target/linux/generic/patches-2.6.31/965-arm_restore_sigmask_v2.patch

   1 From: Mikael Pettersson <mikpe@it.uu.se>
   2 Date: Sat, 15 Aug 2009 11:58:11 +0000 (+0100)
   3 Subject: ARM: 5677/1: ARM support for TIF_RESTORE_SIGMASK/pselect6/ppoll/epoll_pwait
   4 X-Git-Tag: next-20090817~86^2~1^6
   5 X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Fnext%2Flinux-next.git;a=commitdiff_plain;h=369842658a36bcea28ecb643ba4bdb53919330dd
   6
   7 ARM: 5677/1: ARM support for TIF_RESTORE_SIGMASK/pselect6/ppoll/epoll_pwait
   8
   9 This patch adds support for TIF_RESTORE_SIGMASK to ARM's
  10 signal handling, which allows to hook up the pselect6, ppoll,
  11 and epoll_pwait syscalls on ARM.
  12
  13 Tested here with eabi userspace and a test program with a
  14 deliberate race between a child's exit and the parent's
  15 sigprocmask/select sequence. Using sys_pselect6() instead
  16 of sigprocmask/select reliably prevents the race.
  17
  18 The other arch's support for TIF_RESTORE_SIGMASK has evolved
  19 over time:
  20
  21 In 2.6.16:
  22 - add TIF_RESTORE_SIGMASK which parallels TIF_SIGPENDING
  23 - test both when checking for pending signal [changed later]
  24 - reimplement sys_sigsuspend() to use current->saved_sigmask,
  25   TIF_RESTORE_SIGMASK [changed later], and -ERESTARTNOHAND;
  26   ditto for sys_rt_sigsuspend(), but drop private code and
  27   use common code via __ARCH_WANT_SYS_RT_SIGSUSPEND;
  28 - there are now no "extra" calls to do_signal() so its oldset
  29   parameter is always &current->blocked so need not be passed,
  30   also its return value is changed to void
  31 - change handle_signal() to return 0/-errno
  32 - change do_signal() to honor TIF_RESTORE_SIGMASK:
  33   + get oldset from current->saved_sigmask if TIF_RESTORE_SIGMASK
  34     is set
  35   + if handle_signal() was successful then clear TIF_RESTORE_SIGMASK
  36   + if no signal was delivered and TIF_RESTORE_SIGMASK is set then
  37     clear it and restore the sigmask
  38 - hook up sys_pselect6() and sys_ppoll()
  39
  40 In 2.6.19:
  41 - hook up sys_epoll_pwait()
  42
  43 In 2.6.26:
  44 - allow archs to override how TIF_RESTORE_SIGMASK is implemented;
  45   default set_restore_sigmask() sets both TIF_RESTORE_SIGMASK and
  46   TIF_SIGPENDING; archs need now just test TIF_SIGPENDING again
  47   when checking for pending signal work; some archs now implement
  48   TIF_RESTORE_SIGMASK as a secondary/non-atomic thread flag bit
  49 - call set_restore_sigmask() in sys_sigsuspend() instead of setting
  50   TIF_RESTORE_SIGMASK
  51
  52 In 2.6.29-rc:
  53 - kill sys_pselect7() which no arch wanted
  54
  55 So for 2.6.31-rc6/ARM this patch does the following:
  56 - Add TIF_RESTORE_SIGMASK. Use the generic set_restore_sigmask()
  57   which sets both TIF_SIGPENDING and TIF_RESTORE_SIGMASK, so
  58   TIF_RESTORE_SIGMASK need not claim one of the scarce low thread
  59   flags, and existing TIF_SIGPENDING and _TIF_WORK_MASK tests need
  60   not be extended for TIF_RESTORE_SIGMASK.
  61 - sys_sigsuspend() is reimplemented to use current->saved_sigmask
  62   and set_restore_sigmask(), making it identical to most other archs
  63 - The private code for sys_rt_sigsuspend() is removed, instead
  64   generic code supplies it via __ARCH_WANT_SYS_RT_SIGSUSPEND.
  65 - sys_sigsuspend() and sys_rt_sigsuspend() no longer need a pt_regs
  66   parameter, so their assembly code wrappers are removed.
  67 - handle_signal() is changed to return 0 on success or -errno.
  68 - The oldset parameter to do_signal() is now redundant and removed,
  69   and the return value is now also redundant and changed to void.
  70 - do_signal() is changed to honor TIF_RESTORE_SIGMASK:
  71   + get oldset from current->saved_sigmask if TIF_RESTORE_SIGMASK
  72     is set
  73   + if handle_signal() was successful then clear TIF_RESTORE_SIGMASK
  74   + if no signal was delivered and TIF_RESTORE_SIGMASK is set then
  75     clear it and restore the sigmask
  76 - Hook up sys_pselect6, sys_ppoll, and sys_epoll_pwait.
  77
  78 Signed-off-by: Mikael Pettersson <mikpe@it.uu.se>
  79 Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
  80 ---
  81
  82 --- a/arch/arm/include/asm/thread_info.h
  83 +++ b/arch/arm/include/asm/thread_info.h
  84 @@ -141,6 +141,7 @@
  85  #define TIF_USING_IWMMXT       17
  86  #define TIF_MEMDIE             18
  87  #define TIF_FREEZE             19
  88 +#define TIF_RESTORE_SIGMASK    20
  89
  90  #define _TIF_SIGPENDING                (1 << TIF_SIGPENDING)
  91  #define _TIF_NEED_RESCHED      (1 << TIF_NEED_RESCHED)
  92 @@ -148,6 +149,7 @@
  93  #define _TIF_POLLING_NRFLAG    (1 << TIF_POLLING_NRFLAG)
  94  #define _TIF_USING_IWMMXT      (1 << TIF_USING_IWMMXT)
  95  #define _TIF_FREEZE            (1 << TIF_FREEZE)
  96 +#define _TIF_RESTORE_SIGMASK   (1 << TIF_RESTORE_SIGMASK)
  97
  98  /*
  99   * Change these and you break ASM code in entry-common.S
 100 --- a/arch/arm/include/asm/unistd.h
 101 +++ b/arch/arm/include/asm/unistd.h
 102 @@ -360,8 +360,8 @@
 103  #define __NR_readlinkat                        (__NR_SYSCALL_BASE+332)
 104  #define __NR_fchmodat                  (__NR_SYSCALL_BASE+333)
 105  #define __NR_faccessat                 (__NR_SYSCALL_BASE+334)
 106 -                                       /* 335 for pselect6 */
 107 -                                       /* 336 for ppoll */
 108 +#define __NR_pselect6                  (__NR_SYSCALL_BASE+335)
 109 +#define __NR_ppoll                     (__NR_SYSCALL_BASE+336)
 110  #define __NR_unshare                   (__NR_SYSCALL_BASE+337)
 111  #define __NR_set_robust_list           (__NR_SYSCALL_BASE+338)
 112  #define __NR_get_robust_list           (__NR_SYSCALL_BASE+339)
 113 @@ -372,7 +372,7 @@
 114  #define __NR_vmsplice                  (__NR_SYSCALL_BASE+343)
 115  #define __NR_move_pages                        (__NR_SYSCALL_BASE+344)
 116  #define __NR_getcpu                    (__NR_SYSCALL_BASE+345)
 117 -                                       /* 346 for epoll_pwait */
 118 +#define __NR_epoll_pwait               (__NR_SYSCALL_BASE+346)
 119  #define __NR_kexec_load                        (__NR_SYSCALL_BASE+347)
 120  #define __NR_utimensat                 (__NR_SYSCALL_BASE+348)
 121  #define __NR_signalfd                  (__NR_SYSCALL_BASE+349)
 122 @@ -432,6 +432,7 @@
 123  #define __ARCH_WANT_SYS_SIGPENDING
 124  #define __ARCH_WANT_SYS_SIGPROCMASK
 125  #define __ARCH_WANT_SYS_RT_SIGACTION
 126 +#define __ARCH_WANT_SYS_RT_SIGSUSPEND
 127
 128  #if !defined(CONFIG_AEABI) || defined(CONFIG_OABI_COMPAT)
 129  #define __ARCH_WANT_SYS_TIME
 130 --- a/arch/arm/kernel/calls.S
 131 +++ b/arch/arm/kernel/calls.S
 132 @@ -81,7 +81,7 @@
 133                 CALL(sys_ni_syscall)            /* was sys_ssetmask */
 134  /* 70 */       CALL(sys_setreuid16)
 135                 CALL(sys_setregid16)
 136 -               CALL(sys_sigsuspend_wrapper)
 137 +               CALL(sys_sigsuspend)
 138                 CALL(sys_sigpending)
 139                 CALL(sys_sethostname)
 140  /* 75 */       CALL(sys_setrlimit)
 141 @@ -188,7 +188,7 @@
 142                 CALL(sys_rt_sigpending)
 143                 CALL(sys_rt_sigtimedwait)
 144                 CALL(sys_rt_sigqueueinfo)
 145 -               CALL(sys_rt_sigsuspend_wrapper)
 146 +               CALL(sys_rt_sigsuspend)
 147  /* 180 */      CALL(ABI(sys_pread64, sys_oabi_pread64))
 148                 CALL(ABI(sys_pwrite64, sys_oabi_pwrite64))
 149                 CALL(sys_chown16)
 150 @@ -344,8 +344,8 @@
 151                 CALL(sys_readlinkat)
 152                 CALL(sys_fchmodat)
 153                 CALL(sys_faccessat)
 154 -/* 335 */      CALL(sys_ni_syscall)            /* eventually pselect6 */
 155 -               CALL(sys_ni_syscall)            /* eventually ppoll */
 156 +/* 335 */      CALL(sys_pselect6)
 157 +               CALL(sys_ppoll)
 158                 CALL(sys_unshare)
 159                 CALL(sys_set_robust_list)
 160                 CALL(sys_get_robust_list)
 161 @@ -355,7 +355,7 @@
 162                 CALL(sys_vmsplice)
 163                 CALL(sys_move_pages)
 164  /* 345 */      CALL(sys_getcpu)
 165 -               CALL(sys_ni_syscall)            /* eventually epoll_pwait */
 166 +               CALL(sys_epoll_pwait)
 167                 CALL(sys_kexec_load)
 168                 CALL(sys_utimensat)
 169                 CALL(sys_signalfd)
 170 --- a/arch/arm/kernel/entry-common.S
 171 +++ b/arch/arm/kernel/entry-common.S
 172 @@ -373,16 +373,6 @@
 173                 b       sys_clone
 174  ENDPROC(sys_clone_wrapper)
 175
 176 -sys_sigsuspend_wrapper:
 177 -               add     r3, sp, #S_OFF
 178 -               b       sys_sigsuspend
 179 -ENDPROC(sys_sigsuspend_wrapper)
 180 -
 181 -sys_rt_sigsuspend_wrapper:
 182 -               add     r2, sp, #S_OFF
 183 -               b       sys_rt_sigsuspend
 184 -ENDPROC(sys_rt_sigsuspend_wrapper)
 185 -
 186  sys_sigreturn_wrapper:
 187                 add     r0, sp, #S_OFF
 188                 b       sys_sigreturn
 189 --- a/arch/arm/kernel/signal.c
 190 +++ b/arch/arm/kernel/signal.c
 191 @@ -47,57 +47,22 @@
 192         MOV_R7_NR_RT_SIGRETURN, SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN,
 193  };
 194
 195 -static int do_signal(sigset_t *oldset, struct pt_regs * regs, int syscall);
 196 -
 197  /*
 198   * atomically swap in the new signal mask, and wait for a signal.
 199   */
 200 -asmlinkage int sys_sigsuspend(int restart, unsigned long oldmask, old_sigset_t mask, struct pt_regs *regs)
 201 +asmlinkage int sys_sigsuspend(int restart, unsigned long oldmask, old_sigset_t mask)
 202  {
 203 -       sigset_t saveset;
 204 -
 205         mask &= _BLOCKABLE;
 206         spin_lock_irq(&current->sighand->siglock);
 207 -       saveset = current->blocked;
 208 +       current->saved_sigmask = current->blocked;
 209         siginitset(&current->blocked, mask);
 210         recalc_sigpending();
 211         spin_unlock_irq(&current->sighand->siglock);
 212 -       regs->ARM_r0 = -EINTR;
 213 -
 214 -       while (1) {
 215 -               current->state = TASK_INTERRUPTIBLE;
 216 -               schedule();
 217 -               if (do_signal(&saveset, regs, 0))
 218 -                       return regs->ARM_r0;
 219 -       }
 220 -}
 221 -
 222 -asmlinkage int
 223 -sys_rt_sigsuspend(sigset_t __user *unewset, size_t sigsetsize, struct pt_regs *regs)
 224 -{
 225 -       sigset_t saveset, newset;
 226 -
 227 -       /* XXX: Don't preclude handling different sized sigset_t's. */
 228 -       if (sigsetsize != sizeof(sigset_t))
 229 -               return -EINVAL;
 230 -
 231 -       if (copy_from_user(&newset, unewset, sizeof(newset)))
 232 -               return -EFAULT;
 233 -       sigdelsetmask(&newset, ~_BLOCKABLE);
 234 -
 235 -       spin_lock_irq(&current->sighand->siglock);
 236 -       saveset = current->blocked;
 237 -       current->blocked = newset;
 238 -       recalc_sigpending();
 239 -       spin_unlock_irq(&current->sighand->siglock);
 240 -       regs->ARM_r0 = -EINTR;
 241
 242 -       while (1) {
 243 -               current->state = TASK_INTERRUPTIBLE;
 244 -               schedule();
 245 -               if (do_signal(&saveset, regs, 0))
 246 -                       return regs->ARM_r0;
 247 -       }
 248 +       current->state = TASK_INTERRUPTIBLE;
 249 +       schedule();
 250 +       set_restore_sigmask();
 251 +       return -ERESTARTNOHAND;
 252  }
 253
 254  asmlinkage int
 255 @@ -545,7 +510,7 @@
 256  /*
 257   * OK, we're invoking a handler
 258   */
 259 -static void
 260 +static int
 261  handle_signal(unsigned long sig, struct k_sigaction *ka,
 262               siginfo_t *info, sigset_t *oldset,
 263               struct pt_regs * regs, int syscall)
 264 @@ -596,7 +561,7 @@
 265
 266         if (ret != 0) {
 267                 force_sigsegv(sig, tsk);
 268 -               return;
 269 +               return ret;
 270         }
 271
 272         /*
 273 @@ -610,6 +575,7 @@
 274         recalc_sigpending();
 275         spin_unlock_irq(&tsk->sighand->siglock);
 276
 277 +       return 0;
 278  }
 279
 280  /*
 281 @@ -621,11 +587,12 @@
 282   * the kernel can handle, and then we build all the user-level signal handling
 283   * stack-frames in one go after that.
 284   */
 285 -static int do_signal(sigset_t *oldset, struct pt_regs *regs, int syscall)
 286 +static void do_signal(struct pt_regs *regs, int syscall)
 287  {
 288         struct k_sigaction ka;
 289         siginfo_t info;
 290         int signr;
 291 +       sigset_t *oldset;
 292
 293         /*
 294          * We want the common case to go fast, which
 295 @@ -634,18 +601,32 @@
 296          * if so.
 297          */
 298         if (!user_mode(regs))
 299 -               return 0;
 300 +               return;
 301
 302         if (try_to_freeze())
 303                 goto no_signal;
 304
 305         single_step_clear(current);
 306
 307 +       if (test_thread_flag(TIF_RESTORE_SIGMASK))
 308 +               oldset = &current->saved_sigmask;
 309 +       else
 310 +               oldset = &current->blocked;
 311 +
 312         signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 313         if (signr > 0) {
 314 -               handle_signal(signr, &ka, &info, oldset, regs, syscall);
 315 +               if (handle_signal(signr, &ka, &info, oldset, regs, syscall) == 0) {
 316 +                       /*
 317 +                        * A signal was successfully delivered; the saved
 318 +                        * sigmask will have been stored in the signal frame,
 319 +                        * and will be restored by sigreturn, so we can simply
 320 +                        * clear the TIF_RESTORE_SIGMASK flag.
 321 +                        */
 322 +                       if (test_thread_flag(TIF_RESTORE_SIGMASK))
 323 +                               clear_thread_flag(TIF_RESTORE_SIGMASK);
 324 +               }
 325                 single_step_set(current);
 326 -               return 1;
 327 +               return;
 328         }
 329
 330   no_signal:
 331 @@ -697,14 +678,21 @@
 332                     regs->ARM_r0 == -ERESTARTNOINTR) {
 333                         setup_syscall_restart(regs);
 334                 }
 335 +
 336 +               /* If there's no signal to deliver, we just put the saved sigmask
 337 +                * back.
 338 +                */
 339 +               if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
 340 +                       clear_thread_flag(TIF_RESTORE_SIGMASK);
 341 +                       sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
 342 +               }
 343         }
 344         single_step_set(current);
 345 -       return 0;
 346  }
 347
 348  asmlinkage void
 349  do_notify_resume(struct pt_regs *regs, unsigned int thread_flags, int syscall)
 350  {
 351         if (thread_flags & _TIF_SIGPENDING)
 352 -               do_signal(&current->blocked, regs, syscall);
 353 +               do_signal(regs, syscall);
 354  }