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* [PATCH v4 0/2] Fix CET shadow stack token busy bit clear issue
@ 2021-02-19  4:47 Sheng Wei
  2021-02-19  4:47 ` [PATCH v4 1/2] MdePkg/Include: Add CET instructions to Nasm.inc Sheng Wei
  2021-02-19  4:47 ` [PATCH v4 2/2] UefiCpuPkg/CpuExceptionHandlerLib: Clear CET shadow stack token busy bit Sheng Wei
  0 siblings, 2 replies; 4+ messages in thread
From: Sheng Wei @ 2021-02-19  4:47 UTC (permalink / raw)
  To: devel
  Cc: Eric Dong, Ray Ni, Laszlo Ersek, Rahul Kumar, Jiewen Yao,
	Michael D Kinney, Liming Gao, Zhiguang Liu, Roger Feng

If CET shadows stack feature enabled in SMM and stack switch is enabled.
When code execute from SMM handler to SMM exception, CPU will check SMM
exception shadow stack token busy bit if it is cleared or not.
If it is set, it will trigger #DF exception.
If it is not set, CPU will set the busy bit when enter SMM exception.
So, the busy bit should be cleared when return back form SMM exception to
SMM handler. Otherwise, keeping busy bit 1 will cause to trigger #DF
exception when enter SMM exception next time.
So, we use instruction SAVEPREVSSP, CLRSSBSY and RSTORSSP to clear the
shadow stack token busy bit before RETF instruction in SMM exception.
Since open CI is using NASM 2.14.02, it has not supported CET instructions
yet. Use DB xx xx xx xx to replace the assembly instruction before NASM
2.15.01 is used.

Change from patch v1 to patch v2:
1 Add behavior description in source code comment.
2 Structure interrupt shadow stack memory in InitShadowStack().
3 Update commit comment.

Change from patch v2 to patch v3:
1 Add comment /UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c

Change from patch v3 to patch v4:
Update comment and commit message.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3192

Signed-off-by: Sheng Wei <w.sheng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Zhiguang Liu <zhiguang.liu@intel.com>
Cc: Roger Feng <roger.feng@intel.com>

Sheng Wei (2):
  MdePkg/Include: Add CET instructions to Nasm.inc
  UefiCpuPkg/CpuExceptionHandlerLib: Clear CET shadow stack token busy
    bit

 MdePkg/Include/Ia32/Nasm.inc                       | 12 ++++++
 MdePkg/Include/X64/Nasm.inc                        | 12 ++++++
 .../DxeCpuExceptionHandlerLib.inf                  |  3 ++
 .../PeiCpuExceptionHandlerLib.inf                  |  3 ++
 .../SecPeiCpuExceptionHandlerLib.inf               |  4 ++
 .../SmmCpuExceptionHandlerLib.inf                  |  3 ++
 .../X64/Xcode5ExceptionHandlerAsm.nasm             | 46 +++++++++++++++++++++-
 .../Xcode5SecPeiCpuExceptionHandlerLib.inf         |  4 ++
 UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c       | 15 ++++++-
 9 files changed, 99 insertions(+), 3 deletions(-)

-- 
2.16.2.windows.1


^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-02-19 16:57 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2021-02-19  4:47 [PATCH v4 0/2] Fix CET shadow stack token busy bit clear issue Sheng Wei
2021-02-19  4:47 ` [PATCH v4 1/2] MdePkg/Include: Add CET instructions to Nasm.inc Sheng Wei
2021-02-19 16:57   ` [edk2-devel] " Laszlo Ersek
2021-02-19  4:47 ` [PATCH v4 2/2] UefiCpuPkg/CpuExceptionHandlerLib: Clear CET shadow stack token busy bit Sheng Wei

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