Re: how to allocate 9MB of memory in kernel ?

On Thursday 24 July 2008, Misbah khan wrote:

Hi all ...
 
I am uploading the source code which is doing the following :-

1. mapping cpld register using ioremap coping the data to circular buffer
and remapping it to user space .

2. It can also map kernel virtual dma memory to user space if compiled
conditionally .

following is the problem which i am facing ...

1. It is somitimes giving following kernel panic ....

nable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: Oops: 17 [#1]
Modules linked in: fluke_driver tstamp sig_router mvci_spi mvci_sf_pcd
mvci_sci_unidir_s1 mvci_sci_diff mvci_sci_bidir_s
1 mvci_rtmd_s1 mvci_kwiso_s1 mvci_kw1281_s1 mvci_kh_s1 mvci_j1850
mvci_gm_sbc mvci_diagh_s1 g_ether mvci_dcl mvci_can1 f
pga_conf arcotg_udc adc_dac keypad(F) splc501_lcd(F) cpld
CPU: 0
PC is at cascade+0x64/0x8c
LR is at __init_begin+0x3fff8000/0x30
pc : [<c00484ac>]    lr : [<00000000>]    Tainted: GF
sp : c0293ea8  ip : 0040b000  fp : c0293ecc
r10: 8001d9f0  r9 : c0292000  r8 : 00000001
r7 : c0292000  r6 : 0000000c  r5 : c02fa048  r4 : 00000000
r3 : c02fa2f8  r2 : 0000261a  r1 : bf01ab70  r0 : c02fa2f8
Flags: Nzcv  IRQs off  FIQs on  Mode SVC_32  Segment kernel
Control: C5387F
Table: 8698C000  DAC: 00000017
Process swapper (pid: 0, stack limit = 0xc0292250)
Stack: (0xc0293ea8 to 0xc0294000)
3ea0:                   bf01ab70 c02fb440 0000000a 00000000 c02fa048
0000000a
3ec0: c0293efc c0293ed0 c0048810 c0048454 c0293eec c0293ee0 c002a30c
00000001
3ee0: c02f9e44 0000000a 00000002 00000001 c0293f1c c0293f00 c00442a0
c0048794
3f00: c0293f2c 0000001d c0294740 00000000 c0293f2c c0293f20 c00446d4
c0044254
3f20: c0293f4c c0293f30 c00217b0 c0044698 c0293f5c ffffffff 0000ffff
00000001
3f40: c0293fa4 c0293f50 c00209e4 c0021770 00000001 00000001 c0292000
00000000
3f60: c0022068 c0292000 c0298c44 c03121c0 8001da24 4107b364 8001d9f0
c0293fa4
3f80: c0293fa8 c0293f98 c0021d48 c002209c 60000013 ffffffff c0293fbc
c0293fa8
3fa0: c0021d48 c0022074 c02faae0 c02f292c c0293fcc c0293fc0 c00202e0
c0021d24
3fc0: c0293ff4 c0293fd0 c0008848 c00202b4 c00083c4 00000000 00000000
c02f29a8
3fe0: 00000000 00c5387d 00000000 c0293ff8 80008030 c00086e0 00000000
00000000
Backtrace:
[<c0048448>] (cascade+0x0/0x8c) from [<c0048810>]
(run_timer_softirq+0x88/0x1e8)
 r6 = 0000000A  r5 = C02FA048  r4 = 00000000
[<c0048788>] (run_timer_softirq+0x0/0x1e8) from [<c00442a0>]
(__do_softirq+0x58/0xc8)
 r8 = 00000001  r7 = 00000002  r6 = 0000000A  r5 = C02F9E44
 r4 = 00000001
[<c0044248>] (__do_softirq+0x0/0xc8) from [<c00446d4>] (irq_exit+0x48/0x5c)
 r6 = 00000000  r5 = C0294740  r4 = 0000001D
[<c004468c>] (irq_exit+0x0/0x5c) from [<c00217b0>] (asm_do_IRQ+0x4c/0x64)
[<c0021764>] (asm_do_IRQ+0x0/0x64) from [<c00209e4>] (__irq_svc+0x44/0x80)
 r6 = 00000001  r5 = 0000FFFF  r4 = FFFFFFFF
[<c0022068>] (default_idle+0x0/0x3c) from [<c0021d48>] (cpu_idle+0x30/0x5c)
[<c0021d18>] (cpu_idle+0x0/0x5c) from [<c00202e0>] (rest_init+0x38/0x40)
 r5 = C02F292C  r4 = C02FAAE0
[<c00202a8>] (rest_init+0x0/0x40) from [<c0008848>]
(start_kernel+0x174/0x1c0)
[<c00086d4>] (start_kernel+0x0/0x1c0) from [<80008030>] (0x80008030)
Code: e1530005 15822000 ebffffb6 e1a0e004 (e5944000)
 <0>Kernel panic - not syncing: Aiee, killing interrupt handler!


also when i run it on X86 PC i am able to get the data and no panic where in
on the board it is giving the above error ....

2. I can raed the data using the user application when i run it on X86 PC
where in i cant able to read the data when i run it on the board the data i
was getting was always '/0' filled buffer .


Here is the compilete code .............


static int McBSP_DriverOpen(struct inode *inode,struct file *file)
{
	/* Reintialize file operation structure */
	file->f_op=&fluke_fops;

this is already set.

	printk(KERN_DEBUG" fluke driver open success \n");

	if (device_open_count == 0)
	{
		device_open_count = 1;

		/* Reset the read and write index*/
		buf_index_area.write_index=0;
		buf_index_area.read_index=-1;
		buf_index_area.count_index=0;

		#ifdef SIMULATION
		/* Initialize the Timer */
		init_timer(&fluke_timer);
		fluke_timer.expires = jiffies + (HZ*10);//Timer will Expire after 60 sec
		fluke_timer.data = 0;
		fluke_timer.function = (void *)timer_func;
		add_timer(&fluke_timer);
		#endif
	}

	return 0;
}

Using the count in this way is racy, best write the code so
that it can allow multiple opens.

irqreturn_t DataAcqIntHandler(int irq,void *dev_id, struct pt_regs *regs)
{
	printk(KERN_ALERT" In Interrupt Handler\n");
	/* Data present status is set to wake up the read call */
	data_present_status=1;

	/* Wake up the blocked Select call */
	wake_up_interruptible(&wait_queue);

	#ifndef SIMULATION
	/* Clear the interrupt in the interrupt pending registor */
	cpi->ic_scprrh |=DATA_ACQ_INT_CLEAR;
	#endif

	return IRQ_HANDLED;

}/* End of PpsIntrHandler() */

The interrupt handler should be able to deal with shared interrupts,
and needs to check if the interrupt came from this device, returning
IRQ_NONE otherwise.

static int __init McBSP_DriverInit(void)
{
	unsigned int virt_addr = 0;
	int mem = 0;

	//buf_area = vmalloc(sizeof(circularbuffer_S));
	//if(!buf_area)
	//{
	//	printk(KERN_ALERT"vmalloc failed \n");
	//	return -1;
	//}

#if 0
	/*
	* Allocate memory for the circular buffer in the DMA coherent area
	* and algin it in the Cache
	*/
	mem = L1_CACHE_ALIGN(sizeof(circularbuffer_S));

	buf_ptr = (char *)dma_alloc_coherent(NULL, mem, &dma_addr,GFP_KERNEL);

no need for the cast.

	printk(KERN_INFO" buf_ptr = 0x%x \n",(int )buf_ptr);
	if(NULL == buf_ptr )
	{
		printk(KERN_ALERT" Allocation of Memory failure ");
		return -1;
	}

	buf_area = (circularbuffer_S *)(((unsigned int )buf_ptr + PAGE_SIZE - 1) \
			& PAGE_MASK);

	printk(KERN_INFO" buf_area = 0x%x \n",(int )buf_area);

	if(NULL == buf_area)
	{
		printk(KERN_ALERT" Circular buffer memory not allocated \n");
		return -1;
	}

	/* Marking the Pages as reserved */
	for (virt_addr = (unsigned int)buf_area; \
	virt_addr < (unsigned int )buf_area + sizeof(circularbuffer_S);\
	virt_addr += PAGE_SIZE)
	{
		/* Set the pages as reserved */
		SetPageReserved(virt_to_page(virt_addr));
		//mem_map_reserve(virt_to_page(virt_addr));
	}

no need for SetPageReserved, it already is marked as in use through
the allocation.

	phy_addr = virt_to_phys(buf_ptr);

You can't use virt_to_phys to get the dma address. You also don't need that
because you already have it in dma_addr.

	printk(KERN_INFO"Allocated Memory for Circular Buffer at physical
0x0%x\n",phy_addr);

#else

	buf_area = ioremap(0xB2000000,0x4000); //(0xB2000000,0x4000);
//(7700000,900000);
	if(!buf_area)
	{
		printk(KERN_ALERT"ioremap failed \n");
		return -1;
	}

Don't hardcode the numbers here, you should get the values from the
device tree, and use of_iomap().
 

	printk(" Ioremap mapped to virtual 0x0%x \n",buf_area);
	*((unsigned int *)buf_area) = 0xa5a5a5a5;
	printk(" Ioremap data  0x0%x \n",*((unsigned int *)buf_area + 0));

#endif

	/* Device major number is registered to set the driver entry point */
	if(register_chrdev(MAJOR_NO,MODULE_NAME, &fluke_fops)==0)
	{
		printk(KERN_DEBUG" Fluke driver registeration success \n");

	}
	else
	{
		printk(KERN_ALERT" Fluke driver registeration failed \n");
		return -1;
	}

Since it's just one device, it's easier to use a misc_device.
 

	/*
	 * Register Data Acq interrupt request with specified irq and install the
	 * handler
	 */
	 if(request_irq(DATA_ACQ_INT,(void *)DataAcqIntHandler, SA_INTERRUPT,
	 						MODULE_NAME, NULL)==0)
	{
		printk(KERN_DEBUG" Data Acq interrupt request returns success \n");
	}
	else
	{
		printk(KERN_DEBUG" Data Acq interrupt request failed \n");
		unregister_chrdev(MAJOR_NO,MODULE_NAME);
		return -1;

	}

hardcoding interrupt numbers is broken, interrupt numbers are relative to
one interrupt controller. Use irq_of_parse_and_map.

static int McBSP_DriverIoctl(struct inode *inode, struct file *file,\
									unsigned int cmd, unsigned long param)
{
	int i;
	daq_t daq_param;

	printk(KERN_DEBUG"In ioctl command \n");

	switch(cmd)
	{
		case START_ACQ_DATA:

			if(copy_from_user(&daq_param,(void *)param,sizeof(daq_param)))
			{

				return -1;
			}

			/* For Simulation we are writing the data */
			if(WriteBuf() < 0)
			{
				printk(" Writing to the memory failure \n");
				return -1;
			}

			/* Wait for the Interrupt to occur */
			wait_event_interruptible( wait_queue, data_present_status !=0);

			printk("Read Index before read %d\n",buf_index_area.read_index);
			data_present_status=0;

Racy, you could have multiple threads doing this ioctl.
Moreover, you should not block in an ioctl but rather
implement a poll() function for waiting.

			buf_index_area.read_index++;
			buf_index_area.read_index%=NO_FRAMES;

			if(buf_index_area.read_index ==((buf_index_area.write_index +1) %
NO_FRAMES))
			//if(buf_index_area.read_index == buf_index_area.write_index )
			{
				printk("Read failure because read and write index are same\n");
				return -1;
			}

			/* Decrement the count index to indicate the data availibility */
			down(&mutex);
			buf_index_area.count_index--;
			up(&mutex);

New drivers should not use semaphores (up/down) in places where they can use real
mutexes (mutex_lock/mutex_unlock).

static int McBSP_DriverMmap(struct file *file,struct  vm_area_struct *vma)
{

	unsigned long start = vma->vm_start;
	unsigned long size = vma->vm_end - vma->vm_start; //0x900000;
	unsigned long phy_add = virt_to_phys(buf_ptr); //0x7700000;

virt_to_phys doesn't work on vmalloc memory.

	int ret = 0;

	/* Make the mmaped area noncacheable */
	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

	/* Set the Flags to give permissions to Mmaped area */
	vma->vm_flags |=VM_RESERVED;
	vma->vm_flags |=VM_READ;
	vma->vm_flags |=VM_WRITE;
	vma->vm_flags |=VM_IO;
	//vma->vm_flags |=VM_SHARED;
	//vma->vm_flags |=VM_LOCKED;

For memory, you typically want to set vm_page_prot to use non-guarded mapping,
so that user space accesses are faster.

Not sure if VM_IO is right for vmalloc.

	Arnd <><