In subsequent patches we'll arrange for architectures to have an
ftrace_regs which is entirely distinct from pt_regs. In preparation for
this, we need to minimize the use of pt_regs to where strictly
necessary in the core ftrace code.
This patch changes the prototype of arch_ftrace_set_direct_caller() to
take ftrace_regs rather than pt_regs, and moves the extraction of the
pt_regs into arch_ftrace_set_direct_caller().
For x86, we need to move arch_ftrace_set_direct_caller() after the
definition of struct ftrace_regs. As arch_ftrace_set_direct_caller() is
always called with a non-NULL pt_regs by call_direct_funcs() whose ops
have FTRACE_OPS_FL_SAVE_REGS, it's not necessary to add an additional
NULL check.
There should be no functional change as a result of this patch.
Signed-off-by: Mark Rutland <[email protected]>
Cc: Florent Revest <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Steven Rostedt <[email protected]>
---
arch/s390/include/asm/ftrace.h | 3 ++-
arch/x86/include/asm/ftrace.h | 26 +++++++++++++-------------
include/linux/ftrace.h | 4 +++-
kernel/trace/ftrace.c | 3 +--
4 files changed, 19 insertions(+), 17 deletions(-)
diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
index 6f80ec9c04be..53c4d1257549 100644
--- a/arch/s390/include/asm/ftrace.h
+++ b/arch/s390/include/asm/ftrace.h
@@ -67,8 +67,9 @@ static __always_inline void ftrace_instruction_pointer_set(struct ftrace_regs *f
* place the direct caller in the ORIG_GPR2 part of pt_regs. This
* tells the ftrace_caller that there's a direct caller.
*/
-static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr)
+static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs, unsigned long addr)
{
+ struct pt_regs *regs = &fregs->regs;
regs->orig_gpr2 = addr;
}
diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 908d99b127d3..788e7c1f6463 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -34,19 +34,6 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
return addr;
}
-/*
- * When a ftrace registered caller is tracing a function that is
- * also set by a register_ftrace_direct() call, it needs to be
- * differentiated in the ftrace_caller trampoline. To do this, we
- * place the direct caller in the ORIG_AX part of pt_regs. This
- * tells the ftrace_caller that there's a direct caller.
- */
-static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr)
-{
- /* Emulate a call */
- regs->orig_ax = addr;
-}
-
#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
struct ftrace_regs {
struct pt_regs regs;
@@ -72,6 +59,19 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
#define FTRACE_GRAPH_TRAMP_ADDR FTRACE_GRAPH_ADDR
#endif
+/*
+ * When a ftrace registered caller is tracing a function that is
+ * also set by a register_ftrace_direct() call, it needs to be
+ * differentiated in the ftrace_caller trampoline. To do this, we
+ * place the direct caller in the ORIG_AX part of pt_regs. This
+ * tells the ftrace_caller that there's a direct caller.
+ */
+static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs, unsigned long addr)
+{
+ /* Emulate a call */
+ fregs->regs.orig_ax = addr;
+}
+
#ifdef CONFIG_DYNAMIC_FTRACE
struct dyn_arch_ftrace {
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 62557d4bffc2..5ca6c6680460 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -429,6 +429,7 @@ static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsi
}
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
+#ifdef CONFIG_FUNCTION_TRACER
#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
/*
* This must be implemented by the architecture.
@@ -443,9 +444,10 @@ static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsi
* the return from the trampoline jump to the direct caller
* instead of going back to the function it just traced.
*/
-static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs,
+static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs,
unsigned long addr) { }
#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
+#endif /* CONFIG_FUNCTION_TRACER */
#ifdef CONFIG_STACK_TRACER
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index fbf2543111c0..234c5414deee 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2487,14 +2487,13 @@ ftrace_add_rec_direct(unsigned long ip, unsigned long addr,
static void call_direct_funcs(unsigned long ip, unsigned long pip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
- struct pt_regs *regs = ftrace_get_regs(fregs);
unsigned long addr;
addr = ftrace_find_rec_direct(ip);
if (!addr)
return;
- arch_ftrace_set_direct_caller(regs, addr);
+ arch_ftrace_set_direct_caller(fregs, addr);
}
struct ftrace_ops direct_ops = {
--
2.30.2
On Mon, 24 Oct 2022 15:08:43 +0100
Mark Rutland <[email protected]> wrote:
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -429,6 +429,7 @@ static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsi
> }
> #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
>
> +#ifdef CONFIG_FUNCTION_TRACER
Instead of adding the above preprocessor check, the below chunk should be
moved into the CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS block above.
-- Steve
> #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> /*
> * This must be implemented by the architecture.
> @@ -443,9 +444,10 @@ static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsi
> * the return from the trampoline jump to the direct caller
> * instead of going back to the function it just traced.
> */
> -static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs,
> +static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs,
> unsigned long addr) { }
> #endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
> +#endif /* CONFIG_FUNCTION_TRACER */
>
> #ifdef CONFIG_STACK_TRACER
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index fbf2543111c0..234c5414deee 100644
On Mon, Oct 24, 2022 at 10:48:45AM -0400, Steven Rostedt wrote:
> On Mon, 24 Oct 2022 15:08:43 +0100
> Mark Rutland <[email protected]> wrote:
>
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -429,6 +429,7 @@ static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsi
> > }
> > #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
> >
> > +#ifdef CONFIG_FUNCTION_TRACER
>
> Instead of adding the above preprocessor check, the below chunk should be
> moved into the CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS block above.
Sure; but note that doing that naively means 'struct ftrace_regs' won't always
be declared (e.g. if !CONFIG_FUNCTION_TRACER), and will result in warnings, e.g.
| CC arch/x86/kernel/asm-offsets.s
| In file included from ./include/linux/kvm_host.h:32,
| from arch/x86/kernel/../kvm/vmx/vmx.h:5,
| from arch/x86/kernel/asm-offsets.c:22:
| ./include/linux/ftrace.h:444:57: error: ‘struct ftrace_regs’ declared inside parameter list will not be visible outside of this definition or declaration [-Werror]
| 444 | static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs,
| | ^~~~~~~~~~~
| cc1: all warnings being treated as errors
| make[1]: *** [scripts/Makefile.build:118: arch/x86/kernel/asm-offsets.s] Error 1
| make: *** [Makefile:1270: prepare0] Error 2
... so I'll either need to add some ifdeffery, for CONFIG_FUNCTION_TRACER, or I
can hoist the declaration of 'struct ftrace_regs' to not depend on
CONFIG_FUNCTION_TRACER.
I guess the latter is preferable, e.g.
| diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
| index 2b34fec40a39..f201fcbfffb0 100644
| --- a/include/linux/ftrace.h
| +++ b/include/linux/ftrace.h
| @@ -37,9 +37,10 @@ extern void ftrace_boot_snapshot(void);
| static inline void ftrace_boot_snapshot(void) { }
| #endif
|
| -#ifdef CONFIG_FUNCTION_TRACER
| struct ftrace_ops;
| struct ftrace_regs;
| +
| +#ifdef CONFIG_FUNCTION_TRACER
| /*
| * If the arch's mcount caller does not support all of ftrace's
| * features, then it must call an indirect function that
... so I've done that locally for now.
Thanks,
Mark.
On Mon, Oct 24, 2022 at 4:08 PM Mark Rutland <[email protected]> wrote:
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -2487,14 +2487,13 @@ ftrace_add_rec_direct(unsigned long ip, unsigned long addr,
> static void call_direct_funcs(unsigned long ip, unsigned long pip,
> struct ftrace_ops *ops, struct ftrace_regs *fregs)
> {
> - struct pt_regs *regs = ftrace_get_regs(fregs);
Was this ftrace_get_regs() the only reason why we have
config DYNAMIC_FTRACE_WITH_DIRECT_CALLS
depends on DYNAMIC_FTRACE_WITH_REGS
?
If we no longer use it, maybe this should be:
depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS
?
On Mon, Oct 24, 2022 at 06:04:49PM +0100, Mark Rutland wrote:
> On Mon, Oct 24, 2022 at 10:48:45AM -0400, Steven Rostedt wrote:
> > On Mon, 24 Oct 2022 15:08:43 +0100
> > Mark Rutland <[email protected]> wrote:
> >
> > > --- a/include/linux/ftrace.h
> > > +++ b/include/linux/ftrace.h
> > > @@ -429,6 +429,7 @@ static inline int modify_ftrace_direct_multi_nolock(struct ftrace_ops *ops, unsi
> > > }
> > > #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
> > >
> > > +#ifdef CONFIG_FUNCTION_TRACER
> >
> > Instead of adding the above preprocessor check, the below chunk should be
> > moved into the CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS block above.
>
> Sure; but note that doing that naively means 'struct ftrace_regs' won't always
> be declared (e.g. if !CONFIG_FUNCTION_TRACER), and will result in warnings, e.g.
>
> | CC arch/x86/kernel/asm-offsets.s
> | In file included from ./include/linux/kvm_host.h:32,
> | from arch/x86/kernel/../kvm/vmx/vmx.h:5,
> | from arch/x86/kernel/asm-offsets.c:22:
> | ./include/linux/ftrace.h:444:57: error: ‘struct ftrace_regs’ declared inside parameter list will not be visible outside of this definition or declaration [-Werror]
> | 444 | static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs,
> | | ^~~~~~~~~~~
> | cc1: all warnings being treated as errors
> | make[1]: *** [scripts/Makefile.build:118: arch/x86/kernel/asm-offsets.s] Error 1
> | make: *** [Makefile:1270: prepare0] Error 2
>
> ... so I'll either need to add some ifdeffery, for CONFIG_FUNCTION_TRACER, or I
> can hoist the declaration of 'struct ftrace_regs' to not depend on
> CONFIG_FUNCTION_TRACER.
>
> I guess the latter is preferable, e.g.
>
> | diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> | index 2b34fec40a39..f201fcbfffb0 100644
> | --- a/include/linux/ftrace.h
> | +++ b/include/linux/ftrace.h
> | @@ -37,9 +37,10 @@ extern void ftrace_boot_snapshot(void);
> | static inline void ftrace_boot_snapshot(void) { }
> | #endif
> |
> | -#ifdef CONFIG_FUNCTION_TRACER
> | struct ftrace_ops;
> | struct ftrace_regs;
> | +
> | +#ifdef CONFIG_FUNCTION_TRACER
> | /*
> | * If the arch's mcount caller does not support all of ftrace's
> | * features, then it must call an indirect function that
>
> ... so I've done that locally for now.
The kbuild robot complained that this led to x86 getting multiple definitions
of arch_ftrace_set_direct_caller(), so I've also added the below:
| diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
| index 788e7c1f6463c..6f9b9fee04132 100644
| --- a/arch/x86/include/asm/ftrace.h
| +++ b/arch/x86/include/asm/ftrace.h
| @@ -59,6 +59,7 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
| #define FTRACE_GRAPH_TRAMP_ADDR FTRACE_GRAPH_ADDR
| #endif
|
| +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
| /*
| * When a ftrace registered caller is tracing a function that is
| * also set by a register_ftrace_direct() call, it needs to be
| @@ -71,6 +72,7 @@ static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs, unsi
| /* Emulate a call */
| fregs->regs.orig_ax = addr;
| }
| +#endif
|
| #ifdef CONFIG_DYNAMIC_FTRACE
... AFAICT s390 doesn't need similar treatment.
Thanks,
Mark.