kernel/trace: Remove function callback casts
diff mbox series

Message ID 20200614070154.6039-1-oscar.carter@gmx.com
State New
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Series
  • kernel/trace: Remove function callback casts
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Commit Message

Oscar Carter June 14, 2020, 7:01 a.m. UTC
In an effort to enable -Wcast-function-type in the top-level Makefile to
support Control Flow Integrity builds, remove all the function callback
casts.

To do this, use the ftrace_ops_list_func function as a wrapper when the
arch not supports ftrace ops instead of the use of a function cast.

Signed-off-by: Oscar Carter <oscar.carter@gmx.com>
---
 kernel/trace/ftrace.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--
2.20.1

Comments

Steven Rostedt June 15, 2020, 8:17 p.m. UTC | #1
On Sun, 14 Jun 2020 09:01:54 +0200
Oscar Carter <oscar.carter@gmx.com> wrote:

> In an effort to enable -Wcast-function-type in the top-level Makefile to
> support Control Flow Integrity builds, remove all the function callback
> casts.
> 
> To do this, use the ftrace_ops_list_func function as a wrapper when the
> arch not supports ftrace ops instead of the use of a function cast.
> 

We need more tricker than this.

> Signed-off-by: Oscar Carter <oscar.carter@gmx.com>
> ---
>  kernel/trace/ftrace.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index c163c3531faf..ed1efc0e3a25 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -119,13 +119,12 @@ 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,
>  				 struct ftrace_ops *op, struct pt_regs *regs);
> -#else
> +
> +#if !ARCH_SUPPORTS_FTRACE_OPS
>  /* 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)

The reason for the typecast is because this gets called from asm with only two parameters.

>  #endif
> 
>  static inline void ftrace_ops_init(struct ftrace_ops *ops)
> @@ -6860,6 +6859,12 @@ static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
>  }
>  NOKPROBE_SYMBOL(ftrace_ops_list_func);
>  #else
> +static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
> +				 struct ftrace_ops *op, struct pt_regs *regs)
> +{
> +	ftrace_ops_no_ops(ip, parent_ip);
> +}
> +
>  static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip)
>  {
>  	__ftrace_ops_list_func(ip, parent_ip, NULL, NULL);
> --
> 2.20.1
Steven Rostedt June 15, 2020, 8:22 p.m. UTC | #2
On Mon, 15 Jun 2020 16:17:38 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Sun, 14 Jun 2020 09:01:54 +0200
> Oscar Carter <oscar.carter@gmx.com> wrote:
> 
> > In an effort to enable -Wcast-function-type in the top-level Makefile to
> > support Control Flow Integrity builds, remove all the function callback
> > casts.
> > 
> > To do this, use the ftrace_ops_list_func function as a wrapper when the
> > arch not supports ftrace ops instead of the use of a function cast.
> >   
> 
> We need more tricker than this.
> 
> > Signed-off-by: Oscar Carter <oscar.carter@gmx.com>
> > ---
> >  kernel/trace/ftrace.c | 11 ++++++++---
> >  1 file changed, 8 insertions(+), 3 deletions(-)
> > 
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index c163c3531faf..ed1efc0e3a25 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -119,13 +119,12 @@ 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,
> >  				 struct ftrace_ops *op, struct pt_regs *regs);
> > -#else
> > +
> > +#if !ARCH_SUPPORTS_FTRACE_OPS
> >  /* 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)  
> 
> The reason for the typecast is because this gets called from asm with only two parameters.

[ Some how hit a short cut key that sent this before I was finished! :-p ]

As I was saying. This typecast is being paranoid, as archs will call
the ftrace_ops_list_func directly, and only pass in two parameters.

Now one way around this is to instead of having the typecast, I could
use linker magic to create another function that I can define without
the typecast to get the same effect. Similar to what I did in commit:

46f9469247c6f ("ftrace: Rename ftrace_graph_stub to ftrace_stub_graph")

-- Steve



> 
> >  #endif
> > 
> >  static inline void ftrace_ops_init(struct ftrace_ops *ops)
> > @@ -6860,6 +6859,12 @@ static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
> >  }
> >  NOKPROBE_SYMBOL(ftrace_ops_list_func);
> >  #else
> > +static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
> > +				 struct ftrace_ops *op, struct pt_regs *regs)
> > +{
> > +	ftrace_ops_no_ops(ip, parent_ip);
> > +}
> > +
> >  static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip)
> >  {
> >  	__ftrace_ops_list_func(ip, parent_ip, NULL, NULL);
> > --
> > 2.20.1  
>
Steven Rostedt June 17, 2020, 8:28 p.m. UTC | #3
On Mon, 15 Jun 2020 16:22:45 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> As I was saying. This typecast is being paranoid, as archs will call
> the ftrace_ops_list_func directly, and only pass in two parameters.
> 
> Now one way around this is to instead of having the typecast, I could
> use linker magic to create another function that I can define without
> the typecast to get the same effect. Similar to what I did in commit:
> 
> 46f9469247c6f ("ftrace: Rename ftrace_graph_stub to ftrace_stub_graph")

Would something like this work for you?

-- Steve

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index db600ef218d7..120babd9ba44 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -145,13 +145,18 @@
  * 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;
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f060838e9cbb..b775d399026e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -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,
-				 struct ftrace_ops *op, struct pt_regs *regs);
-#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
+/* 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 pt_regs *regs);
 
 static inline void ftrace_ops_init(struct ftrace_ops *ops)
 {
@@ -6859,21 +6854,23 @@ __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,
-				 struct ftrace_ops *op, struct pt_regs *regs)
+void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
+			       struct ftrace_ops *op, struct pt_regs *regs)
 {
 	__ftrace_ops_list_func(ip, parent_ip, NULL, regs);
 }
-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
Oscar Carter June 20, 2020, 2:23 p.m. UTC | #4
On Wed, Jun 17, 2020 at 04:28:00PM -0400, Steven Rostedt wrote:
> On Mon, 15 Jun 2020 16:22:45 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > As I was saying. This typecast is being paranoid, as archs will call
> > the ftrace_ops_list_func directly, and only pass in two parameters.
> >
> > Now one way around this is to instead of having the typecast, I could
> > use linker magic to create another function that I can define without
> > the typecast to get the same effect. Similar to what I did in commit:
> >
> > 46f9469247c6f ("ftrace: Rename ftrace_graph_stub to ftrace_stub_graph")
>
> Would something like this work for you?
>
> -- Steve
>
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index db600ef218d7..120babd9ba44 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -145,13 +145,18 @@
>   * 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;
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index f060838e9cbb..b775d399026e 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -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,
> -				 struct ftrace_ops *op, struct pt_regs *regs);
> -#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
> +/* 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 pt_regs *regs);
>
>  static inline void ftrace_ops_init(struct ftrace_ops *ops)
>  {
> @@ -6859,21 +6854,23 @@ __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,
> -				 struct ftrace_ops *op, struct pt_regs *regs)
> +void arch_ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
> +			       struct ftrace_ops *op, struct pt_regs *regs)
>  {
>  	__ftrace_ops_list_func(ip, parent_ip, NULL, regs);
>  }
> -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

Thanks for your work and the proper patch sent [1].
I will follow the thread to see if I can help.

[1] https://lore.kernel.org/lkml/20200617165616.52241bde@oasis.local.home/

Regards,
Oscar Carter

Patch
diff mbox series

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c163c3531faf..ed1efc0e3a25 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -119,13 +119,12 @@  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,
 				 struct ftrace_ops *op, struct pt_regs *regs);
-#else
+
+#if !ARCH_SUPPORTS_FTRACE_OPS
 /* 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)
@@ -6860,6 +6859,12 @@  static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
 }
 NOKPROBE_SYMBOL(ftrace_ops_list_func);
 #else
+static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
+				 struct ftrace_ops *op, struct pt_regs *regs)
+{
+	ftrace_ops_no_ops(ip, parent_ip);
+}
+
 static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip)
 {
 	__ftrace_ops_list_func(ip, parent_ip, NULL, NULL);