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From: Yang <teddyyyy123@gmail.com>
To: linux-kernel@vger.kernel.org
Subject: should we use $(__USER_DS) or $(__KERNEL_DS) when entering interrupt  handlers?
Date: Thu, 18 Mar 2010 10:38:44 -0700	[thread overview]
Message-ID: <bb057cd21003181038j56992f68p6d72d0058d72f82f@mail.gmail.com> (raw)

in handling an interrupt, kernel first saves all the register contents , in
the SAVE_ALL macro, in the last part of this macro,  it adjusts the
data segment selectors for kernel mode.

in kernel 2.4, the __KERNEL_DS segment is loaded into %ds and %es, at line
98 of:

http://lxr.linux.no/#linux-old+v2.4.31/arch/i386/kernel/entry.S


but in kernel 2.6, __USER_DS segment is loaded into %ds and %es, at line
227 of :
http://lxr.linux.no/#linux+v2.6.33/arch/x86/kernel/entry_32.S


I understand that on x86, all the data segment selector contents are
basically the same, but semantically it's better to use the KERNEL_DS
because we are working in kernel mode?



Thanks!
Yang

                 reply	other threads:[~2010-03-18 17:38 UTC|newest]

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