diff -ruN kozos11/stublib.c kozos12/stublib.c
--- kozos11/stublib.c	Sat Nov 10 16:10:31 2007
+++ kozos12/stublib.c	Sat Nov 10 16:10:33 2007
@@ -100,22 +100,43 @@
 void stub_store_regs(kz_thread *thp)
 {
   memset(registers, 0, sizeof(registers));
-  registers[PC]  = thp->context.env[0]._jb[0]; /* EIP */
-  registers[EBX] = thp->context.env[0]._jb[1]; /* EBX */
-  registers[ESP] = thp->context.env[0]._jb[2]; /* ESP */
-  registers[EBP] = thp->context.env[0]._jb[3]; /* EBP */
-  registers[ESI] = thp->context.env[0]._jb[4]; /* ESI */
-  registers[EDI] = thp->context.env[0]._jb[5]; /* EDI */
+
+  registers[EAX] = thp->context.uap.uc_mcontext.mc_eax;
+  registers[ECX] = thp->context.uap.uc_mcontext.mc_ecx;
+  registers[EDX] = thp->context.uap.uc_mcontext.mc_edx;
+  registers[EBX] = thp->context.uap.uc_mcontext.mc_ebx;
+  registers[ESP] = thp->context.uap.uc_mcontext.mc_esp;
+  registers[EBP] = thp->context.uap.uc_mcontext.mc_ebp;
+  registers[ESI] = thp->context.uap.uc_mcontext.mc_esi;
+  registers[EDI] = thp->context.uap.uc_mcontext.mc_edi;
+  registers[PC]  = thp->context.uap.uc_mcontext.mc_eip;
+  registers[PS]  = thp->context.uap.uc_mcontext.mc_eflags;
+  registers[CS]  = thp->context.uap.uc_mcontext.mc_cs;
+  registers[SS]  = thp->context.uap.uc_mcontext.mc_ss;
+  registers[DS]  = thp->context.uap.uc_mcontext.mc_ds;
+  registers[ES]  = thp->context.uap.uc_mcontext.mc_es;
+  registers[FS]  = thp->context.uap.uc_mcontext.mc_fs;
+  registers[GS]  = thp->context.uap.uc_mcontext.mc_gs;
 }
 
 void stub_restore_regs(kz_thread *thp)
 {
-  thp->context.env[0]._jb[0] = registers[PC];  /* EIP */
-  thp->context.env[0]._jb[1] = registers[EBX]; /* EBX */
-  thp->context.env[0]._jb[2] = registers[ESP]; /* ESP */
-  thp->context.env[0]._jb[3] = registers[EBP]; /* EBP */
-  thp->context.env[0]._jb[4] = registers[ESI]; /* ESI */
-  thp->context.env[0]._jb[5] = registers[EDI]; /* EDI */
+  thp->context.uap.uc_mcontext.mc_eax    = registers[EAX];
+  thp->context.uap.uc_mcontext.mc_ecx    = registers[ECX];
+  thp->context.uap.uc_mcontext.mc_edx    = registers[EDX];
+  thp->context.uap.uc_mcontext.mc_ebx    = registers[EBX];
+  thp->context.uap.uc_mcontext.mc_esp    = registers[ESP];
+  thp->context.uap.uc_mcontext.mc_ebp    = registers[EBP];
+  thp->context.uap.uc_mcontext.mc_esi    = registers[ESI];
+  thp->context.uap.uc_mcontext.mc_edi    = registers[EDI];
+  thp->context.uap.uc_mcontext.mc_eip    = registers[PC];
+  thp->context.uap.uc_mcontext.mc_eflags = registers[PS];
+  thp->context.uap.uc_mcontext.mc_cs     = registers[CS];
+  thp->context.uap.uc_mcontext.mc_ss     = registers[SS];
+  thp->context.uap.uc_mcontext.mc_ds     = registers[DS];
+  thp->context.uap.uc_mcontext.mc_es     = registers[ES];
+  thp->context.uap.uc_mcontext.mc_fs     = registers[FS];
+  thp->context.uap.uc_mcontext.mc_gs     = registers[GS];
 }
 
 int stub_proc(kz_thread *thp, int signo)
diff -ruN kozos11/thread.c kozos12/thread.c
--- kozos11/thread.c	Sat Nov 10 16:10:31 2007
+++ kozos12/thread.c	Sat Nov 10 16:10:33 2007
@@ -4,6 +4,7 @@
 #include <signal.h>
 #include <unistd.h>
 #include <setjmp.h>
+#include <ucontext.h>
 #include <sys/time.h>
 
 #include "kozos.h"
@@ -26,6 +27,7 @@
 static kz_timebuf *timers;
 static kz_thread *sigcalls[SIG_NUM];
 static int debug_sockt = 0;
+static sigset_t block;
 
 kz_thread *current;
 
@@ -429,8 +431,10 @@
   longjmp(current->context.env, 1);
 }
 
-static void thread_intr(int signo)
+static void thread_intr(int signo, siginfo_t *info, ucontext_t *uap)
 {
+  memcpy(&current->context.uap, uap, sizeof(ucontext_t));
+
   /*
    * setjmp()/longjmp() はシグナルマスクを保存し復元するが，
    * _setjmp()/_longjmp() はシグナルマスクを保存しない．
@@ -439,23 +443,32 @@
   if (setjmp(current->context.env) == 0) {
     longjmp(intr_env, signo);
   }
+
+  setcontext(&current->context.uap);
 }
 
 static void thread_start(kz_func func, char *name, int pri, int argc, char *argv[])
 {
+  struct sigaction sa;
+
   memset(threads, 0, sizeof(threads));
   memset(readyque, 0, sizeof(readyque));
   memset(sigcalls, 0, sizeof(sigcalls));
 
   timers = NULL;
 
-  signal(SIGSYS, thread_intr);
-  signal(SIGHUP, thread_intr);
-  signal(SIGALRM, thread_intr);
-  signal(SIGBUS, thread_intr);
-  signal(SIGSEGV, thread_intr);
-  signal(SIGTRAP, thread_intr);
-  signal(SIGILL, thread_intr);
+  memset(&sa, 0, sizeof(sa));
+  sa.sa_sigaction = (void (*)(int, siginfo_t *, void *))thread_intr;
+  sa.sa_flags |= SA_SIGINFO;
+  sa.sa_mask = block;
+
+  sigaction(SIGSYS , &sa, NULL);
+  sigaction(SIGHUP , &sa, NULL);
+  sigaction(SIGALRM, &sa, NULL);
+  sigaction(SIGBUS , &sa, NULL);
+  sigaction(SIGSEGV, &sa, NULL);
+  sigaction(SIGTRAP, &sa, NULL);
+  sigaction(SIGILL , &sa, NULL);
 
   /*
    * current 未定のためにシステムコール発行はできないので，
@@ -470,6 +483,24 @@
 void kz_start(kz_func func, char *name, int pri, int argc, char *argv[])
 {
   int signo;
+
+  /*
+   * setjmp()/longjmp()はシグナルマスクを保存／復旧するので，
+   * intr_env の setjmp() 前にシグナルマスクを設定することでシグナル処理中の
+   * シグナルの発生をマスクし，割り込みハンドラ内でのシグナルを無効とする．
+   * (でないと割り込みハンドラの実行中に intr_env に longjmp() した後に，
+   *  SIGALRM や SIGHUP の発生をハンドリングしてスレッドのディスパッチが
+   *  行われてしまい，誤動作する)
+   */
+  sigemptyset(&block);
+  sigaddset(&block, SIGSYS);
+  sigaddset(&block, SIGHUP);
+  sigaddset(&block, SIGALRM);
+  sigaddset(&block, SIGBUS);
+  sigaddset(&block, SIGSEGV);
+  sigaddset(&block, SIGTRAP);
+  sigaddset(&block, SIGILL);
+  sigprocmask(SIG_BLOCK, &block, NULL);
 
   /*
    * setjmp()は最低位の関数から呼ぶ必要があるので，本体は thread_start() に
diff -ruN kozos11/thread.h kozos12/thread.h
--- kozos11/thread.h	Sat Nov 10 16:10:31 2007
+++ kozos12/thread.h	Sat Nov 10 16:10:33 2007
@@ -4,6 +4,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <setjmp.h>
+#include <ucontext.h>
 
 #include "kozos.h"
 #include "syscall.h"
@@ -36,6 +37,7 @@
 
   struct {
     jmp_buf env;
+    ucontext_t uap;
   } context;
 } kz_thread;