More random compat hacking towards getting bash to build.

I'm now at the build stage where it complains about a bajillion missing
symbols. This is a good place to be!

Kernel/Process.cpp

@@ -1174,6 +1174,22 @@ int Process::sys$uname(utsname* buf)
     return 0;
 }
 
+int Process::sys$isatty(int fd)
+{
+    auto* handle = fileHandleIfExists(fd);
+    if (!handle)
+        return -EBADF;
+    if (!handle->isTTY())
+        return -ENOTTY;
+    return 1;
+}
+
+Unix::sighandler_t Process::sys$signal(int signum, Unix::sighandler_t handler)
+{
+    dbgprintf("sys$signal: %d => L%x\n", signum, handler);
+    return nullptr;
+}
+
 int Process::sys$kill(pid_t pid, int signal)
 {
     if (pid == 0) {

Kernel/Process.h

@@ -7,6 +7,7 @@
 #include <AK/Vector.h>
 #include "i386.h"
 #include <VirtualFileSystem/VirtualFileSystem.h>
+#include <VirtualFileSystem/UnixTypes.h>
 #include "TTY.h"
 
 class FileHandle;
@@ -123,6 +124,8 @@ public:
     int sys$ttyname_r(int fd, char*, size_t);
     pid_t sys$fork(RegisterDump&);
     int sys$execve(const char* filename, const char** argv, const char** envp);
+    Unix::sighandler_t sys$signal(int signum, Unix::sighandler_t);
+    int sys$isatty(int fd);
 
     static void initialize();
 

Kernel/Syscall.cpp

@@ -136,6 +136,10 @@ static DWORD handle(RegisterDump& regs, DWORD function, DWORD arg1, DWORD arg2,
         return current->sys$geteuid();
     case Syscall::PosixGetegid:
         return current->sys$getegid();
+    case Syscall::PosixSignal:
+        return (dword)current->sys$signal((int)arg1, (Unix::sighandler_t)arg2);
+    case Syscall::PosixIsatty:
+        return current->sys$isatty((int)arg1);
     default:
         kprintf("<%u> int0x80: Unknown function %x requested {%x, %x, %x}\n", current->pid(), function, arg1, arg2, arg3);
         break;

Kernel/Syscall.h

@@ -51,6 +51,8 @@ enum Function {
     PosixExecve = 0x2019,
     PosixGeteuid = 0x2020,
     PosixGetegid = 0x2021,
+    PosixSignal = 0x2022,
+    PosixIsatty = 0x2023,
 };
 
 void initialize();