This patch replaces the former prominent use of pointers by references
wherever feasible. This has the following benefits:
* The contract between caller and callee becomes more obvious. When
passing a reference, the contract says that the argument cannot be
a null pointer. The caller is responsible to ensure that. Therefore,
the use of reference eliminates the need to add defensive null-pointer
checks at the callee site, which sometimes merely exist to be on the
safe side. The bottom line is that the code becomes easier to follow.
* Reference members must be initialized via an object initializer,
which promotes a programming style that avoids intermediate object-
construction states. Within core, there are still a few pointers
as member variables left though. E.g., caused by the late association
of 'Platform_thread' objects with their 'Platform_pd' objects.
* If no pointers are present as member variables, we don't need to
manually provide declarations of a private copy constructor and
an assignment operator to avoid -Weffc++ errors "class ... has
pointer data members [-Werror=effc++]".
This patch also changes a few system bindings on NOVA and Fiasco.OC,
e.g., the return value of the global 'cap_map' accessor has become a
reference. Hence, the patch touches a few places outside of core.
Fixes#3135
The patch adjust the code of the base, base-<kernel>, and os repository.
To adapt existing components to fix violations of the best practices
suggested by "Effective C++" as reported by the -Weffc++ compiler
argument. The changes follow the patterns outlined below:
* A class with virtual functions can no longer publicly inherit base
classed without a vtable. The inherited object may either be moved
to a member variable, or inherited privately. The latter would be
used for classes that inherit 'List::Element' or 'Avl_node'. In order
to enable the 'List' and 'Avl_tree' to access the meta data, the
'List' must become a friend.
* Instead of adding a virtual destructor to abstract base classes,
we inherit the new 'Interface' class, which contains a virtual
destructor. This way, single-line abstract base classes can stay
as compact as they are now. The 'Interface' utility resides in
base/include/util/interface.h.
* With the new warnings enabled, all member variables must be explicitly
initialized. Basic types may be initialized with '='. All other types
are initialized with braces '{ ... }' or as class initializers. If
basic types and non-basic types appear in a row, it is nice to only
use the brace syntax (also for basic types) and align the braces.
* If a class contains pointers as members, it must now also provide a
copy constructor and assignment operator. In the most cases, one
would make them private, effectively disallowing the objects to be
copied. Unfortunately, this warning cannot be fixed be inheriting
our existing 'Noncopyable' class (the compiler fails to detect that
the inheriting class cannot be copied and still gives the error).
For now, we have to manually add declarations for both the copy
constructor and assignment operator as private class members. Those
declarations should be prepended with a comment like this:
/*
* Noncopyable
*/
Thread(Thread const &);
Thread &operator = (Thread const &);
In the future, we should revisit these places and try to replace
the pointers with references. In the presence of at least one
reference member, the compiler would no longer implicitly generate
a copy constructor. So we could remove the manual declaration.
Issue #465
Besides adapting the components to the use of base/log.h, the patch
cleans up a few base headers, i.e., it removes unused includes from
root/component.h, specifically base/heap.h and
ram_session/ram_session.h. Hence, components that relied on the implicit
inclusion of those headers have to manually include those headers now.
While adjusting the log messages, I repeatedly stumbled over the problem
that printing char * arguments is ambiguous. It is unclear whether to
print the argument as pointer or null-terminated string. To overcome
this problem, the patch introduces a new type 'Cstring' that allows the
caller to express that the argument should be handled as null-terminated
string. As a nice side effect, with this type in place, the optional len
argument of the 'String' class could be removed. Instead of supplying a
pair of (char const *, size_t), the constructor accepts a 'Cstring'.
This, in turn, clears the way let the 'String' constructor use the new
output mechanism to assemble a string from multiple arguments (and
thereby getting rid of snprintf within Genode in the near future).
To enforce the explicit resolution of the char * ambiguity, the 'char *'
overload of the 'print' function is marked as deleted.
Issue #1987
This patch cleans up the thread API and comes with the following
noteworthy changes:
- Introduced Cpu_session::Weight type that replaces a formerly used
plain integer value to prevent the accidental mix-up of
arguments.
- The enum definition of Cpu_session::DEFAULT_WEIGHT moved to
Cpu_session::Weight::DEFAULT_WEIGHT
- New Thread constructor that takes a 'Env &' as first argument.
The original constructors are now marked as deprecated. For the
common use case where the default 'Weight' and 'Affinity' are
used, a shortcut is provided. In the long term, those two
constructors should be the only ones to remain.
- The former 'Thread<>' class template has been renamed to
'Thread_deprecated'.
- The former 'Thread_base' class is now called 'Thread'.
- The new 'name()' accessor returns the thread's name as 'Name'
object as centrally defined via 'Cpu_session::Name'. It is meant to
replace the old-fashioned 'name' method that takes a buffer and size
as arguments.
- Adaptation of the thread test to the new API
Issue #1954
This patch establishes a common organization of header files
internal to the base framework. The internal headers are located at
'<repository>/src/include/base/internal/'. This structure has been
choosen to make the nature of those headers immediately clear when
included:
#include <base/internal/lock_helper.h>
Issue #1832
This patch updates seL4 from the experimental branch of one year ago to
the master branch of version 2.1. The transition has the following
implications.
In contrast to the experimental branch, the master branch has no way to
manually define the allocation of kernel objects within untyped memory
ranges. Instead, the kernel maintains a built-in allocation policy. This
policy rules out the deallocation of once-used parts of untyped memory.
The only way to reuse memory is to revoke the entire untyped memory
range. Consequently, we cannot share a large untyped memory range for
kernel objects of different protection domains. In order to reuse memory
at a reasonably fine granularity, we need to split the initial untyped
memory ranges into small chunks that can be individually revoked. Those
chunks are called "untyped pages". An untyped page is a 4 KiB untyped
memory region.
The bootstrapping of core has to employ a two-stage allocation approach
now. For creating the initial kernel objects for core, which remain
static during the entire lifetime of the system, kernel objects are
created directly out of the initial untyped memory regions as reported
by the kernel. The so-called "initial untyped pool" keeps track of the
consumption of those untyped memory ranges by mimicking the kernel's
internal allocation policy. Kernel objects created this way can be of
any size. For example the phys CNode, which is used to store page-frame
capabilities is 16 MiB in size. Also, core's CSpace uses a relatively
large CNode.
After the initial setup phase, all remaining untyped memory is turned
into untyped pages. From this point on, new created kernel objects
cannot exceed 4 KiB in size because one kernel object cannot span
multiple untyped memory regions. The capability selectors for untyped
pages are organized similarly to those of page-frame capabilities. There
is a new 2nd-level CNode (UNTYPED_CORE_CNODE) that is dimensioned
according to the maximum amount of physical memory (1M entries, each
entry representing 4 KiB). The CNode is organized such that an index
into the CNode directly corresponds to the physical frame number of the
underlying memory. This way, we can easily determine a untyped page
selector for any physical addresses, i.e., for revoking the kernel
objects allocated at a specific physical page. The downside is the need
for another 16 MiB chunk of meta data. Also, we need to keep in mind
that this approach won't scale to 64-bit systems. We will eventually
need to replace the PHYS_CORE_CNODE and UNTYPED_CORE_CNODE by CNode
hierarchies to model a sparsely populated CNode.
The size constrain of kernel objects has the immediate implication that
the VM CSpaces of protection domains must be organized via several
levels of CNodes. I.e., as the top-level CNode of core has a size of
2^12, the remaining 20 PD-specific CSpace address bits are organized as
a 2nd-level 2^4 padding CNode, a 3rd-level 2^8 CNode, and several
4th-level 2^8 leaf CNodes. The latter contain the actual selectors for
the page tables and page-table entries of the respective PD.
As another slight difference from the experimental branch, the master
branch requires the explicit assignment of page directories to an ASID
pool.
Besides the adjustment to the new seL4 version, the patch introduces a
dedicated type for capability selectors. Previously, we just used to
represent them as unsigned integer values, which became increasingly
confusing. The new type 'Cap_sel' is a PD-local capability selector. The
type 'Cnode_index' is an index into a CNode (which is not generally not
the entire CSpace of the PD).
Fixes#1887
Instead of returning pointers to locked objects via a lookup function,
the new object pool implementation restricts object access to
functors resp. lambda expressions that are applied to the objects
within the pool itself.
Fix#884Fix#1658
For most platforms except of NOVA a distinction between pager entrypoint
and pager activation is not needed, and only exists due to historical
reasons. Moreover, the pager thread's execution path is almost identical
between most platforms excluding NOVA, HW, and Fisco.OC. Therefore,
this commit unifies the pager loop for the other platforms, and removes
the pager activation class.
