get virtual address corresponding to physical addresses in genode

Stefan Kalkowski stefan.kalkowski at ...1...
Mon Jul 24 14:17:13 CEST 2017

On 07/24/2017 12:21 PM, rijurekha at ...71... wrote:
> Hi,
> To get virtual address corresponding to any physical address in genode, we
> generally use:
> Genode::Io_mem_connection _ram_iomem(phy_addr, 4);
> Ram _ram(phy_addr, 4,
> (Genode::addr_t)Genode::env()->rm_session()->attach(_ram_iomem.dataspace()));
> _ram.local() then gives the necessary virtual address. This works
> vm_base.h for run/tz_vmm demo or vm.h for run/vmm, i.e. in the tz vmm user
> space.
> What can we do to get virtual addresses for physical addresses which are
> already mapped?
You can just calculate them for locally mapped devices. In principle
this "Ram" class is nothing more than a helper utility that saves the
virtual and physical start address of a portion of RAM, and helps to
calculate offsets.

> E.g. in the imx53 sabre tablet demo, the 7 GPIO banks are
> already mapped to virtual addresses in os/src/drivers/gpio/imx53/driver.h.
> If we have a physical address (from DFAR) corresponding to the GPIO
> address ranges, how can I get the virtual address in user space files
> corresponding to tz vmm?

In case of the GPIO banks used by the GPIO driver the situation is
different. GPIO driver and VMM are different components with different
address spaces. Here you are sliding into the same problem like with the
UART used by the kernel. You cannot simply alter the memory-mapped I/O
registers within the VMM. I mean technically you can, by adding it as
local device like every other device as well, but you will end up in
devil's kitchen, when altering the registers from two different
"drivers" concurrently.
Instead, you have to analyse semantically what the Linux OS tries to do
with the device, and use the GPIO drivers API appropriatedly.

> Thanks!
> Riju
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Stefan Kalkowski
Genode Labs ยท

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