From: Mikael Pettersson Date: Sat, 15 Aug 2009 11:58:11 +0000 (+0100) Subject: ARM: 5677/1: ARM support for TIF_RESTORE_SIGMASK/pselect6/ppoll/epoll_pwait X-Git-Tag: next-20090817~86^2~1^6 X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Fnext%2Flinux-next.git;a=commitdiff_plain;h=369842658a36bcea28ecb643ba4bdb53919330dd 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 ¤t->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 Signed-off-by: Russell King --- --- a/arch/arm/include/asm/thread_info.h 2009-04-18 18:55:23.000000000 +0200 +++ b/arch/arm/include/asm/thread_info.h 2009-04-18 19:10:22.000000000 +0200 @@ -140,6 +140,7 @@ extern void vfp_sync_state(struct 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 #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 --- a/arch/arm/include/asm/unistd.h 2008-10-11 10:43:49.000000000 +0200 +++ b/arch/arm/include/asm/unistd.h 2009-04-18 19:10:22.000000000 +0200 @@ -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) @@ -428,6 +428,7 @@ #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 --- a/arch/arm/kernel/calls.S 2009-03-24 18:00:31.000000000 +0100 +++ b/arch/arm/kernel/calls.S 2009-04-18 19:10:22.000000000 +0200 @@ -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) --- a/arch/arm/kernel/entry-common.S 2009-04-18 18:55:23.000000000 +0200 +++ b/arch/arm/kernel/entry-common.S 2009-04-18 19:10:22.000000000 +0200 @@ -370,16 +370,6 @@ 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 --- a/arch/arm/kernel/signal.c 2008-12-25 15:54:13.000000000 +0100 +++ b/arch/arm/kernel/signal.c 2009-04-18 19:10:22.000000000 +0200 @@ -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(¤t->sighand->siglock); - saveset = current->blocked; + current->saved_sigmask = current->blocked; siginitset(¤t->blocked, mask); recalc_sigpending(); spin_unlock_irq(¤t->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(¤t->sighand->siglock); - saveset = current->blocked; - current->blocked = newset; - recalc_sigpending(); - spin_unlock_irq(¤t->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 @@ -541,7 +506,7 @@ static inline void restart_syscall(struc /* * 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) @@ -592,7 +557,7 @@ handle_signal(unsigned long sig, struct if (ret != 0) { force_sigsegv(sig, tsk); - return; + return ret; } /* @@ -606,6 +571,7 @@ handle_signal(unsigned long sig, struct recalc_sigpending(); spin_unlock_irq(&tsk->sighand->siglock); + return 0; } /* @@ -617,11 +583,12 @@ handle_signal(unsigned long sig, struct * 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; int signr; + sigset_t *oldset; /* * We want the common case to go fast, which @@ -630,18 +597,32 @@ static int do_signal(sigset_t *oldset, s * if so. */ if (!user_mode(regs)) - return 0; + return; if (try_to_freeze()) goto no_signal; single_step_clear(current); + if (test_thread_flag(TIF_RESTORE_SIGMASK)) + oldset = ¤t->saved_sigmask; + else + oldset = ¤t->blocked; + signr = get_signal_to_deliver(&info, &ka, regs, NULL); if (signr > 0) { - handle_signal(signr, &ka, &info, oldset, regs, syscall); + 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: @@ -693,14 +674,21 @@ static int do_signal(sigset_t *oldset, s regs->ARM_r0 == -ERESTARTNOINTR) { restart_syscall(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, ¤t->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(¤t->blocked, regs, syscall); + do_signal(regs, syscall); }