[Bug 1398975] [NEW] hardware-assisted lock elision hazardous on x86

[Chris J Arges]

Public bug reported:

[Impact]
See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=762195 for a full description of the issue.
HLE extensions are hazardous due to erratum HSD136.

Users that upgrade their intel-microcode could encounter illegal
instruction traps due to microcode updates that blacklist HLE
instructions. Glibc uses those instructions and thus we need to be
defensive and patch them here.

The issue was originally seen here:
https://bugs.launchpad.net/intel/+bug/1370352

[Test Case]
Update to latest intel-microcode with microcode-20140913.dat enabled. Try to boot machine and use applications; check dmesg for trap invalid opcodes in libpthread-2.19.so.

[Regression Potential]
This has been fixed in vivid, so I'm requesting this patch be backported to T/U.

** Affects: glibc (Ubuntu)
     Importance: Undecided
         Status: Fix Released

** Affects: glibc (Ubuntu Trusty)
     Importance: Medium
     Assignee: Chris J Arges (arges)
         Status: In Progress

** Affects: glibc (Ubuntu Utopic)
     Importance: Medium
     Assignee: Chris J Arges (arges)
         Status: In Progress

** Affects: glibc (Debian)
     Importance: Unknown
         Status: Unknown

** Also affects: glibc (Ubuntu Trusty)
   Importance: Undecided
       Status: New

** Also affects: glibc (Ubuntu Utopic)
   Importance: Undecided
       Status: New

** Changed in: glibc (Ubuntu)
       Status: New => Fix Released

** Bug watch added: Debian Bug tracker #762195
   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=762195

** Also affects: glibc (Debian) via
   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=762195
   Importance: Unknown
       Status: Unknown

** Changed in: glibc (Ubuntu Trusty)
     Assignee: (unassigned) => Chris J Arges (arges)

** Changed in: glibc (Ubuntu Utopic)
     Assignee: (unassigned) => Chris J Arges (arges)

** Changed in: glibc (Ubuntu Trusty)
   Importance: Undecided => Medium

** Changed in: glibc (Ubuntu Utopic)
   Importance: Undecided => Medium

** Changed in: glibc (Ubuntu Trusty)
       Status: New => In Progress

** Changed in: glibc (Ubuntu Utopic)
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/1398975

Title:
  hardware-assisted lock elision hazardous on x86

Status in glibc package in Ubuntu:
  Fix Released
Status in glibc source package in Trusty:
  In Progress
Status in glibc source package in Utopic:
  In Progress
Status in glibc package in Debian:
  Unknown

Bug description:
  [Impact]
  See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=762195 for a full description of the issue.
  HLE extensions are hazardous due to erratum HSD136.

  Users that upgrade their intel-microcode could encounter illegal
  instruction traps due to microcode updates that blacklist HLE
  instructions. Glibc uses those instructions and thus we need to be
  defensive and patch them here.

  The issue was originally seen here:
  https://bugs.launchpad.net/intel/+bug/1370352

  [Test Case]
  Update to latest intel-microcode with microcode-20140913.dat enabled. Try to boot machine and use applications; check dmesg for trap invalid opcodes in libpthread-2.19.so.

  [Regression Potential]
  This has been fixed in vivid, so I'm requesting this patch be backported to T/U.

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