Commit 34cdd18b authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

tracing: Use linker magic instead of recasting ftrace_ops_list_func() 

In an effort to enable -Wcast-function-type in the top-level Makefile to
support Control Flow Integrity builds, all function casts need to be
removed.

This means that ftrace_ops_list_func() can no longer be defined as
ftrace_ops_no_ops(). The reason for ftrace_ops_no_ops() is to use that when
an architecture calls ftrace_ops_list_func() with only two parameters
(called from assembly). And to make sure there's no C side-effects, those
archs call ftrace_ops_no_ops() which only has two parameters, as
ftrace_ops_list_func() has four parameters.

Instead of a typecast, use vmlinux.lds.h to define ftrace_ops_list_func() to
arch_ftrace_ops_list_func() that will define the proper set of parameters.

Link: https://lore.kernel.org/r/20200614070154.6039-1-oscar.carter@gmx.com
Link: https://lkml.kernel.org/r/20200617165616.52241bde@oasis.local.home
Link: https://lore.kernel.org/all/20211005053922.GA702049@embeddedor/



Requested-by: default avatarOscar Carter <oscar.carter@gmx.com>
Reported-by: default avatarkernel test robot <lkp@intel.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent affc6592

include/asm-generic/vmlinux.lds.h

+8 −2
Original line number Diff line number Diff line
@@ -164,16 +164,22 @@ 
 * Need to also make ftrace_stub_graph point to ftrace_stub

 * so that the same stub location may have different protocols

 * and not mess up with C verifiers.

 *

 * ftrace_ops_list_func will be defined as arch_ftrace_ops_list_func

 * as some archs will have a different prototype for that function

 * but ftrace_ops_list_func() will have a single prototype.

 */

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

			__start_mcount_loc = .;			\

			KEEP(*(__mcount_loc))			\

			KEEP(*(__patchable_function_entries))	\

			__stop_mcount_loc = .;			\

			ftrace_stub_graph = ftrace_stub;

			ftrace_stub_graph = ftrace_stub;	\

			ftrace_ops_list_func = arch_ftrace_ops_list_func;

#else

# ifdef CONFIG_FUNCTION_TRACER

#  define MCOUNT_REC()	ftrace_stub_graph = ftrace_stub;

#  define MCOUNT_REC()	ftrace_stub_graph = ftrace_stub;	\

			ftrace_ops_list_func = arch_ftrace_ops_list_func;

# else

#  define MCOUNT_REC()

# endif

include/linux/ftrace.h

+10 −2
Original line number Diff line number Diff line
@@ -30,16 +30,26 @@ 
#define ARCH_SUPPORTS_FTRACE_OPS 0

#endif



#ifdef CONFIG_FUNCTION_TRACER

struct ftrace_ops;

struct ftrace_regs;

/*

 * If the arch's mcount caller does not support all of ftrace's

 * features, then it must call an indirect function that

 * does. Or at least does enough to prevent any unwelcome side effects.

 *

 * Also define the function prototype that these architectures use

 * to call the ftrace_ops_list_func().

 */

#if !ARCH_SUPPORTS_FTRACE_OPS

# define FTRACE_FORCE_LIST_FUNC 1

void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip);

#else

# define FTRACE_FORCE_LIST_FUNC 0

void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,

			       struct ftrace_ops *op, struct ftrace_regs *fregs);

#endif

#endif /* CONFIG_FUNCTION_TRACER */



/* Main tracing buffer and events set up */

#ifdef CONFIG_TRACING
@@ -88,8 +98,6 @@ extern int 
ftrace_enable_sysctl(struct ctl_table *table, int write,

		     void *buffer, size_t *lenp, loff_t *ppos);



struct ftrace_ops;



#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS



struct ftrace_regs {

kernel/trace/ftrace.c

+10 −13
Original line number Diff line number Diff line
@@ -119,14 +119,9 @@ struct ftrace_ops __rcu *ftrace_ops_list __read_mostly = &ftrace_list_end; 
ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;

struct ftrace_ops global_ops;



#if ARCH_SUPPORTS_FTRACE_OPS

static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,

/* Defined by vmlinux.lds.h see the commment above arch_ftrace_ops_list_func for details */

void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,

			  struct ftrace_ops *op, struct ftrace_regs *fregs);

#else

/* See comment below, where ftrace_ops_list_func is defined */

static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip);

#define ftrace_ops_list_func ((ftrace_func_t)ftrace_ops_no_ops)

#endif



static inline void ftrace_ops_init(struct ftrace_ops *ops)

{
@@ -7032,21 +7027,23 @@ __ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip, 
 * Note, CONFIG_DYNAMIC_FTRACE_WITH_REGS expects a full regs to be saved.

 * An architecture can pass partial regs with ftrace_ops and still

 * set the ARCH_SUPPORTS_FTRACE_OPS.

 *

 * In vmlinux.lds.h, ftrace_ops_list_func() is defined to be

 * arch_ftrace_ops_list_func.

 */

#if ARCH_SUPPORTS_FTRACE_OPS

static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,

void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,

			       struct ftrace_ops *op, struct ftrace_regs *fregs)

{

	__ftrace_ops_list_func(ip, parent_ip, NULL, fregs);

}

NOKPROBE_SYMBOL(ftrace_ops_list_func);

#else

static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip)

void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip)

{

	__ftrace_ops_list_func(ip, parent_ip, NULL, NULL);

}

NOKPROBE_SYMBOL(ftrace_ops_no_ops);

#endif

NOKPROBE_SYMBOL(arch_ftrace_ops_list_func);



/*

 * If there's only one function registered but it does not support