This Feature PCD causes PiSmmCpuDxe to catch SMM stack overflow at runtime, logging a clear error message, and entering a CPU dead loop. Compared to the chaotic and catastrophic consequences of the stack leaking into, and corrupting, the SMM page table, a stack guard that is enabled by default is vastly superior.
We should not require sane platforms to explicitly opt in to this safeguard; instead, we should require platforms that prefer to live dangerously to opt out of it. Stack overflow in SMM might even give rise to security vulnerabilities. Cc: Jeff Fan <[email protected]> Cc: Jiewen Yao <[email protected]> Cc: Jordan Justen <[email protected]> Cc: Michael D Kinney <[email protected]> Ref: http://thread.gmane.org/gmane.comp.bios.edk2.devel/12864 Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1341733 Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Laszlo Ersek <[email protected]> --- UefiCpuPkg/UefiCpuPkg.dec | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/UefiCpuPkg/UefiCpuPkg.dec b/UefiCpuPkg/UefiCpuPkg.dec index 16637dfdc14b..ef46318a8935 100644 --- a/UefiCpuPkg/UefiCpuPkg.dec +++ b/UefiCpuPkg/UefiCpuPkg.dec @@ -85,11 +85,11 @@ [PcdsFeatureFlag] gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmBlockStartupThisAp|FALSE|BOOLEAN|0x32132108 ## Indicates if SMM Stack Guard will be enabled. - # If enabled, stack overflow in SMM can be caught which eases debugging.<BR><BR> + # If enabled, stack overflow in SMM can be caught, preventing chaotic consequences.<BR><BR> # TRUE - SMM Stack Guard will be enabled.<BR> # FALSE - SMM Stack Guard will be disabled.<BR> # @Prompt Enable SMM Stack Guard. - gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackGuard|FALSE|BOOLEAN|0x1000001C + gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackGuard|TRUE|BOOLEAN|0x1000001C ## Indicates if BSP election in SMM will be enabled. # If enabled, a BSP will be dynamically elected among all processors in each SMI. -- 1.8.3.1 _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
