[RFC,v2,2/6] tracing: Expose ftrace_regs regardless of CONFIG_FUNCTION_TRACER
Commit Message
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
In order to be able to use ftrace_regs even from features unrelated to
function tracer (e.g. kretprobe), expose ftrace_regs structures and
APIs even if the CONFIG_FUNCTION_TRACER=n.
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
include/linux/ftrace.h | 45 ++++++++++++++++++++++++---------------------
1 file changed, 24 insertions(+), 21 deletions(-)
Comments
On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
<mhiramat@kernel.org> wrote:
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index ce156c7704ee..3fb94a1a2461 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -112,11 +112,11 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val
> }
> #endif
>
> -#ifdef CONFIG_FUNCTION_TRACER
> -
> -extern int ftrace_enabled;
> -
> -#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
> +/*
> + * If the architecture doesn't support FTRACE_WITH_ARGS or disable function
nit: disables*
> + * tracer, define the default(pt_regs compatible) ftrace_regs.
> + */
> +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || !defined(CONFIG_FUNCTION_TRACER)
I wonder if we should make things simpler with:
#if defined(HAVE_PT_REGS_COMPAT_FTRACE_REGS) || !defined(CONFIG_FUNCTION_TRACER)
And remove the ftrace_regs definitions that are copy-pastes of this
block in arch specific headers. Then we can enforce in a single point
that HAVE_PT_REGS_COMPAT_FTRACE_REGS holds.
Maybe that's a question for Steven ?
On Wed, 9 Aug 2023 12:29:13 +0200
Florent Revest <revest@chromium.org> wrote:
> On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
> <mhiramat@kernel.org> wrote:
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index ce156c7704ee..3fb94a1a2461 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -112,11 +112,11 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val
> > }
> > #endif
> >
> > -#ifdef CONFIG_FUNCTION_TRACER
> > -
> > -extern int ftrace_enabled;
> > -
> > -#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
> > +/*
> > + * If the architecture doesn't support FTRACE_WITH_ARGS or disable function
>
> nit: disables*
Thanks!
>
> > + * tracer, define the default(pt_regs compatible) ftrace_regs.
> > + */
> > +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || !defined(CONFIG_FUNCTION_TRACER)
>
> I wonder if we should make things simpler with:
>
> #if defined(HAVE_PT_REGS_COMPAT_FTRACE_REGS) || !defined(CONFIG_FUNCTION_TRACER)
>
> And remove the ftrace_regs definitions that are copy-pastes of this
> block in arch specific headers. Then we can enforce in a single point
> that HAVE_PT_REGS_COMPAT_FTRACE_REGS holds.
Here, the "HAVE_PT_REGS_COMPAT_FTRACE_REGS" does not mean that the
ftrace_regs is completely compatible with pt_regs, but on the memory
it wraps struct pt_regs (thus we can just cast the type).
- CONFIG_DYNAMIC_FTRACE_WITH_REGS
ftrace_regs is completely compatible with pt_regs
- CONFIG_DYNAMIC_FTRACE_WITH_ARGS
| ftrace_regs may not compatible with pt_regs
|
+- CONFIG_HAVE_PT_REGS_COMPAT_FTRACE_REGS
but on memory image, ftrace_regs includes pt_regs.
Thank you,
>
> Maybe that's a question for Steven ?
On Wed, Aug 9, 2023 at 4:16 PM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> On Wed, 9 Aug 2023 12:29:13 +0200
> Florent Revest <revest@chromium.org> wrote:
> > > + * tracer, define the default(pt_regs compatible) ftrace_regs.
> > > + */
> > > +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || !defined(CONFIG_FUNCTION_TRACER)
> >
> > I wonder if we should make things simpler with:
> >
> > #if defined(HAVE_PT_REGS_COMPAT_FTRACE_REGS) || !defined(CONFIG_FUNCTION_TRACER)
> >
> > And remove the ftrace_regs definitions that are copy-pastes of this
> > block in arch specific headers. Then we can enforce in a single point
> > that HAVE_PT_REGS_COMPAT_FTRACE_REGS holds.
>
> Here, the "HAVE_PT_REGS_COMPAT_FTRACE_REGS" does not mean that the
> ftrace_regs is completely compatible with pt_regs, but on the memory
> it wraps struct pt_regs (thus we can just cast the type).
But in practice I think that all architectures that chose to wrap a
pt_regs in their ftrace_regs also do:
+#define ftrace_regs_get_instruction_pointer(fregs) \
+ instruction_pointer(ftrace_get_regs(fregs))
+#define ftrace_regs_get_argument(fregs, n) \
+ regs_get_kernel_argument(ftrace_get_regs(fregs), n)
+#define ftrace_regs_get_stack_pointer(fregs) \
+ kernel_stack_pointer(ftrace_get_regs(fregs))
+#define ftrace_regs_return_value(fregs) \
+ regs_return_value(ftrace_get_regs(fregs))
+#define ftrace_regs_set_return_value(fregs, ret) \
+ regs_set_return_value(ftrace_get_regs(fregs), ret)
+#define ftrace_override_function_with_return(fregs) \
+ override_function_with_return(ftrace_get_regs(fregs))
+#define ftrace_regs_query_register_offset(name) \
+ regs_query_register_offset(name)
And are just careful to populate the fields that let these macros
work. So maybe these could be factorized... But anyway, I'm not
particularly a super fan of the idea and I don't think it should
necessarily fit in that series. It's just something that crossed my
mind, if you're not a fan then we should probably not do it ;)
@@ -112,11 +112,11 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val
}
#endif
-#ifdef CONFIG_FUNCTION_TRACER
-
-extern int ftrace_enabled;
-
-#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
+/*
+ * If the architecture doesn't support FTRACE_WITH_ARGS or disable function
+ * tracer, define the default(pt_regs compatible) ftrace_regs.
+ */
+#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || !defined(CONFIG_FUNCTION_TRACER)
struct ftrace_regs {
struct pt_regs regs;
@@ -129,6 +129,22 @@ struct ftrace_regs {
* HAVE_DYNAMIC_FTRACE_WITH_ARGS is set and it supports live kernel patching.
*/
#define ftrace_regs_set_instruction_pointer(fregs, ip) do { } while (0)
+
+#define ftrace_regs_get_instruction_pointer(fregs) \
+ instruction_pointer(ftrace_get_regs(fregs))
+#define ftrace_regs_get_argument(fregs, n) \
+ regs_get_kernel_argument(ftrace_get_regs(fregs), n)
+#define ftrace_regs_get_stack_pointer(fregs) \
+ kernel_stack_pointer(ftrace_get_regs(fregs))
+#define ftrace_regs_return_value(fregs) \
+ regs_return_value(ftrace_get_regs(fregs))
+#define ftrace_regs_set_return_value(fregs, ret) \
+ regs_set_return_value(ftrace_get_regs(fregs), ret)
+#define ftrace_override_function_with_return(fregs) \
+ override_function_with_return(ftrace_get_regs(fregs))
+#define ftrace_regs_query_register_offset(name) \
+ regs_query_register_offset(name)
+
#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs)
@@ -151,22 +167,9 @@ static __always_inline bool ftrace_regs_has_args(struct ftrace_regs *fregs)
return ftrace_get_regs(fregs) != NULL;
}
-#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
-#define ftrace_regs_get_instruction_pointer(fregs) \
- instruction_pointer(ftrace_get_regs(fregs))
-#define ftrace_regs_get_argument(fregs, n) \
- regs_get_kernel_argument(ftrace_get_regs(fregs), n)
-#define ftrace_regs_get_stack_pointer(fregs) \
- kernel_stack_pointer(ftrace_get_regs(fregs))
-#define ftrace_regs_return_value(fregs) \
- regs_return_value(ftrace_get_regs(fregs))
-#define ftrace_regs_set_return_value(fregs, ret) \
- regs_set_return_value(ftrace_get_regs(fregs), ret)
-#define ftrace_override_function_with_return(fregs) \
- override_function_with_return(ftrace_get_regs(fregs))
-#define ftrace_regs_query_register_offset(name) \
- regs_query_register_offset(name)
-#endif
+#ifdef CONFIG_FUNCTION_TRACER
+
+extern int ftrace_enabled;
typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs);