arm: new way of handling ERESTART_RESTARTBLOCK

new "syscall start" flag; handled in syscall_trace() by switching
syscall number to that of syscall_restart(2).  Restarts of that
kind (ERESTART_RESTARTBLOCK) are handled by setting that bit;
syscall number is not modified until the actual call.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 13 insertions, 28 deletions

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 2d0cfc2ba23c..680c623a3d1f 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -148,6 +148,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
 #define TIF_NOTIFY_RESUME       2       /* callback before returning to user */
 #define TIF_SYSCALL_TRACE       8
 #define TIF_SYSCALL_AUDIT       9
+#define TIF_SYSCALL_RESTARTSYS  10
 #define TIF_POLLING_NRFLAG      16
 #define TIF_USING_IWMMXT        17
 #define TIF_MEMDIE              18      /* is terminating due to OOM killer */
@@ -163,9 +164,11 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *,
 #define _TIF_USING_IWMMXT       (1 << TIF_USING_IWMMXT)
 #define _TIF_RESTORE_SIGMASK    (1 << TIF_RESTORE_SIGMASK)
 #define _TIF_SECCOMP            (1 << TIF_SECCOMP)
+#define _TIF_SYSCALL_RESTARTSYS (1 << TIF_SYSCALL_RESTARTSYS)
 
 /* Checks for any syscall work in entry-common.S */
-#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT)
+#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
+                           _TIF_SYSCALL_RESTARTSYS)
 
 /*
  * Change these and you break ASM code in entry-common.S
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 9650c143afc1..d407ebf41801 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -24,6 +24,7 @@
 #include <linux/hw_breakpoint.h>
 #include <linux/regset.h>
 #include <linux/audit.h>
+#include <linux/unistd.h>
 
 #include <asm/pgtable.h>
 #include <asm/traps.h>
@@ -916,6 +917,8 @@ asmlinkage int syscall_trace(int why, struct pt_regs *regs, int scno)
                 audit_syscall_entry(AUDIT_ARCH_ARM, scno, regs->ARM_r0,
                                     regs->ARM_r1, regs->ARM_r2, regs->ARM_r3);
 
+        if (why == 0 && test_and_clear_thread_flag(TIF_SYSCALL_RESTARTSYS))
+                scno = __NR_restart_syscall - __NR_SYSCALL_BASE;
         if (!test_thread_flag(TIF_SYSCALL_TRACE))
                 return scno;
         if (!(current->ptrace & PT_PTRACED))
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index 6b37d4ddf0b6..75c70d1850df 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -624,12 +624,10 @@ static void do_signal(struct pt_regs *regs, int syscall)
                 case -ERESTARTNOHAND:
                 case -ERESTARTSYS:
                 case -ERESTARTNOINTR:
+                case -ERESTART_RESTARTBLOCK:
                         regs->ARM_r0 = regs->ARM_ORIG_r0;
                         regs->ARM_pc = restart_addr;
                         break;
-                case -ERESTART_RESTARTBLOCK:
-                        regs->ARM_r0 = -EINTR;
-                        break;
                 }
         }
 
@@ -647,12 +645,14 @@ static void do_signal(struct pt_regs *regs, int syscall)
                  * debugger has chosen to restart at a different PC.
                  */
                 if (regs->ARM_pc == restart_addr) {
-                        if (retval == -ERESTARTNOHAND
+                        if (retval == -ERESTARTNOHAND ||
+                            retval == -ERESTART_RESTARTBLOCK
                             || (retval == -ERESTARTSYS
                                 && !(ka.sa.sa_flags & SA_RESTART))) {
                                 regs->ARM_r0 = -EINTR;
                                 regs->ARM_pc = continue_addr;
                         }
+                        clear_thread_flag(TIF_SYSCALL_RESTARTSYS);
                 }
 
                 if (test_thread_flag(TIF_RESTORE_SIGMASK))
@@ -679,29 +679,8 @@ static void do_signal(struct pt_regs *regs, int syscall)
                  * ignore the restart.
                  */
                 if (retval == -ERESTART_RESTARTBLOCK
-                    && regs->ARM_pc == continue_addr) {
-                        if (thumb_mode(regs)) {
-                                regs->ARM_r7 = __NR_restart_syscall - __NR_SYSCALL_BASE;
-                                regs->ARM_pc -= 2;
-                        } else {
-#if defined(CONFIG_AEABI) && !defined(CONFIG_OABI_COMPAT)
-                                regs->ARM_r7 = __NR_restart_syscall;
-                                regs->ARM_pc -= 4;
-#else
-                                u32 __user *usp;
-
-                                regs->ARM_sp -= 4;
-                                usp = (u32 __user *)regs->ARM_sp;
-
-                                if (put_user(regs->ARM_pc, usp) == 0) {
-                                        regs->ARM_pc = KERN_RESTART_CODE;
-                                } else {
-                                        regs->ARM_sp += 4;
-                                        force_sigsegv(0, current);
-                                }
-#endif
-                        }
-                }
+                    && regs->ARM_pc == restart_addr)
+                        set_thread_flag(TIF_SYSCALL_RESTARTSYS);
         }
 
         /* If there's no signal to deliver, we just put the saved sigmask