tracing: Use address-of operator on section symbols

Clang warns:

../kernel/trace/trace.c:9335:33: warning: array comparison always
evaluates to true [-Wtautological-compare]
        if (__stop___trace_bprintk_fmt != __start___trace_bprintk_fmt)
                                       ^
1 warning generated.

These are not true arrays, they are linker defined symbols, which are
just addresses. Using the address of operator silences the warning and
does not change the runtime result of the check (tested with some print
statements compiled in with clang + ld.lld and gcc + ld.bfd in QEMU).

Link: http://lkml.kernel.org/r/20200220051011.26113-1-natechancellor@gmail.com
Link: https://github.com/ClangBuiltLinux/linux/issues/893
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6b11e4e2150cea92de1f4c007efe4ea9c0c219e8..02be4ddd4ad5d2dff07ad52d6f1232ab49be691c 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9334,7 +9334,7 @@ __init static int tracer_alloc_buffers(void)
                goto out_free_buffer_mask;
 
        /* Only allocate trace_printk buffers if a trace_printk exists */
-       if (__stop___trace_bprintk_fmt != __start___trace_bprintk_fmt)
+       if (&__stop___trace_bprintk_fmt != &__start___trace_bprintk_fmt)
                /* Must be called before global_trace.buffer is allocated */
                trace_printk_init_buffers();