[PATCH 1/1] Revert "ptrace: PTRACE_DETACH should doflush_ptrace_hw_breakpoint(child)"

From: Oleg Nesterov
Date: Tue Aug 06 2013 - 11:49:19 EST

This reverts commit fab840fc2d542fabcab903db8e03589a6702ba5f.

This commit even has the test-case to prove that the tracee
can be killed by SIGTRAP if the debugger does not remove the
breakpoints before PTRACE_DETACH.

However, this is exactly what wineserver deliberately does,
set_thread_context() calls PTRACE_ATTACH + PTRACE_DETACH just
for PTRACE_POKEUSER(DR*) in between.

So we should revert this fix and document that PTRACE_DETACH
should keep the breakpoints.

Reported-by: Felipe Contreras <felipe.contreras@xxxxxxxxx>
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
kernel/ptrace.c | 1 -
1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 4041f57..a146ee3 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -469,7 +469,6 @@ static int ptrace_detach(struct task_struct *child, unsigned int data)
/* Architecture-specific hardware disable .. */
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
- flush_ptrace_hw_breakpoint(child);


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