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Documentation: x86: convert entry_64.txt to reST 

This converts the plain text documentation to reStructuredText format and
add it to Sphinx TOC tree. No essential content change.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Changbin Du 2019-05-08 23:21:20 +08:00 committed by Jonathan Corbet
parent ac2b4687da
commit c2dea5cda0
2 changed files with 10 additions and 3 deletions
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12
Documentation/x86/entry_64.txt → Documentation/x86/entry_64.rst
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@ -1,3 +1,9 @@
.. SPDX-License-Identifier: GPL-2.0
==============
Kernel Entries
==============
This file documents some of the kernel entries in This file documents some of the kernel entries in
arch/x86/entry/entry_64.S. A lot of this explanation is adapted from arch/x86/entry/entry_64.S. A lot of this explanation is adapted from
an email from Ingo Molnar: an email from Ingo Molnar:
@ -59,7 +65,7 @@ Now, there's a secondary complication: there's a cheap way to test
which mode the CPU is in and an expensive way. which mode the CPU is in and an expensive way.
The cheap way is to pick this info off the entry frame on the kernel The cheap way is to pick this info off the entry frame on the kernel
stack, from the CS of the ptregs area of the kernel stack: stack, from the CS of the ptregs area of the kernel stack::
xorl %ebx,%ebx xorl %ebx,%ebx
testl $3,CS+8(%rsp) testl $3,CS+8(%rsp)
@ -67,7 +73,7 @@ stack, from the CS of the ptregs area of the kernel stack:
SWAPGS SWAPGS
The expensive (paranoid) way is to read back the MSR_GS_BASE value The expensive (paranoid) way is to read back the MSR_GS_BASE value
(which is what SWAPGS modifies): (which is what SWAPGS modifies)::
movl $1,%ebx movl $1,%ebx
movl $MSR_GS_BASE,%ecx movl $MSR_GS_BASE,%ecx
@ -76,7 +82,7 @@ The expensive (paranoid) way is to read back the MSR_GS_BASE value
js 1f /* negative -> in kernel */ js 1f /* negative -> in kernel */
SWAPGS SWAPGS
xorl %ebx,%ebx xorl %ebx,%ebx
1: ret 1: ret
If we are at an interrupt or user-trap/gate-alike boundary then we can If we are at an interrupt or user-trap/gate-alike boundary then we can
use the faster check: the stack will be a reliable indicator of use the faster check: the stack will be a reliable indicator of

1
Documentation/x86/index.rst
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@ -12,3 +12,4 @@ x86-specific Documentation
topology topology
exception-tables exception-tables
kernel-stacks kernel-stacks
entry_64