x86 ptrace: unify TIF_SINGLESTEP

This unifies the treatment of TIF_SINGLESTEP on i386 and x86_64.
The bit is now excluded from _TIF_WORK_MASK on i386 as it has been
on x86_64.  This means the do_notify_resume() path using it is never
used, so TIF_SINGLESTEP is not cleared on returning to user mode.

Both now leave TIF_SINGLESTEP set when returning to user, so that
it's already set on an int $0x80 system call entry.  This removes
the need for testing TF on the system_call path.  Doing it this way
fixes the regression for PTRACE_SINGLESTEP into a sigreturn syscall,
introduced by commit 1e2e99f0e4aa6363e8515ed17011c210c8f1b52a.

The clear_TF_reenable case that sets TIF_SINGLESTEP can only happen
on a non-exception kernel entry, i.e. sysenter/syscall instruction.
That will always get to the syscall exit tracing path.

Signed-off-by: Roland McGrath <roland@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/asm-x86/thread_info.h b/include/asm-x86/thread_info.h
index 895339d2bc0b..fb8d3cdf143e 100644
--- a/include/asm-x86/thread_info.h
+++ b/include/asm-x86/thread_info.h
@@ -124,7 +124,7 @@ struct thread_info {
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK                                                  \
         (0x0000FFFF &                                                   \
-         ~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP|       \
+         ~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|                       \
          _TIF_SECCOMP|_TIF_SYSCALL_EMU))
 
 /* work to do on any return to user space */
@@ -132,7 +132,7 @@ struct thread_info {
 
 /* Only used for 64 bit */
 #define _TIF_DO_NOTIFY_MASK                                             \
-        (_TIF_SIGPENDING|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY|_TIF_HRTICK_RESCHED)
+        (_TIF_SIGPENDING|_TIF_MCE_NOTIFY|_TIF_HRTICK_RESCHED)
 
 /* flags to check in __switch_to() */
 #define _TIF_WORK_CTXSW                                                 \