diff options
| author | Roland McGrath <roland@redhat.com> | 2008-07-09 02:39:29 -0700 |
|---|---|---|
| committer | Roland McGrath <roland@redhat.com> | 2008-07-16 12:15:17 -0700 |
| commit | 380fdd7585a4c2f41b48925eba85c0654b7b858b (patch) | |
| tree | 3e405cd6cb0be449671ef28c6275fd7ad6b99295 /arch/x86/kernel/step.c | |
| parent | d4d67150165df8bf1cc05e532f6efca96f907cab (diff) | |
x86 ptrace: user-sets-TF nits
This closes some arcane holes in single-step handling that can arise
only when user programs set TF directly (via popf or sigreturn) and
then use vDSO (syscall/sysenter) system call entry. In those entry
paths, the clear_TF_reenable case hits and we must check TIF_SINGLESTEP
to be sure our bookkeeping stays correct wrt the user's view of TF.
Signed-off-by: Roland McGrath <roland@redhat.com>
Diffstat (limited to 'arch/x86/kernel/step.c')
| -rw-r--r-- | arch/x86/kernel/step.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c index 0d2cb363ea75..e8b9863ef8c4 100644 --- a/arch/x86/kernel/step.c +++ b/arch/x86/kernel/step.c @@ -108,6 +108,19 @@ static int enable_single_step(struct task_struct *child) unsigned long oflags; /* + * If we stepped into a sysenter/syscall insn, it trapped in + * kernel mode; do_debug() cleared TF and set TIF_SINGLESTEP. + * If user-mode had set TF itself, then it's still clear from + * do_debug() and we need to set it again to restore the user + * state so we don't wrongly set TIF_FORCED_TF below. + * If enable_single_step() was used last and that is what + * set TIF_SINGLESTEP, then both TF and TIF_FORCED_TF are + * already set and our bookkeeping is fine. + */ + if (unlikely(test_tsk_thread_flag(child, TIF_SINGLESTEP))) + regs->flags |= X86_EFLAGS_TF; + + /* * Always set TIF_SINGLESTEP - this guarantees that * we single-step system calls etc.. This will also * cause us to set TF when returning to user mode. |