From 380fdd7585a4c2f41b48925eba85c0654b7b858b Mon Sep 17 00:00:00 2001 From: Roland McGrath Date: Wed, 9 Jul 2008 02:39:29 -0700 Subject: 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 --- arch/x86/kernel/ptrace.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'arch/x86/kernel/ptrace.c') diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index 34e77b16a42a..e37dccce85db 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -1416,6 +1416,16 @@ asmregparm long syscall_trace_enter(struct pt_regs *regs) { long ret = 0; + /* + * 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. If we entered on the slow path, TF was already set. + */ + if (test_thread_flag(TIF_SINGLESTEP)) + regs->flags |= X86_EFLAGS_TF; + /* do the secure computing check first */ secure_computing(regs->orig_ax); -- cgit v1.2.3