7 files changed, 43 insertions, 86 deletions

diff --git a/arch/um/include/os.h b/arch/um/include/os.h
index be71b3d4c961..120ca21a513a 100644
--- a/arch/um/include/os.h
+++ b/arch/um/include/os.h
@@ -14,6 +14,7 @@
 #include "skas/mm_id.h"
 #include "irq_user.h"
 #include "sysdep/tls.h"
+#include "sysdep/archsetjmp.h"
 
 #define OS_TYPE_FILE 1
 #define OS_TYPE_DIR 2
@@ -308,12 +309,9 @@ extern int copy_context_skas0(unsigned long stack, int pid);
 extern void userspace(union uml_pt_regs *regs);
 extern void map_stub_pages(int fd, unsigned long code,
                            unsigned long data, unsigned long stack);
-extern void new_thread(void *stack, void **switch_buf_ptr,
-                         void **fork_buf_ptr, void (*handler)(int));
-extern void thread_wait(void *sw, void *fb);
-extern void switch_threads(void *me, void *next);
-extern int start_idle_thread(void *stack, void *switch_buf_ptr,
-                             void **fork_buf_ptr);
+extern void new_thread(void *stack, jmp_buf *buf, void (*handler)(void));
+extern void switch_threads(jmp_buf *me, jmp_buf *you);
+extern int start_idle_thread(void *stack, jmp_buf *switch_buf);
 extern void initial_thread_cb_skas(void (*proc)(void *),
                                  void *arg);
 extern void halt_skas(void);
diff --git a/arch/um/include/skas/skas.h b/arch/um/include/skas/skas.h
index 853b26f148c5..e88926b16072 100644
--- a/arch/um/include/skas/skas.h
+++ b/arch/um/include/skas/skas.h
@@ -14,8 +14,7 @@ extern int proc_mm, ptrace_faultinfo, ptrace_ldt;
 extern int skas_needs_stub;
 
 extern int user_thread(unsigned long stack, int flags);
-extern void new_thread_proc(void *stack, void (*handler)(int sig));
-extern void new_thread_handler(int sig);
+extern void new_thread_handler(void);
 extern void handle_syscall(union uml_pt_regs *regs);
 extern int new_mm(unsigned long stack);
 extern void get_skas_faultinfo(int pid, struct faultinfo * fi);
diff --git a/arch/um/include/sysdep-i386/archsetjmp.h b/arch/um/include/sysdep-i386/archsetjmp.h
index ea1ba3d42aee..11bafab669e9 100644
--- a/arch/um/include/sysdep-i386/archsetjmp.h
+++ b/arch/um/include/sysdep-i386/archsetjmp.h
@@ -16,4 +16,7 @@ struct __jmp_buf {
 
 typedef struct __jmp_buf jmp_buf[1];
 
+#define JB_IP __eip
+#define JB_SP __esp
+
 #endif                          /* _SETJMP_H */
diff --git a/arch/um/include/sysdep-x86_64/archsetjmp.h b/arch/um/include/sysdep-x86_64/archsetjmp.h
index 454fc60aff6d..9a5e1a6ec800 100644
--- a/arch/um/include/sysdep-x86_64/archsetjmp.h
+++ b/arch/um/include/sysdep-x86_64/archsetjmp.h
@@ -18,4 +18,7 @@ struct __jmp_buf {
 
 typedef struct __jmp_buf jmp_buf[1];
 
+#define JB_IP __rip
+#define JB_SP __rsp
+
 #endif                          /* _SETJMP_H */
diff --git a/arch/um/kernel/skas/process_kern.c b/arch/um/kernel/skas/process_kern.c
index 55caeec8b257..c73d47c57abe 100644
--- a/arch/um/kernel/skas/process_kern.c
+++ b/arch/um/kernel/skas/process_kern.c
@@ -33,7 +33,7 @@ void switch_to_skas(void *prev, void *next)
                 switch_timers(0);
 
         switch_threads(&from->thread.mode.skas.switch_buf,
-                       to->thread.mode.skas.switch_buf);
+                       &to->thread.mode.skas.switch_buf);
 
         arch_switch_to_skas(current->thread.prev_sched, current);
 
@@ -43,21 +43,21 @@ void switch_to_skas(void *prev, void *next)
 
 extern void schedule_tail(struct task_struct *prev);
 
-void new_thread_handler(int sig)
+/* This is called magically, by its address being stuffed in a jmp_buf
+ * and being longjmp-d to.
+ */
+void new_thread_handler(void)
 {
         int (*fn)(void *), n;
         void *arg;
 
-        fn = current->thread.request.u.thread.proc;
-        arg = current->thread.request.u.thread.arg;
-        os_usr1_signal(1);
-        thread_wait(&current->thread.mode.skas.switch_buf,
-                    current->thread.mode.skas.fork_buf);
-
         if(current->thread.prev_sched != NULL)
                 schedule_tail(current->thread.prev_sched);
         current->thread.prev_sched = NULL;
 
+        fn = current->thread.request.u.thread.proc;
+        arg = current->thread.request.u.thread.arg;
+
         /* The return value is 1 if the kernel thread execs a process,
          * 0 if it just exits
          */
@@ -70,22 +70,13 @@ void new_thread_handler(int sig)
         else do_exit(0);
 }
 
-void new_thread_proc(void *stack, void (*handler)(int sig))
-{
-        init_new_thread_stack(stack, handler);
-        os_usr1_process(os_getpid());
-}
-
 void release_thread_skas(struct task_struct *task)
 {
 }
 
-void fork_handler(int sig)
+/* Called magically, see new_thread_handler above */
+void fork_handler(void)
 {
-        os_usr1_signal(1);
-        thread_wait(&current->thread.mode.skas.switch_buf,
-                    current->thread.mode.skas.fork_buf);
-        
         force_flush_all();
         if(current->thread.prev_sched == NULL)
                 panic("blech");
@@ -109,7 +100,7 @@ int copy_thread_skas(int nr, unsigned long clone_flags, unsigned long sp,
                      unsigned long stack_top, struct task_struct * p,
                      struct pt_regs *regs)
 {
-        void (*handler)(int);
+        void (*handler)(void);
 
         if(current->thread.forking){
                 memcpy(&p->thread.regs.regs.skas, &regs->regs.skas,
@@ -128,7 +119,7 @@ int copy_thread_skas(int nr, unsigned long clone_flags, unsigned long sp,
         }
 
         new_thread(task_stack_page(p), &p->thread.mode.skas.switch_buf,
-                   &p->thread.mode.skas.fork_buf, handler);
+                   handler);
         return(0);
 }
 
@@ -182,8 +173,7 @@ int start_uml_skas(void)
         init_task.thread.request.u.thread.proc = start_kernel_proc;
         init_task.thread.request.u.thread.arg = NULL;
         return(start_idle_thread(task_stack_page(&init_task),
-                                 &init_task.thread.mode.skas.switch_buf,
-                                 &init_task.thread.mode.skas.fork_buf));
+                                 &init_task.thread.mode.skas.switch_buf));
 }
 
 int external_pid_skas(struct task_struct *task)
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 42e3d1ed802c..cb9ab54146cc 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -444,56 +444,22 @@ void map_stub_pages(int fd, unsigned long code,
         }
 }
 
-void new_thread(void *stack, void **switch_buf_ptr, void **fork_buf_ptr,
-                void (*handler)(int))
+void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
 {
-        unsigned long flags;
-        jmp_buf switch_buf, fork_buf;
-
-        *switch_buf_ptr = &switch_buf;
-        *fork_buf_ptr = &fork_buf;
-
-        /* Somewhat subtle - siglongjmp restores the signal mask before doing
-         * the longjmp.  This means that when jumping from one stack to another
-         * when the target stack has interrupts enabled, an interrupt may occur
-         * on the source stack.  This is bad when starting up a process because
-         * it's not supposed to get timer ticks until it has been scheduled.
-         * So, we disable interrupts around the sigsetjmp to ensure that
-         * they can't happen until we get back here where they are safe.
-         */
-        flags = get_signals();
-        block_signals();
-        if(UML_SETJMP(&fork_buf) == 0)
-                new_thread_proc(stack, handler);
-
-        remove_sigstack();
-
-        set_signals(flags);
+        (*buf)[0].JB_IP = (unsigned long) handler;
+        (*buf)[0].JB_SP = (unsigned long) stack +
+                (PAGE_SIZE << UML_CONFIG_KERNEL_STACK_ORDER) - sizeof(void *);
 }
 
 #define INIT_JMP_NEW_THREAD 0
-#define INIT_JMP_REMOVE_SIGSTACK 1
-#define INIT_JMP_CALLBACK 2
-#define INIT_JMP_HALT 3
-#define INIT_JMP_REBOOT 4
-
-void thread_wait(void *sw, void *fb)
-{
-        jmp_buf buf, **switch_buf = sw, *fork_buf;
-
-        *switch_buf = &buf;
-        fork_buf = fb;
-        if(UML_SETJMP(&buf) == 0)
-                UML_LONGJMP(fork_buf, INIT_JMP_REMOVE_SIGSTACK);
-}
+#define INIT_JMP_CALLBACK 1
+#define INIT_JMP_HALT 2
+#define INIT_JMP_REBOOT 3
 
-void switch_threads(void *me, void *next)
+void switch_threads(jmp_buf *me, jmp_buf *you)
 {
-        jmp_buf my_buf, **me_ptr = me, *next_buf = next;
-
-        *me_ptr = &my_buf;
-        if(UML_SETJMP(&my_buf) == 0)
-                UML_LONGJMP(next_buf, 1);
+        if(UML_SETJMP(me) == 0)
+                UML_LONGJMP(you, 1);
 }
 
 static jmp_buf initial_jmpbuf;
@@ -503,23 +469,21 @@ static void (*cb_proc)(void *arg);
 static void *cb_arg;
 static jmp_buf *cb_back;
 
-int start_idle_thread(void *stack, void *switch_buf_ptr, void **fork_buf_ptr)
+int start_idle_thread(void *stack, jmp_buf *switch_buf)
 {
-        jmp_buf **switch_buf = switch_buf_ptr;
         int n;
 
         set_handler(SIGWINCH, (__sighandler_t) sig_handler,
                     SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGALRM,
                     SIGVTALRM, -1);
 
-        *fork_buf_ptr = &initial_jmpbuf;
         n = UML_SETJMP(&initial_jmpbuf);
         switch(n){
         case INIT_JMP_NEW_THREAD:
-                new_thread_proc((void *) stack, new_thread_handler);
-                break;
-        case INIT_JMP_REMOVE_SIGSTACK:
-                remove_sigstack();
+                (*switch_buf)[0].JB_IP = (unsigned long) new_thread_handler;
+                (*switch_buf)[0].JB_SP = (unsigned long) stack +
+                        (PAGE_SIZE << UML_CONFIG_KERNEL_STACK_ORDER) -
+                        sizeof(void *);
                 break;
         case INIT_JMP_CALLBACK:
                 (*cb_proc)(cb_arg);
@@ -534,7 +498,7 @@ int start_idle_thread(void *stack, void *switch_buf_ptr, void **fork_buf_ptr)
         default:
                 panic("Bad sigsetjmp return in start_idle_thread - %d\n", n);
         }
-        UML_LONGJMP(*switch_buf, 1);
+        UML_LONGJMP(switch_buf, 1);
 }
 
 void initial_thread_cb_skas(void (*proc)(void *), void *arg)
diff --git a/include/asm-um/processor-generic.h b/include/asm-um/processor-generic.h
index afa4fe1ca9f1..d99bbddffdb9 100644
--- a/include/asm-um/processor-generic.h
+++ b/include/asm-um/processor-generic.h
@@ -13,6 +13,7 @@ struct task_struct;
 #include "asm/ptrace.h"
 #include "choose-mode.h"
 #include "registers.h"
+#include "sysdep/archsetjmp.h"
 
 struct mm_struct;
 
@@ -43,8 +44,7 @@ struct thread_struct {
 #endif
 #ifdef CONFIG_MODE_SKAS
                 struct {
-                        void *switch_buf;
-                        void *fork_buf;
+                        jmp_buf switch_buf;
                         int mm_count;
                 } skas;
 #endif
@@ -138,7 +138,7 @@ extern struct cpuinfo_um cpu_data[];
 
 #ifdef CONFIG_MODE_SKAS
 #define KSTK_REG(tsk, reg) \
-        get_thread_reg(reg, tsk->thread.mode.skas.switch_buf)
+        get_thread_reg(reg, &tsk->thread.mode.skas.switch_buf)
 #else
 #define KSTK_REG(tsk, reg) (0xbadbabe)
 #endif