Build ELF executables with a zero length `GNU_STACK`
program header flagged non-executable.
The stack is never executable on SerenityOS regardless
of whether the `GNU_STACK` header is specified.
Specifically defining this header is more explicit,
as absence of this header implies an executable stack
on other systems (Linux).
These tests were never built for the serenity target. Move their Lagom
build steps to the Lagom CMakeLists.txt, and add serenity build steps
for them. Also, fix the build errors when building them with the
serenity cross-compiler :^)
A new operator, operator""sv was added as of C++17 to support
string_view literals. This allows string_views to be constructed
from string literals and with no runtime cost to find the string
length.
See: https://en.cppreference.com/w/cpp/string/basic_string_view/operator%22%22sv
This change implements that functionality in AK::StringView.
We do have to suppress some warnings about implementing reserved
operators as we are essentially implementing STL functions in AK
as we have no STL :).
For some reason I don't yet understand, building the kernel with -O2
produces a way-too-large kernel on some people's systems.
Since there are some really nice performance benefits from -O2 in
userspace, let's do a compromise and build Userland with -O2 but
put Kernel back into the -Os box for now.
Our TLS implementation relies on the TLS model being "initial-exec".
We previously enforced this by adding the '-ftls-model=initial-exec'
flag in the root CmakeLists file, but that did not affect ports - So
now we put that flag in the gcc spec files.
Closes#5366
This option causes GCC to generate code to prevent "stack clash" style
attacks where a very large stack allocation is used in to jump over the
stack guard page and into whatever's next to it.
To support this, I had to reorganize the "load_elf" function into two
passes. First we map all the dynamic objects, to get their symbols
into the global lookup table. Then we link all the dynamic objects.
So many read-only GOT's! :^)
The dynamic loader will now mark RELRO segments read-only after
performing relocations. This is pretty cool!
Note that this only applies to main executables so far,.
RELRO support for shared libraries will require some reorganizing
of the dynamic loader.
This removes some hard references to the toolchain, some unnecessary
uses of an external install command, and disables a -Werror flag (for
the time being) - only if run inside serenity.
With this, we can build and link the kernel :^)
Running 'ninja install && ninja image && ninja run` is kind of
annoying. I got tired, and came up with this instead, which does the
right thing and I don't have to type out the incantation.
KASAN is a dynamic analysis tool that finds memory errors. It focuses
mostly on finding use-after-free and out-of-bound read/writes bugs.
KASAN works by allocating a "shadow memory" region which is used to store
whether each byte of memory is safe to access. The compiler then instruments
the kernel code and a check is inserted which validates the state of the
shadow memory region on every memory access (load or store).
To fully integrate KASAN into the SerenityOS kernel we need to:
a) Implement the KASAN interface to intercept the injected loads/stores.
void __asan_load*(address);
void __asan_store(address);
b) Setup KASAN region and determine the shadow memory offset + translation.
This might be challenging since Serenity is only 32bit at this time.
Ex: Linux implements kernel address -> shadow address translation like:
static inline void *kasan_mem_to_shadow(const void *addr)
{
return ((unsigned long)addr >> KASAN_SHADOW_SCALE_SHIFT)
+ KASAN_SHADOW_OFFSET;
}
c) Integrating KASAN with Kernel allocators.
The kernel allocators need to be taught how to record allocation state
in the shadow memory region.
This commit only implements the initial steps of this long process:
- A new (default OFF) CMake build flag `ENABLE_KERNEL_ADDRESS_SANITIZER`
- Stubs out enough of the KASAN interface to allow the Kernel to link clean.
Currently the KASAN kernel crashes on boot (triple fault because of the crash
in strlen other sanitizer are seeing) but the goal here is to just get started,
and this should help others jump in and continue making progress on KASAN.
References:
* ASAN Paper: https://static.googleusercontent.com/media/research.google.com/en//pubs/archive/37752.pdf
* KASAN Docs: https://github.com/google/kasan
* NetBSD KASAN Blog: https://blog.netbsd.org/tnf/entry/kernel_address_sanitizer_part_3
* LWN KASAN Article: https://lwn.net/Articles/612153/
* Tracking Issue #5351
This is an external file from https://pci-ids.ucw.cz that's being updated
daily, which was imported a while ago but probably shouldn't live in the
SerenityOS repository in the first place (or else would need manual
maintenance). The legal aspects of redistributing this file as we
currently do are not quite clear to me, they require either GPL (version
2 or later) or 3-clause BSD - Serenity is 2-clause BSD...
The current version we use is 2019.08.08, so quite outdated - and while
most of these devices are obviously not supported, we're still capable
of *listing* them, so having an up-to-date version with recent additions
and fixes would be nice.
This updates the root CMakeLists.txt to check for existence of the file
and download it if not found - effectively on every fresh build. Do note
that this is not a critical file, and the system runs just fine should
this ever fail. :^)
This achieves two things:
- Programs can now intentionally perform arbitrary syscalls by calling
syscall(). This allows us to work on things like syscall fuzzing.
- It restricts the ability of userspace to make syscalls to a single
4KB page of code. In order to call the kernel directly, an attacker
must now locate this page and call through it.
This was done with the help of several scripts, I dump them here to
easily find them later:
awk '/#ifdef/ { print "#cmakedefine01 "$2 }' AK/Debug.h.in
for debug_macro in $(awk '/#ifdef/ { print $2 }' AK/Debug.h.in)
do
find . \( -name '*.cpp' -o -name '*.h' -o -name '*.in' \) -not -path './Toolchain/*' -not -path './Build/*' -exec sed -i -E 's/#ifdef '$debug_macro'/#if '$debug_macro'/' {} \;
done
# Remember to remove WRAPPER_GERNERATOR_DEBUG from the list.
awk '/#cmake/ { print "set("$2" ON)" }' AK/Debug.h.in
Else, there's tons of "-- Set runtime path of" spam at build time,
with apparently no way of disabling the build noise other than turning
of rpaths. If the dynamic loader uses them at some point, we probably
want to set them through cflags/ldflags instead of through cmake's
built-in thing anyways, for that reason.
Modify the user mode runtime to insert stack canaries to find stack corruptions.
The `-fstack-protector-strong` variant was chosen because it catches more
issues than vanilla `-fstack-protector`, but doesn't have substantial
performance impact like `-fstack-protector-all`.
Details:
-fstack-protector enables stack protection for vulnerable functions that contain:
* A character array larger than 8 bytes.
* An 8-bit integer array larger than 8 bytes.
* A call to alloca() with either a variable size or a constant size bigger than 8 bytes.
-fstack-protector-strong enables stack protection for vulnerable functions that contain:
* An array of any size and type.
* A call to alloca().
* A local variable that has its address taken.
Example of it catching corrupting in the `stack-smash` test:
```
courage ~ $ ./user/Tests/LibC/stack-smash
[+] Starting the stack smash ...
Error: Stack protector failure, stack smashing detected!
Shell: Job 1 (/usr/Tests/LibC/stack-smash) Aborted
```
RTTI is still disabled for the Kernel, and for the Dynamic Loader. This
allows for much less awkward navigation of class heirarchies in LibCore,
LibGUI, LibWeb, and LibJS (eventually). Measured RootFS size increase
was < 1%, and libgui.so binary size was ~3.3%. The small binary size
increase here seems worth it :^)
* Add SERENITY_ARCH option to CMake for selecting the target toolchain
* Port all build scripts but continue to use i686
* Update GitHub Actions cache to include BuildIt.sh
Previosuly, generation of the SONAME attribute was disabled.
This caused libraries to have relative paths in DT_NEEDED attributes
(e.g "Libraries/libcore.so" instead of just "libcore.so"),
which caused build errors when the working directory during build was
not $SERENITY_ROOT/Build.
This caused the build of ports that use libraries other than libc.so
to fail (e.g the nesalizer port).
Closes#4457
We now configure the gcc spec files to use a different crt files for
static & PIE binaries.
This relieves us from the need to explicitly specify the desired crt0
file in cmake scripts.
Problem:
- These utility functions are only used in `AK`, but are being defined
in the top-level. This clutters the top-level.
Solution:
- Move the utility functions to `Meta/CMake/utils.cmake` and include
where needed.
- Also, move `all_the_debug_macros.cmake` into `Meta/CMake` directory
to consolidate the location of `*.cmake` script files.
Problem:
- Modifying CXXFLAGS directly is an old CMake style.
- The giant and ever-growing list of `*_DEBUG` macros clutters the
top-level CMakeLists.txt.
Solution:
- Use the more current `add_compile_definitions` function.
- Sort all the debug options so that they are easy to view.
- Move the `*_DEBUG` macros to their own file which can be included
directly.
Problem:
- Functions are duplicated in [PBM,PGM,PPM]Loader class
implementations. They are functionally equivalent. This does not
follow the DRY (Don't Repeat Yourself) principle.
Solution:
- Factor out the common functions into a separate file.
- Refactor common code to generic functions.
- Change `PPM_DEBUG` macro to be `PORTABLE_IMAGE_LOADER_DEBUG` to work
with all the supported types. This requires adding the image type to
the debug log messages for easier debugging.
Problem:
- Appending to CMAKE_CXX_FLAGS for everything is cumbersome.
Solution:
- Use the `add_compile_options` built-in function to handle adding
compiler options (and even de-duplicating).
Problem:
- Setting `CMAKE_CXX_FLAGS` directly to effect the version of the C++
standard being used is no longer the recommended best practice.
Solution:
- Set C++20 mode in the compiler by setting `CMAKE_CXX_STANDARD`.
- Force the build system generator not to fallback to the latest
standard supported by the compiler by enabling
`CMAKE_CXX_STANDARD_REQUIRED`. This shouldn't ever be a problem
though since the toolchain is tightly controlled.
- Disable GNU compiler extensions by disabling `CMAKE_CXX_EXTENSIONS`
to preserve the previous flags.
