From 7c40c6d1b76b38d2adbb71999878961e0149f13f Mon Sep 17 00:00:00 2001 From: Sheng Wei Date: Sun, 7 Feb 2021 15:04:27 +0800 Subject: [PATCH v3 0/1] Fix CET shadow stack token busy bit clear issue 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 REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3192 Signed-off-by: Sheng Wei Cc: Eric Dong Cc: Ray Ni Cc: Laszlo Ersek Cc: Rahul Kumar Cc: Jiewen Yao Cc: Roger Feng Sheng Wei (1): UefiCpuPkg/CpuExceptionHandlerLib: Clear CET shadow stack token busy bit .../DxeCpuExceptionHandlerLib.inf | 3 ++ .../PeiCpuExceptionHandlerLib.inf | 3 ++ .../SecPeiCpuExceptionHandlerLib.inf | 4 ++ .../SmmCpuExceptionHandlerLib.inf | 3 ++ .../X64/Xcode5ExceptionHandlerAsm.nasm | 48 ++++++++++++++++++++-- .../Xcode5SecPeiCpuExceptionHandlerLib.inf | 4 ++ UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c | 15 ++++++- 7 files changed, 76 insertions(+), 4 deletions(-) -- 2.16.2.windows.1