[PATCH 14/18] bpf-preload: Switch to new preload registration method
From: Roberto Sassu <roberto.sassu@huawei.com>
Date: 2022-03-28 17:55:03
Also in:
bpf, linux-arm-kernel, linux-doc, linux-fsdevel, linux-integrity, linux-kselftest, linux-security-module, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [tooling] (bpftool), documentation, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Quentin Monnet, Jonathan Corbet, Linus Torvalds
Modify the automatic generator of the light skeleton by adding three calls to bpf_preload_set_ops() for registering and unregistering a preload method, two in load_skel() (set and unset if there is an error) and one in free_objs_and_skel(). Regenerate the light skeleton of the already preloaded eBPF program iterators_bpf, which will now use the new registration method, and directly call load_skel() and free_objs_and_skel() in the init and fini module entrypoints. Finally, allow users to specify a customized list of eBPF programs to preload with the CONFIG_BPF_PRELOAD_LIST option in the kernel configuration, at build time, or with new kernel option bpf_preload_list=, at run-time. By default, set CONFIG_BPF_PRELOAD_LIST to 'bpf_preload', so that the current preloading behavior is kept unchanged. Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> --- .../admin-guide/kernel-parameters.txt | 8 ++++++ kernel/bpf/inode.c | 16 ++++++++++-- kernel/bpf/preload/Kconfig | 25 +++++++++++++------ kernel/bpf/preload/bpf_preload_kern.c | 20 ++------------- .../bpf/preload/iterators/iterators.lskel.h | 9 +++++-- tools/bpf/bpftool/gen.c | 15 ++++++++--- 6 files changed, 60 insertions(+), 33 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 9927564db88e..732d83764e6e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt@@ -482,6 +482,14 @@ bgrt_disable [ACPI][X86] Disable BGRT to avoid flickering OEM logo. + bpf_preload_list= [BPF] + Specify a list of eBPF programs to preload. + Format: obj_name1,obj_name2,... + Default: bpf_preload + + Specify the list of eBPF programs to preload when the + bpf filesystem is mounted. + bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) bttv.radio= Most important insmod options are available as kernel args too.
diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 619cdef0ba54..c1941c65ce95 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c@@ -22,7 +22,14 @@ #include <linux/bpf_trace.h> #include <linux/bpf_preload.h> -static char *bpf_preload_list_str; +static char *bpf_preload_list_str = CONFIG_BPF_PRELOAD_LIST; + +static int __init bpf_preload_list_setup(char *str) +{ + bpf_preload_list_str = str; + return 1; +} +__setup("bpf_preload_list=", bpf_preload_list_setup); static void *bpf_any_get(void *raw, enum bpf_type type) {
@@ -732,7 +739,12 @@ static bool bpf_preload_list_mod_get(void) struct bpf_preload_ops_item *cur; bool ret = false; - ret |= bpf_preload_mod_get("bpf_preload", &bpf_preload_ops); + /* + * Keep the legacy registration method, but do not attempt to load + * bpf_preload.ko, as it switched to the new registration method. + */ + if (bpf_preload_ops) + ret |= bpf_preload_mod_get("bpf_preload", &bpf_preload_ops); list_for_each_entry(cur, &preload_list, list) ret |= bpf_preload_mod_get(cur->obj_name, &cur->ops);
diff --git a/kernel/bpf/preload/Kconfig b/kernel/bpf/preload/Kconfig
index c9d45c9d6918..f878e537b0ff 100644
--- a/kernel/bpf/preload/Kconfig
+++ b/kernel/bpf/preload/Kconfig@@ -4,7 +4,7 @@ config USERMODE_DRIVER default n menuconfig BPF_PRELOAD - bool "Preload BPF file system with kernel specific program and map iterators" + bool "Preload eBPF programs" depends on BPF depends on BPF_SYSCALL # The dependency on !COMPILE_TEST prevents it from being enabled
@@ -12,15 +12,26 @@ menuconfig BPF_PRELOAD depends on !COMPILE_TEST select USERMODE_DRIVER help - This builds kernel module with several embedded BPF programs that are - pinned into BPF FS mount point as human readable files that are - useful in debugging and introspection of BPF programs and maps. + This enables preloading eBPF programs chosen from the kernel + configuration or from the kernel option bpf_preload_list=. if BPF_PRELOAD config BPF_PRELOAD_UMD - tristate "bpf_preload kernel module" + tristate "Preload BPF file system with kernel specific program and map iterators" default m help - This builds bpf_preload kernel module with embedded BPF programs for - introspection in bpffs. + This builds bpf_preload kernel module with several embedded BPF + programs that are pinned into BPF FS mount point as human readable + files that are useful in debugging and introspection of BPF programs + and maps. + +config BPF_PRELOAD_LIST + string "Ordered list of eBPF programs to preload" + default "bpf_preload" + help + A comma-separated list of eBPF programs to preload. Any eBPF program + left off this list will be ignored. This can be controlled at boot + with the "bpf_preload_list=" parameter. + + If unsure, leave this as the default. endif
diff --git a/kernel/bpf/preload/bpf_preload_kern.c b/kernel/bpf/preload/bpf_preload_kern.c
index 3839af367200..c6d97872225b 100644
--- a/kernel/bpf/preload/bpf_preload_kern.c
+++ b/kernel/bpf/preload/bpf_preload_kern.c@@ -5,22 +5,6 @@ #include <linux/bpf_preload.h> #include "iterators/iterators.lskel.h" -static int __init load(void) -{ - int err; - - err = load_skel(); - if (err) - return err; - bpf_preload_ops = &ops; - return err; -} - -static void __exit fini(void) -{ - bpf_preload_ops = NULL; - free_objs_and_skel(); -} -late_initcall(load); -module_exit(fini); +late_initcall(load_skel); +module_exit(free_objs_and_skel); MODULE_LICENSE("GPL");
diff --git a/kernel/bpf/preload/iterators/iterators.lskel.h b/kernel/bpf/preload/iterators/iterators.lskel.h
index 7595fc283a65..5e999564cc7a 100644
--- a/kernel/bpf/preload/iterators/iterators.lskel.h
+++ b/kernel/bpf/preload/iterators/iterators.lskel.h@@ -440,6 +440,8 @@ static struct iterators_bpf *skel; static void free_objs_and_skel(void) { + bpf_preload_set_ops("bpf_preload", THIS_MODULE, NULL); + if (!IS_ERR_OR_NULL(dump_bpf_map_link)) bpf_link_put(dump_bpf_map_link); if (!IS_ERR_OR_NULL(dump_bpf_prog_link))
@@ -481,11 +483,14 @@ static struct bpf_preload_ops ops = { static int load_skel(void) { - int err; + int err = -ENOMEM; + + if (!bpf_preload_set_ops("bpf_preload", THIS_MODULE, &ops)) + return 0; skel = iterators_bpf__open(); if (!skel) - return -ENOMEM; + goto out; err = iterators_bpf__load(skel); if (err)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 5593cbee1846..af939183f57a 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c@@ -700,7 +700,10 @@ static void codegen_preload_free(struct bpf_object *obj, const char *obj_name) \n\ static void free_objs_and_skel(void) \n\ { \n\ - "); + bpf_preload_set_ops(\"%s\", THIS_MODULE, NULL); \n\ + \n\ + ", !strcmp(obj_name, "iterators_bpf") ? + "bpf_preload" : obj_name); bpf_object__for_each_program(prog, obj) { codegen("\
@@ -864,11 +867,14 @@ static void codegen_preload_load(struct bpf_object *obj, const char *obj_name) \n\ static int load_skel(void) \n\ { \n\ - int err; \n\ + int err = -ENOMEM; \n\ + \n\ + if (!bpf_preload_set_ops(\"%2$s\", THIS_MODULE, &ops)) \n\ + return 0; \n\ \n\ skel = %1$s__open(); \n\ if (!skel) \n\ - return -ENOMEM; \n\ + goto out; \n\ \n\ err = %1$s__load(skel); \n\ if (err) \n\
@@ -877,7 +883,8 @@ static void codegen_preload_load(struct bpf_object *obj, const char *obj_name) err = %1$s__attach(skel); \n\ if (err) \n\ goto out; \n\ - ", obj_name); + ", obj_name, !strcmp(obj_name, "iterators_bpf") ? + "bpf_preload" : obj_name); bpf_object__for_each_program(prog, obj) { codegen("\
--
2.32.0