[PATCH 5/5][RESEND] tracing/function-graph-tracer: drop the kernel_text_address check

[PATCH 5/5][RESEND] tracing/function-graph-tracer: drop the kernel_text_address check

[Frederic Weisbecker]

When the function graph tracer picks a return address, it ensures this address
is really a kernel text one by calling __kernel_text_address()
Actually this path has never been taken. Its role was more likely to debug the tracer
on the beginning of its development but this function is wasteful since it is called
for every traced function.

The fault check is already sufficient.

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
 arch/x86/kernel/ftrace.c |    7 -------
 kernel/extable.c         |    4 ++--
 kernel/module.c          |    2 +-
 3 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 4d33224..a9e7c43 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -510,13 +510,6 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 		return;
 	}
 
-	if (unlikely(!__kernel_text_address(old))) {
-		ftrace_graph_stop();
-		*parent = old;
-		WARN_ON(1);
-		return;
-	}
-
 	calltime = cpu_clock(raw_smp_processor_id());
 
 	if (push_return_trace(old, calltime,
diff --git a/kernel/extable.c b/kernel/extable.c
index e136ed8..0df6253 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -41,7 +41,7 @@ const struct exception_table_entry *search_exception_tables(unsigned long addr)
 	return e;
 }
 
-__notrace_funcgraph int core_kernel_text(unsigned long addr)
+int core_kernel_text(unsigned long addr)
 {
 	if (addr >= (unsigned long)_stext &&
 	    addr <= (unsigned long)_etext)
@@ -54,7 +54,7 @@ __notrace_funcgraph int core_kernel_text(unsigned long addr)
 	return 0;
 }
 
-__notrace_funcgraph int __kernel_text_address(unsigned long addr)
+int __kernel_text_address(unsigned long addr)
 {
 	if (core_kernel_text(addr))
 		return 1;
diff --git a/kernel/module.c b/kernel/module.c
index ba22484..22d7379 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2735,7 +2735,7 @@ int is_module_address(unsigned long addr)
 
 
 /* Is this a valid kernel address? */
-__notrace_funcgraph struct module *__module_text_address(unsigned long addr)
+struct module *__module_text_address(unsigned long addr)
 {
 	struct module *mod;
 
-- 
1.6.1

Re: [PATCH 5/5][RESEND] tracing/function-graph-tracer: drop the kernel_text_address check

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> When the function graph tracer picks a return address, it ensures this address
> is really a kernel text one by calling __kernel_text_address()
> Actually this path has never been taken. Its role was more likely to debug the tracer
> on the beginning of its development but this function is wasteful since it is called
> for every traced function.
> 
> The fault check is already sufficient.
> 
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> ---
>  arch/x86/kernel/ftrace.c |    7 -------
>  kernel/extable.c         |    4 ++--
>  kernel/module.c          |    2 +-
>  3 files changed, 3 insertions(+), 10 deletions(-)

Applied to tip/tracing/ftrace, thanks Frederic!

	Ingo