lkml.org 
[lkml]   [2014]   [Jan]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[for-next][PATCH] tracing/probes: Fix build break on !CONFIG_KPROBE_EVENT

git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
for-next

Head SHA1: e0d18fe063464cb3f1a6d1939e4fcf47d92d8386


Namhyung Kim (1):
tracing/probes: Fix build break on !CONFIG_KPROBE_EVENT

----
kernel/trace/trace_probe.h | 8 ++++++++
kernel/trace/trace_uprobe.c | 8 --------
2 files changed, 8 insertions(+), 8 deletions(-)
---------------------------
commit e0d18fe063464cb3f1a6d1939e4fcf47d92d8386
Author: Namhyung Kim <namhyung.kim@lge.com>
Date: Fri Jan 3 14:12:46 2014 +0900

tracing/probes: Fix build break on !CONFIG_KPROBE_EVENT

When kprobe-based dynamic event tracer is not enabled, it caused
following build error:

kernel/built-in.o: In function `traceprobe_update_arg':
(.text+0x10c8dd): undefined reference to `fetch_symbol_u8'
kernel/built-in.o: In function `traceprobe_update_arg':
(.text+0x10c8e9): undefined reference to `fetch_symbol_u16'
kernel/built-in.o: In function `traceprobe_update_arg':
(.text+0x10c8f5): undefined reference to `fetch_symbol_u32'
kernel/built-in.o: In function `traceprobe_update_arg':
(.text+0x10c901): undefined reference to `fetch_symbol_u64'
kernel/built-in.o: In function `traceprobe_update_arg':
(.text+0x10c909): undefined reference to `fetch_symbol_string'
kernel/built-in.o: In function `traceprobe_update_arg':
(.text+0x10c913): undefined reference to `fetch_symbol_string_size'
...

It was due to the fetch methods are referred from CHECK_FETCH_FUNCS
macro and since it was only defined in trace_kprobe.c. Move NULL
definition of such fetch functions to the header file.

Note, it also requires CONFIG_BRANCH_PROFILING enabled to trigger
this failure as well. This is because the "fetch_symbol_*" variables
are referenced in a "else if" statement that will only call
update_symbol_cache(), which is a static inline stub function
when CONFIG_KPROBE_EVENT is not enabled. gcc is smart enough
to optimize this "else if" out and that also removes the code that
references the undefined variables.

But when BRANCH_PROFILING is enabled, it fools gcc into keeping
the if statement around and thus references the undefined symbols
and fails to build.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index e29d743..b73574a 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -243,6 +243,14 @@ unsigned long update_symbol_cache(struct symbol_cache *sc);
void free_symbol_cache(struct symbol_cache *sc);
struct symbol_cache *alloc_symbol_cache(const char *sym, long offset);
#else
+/* uprobes do not support symbol fetch methods */
+#define fetch_symbol_u8 NULL
+#define fetch_symbol_u16 NULL
+#define fetch_symbol_u32 NULL
+#define fetch_symbol_u64 NULL
+#define fetch_symbol_string NULL
+#define fetch_symbol_string_size NULL
+
struct symbol_cache {
};
static inline unsigned long __used update_symbol_cache(struct symbol_cache *sc)
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 1fdea6d..79e52d9 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -172,14 +172,6 @@ static __kprobes void FETCH_FUNC_NAME(memory, string_size)(struct pt_regs *regs,
*(u32 *)dest = len;
}

-/* uprobes do not support symbol fetch methods */
-#define fetch_symbol_u8 NULL
-#define fetch_symbol_u16 NULL
-#define fetch_symbol_u32 NULL
-#define fetch_symbol_u64 NULL
-#define fetch_symbol_string NULL
-#define fetch_symbol_string_size NULL
-
static unsigned long translate_user_vaddr(void *file_offset)
{
unsigned long base_addr;

\
 
 \ /
  Last update: 2014-01-06 17:01    [W:0.039 / U:0.652 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site