2018-11-28 08:14:37

by Anders Roxell

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

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 <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Signen-off-by: Anders Roxell <[email protected]>
---
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

2018-11-28 14:07:43

by Steven Rostedt

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

On Wed, 28 Nov 2018 09:12:39 +0100
Anders Roxell <[email protected]> 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 <[email protected]>
> Signed-off-by: Arnd Bergmann <[email protected]>
> Signen-off-by: Anders Roxell <[email protected]>
> ---

Acked-by: Steven Rostedt (VMware) <[email protected]>

-- Steve