I’m currently developing a simple trustzone device driver running in Normal World to communicate with Genode in Secure World. I’m using IMX53 QSB, Genode 15.02 as Secure OS, and customized Linux as OS for Normal World.
In Normal World, my simple device driver calls smc instruction inside module_init(). The instruction is invoked with the command structure (named by “struct smc_cmd”). The physical address of "struct smc_cmd" is passing to Genode via _vm->state()->r1. There exists two physical addresses inside “struct smc_cmd": one for request buffer and the other for response buffer where the response buffer is allocated by kzalloc(). For the address conversion, I used virt_to_phys().
In Secure World (Genode), I’m modifying the tz_vmm source code for this experiment. I’m succeed in reading the request buffer from Normal World by directly accessing the physical address of the request buffer :
PINF("req_buf = %s (0x%x)", (char*)((struct smc_cmd*)cmd_addr)->req_buf_phys, ((struct smc_cmd*)cmd_addr)->req_buf_phys);
Ridiculously and Unfortunately, I’m in trouble to write some characters in response buffer (whose address is the physical address of Normal World). I used Genode::memcpy() to write the characters as follows where cmd_addr is the physical address of the command structure passed from Normal World :
/* acquire data to be written into memory space of normal world */ Genode::memcpy(tmp, (const char*) "From Secure World", strlen("From Secure World")); tmp[17] = '\0';
/* write a data into resp_buf_phys */ Genode::memcpy((char*)((struct smc_cmd*)cmd_addr)->resp_buf_phys, (const char*) tmp, sizeof(tmp));
/* printout contents of memory for debug */ PINF("res_buf = %s (0x%x)", (char*)((struct smc_cmd*)cmd_addr)->resp_buf_phys, ((struct smc_cmd*)cmd_addr)->resp_buf_phys);
It seems that the writing operation in Secure World is successful since the last PINF() shows me the “From Secure World” in console.
However, when I read the address (converted from the physical address using phys_to_virt()) in my device driver, I can only see the empty string (initial status).
My questions are :
Do I need another approach to write the physical memory of Normal World in the side of Genode? Is there any simple example or any volunteer to share an example for this kind of operation? Is there any comment to implement this kind of example?