ARM: 5677/1: ARM support for TIF_RESTORE_SIGMASK/pselect6/ppoll/epoll_pwait

This patch adds support for TIF_RESTORE_SIGMASK to ARM's
signal handling, which allows to hook up the pselect6, ppoll,
and epoll_pwait syscalls on ARM.

Tested here with eabi userspace and a test program with a
deliberate race between a child's exit and the parent's
sigprocmask/select sequence. Using sys_pselect6() instead
of sigprocmask/select reliably prevents the race.

The other arch's support for TIF_RESTORE_SIGMASK has evolved
over time:

In 2.6.16:
- add TIF_RESTORE_SIGMASK which parallels TIF_SIGPENDING
- test both when checking for pending signal [changed later]
- reimplement sys_sigsuspend() to use current->saved_sigmask,
  TIF_RESTORE_SIGMASK [changed later], and -ERESTARTNOHAND;
  ditto for sys_rt_sigsuspend(), but drop private code and
  use common code via __ARCH_WANT_SYS_RT_SIGSUSPEND;
- there are now no "extra" calls to do_signal() so its oldset
  parameter is always &current->blocked so need not be passed,
  also its return value is changed to void
- change handle_signal() to return 0/-errno
- change do_signal() to honor TIF_RESTORE_SIGMASK:
  + get oldset from current->saved_sigmask if TIF_RESTORE_SIGMASK
    is set
  + if handle_signal() was successful then clear TIF_RESTORE_SIGMASK
  + if no signal was delivered and TIF_RESTORE_SIGMASK is set then
    clear it and restore the sigmask
- hook up sys_pselect6() and sys_ppoll()

In 2.6.19:
- hook up sys_epoll_pwait()

In 2.6.26:
- allow archs to override how TIF_RESTORE_SIGMASK is implemented;
  default set_restore_sigmask() sets both TIF_RESTORE_SIGMASK and
  TIF_SIGPENDING; archs need now just test TIF_SIGPENDING again
  when checking for pending signal work; some archs now implement
  TIF_RESTORE_SIGMASK as a secondary/non-atomic thread flag bit
- call set_restore_sigmask() in sys_sigsuspend() instead of setting
  TIF_RESTORE_SIGMASK

In 2.6.29-rc:
- kill sys_pselect7() which no arch wanted

So for 2.6.31-rc6/ARM this patch does the following:
- Add TIF_RESTORE_SIGMASK. Use the generic set_restore_sigmask()
  which sets both TIF_SIGPENDING and TIF_RESTORE_SIGMASK, so
  TIF_RESTORE_SIGMASK need not claim one of the scarce low thread
  flags, and existing TIF_SIGPENDING and _TIF_WORK_MASK tests need
  not be extended for TIF_RESTORE_SIGMASK.
- sys_sigsuspend() is reimplemented to use current->saved_sigmask
  and set_restore_sigmask(), making it identical to most other archs
- The private code for sys_rt_sigsuspend() is removed, instead
  generic code supplies it via __ARCH_WANT_SYS_RT_SIGSUSPEND.
- sys_sigsuspend() and sys_rt_sigsuspend() no longer need a pt_regs
  parameter, so their assembly code wrappers are removed.
- handle_signal() is changed to return 0 on success or -errno.
- The oldset parameter to do_signal() is now redundant and removed,
  and the return value is now also redundant and changed to void.
- do_signal() is changed to honor TIF_RESTORE_SIGMASK:
  + get oldset from current->saved_sigmask if TIF_RESTORE_SIGMASK
    is set
  + if handle_signal() was successful then clear TIF_RESTORE_SIGMASK
  + if no signal was delivered and TIF_RESTORE_SIGMASK is set then
    clear it and restore the sigmask
- Hook up sys_pselect6, sys_ppoll, and sys_epoll_pwait.

Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 73394e5..e20d805 100644 (file)
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -140,6 +140,7 @@ extern void vfp_sync_state(struct thread_info *thread);
 #define TIF_USING_IWMMXT       17
 #define TIF_MEMDIE             18
 #define TIF_FREEZE             19
+#define TIF_RESTORE_SIGMASK    20
 
 #define _TIF_SIGPENDING                (1 << TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED      (1 << TIF_NEED_RESCHED)
@@ -147,6 +148,7 @@ extern void vfp_sync_state(struct thread_info *thread);
 #define _TIF_POLLING_NRFLAG    (1 << TIF_POLLING_NRFLAG)
 #define _TIF_USING_IWMMXT      (1 << TIF_USING_IWMMXT)
 #define _TIF_FREEZE            (1 << TIF_FREEZE)
+#define _TIF_RESTORE_SIGMASK   (1 << TIF_RESTORE_SIGMASK)
 
 /*
  * Change these and you break ASM code in entry-common.S

diff --git a/arch/arm/include/asm/unistd.h b/arch/arm/include/asm/unistd.h
index 0e97b8c..9122c9e 100644 (file)
--- a/arch/arm/include/asm/unistd.h
+++ b/arch/arm/include/asm/unistd.h
@@ -360,8 +360,8 @@
 #define __NR_readlinkat                        (__NR_SYSCALL_BASE+332)
 #define __NR_fchmodat                  (__NR_SYSCALL_BASE+333)
 #define __NR_faccessat                 (__NR_SYSCALL_BASE+334)
-                                       /* 335 for pselect6 */
-                                       /* 336 for ppoll */
+#define __NR_pselect6                  (__NR_SYSCALL_BASE+335)
+#define __NR_ppoll                     (__NR_SYSCALL_BASE+336)
 #define __NR_unshare                   (__NR_SYSCALL_BASE+337)
 #define __NR_set_robust_list           (__NR_SYSCALL_BASE+338)
 #define __NR_get_robust_list           (__NR_SYSCALL_BASE+339)
@@ -372,7 +372,7 @@
 #define __NR_vmsplice                  (__NR_SYSCALL_BASE+343)
 #define __NR_move_pages                        (__NR_SYSCALL_BASE+344)
 #define __NR_getcpu                    (__NR_SYSCALL_BASE+345)
-                                       /* 346 for epoll_pwait */
+#define __NR_epoll_pwait               (__NR_SYSCALL_BASE+346)
 #define __NR_kexec_load                        (__NR_SYSCALL_BASE+347)
 #define __NR_utimensat                 (__NR_SYSCALL_BASE+348)
 #define __NR_signalfd                  (__NR_SYSCALL_BASE+349)
@@ -432,6 +432,7 @@
 #define __ARCH_WANT_SYS_SIGPENDING
 #define __ARCH_WANT_SYS_SIGPROCMASK
 #define __ARCH_WANT_SYS_RT_SIGACTION
+#define __ARCH_WANT_SYS_RT_SIGSUSPEND
 
 #if !defined(CONFIG_AEABI) || defined(CONFIG_OABI_COMPAT)
 #define __ARCH_WANT_SYS_TIME

diff --git a/arch/arm/kernel/calls.S b/arch/arm/kernel/calls.S
index f776e72..ecfa989 100644 (file)
--- a/arch/arm/kernel/calls.S
+++ b/arch/arm/kernel/calls.S
@@ -81,7 +81,7 @@
                CALL(sys_ni_syscall)            /* was sys_ssetmask */
 /* 70 */       CALL(sys_setreuid16)
                CALL(sys_setregid16)
-               CALL(sys_sigsuspend_wrapper)
+               CALL(sys_sigsuspend)
                CALL(sys_sigpending)
                CALL(sys_sethostname)
 /* 75 */       CALL(sys_setrlimit)
@@ -188,7 +188,7 @@
                CALL(sys_rt_sigpending)
                CALL(sys_rt_sigtimedwait)
                CALL(sys_rt_sigqueueinfo)
-               CALL(sys_rt_sigsuspend_wrapper)
+               CALL(sys_rt_sigsuspend)
 /* 180 */      CALL(ABI(sys_pread64, sys_oabi_pread64))
                CALL(ABI(sys_pwrite64, sys_oabi_pwrite64))
                CALL(sys_chown16)
@@ -344,8 +344,8 @@
                CALL(sys_readlinkat)
                CALL(sys_fchmodat)
                CALL(sys_faccessat)
-/* 335 */      CALL(sys_ni_syscall)            /* eventually pselect6 */
-               CALL(sys_ni_syscall)            /* eventually ppoll */
+/* 335 */      CALL(sys_pselect6)
+               CALL(sys_ppoll)
                CALL(sys_unshare)
                CALL(sys_set_robust_list)
                CALL(sys_get_robust_list)
@@ -355,7 +355,7 @@
                CALL(sys_vmsplice)
                CALL(sys_move_pages)
 /* 345 */      CALL(sys_getcpu)
-               CALL(sys_ni_syscall)            /* eventually epoll_pwait */
+               CALL(sys_epoll_pwait)
                CALL(sys_kexec_load)
                CALL(sys_utimensat)
                CALL(sys_signalfd)

diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index 366e509..bfa7f0a 100644 (file)
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -373,16 +373,6 @@ sys_clone_wrapper:
                b       sys_clone
 ENDPROC(sys_clone_wrapper)
 
-sys_sigsuspend_wrapper:
-               add     r3, sp, #S_OFF
-               b       sys_sigsuspend
-ENDPROC(sys_sigsuspend_wrapper)
-
-sys_rt_sigsuspend_wrapper:
-               add     r2, sp, #S_OFF
-               b       sys_rt_sigsuspend
-ENDPROC(sys_rt_sigsuspend_wrapper)
-
 sys_sigreturn_wrapper:
                add     r0, sp, #S_OFF
                b       sys_sigreturn

diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 93bb424..e27ee1f 100644 (file)
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -47,57 +47,22 @@ const unsigned long sigreturn_codes[7] = {
        MOV_R7_NR_RT_SIGRETURN, SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN,
 };
 
-static int do_signal(sigset_t *oldset, struct pt_regs * regs, int syscall);
-
 /*
  * atomically swap in the new signal mask, and wait for a signal.
  */
-asmlinkage int sys_sigsuspend(int restart, unsigned long oldmask, old_sigset_t mask, struct pt_regs *regs)
+asmlinkage int sys_sigsuspend(int restart, unsigned long oldmask, old_sigset_t mask)
 {
-       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->ARM_r0 = -EINTR;
-
-       while (1) {
-               current->state = TASK_INTERRUPTIBLE;
-               schedule();
-               if (do_signal(&saveset, regs, 0))
-                       return regs->ARM_r0;
-       }
-}
-
-asmlinkage int
-sys_rt_sigsuspend(sigset_t __user *unewset, size_t sigsetsize, struct pt_regs *regs)
-{
-       sigset_t saveset, newset;
-
-       /* XXX: Don't preclude handling different sized sigset_t's. */
-       if (sigsetsize != sizeof(sigset_t))
-               return -EINVAL;
-
-       if (copy_from_user(&newset, unewset, 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->ARM_r0 = -EINTR;
 
-       while (1) {
-               current->state = TASK_INTERRUPTIBLE;
-               schedule();
-               if (do_signal(&saveset, regs, 0))
-                       return regs->ARM_r0;
-       }
+       current->state = TASK_INTERRUPTIBLE;
+       schedule();
+       set_restore_sigmask();
+       return -ERESTARTNOHAND;
 }
 
 asmlinkage int 
@@ -545,7 +510,7 @@ static inline void setup_syscall_restart(struct pt_regs *regs)
 /*
  * OK, we're invoking a handler
  */    
-static void
+static int
 handle_signal(unsigned long sig, struct k_sigaction *ka,
              siginfo_t *info, sigset_t *oldset,
              struct pt_regs * regs, int syscall)
@@ -596,7 +561,7 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
 
        if (ret != 0) {
                force_sigsegv(sig, tsk);
-               return;
+               return ret;
        }
 
        /*
@@ -610,6 +575,7 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
        recalc_sigpending();
        spin_unlock_irq(&tsk->sighand->siglock);
 
+       return 0;
 }
 
 /*
@@ -621,7 +587,7 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
  * the kernel can handle, and then we build all the user-level signal handling
  * stack-frames in one go after that.
  */
-static int do_signal(sigset_t *oldset, struct pt_regs *regs, int syscall)
+static void do_signal(struct pt_regs *regs, int syscall)
 {
        struct k_sigaction ka;
        siginfo_t info;
@@ -634,7 +600,7 @@ static int do_signal(sigset_t *oldset, struct pt_regs *regs, int syscall)
         * if so.
         */
        if (!user_mode(regs))
-               return 0;
+               return;
 
        if (try_to_freeze())
                goto no_signal;
@@ -643,9 +609,24 @@ static int do_signal(sigset_t *oldset, struct pt_regs *regs, int syscall)
 
        signr = get_signal_to_deliver(&info, &ka, regs, NULL);
        if (signr > 0) {
-               handle_signal(signr, &ka, &info, oldset, regs, syscall);
+               sigset_t *oldset;
+
+               if (test_thread_flag(TIF_RESTORE_SIGMASK))
+                       oldset = &current->saved_sigmask;
+               else
+                       oldset = &current->blocked;
+               if (handle_signal(signr, &ka, &info, oldset, regs, syscall) == 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);
+               }
                single_step_set(current);
-               return 1;
+               return;
        }
 
  no_signal:
@@ -697,14 +678,21 @@ static int do_signal(sigset_t *oldset, struct pt_regs *regs, int syscall)
                    regs->ARM_r0 == -ERESTARTNOINTR) {
                        setup_syscall_restart(regs);
                }
+
+               /* 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);
+               }
        }
        single_step_set(current);
-       return 0;
 }
 
 asmlinkage void
 do_notify_resume(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 {
        if (thread_flags & _TIF_SIGPENDING)
-               do_signal(&current->blocked, regs, syscall);
+               do_signal(regs, syscall);
 }