From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raj Patil Date: Fri, 30 May 2003 16:21:54 +0000 Subject: Re: [Linux-ia64] sys_clone() related info/help/pointer needed MIME-Version: 1 Content-Type: multipart/mixed; boundary="0-249732772-1054311714=:64176" Message-Id: List-Id: References: In-Reply-To: To: linux-ia64@vger.kernel.org --0-249732772-1054311714=:64176 Content-Type: text/plain; charset=us-ascii Thanks for your comments/info David. (was out for few days...) One thing I am not clear is why should it be different when sys_clone() is called as part of the regulare syscall and from a module as another syscall. Both of them are going through the same path; sys_clone(), do_fork(), copy_thread(). Am I missing something vey obvious to see the difference? BTW: I bought "ia-64 linux kernel design and implementation" book. It is very well wriiten. I am going through the 3rd chapter on threads for clone2()/ switch_stack/copy_thread etc. It will take some time to digest the info.... Thanks, Raj David Mosberger wrote: >>>>> On Thu, 22 May 2003 13:36:19 -0700 (PDT), Raj Patil said: Raj> The progam basically adds an entry to syscall table, and when Raj> this new syscall is called, it simply calls sys_clone() with Raj> same arguments. (like making a duplicate sys_clone call) Raj> static long my_call(unsigned long flags, unsigned long sz) { Raj> rc=sys_clone(flags, sz); /* sys_clone is exported */ ...... } Raj> Everything seems to work excpet that the child process created Raj> is not getting executed. clone() (or, more correctly: clone2()) is special: it needs both a pt_regs and a switch_stack structure at the top of the stack (see comments in arch/ia64/kernel/process.c for copy_thread()). Your test-case doesn't work because it probably isn't creating the switch_stack structure at all. --david --------------------------------- Do you Yahoo!? Free online calendar with sync to Outlook(TM). --0-249732772-1054311714=:64176 Content-Type: text/html; charset=us-ascii
Thanks for your comments/info David.
(was out for few days...)
 
One thing I am not clear is why should it be different when sys_clone()
is called as part of the regulare syscall and from a module as another
syscall. Both of them are going through the same path; sys_clone(),
do_fork(), copy_thread(). Am I missing something vey obvious to see the
difference?
 
BTW: I bought "ia-64 linux kernel design and implementation" book.
         It is very well wriiten.
         I am going through the 3rd chapter on threads for clone2()/
        switch_stack/copy_thread etc. It will take some time to digest
         the info....
 
Thanks,
Raj

David Mosberger <davidm@napali.hpl.hp.com> wrote:

>>>>> On Thu, 22 May 2003 13:36:19 -0700 (PDT), Raj Patil said:

Raj> The progam basically adds an entry to syscall table, and when
Raj> this new syscall is called, it simply calls sys_clone() with
Raj> same arguments. (like making a duplicate sys_clone call)
Raj> static long my_call(unsigned long flags, unsigned long sz) {
Raj> rc=sys_clone(flags, sz); /* sys_clone is exported */ ...... }
Raj> Everything seems to work excpet that the child process created
Raj> is not getting executed.

clone() (or, more correctly: clone2()) is special: it needs both a
pt_regs and a switch_stack structure at the top of the stack (see
comments in arch/ia64/kernel/process.c for copy_thread()). Your
test-case doesn't work because it probably isn't creating the
switch_stack structure at all.

--david

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