[PATCH 1/2] kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc as notrace

[PATCH 1/2] kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc as notrace

[Anders Roxell]

Since __sanitizer_cov_trace_pc is marked as notrace, function calls in
__sanitizer_cov_trace_pc shouldn't be traced either. The function
ftrace_graph_caller() gets called for each function that isn't marked
'notrace', like canonicalize_ip(). This is the call trace from a run:

[  139.644550]  ftrace_graph_caller+0x1c/0x24
[  139.648352]  canonicalize_ip+0x18/0x28
[  139.652313]  __sanitizer_cov_trace_pc+0x14/0x58
[  139.656184]  sched_clock+0x34/0x1e8
[  139.659759]  trace_clock_local+0x40/0x88
[  139.663722]  ftrace_push_return_trace+0x8c/0x1f0
[  139.667767]  prepare_ftrace_return+0xa8/0x100
[  139.671709]  ftrace_graph_caller+0x1c/0x24

Rework so that the functions check_kcov_mode and canonicalize_ip that is
callef from __sanitizer_cov_trace_pc also is marked as notrace.

Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signen-off-by: Anders Roxell <anders.roxell@linaro.org>
---
 kernel/kcov.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/kcov.c b/kernel/kcov.c
index 3ebd09efe72a..97959d7b77e2 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -56,7 +56,7 @@ struct kcov {
 	struct task_struct	*t;
 };
 
-static bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
+static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
 {
 	unsigned int mode;
 
@@ -78,7 +78,7 @@ static bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
 	return mode == needed_mode;
 }
 
-static unsigned long canonicalize_ip(unsigned long ip)
+static notrace unsigned long canonicalize_ip(unsigned long ip)
 {
 #ifdef CONFIG_RANDOMIZE_BASE
 	ip -= kaslr_offset();
-- 
2.19.2

Re: [PATCH 1/2] kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc as notrace

[Steven Rostedt]

On Wed, 28 Nov 2018 09:12:39 +0100
Anders Roxell <anders.roxell@linaro.org> wrote:

> Since __sanitizer_cov_trace_pc is marked as notrace, function calls in
> __sanitizer_cov_trace_pc shouldn't be traced either. The function
> ftrace_graph_caller() gets called for each function that isn't marked
> 'notrace', like canonicalize_ip(). This is the call trace from a run:
> 
> [  139.644550]  ftrace_graph_caller+0x1c/0x24
> [  139.648352]  canonicalize_ip+0x18/0x28
> [  139.652313]  __sanitizer_cov_trace_pc+0x14/0x58
> [  139.656184]  sched_clock+0x34/0x1e8
> [  139.659759]  trace_clock_local+0x40/0x88
> [  139.663722]  ftrace_push_return_trace+0x8c/0x1f0
> [  139.667767]  prepare_ftrace_return+0xa8/0x100
> [  139.671709]  ftrace_graph_caller+0x1c/0x24
> 
> Rework so that the functions check_kcov_mode and canonicalize_ip that is
> callef from __sanitizer_cov_trace_pc also is marked as notrace.
> 
> Co-developed-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Signen-off-by: Anders Roxell <anders.roxell@linaro.org>
> ---

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve