[v2,2/4] arm64: unwind: Prohibit probing on return_address()
diff mbox series

Message ID 156378172702.12011.1144595747474511323.stgit@devnote2
State Superseded
Headers show
Series
  • arm64: kprobes: Fix some bugs in arm64 kprobes
Related show

Commit Message

Masami Hiramatsu July 22, 2019, 7:48 a.m. UTC
Prohibit probing on return_address() and subroutines which
is called from return_address(), since the it is invoked from
trace_hardirqs_off() which is also kprobe blacklisted.

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 arch/arm64/kernel/return_address.c |    4 +++-
 arch/arm64/kernel/stacktrace.c     |    3 +++
 2 files changed, 6 insertions(+), 1 deletion(-)

Comments

James Morse July 23, 2019, 4:04 p.m. UTC | #1
Hi,

On 22/07/2019 08:48, Masami Hiramatsu wrote:
> Prohibit probing on return_address() and subroutines which
> is called from return_address(), since the it is invoked from
> trace_hardirqs_off() which is also kprobe blacklisted.

(Nits: "which are called" and "since it is")


> diff --git a/arch/arm64/kernel/return_address.c b/arch/arm64/kernel/return_address.c
> index b21cba90f82d..7f8a143268b0 100644
> --- a/arch/arm64/kernel/return_address.c
> +++ b/arch/arm64/kernel/return_address.c
> @@ -8,6 +8,7 @@
>  
>  #include <linux/export.h>
>  #include <linux/ftrace.h>
> +#include <linux/kprobes.h>
>  
>  #include <asm/stack_pointer.h>
>  #include <asm/stacktrace.h>
> @@ -17,7 +18,7 @@ struct return_address_data {
>  	void *addr;
>  };
>  
> -static int save_return_addr(struct stackframe *frame, void *d)
> +static nokprobe_inline int save_return_addr(struct stackframe *frame, void *d)

This nokprobe_inline ends up as __always_inline if kprobes is enabled.
What do we expect the compiler to do with this? save_return_addr is passed as a
function-pointer to walk_stackframe()... I don't see how the compiler can inline it!

This would be needed for on_accessible_stack().
Should we cover ftrace_graph_get_ret_stack()?, or is that already in hand?


>  {
>  	struct return_address_data *data = d;
>  
> @@ -52,3 +53,4 @@ void *return_address(unsigned int level)
>  		return NULL;
>  }
>  EXPORT_SYMBOL_GPL(return_address);
> +NOKPROBE_SYMBOL(return_address);


Thanks,

James
Masami Hiramatsu July 24, 2019, 7:39 a.m. UTC | #2
On Tue, 23 Jul 2019 17:04:21 +0100
James Morse <james.morse@arm.com> wrote:

> Hi,
> 
> On 22/07/2019 08:48, Masami Hiramatsu wrote:
> > Prohibit probing on return_address() and subroutines which
> > is called from return_address(), since the it is invoked from
> > trace_hardirqs_off() which is also kprobe blacklisted.
> 
> (Nits: "which are called" and "since it is")

Thanks!

> 
> 
> > diff --git a/arch/arm64/kernel/return_address.c b/arch/arm64/kernel/return_address.c
> > index b21cba90f82d..7f8a143268b0 100644
> > --- a/arch/arm64/kernel/return_address.c
> > +++ b/arch/arm64/kernel/return_address.c
> > @@ -8,6 +8,7 @@
> >  
> >  #include <linux/export.h>
> >  #include <linux/ftrace.h>
> > +#include <linux/kprobes.h>
> >  
> >  #include <asm/stack_pointer.h>
> >  #include <asm/stacktrace.h>
> > @@ -17,7 +18,7 @@ struct return_address_data {
> >  	void *addr;
> >  };
> >  
> > -static int save_return_addr(struct stackframe *frame, void *d)
> > +static nokprobe_inline int save_return_addr(struct stackframe *frame, void *d)
> 
> This nokprobe_inline ends up as __always_inline if kprobes is enabled.
> What do we expect the compiler to do with this? save_return_addr is passed as a
> function-pointer to walk_stackframe()... I don't see how the compiler can inline it!

Oops, that's my mistake. Then it should be NOKPROBE_SYMBOL.

> 
> This would be needed for on_accessible_stack().
> Should we cover ftrace_graph_get_ret_stack()?, or is that already in hand?

No, that is OK. It just covers that the functions which are involved in
the kprobe execution path. ftrace_graph_ret_stack() is out of the debug
exception handler.

Thank you,

> >  {
> >  	struct return_address_data *data = d;
> >  
> > @@ -52,3 +53,4 @@ void *return_address(unsigned int level)
> >  		return NULL;
> >  }
> >  EXPORT_SYMBOL_GPL(return_address);
> > +NOKPROBE_SYMBOL(return_address);
> 
> 
> Thanks,
> 
> James

Patch
diff mbox series

diff --git a/arch/arm64/kernel/return_address.c b/arch/arm64/kernel/return_address.c
index b21cba90f82d..7f8a143268b0 100644
--- a/arch/arm64/kernel/return_address.c
+++ b/arch/arm64/kernel/return_address.c
@@ -8,6 +8,7 @@ 
 
 #include <linux/export.h>
 #include <linux/ftrace.h>
+#include <linux/kprobes.h>
 
 #include <asm/stack_pointer.h>
 #include <asm/stacktrace.h>
@@ -17,7 +18,7 @@  struct return_address_data {
 	void *addr;
 };
 
-static int save_return_addr(struct stackframe *frame, void *d)
+static nokprobe_inline int save_return_addr(struct stackframe *frame, void *d)
 {
 	struct return_address_data *data = d;
 
@@ -52,3 +53,4 @@  void *return_address(unsigned int level)
 		return NULL;
 }
 EXPORT_SYMBOL_GPL(return_address);
+NOKPROBE_SYMBOL(return_address);
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 62d395151abe..cd7dab54d17b 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -7,6 +7,7 @@ 
 #include <linux/kernel.h>
 #include <linux/export.h>
 #include <linux/ftrace.h>
+#include <linux/kprobes.h>
 #include <linux/sched.h>
 #include <linux/sched/debug.h>
 #include <linux/sched/task_stack.h>
@@ -73,6 +74,7 @@  int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 
 	return 0;
 }
+NOKPROBE_SYMBOL(unwind_frame);
 
 void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 		     int (*fn)(struct stackframe *, void *), void *data)
@@ -87,6 +89,7 @@  void notrace walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 			break;
 	}
 }
+NOKPROBE_SYMBOL(walk_stackframe);
 
 #ifdef CONFIG_STACKTRACE
 struct stack_trace_data {