[Bug c/28281] New: gcc uses the wrong segment register for TLS access for -fstack-protector in kernel mode

[Bug c/28281] New: gcc uses the wrong segment register for TLS access for -fstack-protector in kernel mode

[arjan at linux dot intel dot com]

Userspace and kernel space use a different segment register for TLS access in
x86_64. (This is so that a syscall doesn't need to switch these registers most
of the time, so good for performance)

This means that the kernel cannot use -fstack-protector currently, which is sad
since today another buffer overflow has been found in the linux kernel.

The solution is quite simple, and I will attach a patch to fix this next; just
use a different segement register for the mc_kernel model.

(the patch is trivial; it copies a line and changes a few characters in it, and
then places an if around it)


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           Summary: gcc uses the wrong segment register for TLS access for -
                    fstack-protector in kernel mode
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: arjan at linux dot intel dot com
  GCC host triplet: x86_64-unknown-linux-gnu
GCC target triplet: x86_64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28281

[Bug c/28281] gcc uses the wrong segment register for TLS access for -fstack-protector in kernel mode

[arjan at linux dot intel dot com]

------- Comment #1 from arjan at linux dot intel dot com  2006-07-06 09:24 -------
Created an attachment (id=11839)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11839&action=view)
patch to fix this issue, including a testcase

patch + testcase for this issue

2006-07-06  Arjan van de Ven <arjan@linux.intel.com>
        * config/i386/i386.md: add conditonal for kernel side
        stack-protector


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28281

[Bug c/28281] gcc uses the wrong segment register for TLS access for -fstack-protector in kernel mode

[arjan at linux dot intel dot com]

------- Comment #2 from arjan at linux dot intel dot com  2006-07-06 09:49 -------
Created an attachment (id=11842)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11842&action=view)
updated patch

updated patch; it helps if I send the non-test version of the testsuite test so
that it actually tests the right behavior


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28281

[Bug c/28281] gcc uses the wrong segment register for TLS access for -fstack-protector in kernel mode

[arjan at linux dot intel dot com]

------- Comment #3 from arjan at linux dot intel dot com  2006-07-06 11:08 -------
Created an attachment (id=11844)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11844&action=view)
updates with Jakub's comments

updates with jakubs comments


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28281

[Bug target/28281] gcc uses the wrong segment register for TLS access for -fstack-protector in kernel mode

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
          Component|c                           |target


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28281

[Bug target/28281] gcc uses the wrong segment register for TLS access for -fstack-protector in kernel mode

[arjan at linux dot intel dot com]

------- Comment #4 from arjan at linux dot intel dot com  2006-07-29 07:46 -------
fixed in current SVN


-- 

arjan at linux dot intel dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28281

[Bug target/28281] gcc uses the wrong segment register for TLS access for -fstack-protector in kernel mode

[belyshev at depni dot sinp dot msu dot ru]

-- 

belyshev at depni dot sinp dot msu dot ru changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.2.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28281