fgraph: Fix function type mismatches of ftrace_graph_return using ftrace_stub
authorSteven Rostedt (VMware) <rostedt@goodmis.org>
Tue, 15 Oct 2019 13:00:55 +0000 (09:00 -0400)
committerSteven Rostedt (VMware) <rostedt@goodmis.org>
Thu, 14 Nov 2019 18:13:43 +0000 (13:13 -0500)
commitb83b43ffc6e4b514ca034a0fbdee01322e2f7022
tree8e8d830664e6faf98589f241bd0ccba44802f8c8
parent953ae45a0c25e09428d4a03d7654f97ab8a36647
fgraph: Fix function type mismatches of ftrace_graph_return using ftrace_stub

The C compiler is allowing more checks to make sure that function pointers
are assigned to the correct prototype function. Unfortunately, the function
graph tracer uses a special name with its assigned ftrace_graph_return
function pointer that maps to a stub function used by the function tracer
(ftrace_stub). The ftrace_graph_return variable is compared to the
ftrace_stub in some archs to know if the function graph tracer is enabled or
not. This means we can not just simply create a new function stub that
compares it without modifying all the archs.

Instead, have the linker script create a function_graph_stub that maps to
ftrace_stub, and this way we can define the prototype for it to match the
prototype of ftrace_graph_return, and make the compiler checks all happy!

Link: http://lkml.kernel.org/r/20191015090055.789a0aed@gandalf.local.home
Cc: linux-sh@vger.kernel.org
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Reported-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
arch/sh/boot/compressed/misc.c
include/asm-generic/vmlinux.lds.h
kernel/trace/fgraph.c