Merge branch 'bpf: Speed up symbol resolving in kprobe multi link'

Jiri Olsa says:

====================

hi,
sending additional fix for symbol resolving in kprobe multi link
requested by Alexei and Andrii [1].

This speeds up bpftrace kprobe attachment, when using pure symbols
(3344 symbols) to attach:

Before:

  # perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* {  } i:ms:1 { exit(); }'
  ...
  6.5681 +- 0.0225 seconds time elapsed  ( +-  0.34% )

After:

  # perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* {  } i:ms:1 { exit(); }'
  ...
  0.5661 +- 0.0275 seconds time elapsed  ( +-  4.85% )

v6 changes:
  - rewrote patch 1 changelog and fixed the line length [Christoph]

v5 changes:
  - added acks [Masami]
  - workaround in selftest for RCU warning by filtering out several
    functions to attach

v4 changes:
  - fix compile issue [kernel test robot]
  - added acks [Andrii]

v3 changes:
  - renamed kallsyms_lookup_names to ftrace_lookup_symbols
    and moved it to ftrace.c [Masami]
  - added ack [Andrii]
  - couple small test fixes [Andrii]

v2 changes (first version [2]):
  - removed the 2 seconds check [Alexei]
  - moving/forcing symbols sorting out of kallsyms_lookup_names function [Alexei]
  - skipping one array allocation and copy_from_user [Andrii]
  - several small fixes [Masami,Andrii]
  - build fix [kernel test robot]

thanks,
jirka

[1] https://lore.kernel.org/bpf/CAEf4BzZtQaiUxQ-sm_hH2qKPRaqGHyOfEsW96DxtBHRaKLoL3Q@mail.gmail.com/
[2] https://lore.kernel.org/bpf/20220407125224.310255-1-jolsa@kernel.org/
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 12 insertions, 1 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 4816b7e11047..820500430eae 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -303,6 +303,8 @@ int unregister_ftrace_function(struct ftrace_ops *ops);
 extern void ftrace_stub(unsigned long a0, unsigned long a1,
 			struct ftrace_ops *op, struct ftrace_regs *fregs);
 
+
+int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs);
 #else /* !CONFIG_FUNCTION_TRACER */
 /*
  * (un)register_ftrace_function must be a macro since the ops parameter
@@ -313,6 +315,10 @@ extern void ftrace_stub(unsigned long a0, unsigned long a1,
 static inline void ftrace_kill(void) { }
 static inline void ftrace_free_init_mem(void) { }
 static inline void ftrace_free_mem(struct module *mod, void *start, void *end) { }
+static inline int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs)
+{
+	return -EOPNOTSUPP;
+}
 #endif /* CONFIG_FUNCTION_TRACER */
 
 struct ftrace_func_entry {
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index ce1bd2fbf23e..ad39636e0c3f 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -65,11 +65,11 @@ static inline void *dereference_symbol_descriptor(void *ptr)
 	return ptr;
 }
 
+#ifdef CONFIG_KALLSYMS
 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
 				      unsigned long),
 			    void *data);
 
-#ifdef CONFIG_KALLSYMS
 /* Lookup the address for a symbol. Returns 0 if not found. */
 unsigned long kallsyms_lookup_name(const char *name);
 
@@ -163,6 +163,11 @@ static inline bool kallsyms_show_value(const struct cred *cred)
 	return false;
 }
 
+static inline int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
+					  unsigned long), void *data)
+{
+	return -EOPNOTSUPP;
+}
 #endif /*CONFIG_KALLSYMS*/
 
 static inline void print_ip_sym(const char *loglvl, unsigned long ip)