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>

1 files changed, 5 insertions, 5 deletions

diff --git a/arch/arm/kernel/calls.S b/arch/arm/kernel/calls.S
index f776e72a4cb8..ecfa98954d1d 100644
--- 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)