bpf: Add name to struct bpf_ksym

Adding name to 'struct bpf_ksym' object to carry the name
of the symbol for bpf_prog, bpf_trampoline, bpf_dispatcher
objects.

The current benefit is that name is now generated only when
the symbol is added to the list, so we don't need to generate
it every time it's accessed.

The future benefit is that we will have all the bpf objects
symbols represented by struct bpf_ksym.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200312195610.346362-5-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

4 files changed, 12 insertions, 14 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 6ca3d5c8ccf3..047b44deb3c5 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -18,6 +18,7 @@
 #include <linux/refcount.h>
 #include <linux/mutex.h>
 #include <linux/module.h>
+#include <linux/kallsyms.h>
 
 struct bpf_verifier_env;
 struct bpf_verifier_log;
@@ -474,6 +475,7 @@ void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start);
 struct bpf_ksym {
 	unsigned long		 start;
 	unsigned long		 end;
+	char			 name[KSYM_NAME_LEN];
 };
 
 enum bpf_tramp_prog_type {
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 6249679275b3..9b5aa5c483cc 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1083,7 +1083,6 @@ bpf_address_lookup(unsigned long addr, unsigned long *size,
 
 void bpf_prog_kallsyms_add(struct bpf_prog *fp);
 void bpf_prog_kallsyms_del(struct bpf_prog *fp);
-void bpf_get_prog_name(const struct bpf_prog *prog, char *sym);
 
 #else /* CONFIG_BPF_JIT */
 
@@ -1152,11 +1151,6 @@ static inline void bpf_prog_kallsyms_del(struct bpf_prog *fp)
 {
 }
 
-static inline void bpf_get_prog_name(const struct bpf_prog *prog, char *sym)
-{
-	sym[0] = '\0';
-}
-
 #endif /* CONFIG_BPF_JIT */
 
 void bpf_prog_kallsyms_del_all(struct bpf_prog *fp);
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index e587d6306d7c..f6800c2d4b01 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -535,8 +535,10 @@ bpf_prog_ksym_set_addr(struct bpf_prog *prog)
 	prog->aux->ksym.end   = addr + hdr->pages * PAGE_SIZE;
 }
 
-void bpf_get_prog_name(const struct bpf_prog *prog, char *sym)
+static void
+bpf_prog_ksym_set_name(struct bpf_prog *prog)
 {
+	char *sym = prog->aux->ksym.name;
 	const char *end = sym + KSYM_NAME_LEN;
 	const struct btf_type *type;
 	const char *func_name;
@@ -643,6 +645,7 @@ void bpf_prog_kallsyms_add(struct bpf_prog *fp)
 		return;
 
 	bpf_prog_ksym_set_addr(fp);
+	bpf_prog_ksym_set_name(fp);
 
 	spin_lock_bh(&bpf_lock);
 	bpf_prog_ksym_node_add(fp->aux);
@@ -681,7 +684,7 @@ const char *__bpf_address_lookup(unsigned long addr, unsigned long *size,
 		unsigned long symbol_start = prog->aux->ksym.start;
 		unsigned long symbol_end = prog->aux->ksym.end;
 
-		bpf_get_prog_name(prog, sym);
+		strncpy(sym, prog->aux->ksym.name, KSYM_NAME_LEN);
 
 		ret = sym;
 		if (size)
@@ -738,7 +741,7 @@ int bpf_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 		if (it++ != symnum)
 			continue;
 
-		bpf_get_prog_name(aux->prog, sym);
+		strncpy(sym, aux->ksym.name, KSYM_NAME_LEN);
 
 		*value = (unsigned long)aux->prog->bpf_func;
 		*type  = BPF_SYM_ELF_TYPE;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index bbdfac0182f4..9b89ef176247 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8255,23 +8255,22 @@ static void perf_event_bpf_emit_ksymbols(struct bpf_prog *prog,
 					 enum perf_bpf_event_type type)
 {
 	bool unregister = type == PERF_BPF_EVENT_PROG_UNLOAD;
-	char sym[KSYM_NAME_LEN];
 	int i;
 
 	if (prog->aux->func_cnt == 0) {
-		bpf_get_prog_name(prog, sym);
 		perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF,
 				   (u64)(unsigned long)prog->bpf_func,
-				   prog->jited_len, unregister, sym);
+				   prog->jited_len, unregister,
+				   prog->aux->ksym.name);
 	} else {
 		for (i = 0; i < prog->aux->func_cnt; i++) {
 			struct bpf_prog *subprog = prog->aux->func[i];
 
-			bpf_get_prog_name(subprog, sym);
 			perf_event_ksymbol(
 				PERF_RECORD_KSYMBOL_TYPE_BPF,
 				(u64)(unsigned long)subprog->bpf_func,
-				subprog->jited_len, unregister, sym);
+				subprog->jited_len, unregister,
+				prog->aux->ksym.name);
 		}
 	}
 }