Commit b83b43ff authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

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: default avatarSami Tolvanen <samitolvanen@google.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 953ae45a

arch/sh/boot/compressed/misc.c

+5 −0
Original line number Original line Diff line number Diff line
@@ -111,6 +111,11 @@ void __stack_chk_fail(void) 
	error("stack-protector: Kernel stack is corrupted\n");

	error("stack-protector: Kernel stack is corrupted\n");

}

}





/* Needed because vmlinux.lds.h references this */

void ftrace_stub(void)

{

}



#ifdef CONFIG_SUPERH64

#ifdef CONFIG_SUPERH64

#define stackalign	8

#define stackalign	8

#else

#else

include/asm-generic/vmlinux.lds.h

+14 −3
Original line number Original line Diff line number Diff line
@@ -111,19 +111,30 @@ 




#ifdef CONFIG_FTRACE_MCOUNT_RECORD

#ifdef CONFIG_FTRACE_MCOUNT_RECORD

#ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY

#ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY

/*

 * Need to also make ftrace_graph_stub point to ftrace_stub

 * so that the same stub location may have different protocols

 * and not mess up with C verifiers.

 */

#define MCOUNT_REC()	. = ALIGN(8);				\

#define MCOUNT_REC()	. = ALIGN(8);				\

			__start_mcount_loc = .;			\

			__start_mcount_loc = .;			\

			KEEP(*(__patchable_function_entries))	\

			KEEP(*(__patchable_function_entries))	\

			__stop_mcount_loc = .;

			__stop_mcount_loc = .;			\

			ftrace_graph_stub = ftrace_stub;

#else

#else

#define MCOUNT_REC()	. = ALIGN(8);				\

#define MCOUNT_REC()	. = ALIGN(8);				\

			__start_mcount_loc = .;			\

			__start_mcount_loc = .;			\

			KEEP(*(__mcount_loc))			\

			KEEP(*(__mcount_loc))			\

			__stop_mcount_loc = .;

			__stop_mcount_loc = .;			\

			ftrace_graph_stub = ftrace_stub;

#endif

#endif

#else

#else

# ifdef CONFIG_FUNCTION_TRACER

#  define MCOUNT_REC()	ftrace_graph_stub = ftrace_stub;

# else

#  define MCOUNT_REC()

#  define MCOUNT_REC()

# endif

# endif

#endif





#ifdef CONFIG_TRACE_BRANCH_PROFILING

#ifdef CONFIG_TRACE_BRANCH_PROFILING

#define LIKELY_PROFILE()	__start_annotated_branch_profile = .;	\

#define LIKELY_PROFILE()	__start_annotated_branch_profile = .;	\

kernel/trace/fgraph.c

+8 −3
Original line number Original line Diff line number Diff line
@@ -332,9 +332,14 @@ int ftrace_graph_entry_stub(struct ftrace_graph_ent *trace) 
	return 0;

	return 0;

}

}





/*

 * Simply points to ftrace_stub, but with the proper protocol.

 * Defined by the linker script in linux/vmlinux.lds.h

 */

extern void ftrace_graph_stub(struct ftrace_graph_ret *);



/* The callbacks that hook a function */

/* The callbacks that hook a function */

trace_func_graph_ret_t ftrace_graph_return =

trace_func_graph_ret_t ftrace_graph_return = ftrace_graph_stub;

			(trace_func_graph_ret_t)ftrace_stub;

trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub;

trace_func_graph_ent_t ftrace_graph_entry = ftrace_graph_entry_stub;

static trace_func_graph_ent_t __ftrace_graph_entry = ftrace_graph_entry_stub;

static trace_func_graph_ent_t __ftrace_graph_entry = ftrace_graph_entry_stub;
@@ -614,7 +619,7 @@ void unregister_ftrace_graph(struct fgraph_ops *gops) 
		goto out;

		goto out;





	ftrace_graph_active--;

	ftrace_graph_active--;

	ftrace_graph_return = (trace_func_graph_ret_t)ftrace_stub;

	ftrace_graph_return = ftrace_graph_stub;

	ftrace_graph_entry = ftrace_graph_entry_stub;

	ftrace_graph_entry = ftrace_graph_entry_stub;

	__ftrace_graph_entry = ftrace_graph_entry_stub;

	__ftrace_graph_entry = ftrace_graph_entry_stub;

	ftrace_shutdown(&graph_ops, FTRACE_STOP_FUNC_RET);

	ftrace_shutdown(&graph_ops, FTRACE_STOP_FUNC_RET);

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