This is my function : static spinlock_t xgr_learn_lock = SPIN_LOCK_UNLOCKED; static int piga_seq_cpt = 1; /* * Function called for each systemcall (Hook SELinux avc function) */ int piga_control(u32 ssid, ...., struct av_decision * avd) { /* * Here my hypercall work but block my vm with this error : * " BUG: scheduling while atomic ... " */ spin_lock_bh(&xgr_learn_lock); if ( in_atomic()) kvm_hypercall2 ( 6, (unsigned long)2 ,(unsigned long)piga_seq_cpt); spin_unlock_bh(&xgr_learn_lock); if (piga_on == 1) { /* * Here my hypercall make a kernel panic with this error: * " divide error: 0000 [#1] SMP" */ spin_lock_bh(&xgr_learn_lock); set_current_state(TASK_UNINTERRUPTIBLE); kvm_hypercall2 ( 6, (unsigned long)2 ,(unsigned long)piga_seq_cpt); set_current_state(TASK_RUNNING); spin_lock_bh(&xgr_learn_lock); } }

Date: Wed, 8 Jun 2011 15:52:33 +0530 Subject: Re: Problems with hypercalls From: fs.rajat@gmail.com To: mulyadi.santosa@gmail.com CC: tricheurs@hotmail.fr; kernelnewbies@kernelnewbies.org

are you doing 64bit devision on 32 bit arch? If that is the case, do_div is worth considering.

On Wed, Jun 8, 2011 at 3:25 PM, Mulyadi Santosa <mulyadi.santosa@gmail.com> wrote:

...

On Tue, Jun 7, 2011 at 15:39, emilie lefebvre <tricheurs@hotmail.fr> wrote:

...

"divide error: 0000 [#1] SMP ... [<ffffffff813f8cdd>] panic+0x78/0x137 [<ffffffff813fcb94>] oops_end+0xe4/0x100 [<ffffffff8101021b>] die+0x5b/0x90 [<ffffffff813fc444>] do_trap+0xc4/0x160 [<ffffffff8100df2f>] do_divide_error+0x8f/0xb0 [<ffffffff811f974c>] ? my_function+0xdc/0xe70 "

Could you have any suggestions ?

Could you show us your code? perhaps by pasting them somewhere?

...

From what I guess, sounds like your code did some math (directly or indirectly) that fiddle with floating point numbers?

-- regards,

Mulyadi Santosa Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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perhaps this example will provide u with more info: http://a380.informatik.uni-bremen.de/lxr/source/arch/x86/lguest/boot.c I think the correct step is to disable IRQ instead - before every call to kvm_hypercallX(). The reason is given in the remark: 110 /* 111 * Disable interrupts if not already disabled: we don't want an 112 * interrupt handler making a hypercall while we're already doing 113 * one! 114 */ On Wed, Jun 8, 2011 at 10:54 PM, emilie lefebvre <tricheurs@hotmail.fr> wrote:

This is my function :

static spinlock_t xgr_learn_lock = SPIN_LOCK_UNLOCKED; static int piga_seq_cpt = 1;

/* * Function called for each systemcall (Hook SELinux avc function) */ int piga_control(u32 ssid, ...., struct av_decision * avd) {

/* * Here my hypercall work but block my vm with this error : *                " BUG: scheduling while atomic ... " */

spin_lock_bh(&xgr_learn_lock);   if ( in_atomic())            kvm_hypercall2 ( 6, (unsigned long)2 ,(unsigned long)piga_seq_cpt);   spin_unlock_bh(&xgr_learn_lock);

 if (piga_on == 1) { /* * Here my hypercall make a kernel panic with this error: *             " divide error: 0000 [#1] SMP" */                 spin_lock_bh(&xgr_learn_lock);                 set_current_state(TASK_UNINTERRUPTIBLE);                 kvm_hypercall2 ( 6, (unsigned long)2 ,(unsigned long)piga_seq_cpt);                 set_current_state(TASK_RUNNING);                 spin_lock_bh(&xgr_learn_lock); } }

I think u generally set TASK_UNINTERRUPTIBLE whenever about to modify the scheduling task list (eg, wait queue manipulation) or about to call "schedule()" (ie, doing your own scheduling). The function set_current_state() literally just set the variable value only, it does not disable interrupt. -- Regards, Peter Teoh

I guessed the cause of the error is really somewhere else - nothing to do with this part. But without a full view of the entire source - it is hard to diagnose the bugs. (Perhaps even more difficult if full view is available). But I have no problem insmod lg.ko in drivers/lguest directory (after CONFIG_LGUEST is set to "m"), and lguest is not a simple example I must say. And to get a better understanding on how to use the kvm_hypercall APIs, just go to the kernel source's drivers/lguest directory and enter "make" and it will churns lots of information (totalling about 7000+ lines) teaching you the basic of KVM - both how the KVM hypervisor works, and how the lguest work. And if u are lazy to do a "make" this is my version: https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B1hg6_Fvn... On Thu, Jun 9, 2011 at 4:35 PM, emilie lefebvre <tricheurs@hotmail.fr> wrote:

Hi, I try this :

 local_irq_save(flags);  kvm_hypercall2 ( 6, 2, 2);  local_irq_restore(flags);

But I still have my kernel panic with "divide error: 0000 [#1] SMP" that I don't understand! with or without lock, nothing change, the same when I change the current state.

I tried to move my hypercall and I still don't understand why it works just before my test "if (piga_on == 1)" without any protections (like disable interrupts) and not after..

Thank you for trying to help me

...

Date: Thu, 9 Jun 2011 09:46:12 +0800 Subject: Re: Problems with hypercalls From: htmldeveloper@gmail.com To: tricheurs@hotmail.fr CC: kernelnewbies@kernelnewbies.org

perhaps this example will provide u with more info:

http://a380.informatik.uni-bremen.de/lxr/source/arch/x86/lguest/boot.c

I think the correct step is to disable IRQ instead - before every call to kvm_hypercallX(). The reason is given in the remark:

110 /* 111 * Disable interrupts if not already disabled: we don't want an 112 * interrupt handler making a hypercall while we're already doing 113 * one! 114 */

On Wed, Jun 8, 2011 at 10:54 PM, emilie lefebvre <tricheurs@hotmail.fr> wrote:

...

This is my function :

static spinlock_t xgr_learn_lock = SPIN_LOCK_UNLOCKED; static int piga_seq_cpt = 1;

/* * Function called for each systemcall (Hook SELinux avc function) */ int piga_control(u32 ssid, ...., struct av_decision * avd) {

/* * Here my hypercall work but block my vm with this error : *                " BUG: scheduling while atomic ... " */

spin_lock_bh(&xgr_learn_lock);   if ( in_atomic())            kvm_hypercall2 ( 6, (unsigned long)2 ,(unsigned long)piga_seq_cpt);   spin_unlock_bh(&xgr_learn_lock);

 if (piga_on == 1) { /* * Here my hypercall make a kernel panic with this error: *             " divide error: 0000 [#1] SMP" */                 spin_lock_bh(&xgr_learn_lock);                 set_current_state(TASK_UNINTERRUPTIBLE);                 kvm_hypercall2 ( 6, (unsigned long)2 ,(unsigned long)piga_seq_cpt);                 set_current_state(TASK_RUNNING);                 spin_lock_bh(&xgr_learn_lock); } }

I think u generally set TASK_UNINTERRUPTIBLE whenever about to modify the scheduling task list (eg, wait queue manipulation) or about to call "schedule()" (ie, doing your own scheduling). The function set_current_state() literally just set the variable value only, it does not disable interrupt.

-- Regards, Peter Teoh

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-- Regards, Peter Teoh