[seL4] Re: Device memory access issue on sel4 user driver

Hi All, I did some test with different reg. I performed read of some reg and could see that I can read the value correct as per the data sheet (default values) Then I tried to write and then read back the same. It gave halt with error as : "Kernel entry via unknown syscall, word: 3" Please find attached zip file with the code change, data sheet reg reference, and the output log. Can you suggest as what can cause this error because the data sheet says it's read/write reg with default enable. Regards, Misbah On Thu, 24 Oct 2024, 9:33 pm misbah khan, wrote:

Hello sel4 developers,

I am using seL4 for in our arm64 based hardware platform.

I need to write a simple driver where i need to read/write some memory mapped registers

The device physical address is "0x40520000"

When i print the bootinfo using the below code:

/*-- filter TaskContent("untyped-start", TaskContentType.ALL, subtask='init') -*/

printf(" CSlot \tPaddr \tSize\tType\n");

for (seL4_CPtr slot = info->untyped.start; slot != info->untyped.end; slot++) {

seL4_UntypedDesc *desc = &info->untypedList[slot - info->untyped.start];

printf("%8p\t%16p\t2^%d\t%s\n", (void *) slot, (void *) desc->paddr, desc->sizeBits, desc->isDevice ? "device untyped" : "untyped");

I get the following output:

CSlot Paddr Size Type

0x1ac 0 2^30 device untyped

0x1ad 0x40000000 2^28 device untyped

0x1ae 0x50000000 2^23 device untyped

0x1af 0x50810000 2^16 device untyped

0x1b0 0x50820000 2^17 device untyped

I am mappint the physical address to virtual and trying to access it as:

va = ps_io_map(&ops.io_mapper, (uintptr_t) 0x40520000,0x3000, PS_MEM_NORMAL);

ZF_LOGE("Physical address 0x%x mapped to virtual address %p \n",DEV_REG_PADDR,va);

for(int j=0;j

{

ZF_LOGE("Loc %d --> 0x%x ",j,*(unsigned int*)(va+j));

}

I am able to access some registers, but then it gives a fault (after printing 5-6 register values)

Similar is the behaviour with any reg between the range 0x40000000 - 0x50000000

Attaching the sample code and output: I am able to access first two address location, after that it gives halt.

Regards, Misbah