[PATCH] Handle TIF_RESTORE_SIGMASK for i386

Handle TIF_RESTORE_SIGMASK as added by David Woodhouse's patch entitled:

        [PATCH] 2/3 Add TIF_RESTORE_SIGMASK support for arch/powerpc
        [PATCH] 3/3 Generic sys_rt_sigsuspend

It does the following:

 (1) Declares TIF_RESTORE_SIGMASK for i386.

 (2) Invokes it over to do_signal() when TIF_RESTORE_SIGMASK is set.

 (3) Makes do_signal() support TIF_RESTORE_SIGMASK, using the signal mask saved
     in current->saved_sigmask.

 (4) Discards sys_rt_sigsuspend() from the arch, using the generic one instead.

 (5) Makes sys_sigsuspend() save the signal mask and set TIF_RESTORE_SIGMASK
     rather than attempting to fudge the return registers.

 (6) Makes sys_sigsuspend() return -ERESTARTNOHAND rather than looping
     intrinsically.

 (7) Makes setup_frame(), setup_rt_frame() and handle_signal() return 0 or
     -EFAULT rather than true/false to be consistent with the rest of the
     kernel.

Due to the fact do_signal() is then only called from one place:

 (8) Makes do_signal() no longer have a return value is it was just being
     ignored; force_sig() takes care of this.

 (9) Discards the old sigmask argument to do_signal() as it's no longer
     necessary.

(10) Makes do_signal() static.

(11) Marks the second argument to do_notify_resume() as unused. The unused
     argument should remain in the middle as the arguments are passed in as
     registers, and the ordering is specific in entry.S

Given the way do_signal() is now no longer called from sys_{,rt_}sigsuspend(),
they no longer need access to the exception frame, and so can just take
arguments normally.

This patch depends on sys_rt_sigsuspend patch.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 51 insertions, 62 deletions

diff --git a/arch/i386/kernel/signal.c b/arch/i386/kernel/signal.c
index adcd069db91e..963616d364ec 100644
--- a/arch/i386/kernel/signal.c
+++ b/arch/i386/kernel/signal.c
@@ -37,51 +37,17 @@
 asmlinkage int
 sys_sigsuspend(int history0, int history1, old_sigset_t mask)
 {
-        struct pt_regs * regs = (struct pt_regs *) &history0;
-        sigset_t saveset;
-
         mask &= _BLOCKABLE;
         spin_lock_irq(&current->sighand->siglock);
-        saveset = current->blocked;
+        current->saved_sigmask = current->blocked;
         siginitset(&current->blocked, mask);
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
-        regs->eax = -EINTR;
-        while (1) {
-                current->state = TASK_INTERRUPTIBLE;
-                schedule();
-                if (do_signal(regs, &saveset))
-                        return -EINTR;
-        }
-}
-
-asmlinkage int
-sys_rt_sigsuspend(struct pt_regs regs)
-{
-        sigset_t saveset, newset;
-
-        /* XXX: Don't preclude handling different sized sigset_t's.  */
-        if (regs.ecx != sizeof(sigset_t))
-                return -EINVAL;
-
-        if (copy_from_user(&newset, (sigset_t __user *)regs.ebx, sizeof(newset)))
-                return -EFAULT;
-        sigdelsetmask(&newset, ~_BLOCKABLE);
-
-        spin_lock_irq(&current->sighand->siglock);
-        saveset = current->blocked;
-        current->blocked = newset;
-        recalc_sigpending();
-        spin_unlock_irq(&current->sighand->siglock);
-
-        regs.eax = -EINTR;
-        while (1) {
-                current->state = TASK_INTERRUPTIBLE;
-                schedule();
-                if (do_signal(&regs, &saveset))
-                        return -EINTR;
-        }
+        current->state = TASK_INTERRUPTIBLE;
+        schedule();
+        set_thread_flag(TIF_RESTORE_SIGMASK);
+        return -ERESTARTNOHAND;
 }
 
 asmlinkage int 
@@ -433,11 +399,11 @@ static int setup_frame(int sig, struct k_sigaction *ka,
                 current->comm, current->pid, frame, regs->eip, frame->pretcode);
 #endif
 
-        return 1;
+        return 0;
 
 give_sigsegv:
         force_sigsegv(sig, current);
-        return 0;
+        return -EFAULT;
 }
 
 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
@@ -527,11 +493,11 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                 current->comm, current->pid, frame, regs->eip, frame->pretcode);
 #endif
 
-        return 1;
+        return 0;
 
 give_sigsegv:
         force_sigsegv(sig, current);
-        return 0;
+        return -EFAULT;
 }
 
 /*
@@ -581,7 +547,7 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
         else
                 ret = setup_frame(sig, ka, oldset, regs);
 
-        if (ret) {
+        if (ret == 0) {
                 spin_lock_irq(&current->sighand->siglock);
                 sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
                 if (!(ka->sa.sa_flags & SA_NODEFER))
@@ -598,11 +564,12 @@ handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
  * want to handle. Thus you cannot kill init even with a SIGKILL even by
  * mistake.
  */
-int fastcall do_signal(struct pt_regs *regs, sigset_t *oldset)
+static void fastcall do_signal(struct pt_regs *regs)
 {
         siginfo_t info;
         int signr;
         struct k_sigaction ka;
+        sigset_t *oldset;
 
         /*
          * We want the common case to go fast, which
@@ -613,12 +580,14 @@ int fastcall do_signal(struct pt_regs *regs, sigset_t *oldset)
          * CS suffices.
          */
         if (!user_mode(regs))
-                return 1;
+                return;
 
         if (try_to_freeze())
                 goto no_signal;
 
-        if (!oldset)
+        if (test_thread_flag(TIF_RESTORE_SIGMASK))
+                oldset = &current->saved_sigmask;
+        else
                 oldset = &current->blocked;
 
         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
@@ -628,38 +597,55 @@ int fastcall do_signal(struct pt_regs *regs, sigset_t *oldset)
                  * have been cleared if the watchpoint triggered
                  * inside the kernel.
                  */
-                if (unlikely(current->thread.debugreg[7])) {
+                if (unlikely(current->thread.debugreg[7]))
                         set_debugreg(current->thread.debugreg[7], 7);
-                }
 
                 /* Whee!  Actually deliver the signal.  */
-                return handle_signal(signr, &info, &ka, oldset, regs);
+                if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
+                        /* a signal was successfully delivered; the saved
+                         * sigmask will have been stored in the signal frame,
+                         * and will be restored by sigreturn, so we can simply
+                         * clear the TIF_RESTORE_SIGMASK flag */
+                        if (test_thread_flag(TIF_RESTORE_SIGMASK))
+                                clear_thread_flag(TIF_RESTORE_SIGMASK);
+                }
+
+                return;
         }
 
- no_signal:
+no_signal:
         /* Did we come from a system call? */
         if (regs->orig_eax >= 0) {
                 /* Restart the system call - no handlers present */
-                if (regs->eax == -ERESTARTNOHAND ||
-                    regs->eax == -ERESTARTSYS ||
-                    regs->eax == -ERESTARTNOINTR) {
+                switch (regs->eax) {
+                case -ERESTARTNOHAND:
+                case -ERESTARTSYS:
+                case -ERESTARTNOINTR:
                         regs->eax = regs->orig_eax;
                         regs->eip -= 2;
-                }
-                if (regs->eax == -ERESTART_RESTARTBLOCK){
+                        break;
+
+                case -ERESTART_RESTARTBLOCK:
                         regs->eax = __NR_restart_syscall;
                         regs->eip -= 2;
+                        break;
                 }
         }
-        return 0;
+
+        /* if there's no signal to deliver, we just put the saved sigmask
+         * back */
+        if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
+                clear_thread_flag(TIF_RESTORE_SIGMASK);
+                sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
+        }
 }
 
 /*
  * notification of userspace execution resumption
- * - triggered by current->work.notify_resume
+ * - triggered by the TIF_WORK_MASK flags
  */
 __attribute__((regparm(3)))
-void do_notify_resume(struct pt_regs *regs, sigset_t *oldset,
+void do_notify_resume(struct pt_regs *regs, void *_unused,
                       __u32 thread_info_flags)
 {
         /* Pending single-step? */
@@ -667,9 +653,10 @@ void do_notify_resume(struct pt_regs *regs, sigset_t *oldset,
                 regs->eflags |= TF_MASK;
                 clear_thread_flag(TIF_SINGLESTEP);
         }
+
         /* deal with pending signal delivery */
-        if (thread_info_flags & _TIF_SIGPENDING)
-                do_signal(regs,oldset);
+        if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
+                do_signal(regs);
         
         clear_thread_flag(TIF_IRET);
 }
diff --git a/include/asm-i386/signal.h b/include/asm-i386/signal.h
index 76524b4052ac..026fd231488d 100644
--- a/include/asm-i386/signal.h
+++ b/include/asm-i386/signal.h
@@ -218,7 +218,6 @@ static __inline__ int sigfindinword(unsigned long word)
 }
 
 struct pt_regs;
-extern int FASTCALL(do_signal(struct pt_regs *regs, sigset_t *oldset));
 
 #define ptrace_signal_deliver(regs, cookie)             \
         do {                                            \
diff --git a/include/asm-i386/thread_info.h b/include/asm-i386/thread_info.h
index 2493e77e8c30..e20e99551d71 100644
--- a/include/asm-i386/thread_info.h
+++ b/include/asm-i386/thread_info.h
@@ -140,6 +140,7 @@ register unsigned long current_stack_pointer asm("esp") __attribute_used__;
 #define TIF_SYSCALL_EMU         6       /* syscall emulation active */
 #define TIF_SYSCALL_AUDIT       7       /* syscall auditing active */
 #define TIF_SECCOMP             8       /* secure computing */
+#define TIF_RESTORE_SIGMASK     9       /* restore signal mask in do_signal() */
 #define TIF_POLLING_NRFLAG      16      /* true if poll_idle() is polling TIF_NEED_RESCHED */
 #define TIF_MEMDIE              17
 
@@ -152,6 +153,7 @@ register unsigned long current_stack_pointer asm("esp") __attribute_used__;
 #define _TIF_SYSCALL_EMU        (1<<TIF_SYSCALL_EMU)
 #define _TIF_SYSCALL_AUDIT      (1<<TIF_SYSCALL_AUDIT)
 #define _TIF_SECCOMP            (1<<TIF_SECCOMP)
+#define _TIF_RESTORE_SIGMASK    (1<<TIF_RESTORE_SIGMASK)
 #define _TIF_POLLING_NRFLAG     (1<<TIF_POLLING_NRFLAG)
 
 /* work to do on interrupt/exception return */
diff --git a/include/asm-i386/unistd.h b/include/asm-i386/unistd.h
index e3028aaf6d83..3400441b3f91 100644
--- a/include/asm-i386/unistd.h
+++ b/include/asm-i386/unistd.h
@@ -430,6 +430,7 @@ __syscall_return(type,__res); \
 #define __ARCH_WANT_SYS_SIGPENDING
 #define __ARCH_WANT_SYS_SIGPROCMASK
 #define __ARCH_WANT_SYS_RT_SIGACTION
+#define __ARCH_WANT_SYS_RT_SIGSUSPEND
 #endif
 
 #ifdef __KERNEL_SYSCALLS__