feat: extend stopchldtarget with syscall4 and syscall6

user/ulib.c

@@ -11,6 +11,41 @@ static long syscall3(long number, long a1, long a2, long a3)
     return ret;
 }
 
+/* Same trap as syscall3, with a 4th argument -- passed in r10, not rcx,
+   the same choice the real Linux x86-64 syscall ABI makes (rcx is already
+   spoken for by the `int $0x80`/syscall instruction's own use, so a fourth
+   argument needs a register the trap does not otherwise touch). Only
+   userSigAction needs one today. */
+static long syscall4(long number, long a1, long a2, long a3, long a4)
+{
+    long ret;
+    register long a4Reg __asm__("r10") = a4;
+    __asm__ volatile(
+        "int $0x80"
+        : "=a"(ret)
+        : "a"(number), "D"(a1), "S"(a2), "d"(a3), "r"(a4Reg)
+        : "memory", "rcx", "r11");
+    return ret;
+}
+
+/* Same trap again, with a 5th and 6th argument in r8/r9 -- the same real
+   Linux x86-64 syscall ABI register order this file's own 4th-argument
+   choice (r10) already follows, continued one register further. Only
+   userMmap needs this many today. */
+static long syscall6(long number, long a1, long a2, long a3, long a4, long a5, long a6)
+{
+    long ret;
+    register long a4Reg __asm__("r10") = a4;
+    register long a5Reg __asm__("r8") = a5;
+    register long a6Reg __asm__("r9") = a6;
+    __asm__ volatile(
+        "int $0x80"
+        : "=a"(ret)
+        : "a"(number), "D"(a1), "S"(a2), "d"(a3), "r"(a4Reg), "r"(a5Reg), "r"(a6Reg)
+        : "memory", "rcx", "r11");
+    return ret;
+}
+
 long userWrite(int fd, const char* buffer, unsigned long length)
 {
     return syscall3(sysWrite, fd, (long)buffer, (long)length);
@@ -46,6 +81,16 @@ void userSleep(unsigned long milliseconds)
     syscall3(sysSleep, (long)milliseconds, 0, 0);
 }
 
+unsigned long userAlarm(unsigned long seconds)
+{
+    return (unsigned long)syscall3(sysAlarm, (long)seconds, 0, 0);
+}
+
+long userPoll(PollFd* fds, unsigned long nfds, long timeoutMs)
+{
+    return syscall3(sysPoll, (long)fds, (long)nfds, timeoutMs);
+}
+
 long userOpen(const char* path, unsigned int flags)
 {
     return syscall3(sysOpen, (long)path, (long)flags, 0);