[PATCH 2/3] x86: set_personality_ia32() abuses TS_COMPAT

[Oleg Nesterov]

set_personality_ia32() sets TS_COMPAT for unknown reason.

This doesn't hurt but this is unneeded and confusing, TS_COMPAT
means we are inside the 32bit syscall.

In fact I'd say this is not right, but fortunetely do_execve() can
never return something which could confuse syscall_get_error().
And apart from do_signal() we never check TS_COMPAT during return
to user-mode.

Another reason why I think this is not right. I am not sure I fully
understand this asm, but it seems to me that system_call_fastpath
can "leak" TS_COMPAT. While probably this doesn't really matter, we
can return to user-mode with this bit set.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---

 arch/x86/kernel/process_64.c |    3 ---
 1 file changed, 3 deletions(-)

--- exec/arch/x86/kernel/process_64.c~2_dont_set_compat	2010-02-16 13:26:34.000000000 +0100
+++ exec/arch/x86/kernel/process_64.c	2010-02-16 13:46:25.000000000 +0100
@@ -528,9 +528,6 @@ void set_personality_ia32(void)
 	/* Make sure to be in 32bit mode */
 	set_thread_flag(TIF_IA32);
 	current->personality |= force_personality32;
-
-	/* Prepare the first "return" to user space */
-	current_thread_info()->status |= TS_COMPAT;
 }
 
 unsigned long get_wchan(struct task_struct *p)

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