Kernel+LibC: Tidy up assertion failures with a dedicated syscall

This patch adds sys$abort() which immediately crashes the process with
SIGABRT. This makes assertion backtraces a lot nicer by removing all
the gunk that otherwise happens between __assertion_failed() and
actually crashing from the SIGABRT.

Kernel/API/Syscall.h

@@ -197,7 +197,8 @@ namespace Kernel {
     S(allocate_tls)           \
     S(prctl)                  \
     S(mremap)                 \
-    S(set_coredump_metadata)
+    S(set_coredump_metadata)  \
+    S(abort)
 
 namespace Syscall {
 

Kernel/CMakeLists.txt

@@ -104,6 +104,7 @@ set(KERNEL_SOURCES
     SharedBuffer.cpp
     StdLib.cpp
     Syscall.cpp
+    Syscalls/abort.cpp
     Syscalls/access.cpp
     Syscalls/alarm.cpp
     Syscalls/beep.cpp

Kernel/Process.h

@@ -365,6 +365,7 @@ public:
     void* sys$allocate_tls(size_t);
     int sys$prctl(int option, FlatPtr arg1, FlatPtr arg2);
     int sys$set_coredump_metadata(Userspace<const Syscall::SC_set_coredump_metadata_params*>);
+    void sys$abort();
 
     template<bool sockname, typename Params>
     int get_sock_or_peer_name(const Params&);

Kernel/Syscalls/abort.cpp

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * 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/StringView.h>
+#include <Kernel/FileSystem/VirtualFileSystem.h>
+#include <Kernel/Process.h>
+
+namespace Kernel {
+
+void Process::sys$abort()
+{
+    cli();
+    crash(SIGABRT, 0);
+}
+
+}

Libraries/LibC/assert.cpp

@@ -47,8 +47,8 @@ void __assertion_failed(const char* msg)
         { msg, strlen(msg) },
     };
     syscall(SC_set_coredump_metadata, &params);
-
-    abort();
+    syscall(SC_abort);
+    for (;;) { }
 }
 #endif
 }