diff mbox series

[2/6] ptrace: introduce ptrace_syscall_enter to consolidate PTRACE_SYSEMU handling

Message ID 20190228183220.15626-3-sudeep.holla@arm.com
State Superseded
Headers show
Series ptrace: consolidate PTRACE_SYSEMU handling and add support for arm64 | expand

Commit Message

Sudeep Holla Feb. 28, 2019, 6:32 p.m. UTC
Currently each architecture handles PTRACE_SYSEMU in very similar way.
It's completely arch independent and can be handled in the code helping
to consolidate PTRACE_SYSEMU handling.

Let's introduce a hook 'ptrace_syscall_enter' that arch specific syscall
entry code can call.

Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

---
 include/linux/ptrace.h |  1 +
 kernel/ptrace.c        | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

-- 
2.17.1

Comments

Haibo Xu (Arm Technology China) March 4, 2019, 8:03 a.m. UTC | #1
On 2019/3/1 2:32, Sudeep Holla wrote:
> Currently each architecture handles PTRACE_SYSEMU in very similar way.

> It's completely arch independent and can be handled in the code helping

> to consolidate PTRACE_SYSEMU handling.

>

> Let's introduce a hook 'ptrace_syscall_enter' that arch specific syscall

> entry code can call.

>


The 'ptrace_syscall_enter' is dedicated for PTRACE_SYSEMU flag,
So I suggest to rename the function to something like 'ptrace_syscall_emu_enter".

> +/*

> + * Hook to check and report for PTRACE_SYSEMU, can be called from arch

> + * arch syscall entry code

> + */

> +long ptrace_syscall_enter(struct pt_regs *regs)

> +{

> +#ifdef TIF_SYSCALL_EMU

> +if (test_thread_flag(TIF_SYSCALL_EMU)) {

> +if (tracehook_report_syscall_entry(regs));


Shall we remove the semi-colon at end of the above line?

> +return -1L;

> +}

> +#endif

> +return 0;

> +}

> +

>  /*

>   * Detach all tasks we were using ptrace on. Called with tasklist held

>   * for writing.

>

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Sudeep Holla March 4, 2019, 10:46 a.m. UTC | #2
On Mon, Mar 04, 2019 at 08:03:47AM +0000, Haibo Xu (Arm Technology China) wrote:
> On 2019/3/1 2:32, Sudeep Holla wrote:

> > Currently each architecture handles PTRACE_SYSEMU in very similar way.

> > It's completely arch independent and can be handled in the code helping

> > to consolidate PTRACE_SYSEMU handling.

> > 

> > Let's introduce a hook 'ptrace_syscall_enter' that arch specific syscall

> > entry code can call.

> > 

> 

> The 'ptrace_syscall_enter' is dedicated for PTRACE_SYSEMU flag,

> So I suggest to rename the function to something like 'ptrace_syscall_emu_enter".

> 


I am fine to rename.

> > +/*

> > + * Hook to check and report for PTRACE_SYSEMU, can be called from arch

> > + * arch syscall entry code

> > + */

> > +long ptrace_syscall_enter(struct pt_regs *regs)

> > +{

> > +#ifdef TIF_SYSCALL_EMU

> > +	if (test_thread_flag(TIF_SYSCALL_EMU)) {

> > +		if (tracehook_report_syscall_entry(regs));

> 

> Shall we remove the semi-colon at end of the above line?

> 


Added intentionally to keep GCC happy.

--
Regards,
Sudeep
Segher Boessenkool March 4, 2019, 12:23 p.m. UTC | #3
On Mon, Mar 04, 2019 at 10:46:43AM +0000, Sudeep Holla wrote:
> On Mon, Mar 04, 2019 at 08:03:47AM +0000, Haibo Xu (Arm Technology China) wrote:

> > On 2019/3/1 2:32, Sudeep Holla wrote:

> > > +long ptrace_syscall_enter(struct pt_regs *regs)

> > > +{

> > > +#ifdef TIF_SYSCALL_EMU

> > > +	if (test_thread_flag(TIF_SYSCALL_EMU)) {

> > > +		if (tracehook_report_syscall_entry(regs));

> > 

> > Shall we remove the semi-colon at end of the above line?

> 

> Added intentionally to keep GCC happy.


GCC warns because the user explicitly asked for it, with __must_check.
If you want to do things with an "if" like this, you should write e.g.

		if (tracehook_report_syscall_entry(regs))
			/*
			 * We can ignore the return code here, because of
			 * X and Y and Z.
			 */
			;

Or it probably is nicer to use a block:

		if (tracehook_report_syscall_entry(regs)) {
			/*
			 * We can ignore the return code here, because of
			 * X and Y and Z.
			 */
		}

The point is, you *always* should have a nice fat comment if you are
ignoring the return code of a __must_check function.


Segher
Sudeep Holla March 4, 2019, 12:27 p.m. UTC | #4
On Mon, Mar 04, 2019 at 06:23:32AM -0600, Segher Boessenkool wrote:
> On Mon, Mar 04, 2019 at 10:46:43AM +0000, Sudeep Holla wrote:

> > On Mon, Mar 04, 2019 at 08:03:47AM +0000, Haibo Xu (Arm Technology China) wrote:

> > > On 2019/3/1 2:32, Sudeep Holla wrote:

> > > > +long ptrace_syscall_enter(struct pt_regs *regs)

> > > > +{

> > > > +#ifdef TIF_SYSCALL_EMU

> > > > +	if (test_thread_flag(TIF_SYSCALL_EMU)) {

> > > > +		if (tracehook_report_syscall_entry(regs));

> > >

> > > Shall we remove the semi-colon at end of the above line?

> >

> > Added intentionally to keep GCC happy.

>

> GCC warns because the user explicitly asked for it, with __must_check.

> If you want to do things with an "if" like this, you should write e.g.

>

> 		if (tracehook_report_syscall_entry(regs))

> 			/*

> 			 * We can ignore the return code here, because of

> 			 * X and Y and Z.

> 			 */

> 			;

>

> Or it probably is nicer to use a block:

>

> 		if (tracehook_report_syscall_entry(regs)) {

> 			/*

> 			 * We can ignore the return code here, because of

> 			 * X and Y and Z.

> 			 */

> 		}

>

> The point is, you *always* should have a nice fat comment if you are

> ignoring the return code of a __must_check function.

>


Agreed, will add the comment.

--
Regards,
Sudeep
diff mbox series

Patch

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index edb9b040c94c..e30f51e3363e 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -407,6 +407,7 @@  static inline void user_single_step_report(struct pt_regs *regs)
 #define current_user_stack_pointer() user_stack_pointer(current_pt_regs())
 #endif
 
+extern long ptrace_syscall_enter(struct pt_regs *regs);
 extern int task_current_syscall(struct task_struct *target, long *callno,
 				unsigned long args[6], unsigned int maxargs,
 				unsigned long *sp, unsigned long *pc);
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 4fa3b7f4c3c7..6724eaf98e79 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -29,6 +29,7 @@ 
 #include <linux/hw_breakpoint.h>
 #include <linux/cn_proc.h>
 #include <linux/compat.h>
+#include <linux/tracehook.h>
 
 /*
  * Access another process' address space via ptrace.
@@ -557,6 +558,21 @@  static int ptrace_detach(struct task_struct *child, unsigned int data)
 	return 0;
 }
 
+/*
+ * Hook to check and report for PTRACE_SYSEMU, can be called from arch
+ * arch syscall entry code
+ */
+long ptrace_syscall_enter(struct pt_regs *regs)
+{
+#ifdef TIF_SYSCALL_EMU
+	if (test_thread_flag(TIF_SYSCALL_EMU)) {
+		if (tracehook_report_syscall_entry(regs));
+		return -1L;
+	}
+#endif
+	return 0;
+}
+
 /*
  * Detach all tasks we were using ptrace on. Called with tasklist held
  * for writing.