Hi Aditya,

passing non-POD objects such as connected lists, maps, etc. as RPC arguments is not supposed to work. The reason is that a pointer with a meaning in one address space is meaningless in another address space. Please refer to the Section 8.12 of the manual [1] and particularly Section 8.12.2 for more details about the RPC mechanism.

To transfer bulk data from one component to another, you may need to manually serialize your information to a shared memory buffer, to be picked up on the receiving side. See section 3.6 for the various approaches of inter-component communication.

[1] http://genode.org/files/53bcb8e33fe6602fed25edc3c7b922c5/manual-2015-04-27.p...

Cheers Norman

On 05/11/2015 10:49 PM, Aditya Kousik wrote:

Hello,

Calling Rpc_<method>(args, ...) from Session_client causes segfault 11 when I try to pass anything other than a default datatype. I'm trying to pass an object of std::string, and it prints the string inside the <method> just fine, but when I make the call<Rpc_method>(st), it breaks.

I tried working around this by creating a char* pointer instead. Print inside this method works and the rpc to session_component method also reaches, but whatever pointer I receive in the session_component is garbage data. How do I fix the RPC calls?

Thanks, Aditya.

Hello Dr. Norman,

I stumbled upon some useful examples in test/ds_ownership and general search showed me how to pull off shared memory. It's an interesting implementation.

What I did: Server: Ram_dataspace_capability ds = env()->ram_session()->alloc(SIZE); void* arg = env()->rm_session()->attach(ds);

I returned this ds through a getDataspace() RPC method on the server side to the invoking client. I'm able to effectively write bulk data between components. Thank you for directing me toward this.

I have a couple of spinoff questions though. 1. Initially I tried creating a Ram_connection ram1 and allocated as in the ds_ownership program

ram1.ref_account(env()->ram_session->cap()); env()->ram_session()->transfer_quota(ram1.cap(), 8*1024);

Then Ram_dataspace_capability ds = ram1.alloc(SIZE); and attached ds to RM session and sent back ds. But the client threw a C++ IPC error and called abort().

A) Is this because ram1 was local to the server?

B) Is the transfer quota mechanism is similar to the transfer_quota from the client during the creation of a session in the constructor?

2. I'm still trying to get my head around the concept of a capability. I tried going through the definition of a capability in base/capability.h, but I seemed to get nowhere. What can a user do with a capability - mechanisms such as attach and detach with the help of a capability etc.

I'm sure you've had similar questions asked before. Thank you taking the time to respond.

Regards, Aditya

On Mon, May 11, 2015 at 2:32 PM, Aditya Kousik <adit267.kousik@...9...> wrote:

Hello Norman,

This documentation is quite exquisite, I'm just laying my eyes on it. Are there any implementation examples to support the sequence diagrams? They'll help map the theory to the implementation.

Cheers, Aditya

On Mon, May 11, 2015 at 2:02 PM, Norman Feske < norman.feske@...1...> wrote:

...

Hi Aditya,

passing non-POD objects such as connected lists, maps, etc. as RPC arguments is not supposed to work. The reason is that a pointer with a meaning in one address space is meaningless in another address space. Please refer to the Section 8.12 of the manual [1] and particularly Section 8.12.2 for more details about the RPC mechanism.

To transfer bulk data from one component to another, you may need to manually serialize your information to a shared memory buffer, to be picked up on the receiving side. See section 3.6 for the various approaches of inter-component communication.

[1]

http://genode.org/files/53bcb8e33fe6602fed25edc3c7b922c5/manual-2015-04-27.p...

Cheers Norman

On 05/11/2015 10:49 PM, Aditya Kousik wrote:

...

Hello,

Calling Rpc_<method>(args, ...) from Session_client causes segfault 11 when I try to pass anything other than a default datatype. I'm trying to pass an object of std::string, and it prints the string inside the <method> just fine, but when I make the call<Rpc_method>(st), it breaks.

I tried working around this by creating a char* pointer instead. Print inside this method works and the rpc to session_component method also reaches, but whatever pointer I receive in the session_component is garbage data. How do I fix the RPC calls?

Thanks, Aditya.

-- Dr.-Ing. Norman Feske Genode Labs

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