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authorBjörn Töpel <bjorn.topel@intel.com>2019-12-13 20:51:08 +0300
committerAlexei Starovoitov <ast@kernel.org>2019-12-14 00:09:32 +0300
commit75ccbef6369e94ecac696a152a998a978d41376b (patch)
treec1d92822ed470de368dfe5a102af694ffb1ee7e3 /include/linux/bpf.h
parent98e8627efcada18ac043a77b9101b4b4c768090b (diff)
downloadlinux-75ccbef6369e94ecac696a152a998a978d41376b.tar.xz
bpf: Introduce BPF dispatcher
The BPF dispatcher is a multi-way branch code generator, mainly targeted for XDP programs. When an XDP program is executed via the bpf_prog_run_xdp(), it is invoked via an indirect call. The indirect call has a substantial performance impact, when retpolines are enabled. The dispatcher transform indirect calls to direct calls, and therefore avoids the retpoline. The dispatcher is generated using the BPF JIT, and relies on text poking provided by bpf_arch_text_poke(). The dispatcher hijacks a trampoline function it via the __fentry__ nop of the trampoline. One dispatcher instance currently supports up to 64 dispatch points. A user creates a dispatcher with its corresponding trampoline with the DEFINE_BPF_DISPATCHER macro. Signed-off-by: Björn Töpel <bjorn.topel@intel.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20191213175112.30208-3-bjorn.topel@gmail.com
Diffstat (limited to 'include/linux/bpf.h')
-rw-r--r--include/linux/bpf.h56
1 files changed, 56 insertions, 0 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 5d744828b399..53ae4a50abe4 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -470,12 +470,61 @@ struct bpf_trampoline {
void *image;
u64 selector;
};
+
+#define BPF_DISPATCHER_MAX 64 /* Fits in 2048B */
+
+struct bpf_dispatcher_prog {
+ struct bpf_prog *prog;
+ refcount_t users;
+};
+
+struct bpf_dispatcher {
+ /* dispatcher mutex */
+ struct mutex mutex;
+ void *func;
+ struct bpf_dispatcher_prog progs[BPF_DISPATCHER_MAX];
+ int num_progs;
+ void *image;
+ u32 image_off;
+};
+
#ifdef CONFIG_BPF_JIT
struct bpf_trampoline *bpf_trampoline_lookup(u64 key);
int bpf_trampoline_link_prog(struct bpf_prog *prog);
int bpf_trampoline_unlink_prog(struct bpf_prog *prog);
void bpf_trampoline_put(struct bpf_trampoline *tr);
void *bpf_jit_alloc_exec_page(void);
+#define BPF_DISPATCHER_INIT(name) { \
+ .mutex = __MUTEX_INITIALIZER(name.mutex), \
+ .func = &name##func, \
+ .progs = {}, \
+ .num_progs = 0, \
+ .image = NULL, \
+ .image_off = 0 \
+}
+
+#define DEFINE_BPF_DISPATCHER(name) \
+ noinline unsigned int name##func( \
+ const void *ctx, \
+ const struct bpf_insn *insnsi, \
+ unsigned int (*bpf_func)(const void *, \
+ const struct bpf_insn *)) \
+ { \
+ return bpf_func(ctx, insnsi); \
+ } \
+ EXPORT_SYMBOL(name##func); \
+ struct bpf_dispatcher name = BPF_DISPATCHER_INIT(name);
+#define DECLARE_BPF_DISPATCHER(name) \
+ unsigned int name##func( \
+ const void *ctx, \
+ const struct bpf_insn *insnsi, \
+ unsigned int (*bpf_func)(const void *, \
+ const struct bpf_insn *)); \
+ extern struct bpf_dispatcher name;
+#define BPF_DISPATCHER_FUNC(name) name##func
+#define BPF_DISPATCHER_PTR(name) (&name)
+void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from,
+ struct bpf_prog *to);
#else
static inline struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
{
@@ -490,6 +539,13 @@ static inline int bpf_trampoline_unlink_prog(struct bpf_prog *prog)
return -ENOTSUPP;
}
static inline void bpf_trampoline_put(struct bpf_trampoline *tr) {}
+#define DEFINE_BPF_DISPATCHER(name)
+#define DECLARE_BPF_DISPATCHER(name)
+#define BPF_DISPATCHER_FUNC(name) bpf_dispatcher_nopfunc
+#define BPF_DISPATCHER_PTR(name) NULL
+static inline void bpf_dispatcher_change_prog(struct bpf_dispatcher *d,
+ struct bpf_prog *from,
+ struct bpf_prog *to) {}
#endif
struct bpf_func_info_aux {