Re: [uml-devel] Explaination of system call function flow in TT mode

2006-02-09 Thread Young Koh
Hi, I have a question about system call implementation in tt mode. it seems that an invoked system call will be executed in tracee's context. (the tracer sends SIGUSR2 to the tracee and tracee executes the system call in usr2_handler) however, 'current' macro, which is used to find the current

Re: [uml-devel] Explaination of system call function flow in TT mode

2006-02-09 Thread Jeff Dike
On Thu, Feb 09, 2006 at 05:08:59PM -0500, Young Koh wrote: I have a question about system call implementation in tt mode. it seems that an invoked system call will be executed in tracee's context. (the tracer sends SIGUSR2 to the tracee and tracee executes the system call in usr2_handler)

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-18 Thread Bodo Stroesser
Jeff Dike wrote: On Tue, May 17, 2005 at 01:56:55PM -0400, Young Koh wrote: the tracer (UML kernel) saves and restores the tracee's registers using ptrace() in order to get syscall paramaters and save the return value. while doing this, the tracer would need to care about only six registers(eax,

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-18 Thread Young Koh
Yeah, this is reasonable. You have to be careful that you save and restore any registers that might be used by one of the stubs, but they don't use FP. I also thought about not saving FP-regs on each kernel entry. But if you do this optimization, you need to save / restore FP-regs on

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-18 Thread Jeff Dike
On Wed, May 18, 2005 at 11:47:23AM +0200, Bodo Stroesser wrote: I also thought about not saving FP-regs on each kernel entry. But if you do this optimization, you need to save / restore FP-regs on switch_to. Also you need to get the FP-regs when setting up a signal-handler stackframe. And

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-18 Thread Bodo Stroesser
Jeff Dike wrote: On Wed, May 18, 2005 at 11:47:23AM +0200, Bodo Stroesser wrote: I also thought about not saving FP-regs on each kernel entry. But if you do this optimization, you need to save / restore FP-regs on switch_to. Also you need to get the FP-regs when setting up a signal-handler

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-18 Thread Bodo Stroesser
Blaisorblade wrote: On Wednesday 18 May 2005 15:24, Young Koh wrote: Yeah, this is reasonable. You have to be careful that you save and restore any registers that might be used by one of the stubs, but they don't use FP. I also thought about not saving FP-regs on each kernel entry. But if you do

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-18 Thread Blaisorblade
On Wednesday 18 May 2005 17:20, Bodo Stroesser wrote: Jeff Dike wrote: On Wed, May 18, 2005 at 11:47:23AM +0200, Bodo Stroesser wrote: I also thought about not saving FP-regs on each kernel entry. But if you do this optimization, you need to save / restore FP-regs on switch_to. Also you

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-18 Thread Jeff Dike
On Wed, May 18, 2005 at 04:57:47PM +0200, Blaisorblade wrote: In this case, instead, for SKAS mode, we must switch the registers manually, since we have collapsed everything in one host process. For TT and SKAS0 mode, instead, it's not needed, right Jeff and Bodo? Correct. Jeff

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-16 Thread Young Koh
Hi, Could you explain what happens in SKAS mode, then? How a UML kenel in SKAS mode handles the UML system calls differently from one in TT mode? i tried to understand from the code, but i had hard time to understand. Thank you very much! On 1/28/05, Blaisorblade [EMAIL PROTECTED] wrote: On

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-16 Thread Blaisorblade
On Monday 16 May 2005 16:08, Young Koh wrote: Hi, Could you explain what happens in SKAS mode, then? How a UML kenel in SKAS mode handles the UML system calls differently from one in TT mode? i tried to understand from the code, but i had hard time to understand. The usage of PTRACE_SYSCALL

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-16 Thread Blaisorblade
On Monday 16 May 2005 20:52, Young Koh wrote: Hi, Thanks for the reply. Let me have one following question. As my understand, in SKAS mode, tracer and tracee are different host processes, and they have UML kernel code and application code respectively. (in TT mode, tracee has both kernel and

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-16 Thread Blaisorblade
On Tuesday 17 May 2005 02:09, Young Koh wrote: Ok, now i'm getting close. Thanks a lot!!! but i have two more :) 1) in SKAS mode, the tracer (UML kernel) will execute a system call for the tracee (the user process). But what if the system call blocks? then, the tracer, the UML kernel, will

Re: [uml-devel] Explaination of system call function flow in TT mode

2005-05-16 Thread Jeff Dike
On Mon, May 16, 2005 at 02:52:37PM -0400, Young Koh wrote: Suppose the tracee attmpts to invoke a host system call. then, it will be intercepted by the tracer as in TT mode. (In TT mode, the tracer turns off tracing and sends SIGUSR2 to the tracee, and then, the signal handler in the tracee

[uml-devel] Explaination of system call function flow in TT mode

2005-01-28 Thread Blaisorblade
On Wednesday 26 January 2005 15:33, Alex LIU wrote: Hi,Blaisorblade: I have studied the TT mode of UML source code 2.6.7 for some time.But I still can't work out the system call function flow in TT mode.I have read some documents and comments on that but all of them are very rough... Is