Commit e0d18fe0 authored by Namhyung Kim's avatar Namhyung Kim Committed by Steven Rostedt

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: default avatarkbuild test robot <fengguang.wu@intel.com>
Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent b7e0bf34
......@@ -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)
......
......@@ -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;
......
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