Kernel+LibC: Clean up how assertions work in the kernel and LibC

This also brings LibC's abort() function closer to the spec.

Userland/DevTools/UserspaceEmulator/Emulator.h

@@ -163,7 +163,6 @@ private:
     int virt$connect(int sockfd, FlatPtr address, socklen_t address_size);
     int virt$shutdown(int sockfd, int how);
     void virt$sync();
-    void virt$abort();
     void virt$exit(int);
     ssize_t virt$getrandom(FlatPtr buffer, size_t buffer_size, unsigned int flags);
     int virt$chdir(FlatPtr, size_t);

Userland/DevTools/UserspaceEmulator/Emulator_syscalls.cpp

@@ -220,9 +220,6 @@ u32 Emulator::virt_syscall(u32 function, u32 arg1, u32 arg2, u32 arg3)
     case SC_sync:
         virt$sync();
         return 0;
-    case SC_abort:
-        virt$abort();
-        return 0;
     case SC_exit:
         virt$exit((int)arg1);
         return 0;
@@ -1036,14 +1033,6 @@ void Emulator::virt$sync()
     syscall(SC_sync);
 }
 
-void Emulator::virt$abort()
-{
-    reportln("\n=={}==  \033[33;1mSyscall: abort\033[0m, shutting down!", getpid());
-    m_exit_status = 127;
-    m_shutdown = true;
-    dump_backtrace();
-}
-
 void Emulator::virt$exit(int status)
 {
     reportln("\n=={}==  \033[33;1mSyscall: exit({})\033[0m, shutting down!", getpid(), status);

Userland/Libraries/LibC/assert.cpp

@@ -48,13 +48,12 @@ void __assertion_failed(const char* msg)
         { msg, strlen(msg) },
     };
     syscall(SC_set_coredump_metadata, &params);
-    syscall(SC_abort);
-    for (;;) { }
+    abort();
 }
 #endif
 }
 
-void __crash()
+void _abort()
 {
     asm volatile("ud2");
     __builtin_unreachable();

Userland/Libraries/LibC/assert.h

@@ -31,7 +31,7 @@
 __BEGIN_DECLS
 
 #ifdef DEBUG
-__attribute__((noreturn)) void __assertion_failed(const char* msg);
+[[noreturn]] void __assertion_failed(const char* msg);
 #    define __stringify_helper(x) #    x
 #    define __stringify(x) __stringify_helper(x)
 #    define assert(expr)                                                           \
@@ -42,12 +42,11 @@ __attribute__((noreturn)) void __assertion_failed(const char* msg);
 #    define VERIFY_NOT_REACHED() assert(false)
 #else
 #    define assert(expr) ((void)(0))
-#    define VERIFY_NOT_REACHED() CRASH()
+#    define VERIFY_NOT_REACHED() _abort()
 #endif
 
-__attribute__((noreturn)) void __crash();
+[[noreturn]] void _abort();
 
-#define CRASH() __crash()
 #define VERIFY assert
 #define TODO VERIFY_NOT_REACHED
 

Userland/Libraries/LibC/stdlib.cpp

@@ -249,8 +249,12 @@ void abort()
     // For starters, send ourselves a SIGABRT.
     raise(SIGABRT);
     // If that didn't kill us, try harder.
-    raise(SIGKILL);
-    _exit(127);
+    sigset_t set;
+    sigemptyset(&set);
+    sigaddset(&set, SIGABRT);
+    sigprocmask(SIG_UNBLOCK, &set, nullptr);
+    raise(SIGABRT);
+    _abort();
 }
 
 static HashTable<const char*> s_malloced_environment_variables;

Userland/Tests/Kernel/fuzz-syscalls.cpp

@@ -38,7 +38,7 @@
 
 static bool is_deadly_syscall(int fn)
 {
-    return fn == SC_exit || fn == SC_fork || fn == SC_sigreturn || fn == SC_exit_thread || fn == SC_abort;
+    return fn == SC_exit || fn == SC_fork || fn == SC_sigreturn || fn == SC_exit_thread;
 }
 
 static bool is_unfuzzable_syscall(int fn)