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report_rom: clear stale content

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When replacing a report with a smaller one, the corresponding ROM
dataspace should not contain any traces of the old report. Otherwise,
the consumer of the ROM dataspace may mistake the stale content as
meaningful information. This is particularly annoying when manually
inspecting reports. This patch overwrites the stale content with zeros.
This commit is contained in:
Norman Feske 2015-06-16 15:19:15 +02:00 committed by Christian Helmuth
parent cc74204801
commit 4616f540df
1 changed files with 13 additions and 2 deletions
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15
repos/os/src/server/report_rom/rom_service.h
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@ -41,6 +41,8 @@ class Rom::Session_component : public Genode::Rpc_object<Genode::Rom_session>,
Lazy_volatile_object<Genode::Attached_ram_dataspace> _ds;
size_t _content_size = 0;
Genode::Signal_context_capability _sigh;
public:
@ -65,7 +67,7 @@ class Rom::Session_component : public Genode::Rpc_object<Genode::Rom_session>,
_ds.construct(env()->ram_session(), _module.size());
/* fill dataspace content with report contained in module */
_module.read_content(_ds->local_addr<char>(), _ds->size());
_content_size = _module.read_content(_ds->local_addr<char>(), _ds->size());
/* cast RAM into ROM dataspace capability */
Dataspace_capability ds_cap = static_cap_cast<Dataspace>(_ds->cap());
@ -78,7 +80,16 @@ class Rom::Session_component : public Genode::Rpc_object<Genode::Rom_session>,
if (!_ds.is_constructed() || _module.size() > _ds->size())
return false;
_module.read_content(_ds->local_addr<char>(), _ds->size());
size_t const new_content_size =
_module.read_content(_ds->local_addr<char>(), _ds->size());
/* clear difference between old and new content */
if (new_content_size < _content_size)
Genode::memset(_ds->local_addr<char>() + new_content_size, 0,
_content_size - new_content_size);
_content_size = new_content_size;
return true;
}