kfunc_multi_st_ops_test_1(&args);

	if (ret != MAP2_MAGIC)

		test_err++;



	return 0;

}



SEC("syscall")

int syscall_prog(void *ctx)

{

	struct st_ops_args args = {};

	int ret;



	ret = bpf_kfunc_multi_st_ops_test_1(&args);

	if (ret != MAP2_MAGIC)

		test_err++;



	return 0;

}



SEC(".struct_ops.link")

struct bpf_testmod_multi_st_ops st_ops_map = {

	.test_1 = (void *)test_1,

};