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Revert "LibC: Implement Itanium C++ ABI for static variable guards"

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This reverts commit cdbbe14062.
This commit is contained in:
Andreas Kling 2020-05-20 14:23:31 +02:00
parent 250c3b363d
commit ef776c1e68
Notes: sideshowbarker 2024-07-19 06:19:12 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/ef776c1e681
6 changed files with 11 additions and 159 deletions
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1
Libraries/CMakeLists.txt
View file

@ -2,7 +2,6 @@ add_subdirectory(LibAudio)
add_subdirectory(LibC)
add_subdirectory(LibCore)
add_subdirectory(LibCrypto)
add_subdirectory(LibCxx)
add_subdirectory(LibDebug)
add_subdirectory(LibDesktop)
add_subdirectory(LibGemini)

6
Libraries/LibC/CMakeLists.txt
View file

@ -3,7 +3,7 @@ set(LIBC_SOURCES
assert.cpp
crt0.cpp
ctype.cpp
cxaatexit.cpp
cxxabi.cpp
dirent.cpp
dlfcn.cpp
fcntl.cpp
@ -51,6 +51,8 @@ file(GLOB AK_SOURCES "../../AK/*.cpp")
file(GLOB ELF_SOURCES "../LibELF/*.cpp")
set(ELF_SOURCES ${ELF_SOURCES} ../LibELF/Arch/i386/plt_trampoline.S)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DSERENITY_LIBC_BUILD")
add_library(crt0 STATIC crt0.cpp)
add_custom_command(
TARGET crt0
@ -60,4 +62,4 @@ add_custom_command(
set(SOURCES ${LIBC_SOURCES} ${AK_SOURCES} ${ELF_SOURCES})
serenity_libc(LibC c)
target_link_libraries(LibC crt0)
add_dependencies(LibC LibM LibCxx)
add_dependencies(LibC LibM)

1
Libraries/LibC/cxaatexit.cpp → Libraries/LibC/cxxabi.cpp
View file

@ -25,6 +25,7 @@
*/
#include <AK/Types.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>

7
Libraries/LibCxx/CMakeLists.txt
View file

@ -1,7 +0,0 @@
set(SOURCES
CxaGuard.cpp
)
# Shhh don't worry gcc, we are totally libstdc++
serenity_libc(LibCxx stdc++)
target_link_libraries(LibCxx LibC)

148
Libraries/LibCxx/CxaGuard.cpp
View file

@ -1,148 +0,0 @@
/*
* Copyright (c) 2020, Andrew Kaster <andrewdkaster@gmail.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <AK/Atomic.h>
#include <serenity.h>
#include <stdint.h>
#include <sys/types.h>
// Static variable guard logic, using futexes
// Written while looking at libc++ from a distance ;) This is super tricky...
// From itanium spec: Get passed a pointer to a 64 bit guard "object"
// [ 1 guard byte (checked by compiler), 7 bytes to work with ]
class CxaGuard {
public:
enum GuardState : uint8_t {
NotInitialized = 0,
DoneInit = 1,
InitInProgress = 2,
WaitingOnInit = 4
};
CxaGuard(uint64_t* guard_pointer)
: m_full_guard_var(guard_pointer)
, m_compiler_guard_byte((uint8_t*)guard_pointer)
, m_local_state_byte(&((uint8_t*)guard_pointer)[1])
{
}
int acquire()
{
// Someone else already initailzied this by storing to the 'really done' slot
if (GuardState::NotInitialized != m_compiler_guard_byte.load(AK::memory_order_acquire))
return 0;
// Time to begin the waiting game..
while (true) {
// Try to claim initialization for this thread from the initial state
uint8_t last_state = GuardState::NotInitialized;
if (m_local_state_byte.compare_exchange_strong(last_state, GuardState::InitInProgress, AK::memory_order_acq_rel))
return 1; // Tell compiler-generated code to init the variable
// Someone else set the state to done, we're done here
if (last_state == DoneInit)
return 0;
// Someone else set InitInProgress, time to wait (maybe)
if (last_state & GuardState::InitInProgress) {
// Try to set the in progress + done bits
if ((last_state & GuardState::WaitingOnInit) == 0) {
if (!m_local_state_byte.compare_exchange_strong(last_state, (GuardState::InitInProgress | GuardState::WaitingOnInit), AK::memory_order_acq_rel)) {
if (last_state == GuardState::DoneInit)
return 0;
if (last_state == GuardState::NotInitialized)
continue; // start over, and try to initialize in this thread
// else wait, someone else set the wait bit before us
}
}
// State is InitInProgress | WaitingOnInit, time to sleep
wait_on_futex();
}
}
}
void release()
{
// Store the value the compiler will look at, we're done! yay
m_compiler_guard_byte.store(GuardState::DoneInit, AK::memory_order_release);
// Set the value other threads chilling in our loop will look at to done
uint8_t old_local_state = m_local_state_byte.exchange(GuardState::DoneInit, AK::memory_order_acq_rel);
// Wake up sleepy heads, the variable is initialized!
if (old_local_state & GuardState::WaitingOnInit)
wake_futex();
}
void abort()
{
uint8_t old_local_state = m_local_state_byte.exchange(GuardState::NotInitialized, AK::memory_order_acq_rel);
// Wake up sleepy heads, someone else gets to try...
if (old_local_state & GuardState::WaitingOnInit)
wake_futex();
}
private:
void wait_on_futex()
{
int futex_value = (GuardState::InitInProgress | GuardState::WaitingOnInit) << 8;
futex((int32_t*)m_full_guard_var, FUTEX_WAIT, futex_value, nullptr);
}
void wake_futex()
{
futex((int32_t*)m_full_guard_var, FUTEX_WAKE, INT32_MAX, nullptr);
}
void* m_full_guard_var;
AtomicRef<uint8_t> m_compiler_guard_byte;
AtomicRef<uint8_t> m_local_state_byte; // we'll load and set this atomically
// Note that we're not using 6/8 bytes of the guard object...
};
extern "C" {
int __cxa_guard_acquire(uint64_t* guard_object)
{
CxaGuard g(guard_object);
return g.acquire();
}
void __cxa_guard_release(uint64_t* guard_object)
{
CxaGuard g(guard_object);
g.release();
}
void __cxa_guard_abort(uint64_t* guard_object)
{
CxaGuard g(guard_object);
g.abort();
}
} // extern "C"

7
Toolchain/BuildIt.sh
View file

@ -230,7 +230,7 @@ pushd "$DIR/Build/"
pushd "$BUILD"
cmake ..
"$MAKE" LibC
install -D Libraries/LibC/libc.a Libraries/LibM/libm.a Libraries/LibCxx/libstdc++.a Root/usr/lib/
install -D Libraries/LibC/libc.a Libraries/LibM/libm.a Root/usr/lib/
SRC_ROOT=$(realpath "$DIR"/..)
for header in "$SRC_ROOT"/Libraries/Lib{C,M}/**/*.h; do
target=$(echo "$header" | sed -e "s@$SRC_ROOT/Libraries/LibC@@" -e "s@$SRC_ROOT/Libraries/LibM@@")
@ -239,6 +239,11 @@ pushd "$DIR/Build/"
unset SRC_ROOT
popd
echo "XXX build libstdc++"
"$MAKE" all-target-libstdc++-v3 || exit 1
echo "XXX install libstdc++"
"$MAKE" install-target-libstdc++-v3 || exit 1
if [ "$(uname -s)" = "OpenBSD" ]; then
cd "$DIR/Local/libexec/gcc/i686-pc-serenity/$GCC_VERSION" && ln -sf liblto_plugin.so.0.0 liblto_plugin.so
fi