linux-kernel - RE: [patch 1/14] x86, ptrace: add arch_ptrace_report

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Date:	Fri, 27 Mar 2009 15:12:35 +0000
From:	"Metzger, Markus T" <markus.t.metzger@...el.com>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>,
	"markus.t.metzger@...il.com" <markus.t.metzger@...il.com>,
	"roland@...hat.com" <roland@...hat.com>,
	"eranian@...glemail.com" <eranian@...glemail.com>,
	"Villacis, Juan" <juan.villacis@...el.com>,
	"ak@...ux.jf.intel.com" <ak@...ux.jf.intel.com>
Subject: RE: [patch 1/14] x86, ptrace: add arch_ptrace_report_exit

>-----Original Message-----
>From: Oleg Nesterov [mailto:oleg@...hat.com]
>Sent: Friday, March 27, 2009 3:20 PM
>To: Metzger, Markus T
>Cc: linux-kernel@...r.kernel.org; mingo@...e.hu; tglx@...utronix.de; hpa@...or.com;
>markus.t.metzger@...il.com; roland@...hat.com; eranian@...glemail.com; Villacis, Juan;
>ak@...ux.jf.intel.com
>Subject: Re: [patch 1/14] x86, ptrace: add arch_ptrace_report_exit
>
>On 03/27, Markus Metzger wrote:
>>
>> --- git-tip.orig/include/linux/ptrace.h	2009-03-23 10:45:30.000000000 +0100
>> +++ git-tip/include/linux/ptrace.h	2009-03-23 11:31:21.000000000 +0100
>> @@ -335,6 +335,23 @@ static inline void user_enable_block_ste
>>  #define arch_ptrace_fork(child, clone_flags)	do { } while (0)
>>  #endif
>>
>> +#ifndef arch_ptrace_report_exit
>> +/**
>> + * arch_ptrace_report_exit - Do machine specific work for exiting ptraced tasks
>> + * @exit_code:	current->exit_code value
>> + *
>> + * This is called early from do_exit() with no locks held after we notified the
>> + * ptracer.
>> + */
>> +#define arch_ptrace_report_exit(exit_code)	do { } while (0)
>> +#endif
>> +
>> +static inline void ptrace_report_exit(long *exit_code)
>> +{
>> +	ptrace_event(PT_TRACE_EXIT, PTRACE_EVENT_EXIT, *exit_code);
>> +	arch_ptrace_report_exit(*exit_code);
>> +}
>> +
>>  extern int task_current_syscall(struct task_struct *target, long *callno,
>>  				unsigned long args[6], unsigned int maxargs,
>>  				unsigned long *sp, unsigned long *pc);
>> Index: git-tip/include/linux/tracehook.h
>> ===================================================================
>> --- git-tip.orig/include/linux/tracehook.h	2009-03-23 10:45:30.000000000 +0100
>> +++ git-tip/include/linux/tracehook.h	2009-03-23 11:31:21.000000000 +0100
>> @@ -211,7 +211,7 @@ static inline void tracehook_report_exec
>>   */
>>  static inline void tracehook_report_exit(long *exit_code)
>>  {
>> -	ptrace_event(PT_TRACE_EXIT, PTRACE_EVENT_EXIT, *exit_code);
>> +	ptrace_report_exit(exit_code);
>>  }
>
>This needs Rolan'd review.
>
>But I'd say this has nothing to do with tracehooks. And why do
>you pass *exit_code to arch_ptrace_report_exit() ?
>
>Just add arch_ptrace_report_exit(void) into do_exit() ?
>
>>From the 3/14 patch:
>
>	#define arch_ptrace_report_exit(code) x86_ptrace_report_exit(code)
>
>	void x86_ptrace_report_exit(long exit_code)
>	{
>	       ptrace_bts_exit();
>	}
>
>This is a bit strange. Why do we need 2 functions, ptrace_bts_exit() and
>x86_ptrace_report_exit() which just calls the first one?

I did not want to take any shortcuts. I try to maintain the structure 
general_function()->ptrace_report()->arch_ptrace_report().

Recently, tracehook_report_whatever() calls were added which either do the
ptrace work directly or call a ptrace function. I try to use those calls, where possible.

It does not clutter the general code with x86 specific, or worse x86 branch trace
recording specific calls.


If people don't like these ptrace_whatever() and arch_ptrace_whatever() calls I add,
I can remove them and add my calls directly where I need them.

regards,
markus.

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