On 10/27/05, AnupM <anupm@xxxxxxxxx> wrote:
> hi
> i am writting frame buffer driver for pxa 255
> kernel version 2.6.13
> i have modified arch/arm/mach-pxa/generic.c as follows
> /* virtual physical length type */
> { 0xf2000000, 0x40000000, 0x02000000, MT_DEVICE }, /* Devs */
> { 0xf4000000, 0x44000000, 0x00100000, MT_DEVICE }, /* LCD */
> { 0xf6000000, 0x48000000, 0x00100000, MT_DEVICE }, /* Mem Ctl */
> { 0xf8000000, 0x4c000000, 0x00100000, MT_DEVICE }, /* USB host */
> { 0xfa000000, 0x50000000, 0x00100000, MT_DEVICE }, /* Camera */
> { 0xfe000000, 0x58000000, 0x00100000, MT_DEVICE }, /* IMem ctl */
> { 0xff000000, 0x00000000, 0x00100000, MT_DEVICE }, /* UNCACHED_PHYS_0 */
> { 0xff200000, 0xa0ffc000, 0x00004000, MT_DEVICE } // this part is
> added.
>
> the driver gets registered properly.when i write data to virtual address
> 0xff200000 from kernel space ,it works successfully
> but if i write to same virtual address from user space , i get a
> segmentation fault
>
Are you getting kernel panic ? from seg fault in user space ? or
getting seg fault in kernel space while accessing memory from user
space ?
> i am not why this is happening.
I don't know about ARM architecture, but I am pretty sure you won't be
able to access Kernel Virtual Address in User Space directly without
mapping it from kernel to user space (can be through mmap) ! (CMIIW)
--
Fawad Lateef
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