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Subject[PATCH] x86: kill handle_signal()->set_fs()
handle_signal()->set_fs() has a nice comment which explains what
set_fs() is, but it doesn't explain why it is needed and why it
depends on CONFIG_X86_64.

Afaics, the history of this confusion is:

1. I guess today nobody can explain why it was needed
in arch/i386/kernel/signal.c, perhaps it was always
wrong. This predates 2.4.0 kernel.

2. then it was copy-and-past'ed to the new x86_64 arch.

3. then it was removed from i386 (but not from x86_64)
by b93b6ca3 "i386: remove unnecessary code".

4. then it was reintroduced under CONFIG_X86_64 when x86
unified i386 and x86_64, because the patch above didn't
touch x86_64.

Remove it. ->addr_limit should be correct. Even if it was possible
that it is wrong, it is too late to fix it after setup_rt_frame().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

arch/x86/kernel/signal.c | 9 ---------
1 file changed, 9 deletions(-)

--- ptrace/arch/x86/kernel/signal.c~1_kill_set_fs 2011-05-22 16:27:28.000000000 +0200
+++ ptrace/arch/x86/kernel/signal.c 2011-07-10 18:06:30.000000000 +0200
@@ -717,15 +717,6 @@ handle_signal(unsigned long sig, siginfo
if (ret)
return ret;

-#ifdef CONFIG_X86_64
- /*
- * This has nothing to do with segment registers,
- * despite the name. This magic affects uaccess.h
- * macros' behavior. Reset it to the normal setting.
- */
- set_fs(USER_DS);
-#endif
-
/*
* Clear the direction flag as per the ABI for function entry.
*/


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