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nit_fb: prevent enlarging mode when out of RAM

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This patch adds a safety check to nit_fb to ensures that nit_fb never
runs out of RAM. Should the available RAM not suffice for resizing the
virtual framebuffer to a new mode, it keeps the current mode.
This commit is contained in:
Norman Feske 2018-02-09 20:52:46 +01:00
parent 013eb506a8
commit 69ac68ca98
1 changed files with 38 additions and 4 deletions
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42
repos/os/src/server/nit_fb/main.cc
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@ -27,6 +27,7 @@ namespace Nit_fb {
using Genode::Static_root;
using Genode::Signal_handler;
using Genode::Xml_node;
using Genode::size_t;
typedef Genode::Surface_base::Point Point;
typedef Genode::Surface_base::Area Area;
@ -95,6 +96,8 @@ namespace Framebuffer { struct Session_component; }
struct Framebuffer::Session_component : Genode::Rpc_object<Framebuffer::Session>
{
Genode::Pd_session const &_pd;
Nitpicker::Connection &_nitpicker;
Framebuffer::Session &_nit_fb = *_nitpicker.framebuffer();
@ -113,6 +116,14 @@ struct Framebuffer::Session_component : Genode::Rpc_object<Framebuffer::Session>
*/
Framebuffer::Mode _next_mode;
typedef Genode::size_t size_t;
/*
* Number of bytes used for backing the current virtual framebuffer at
* nitpicker.
*/
size_t _buffer_num_bytes = 0;
/*
* Mode that was returned to the client at the last call of
* 'Framebuffer:mode'. The virtual framebuffer must correspond to this
@ -123,15 +134,27 @@ struct Framebuffer::Session_component : Genode::Rpc_object<Framebuffer::Session>
bool _dataspace_is_new = true;
bool _ram_suffices_for_mode(Framebuffer::Mode mode) const
{
/* calculation in bytes */
size_t const used = _buffer_num_bytes,
needed = Nitpicker::Session::ram_quota(mode, false),
usable = _pd.avail_ram().value,
preserved = 64*1024;
return used + usable > needed + preserved;
}
/**
* Constructor
*/
Session_component(Nitpicker::Connection &nitpicker,
Session_component(Genode::Pd_session const &pd,
Nitpicker::Connection &nitpicker,
View_updater &view_updater,
Framebuffer::Mode initial_mode)
:
_nitpicker(nitpicker), _view_updater(view_updater),
_pd(pd), _nitpicker(nitpicker), _view_updater(view_updater),
_next_mode(initial_mode)
{ }
@ -141,7 +164,14 @@ struct Framebuffer::Session_component : Genode::Rpc_object<Framebuffer::Session>
if (Nitpicker::Area(_next_mode.width(), _next_mode.height()) == size)
return;
_next_mode = Framebuffer::Mode(size.w(), size.h(), _next_mode.format());
Framebuffer::Mode const mode(size.w(), size.h(), _next_mode.format());
if (!_ram_suffices_for_mode(mode)) {
Genode::warning("insufficient RAM for mode ", mode);
return;
}
_next_mode = mode;
if (_mode_sigh.valid())
Genode::Signal_transmitter(_mode_sigh).submit();
@ -161,6 +191,10 @@ struct Framebuffer::Session_component : Genode::Rpc_object<Framebuffer::Session>
{
_nitpicker.buffer(_active_mode, false);
_buffer_num_bytes =
Genode::max(_buffer_num_bytes,
Nitpicker::Session::ram_quota(_active_mode, false));
/*
* We defer the update of the view until the client calls refresh the
* next time. This avoid showing the empty buffer as an intermediate
@ -271,7 +305,7 @@ struct Nit_fb::Main : View_updater
* Input and framebuffer sessions provided to our client
*/
Input::Session_component input_session { env, env.ram() };
Framebuffer::Session_component fb_session { nitpicker, *this, _initial_mode() };
Framebuffer::Session_component fb_session { env.pd(), nitpicker, *this, _initial_mode() };
/*
* Attach root interfaces to the entry point