[edk2-devel] [PATCH v5 08/28] UefiCpuPkg: Always Set Stack Guard in MpPei Init
Laszlo Ersek
lersek at redhat.com
Mon Oct 9 07:28:16 UTC 2023
On 10/9/23 02:07, Taylor Beebe wrote:
> Memory protection is not set in PEI and ingested during and
> after DXE handoff. This paradigm means that the platform cannot
> reliably query the stack guard setting during MpInit. Because the
> execution path of PEI consistent and no third party
> code is executed, setting the stack guard in MpInit on every
> boot should be fine.
I don't understand this commit message at all -- I don't understand any
one of those sentences. Please explain in detail.
This is an intrusive change; it basically forces all platforms that use
CpuMpPei to a mode with PcdCpuStackGuard=TRUE. That may not be
consistent with what a platform wants, plus it seems to invalidate the
definition of PcdCpuStackGuard.
Is the problem that PcdGetBool() does not work? (I'd doubt that;
PcdCpuStackGuard can only be fixed-at-build.)
You could make the argument that PcdCpuStackGuard is *already* mis-used
in CpuMpPei, given that the PCD's definition says
## Indicates if UEFI Stack Guard will be enabled.
# If enabled, stack overflow in UEFI can be caught, preventing chaotic consequences.<BR><BR>
and "UEFI" is not PEI. But if this is your argument, then that's what
the commit message should state.
Thanks,
Laszlo
>
> Signed-off-by: Taylor Beebe <taylor.d.beebe at gmail.com>
> Cc: Eric Dong <eric.dong at intel.com>
> Cc: Ray Ni <ray.ni at intel.com>
> Cc: Rahul Kumar <rahul1.kumar at intel.com>
> Cc: Gerd Hoffmann <kraxel at redhat.com>
> ---
> UefiCpuPkg/CpuMpPei/CpuMpPei.c | 8 +++-----
> UefiCpuPkg/CpuMpPei/CpuPaging.c | 16 ++++++++--------
> UefiCpuPkg/CpuMpPei/CpuMpPei.h | 3 ++-
> UefiCpuPkg/CpuMpPei/CpuMpPei.inf | 1 -
> 4 files changed, 13 insertions(+), 15 deletions(-)
>
> diff --git a/UefiCpuPkg/CpuMpPei/CpuMpPei.c b/UefiCpuPkg/CpuMpPei/CpuMpPei.c
> index b504bea3cfeb..ca0c6bdb4b21 100644
> --- a/UefiCpuPkg/CpuMpPei/CpuMpPei.c
> +++ b/UefiCpuPkg/CpuMpPei/CpuMpPei.c
> @@ -469,10 +469,6 @@ InitializeMpExceptionStackSwitchHandlers (
> EFI_STATUS Status;
> UINT8 *Buffer;
>
> - if (!PcdGetBool (PcdCpuStackGuard)) {
> - return;
> - }
> -
> Status = MpInitLibGetNumberOfProcessors (&NumberOfProcessors, NULL);
> ASSERT_EFI_ERROR (Status);
>
> @@ -589,7 +585,9 @@ InitializeCpuMpWorker (
> //
> // Special initialization for the sake of Stack Guard
> //
> - InitializeMpExceptionStackSwitchHandlers ();
> + if (mInitStackGuard) {
> + InitializeMpExceptionStackSwitchHandlers ();
> + }
>
> //
> // Update and publish CPU BIST information
> diff --git a/UefiCpuPkg/CpuMpPei/CpuPaging.c b/UefiCpuPkg/CpuMpPei/CpuPaging.c
> index b7ddb0005b6f..0ab8ceeee8a6 100644
> --- a/UefiCpuPkg/CpuMpPei/CpuPaging.c
> +++ b/UefiCpuPkg/CpuMpPei/CpuPaging.c
> @@ -68,6 +68,8 @@ EFI_PEI_NOTIFY_DESCRIPTOR mPostMemNotifyList[] = {
> }
> };
>
> +BOOLEAN mInitStackGuard = FALSE;
> +
> /**
> The function will check if IA32 PAE is supported.
>
> @@ -532,7 +534,7 @@ SetupStackGuardPage (
> }
>
> /**
> - Enable/setup stack guard for each processor if PcdCpuStackGuard is set to TRUE.
> + Enable/setup stack guard for each processor.
>
> Doing this in the memory-discovered callback is to make sure the Stack Guard
> feature to cover as most PEI code as possible.
> @@ -553,7 +555,6 @@ MemoryDiscoveredPpiNotifyCallback (
> )
> {
> EFI_STATUS Status;
> - BOOLEAN InitStackGuard;
> EDKII_MIGRATED_FV_INFO *MigratedFvInfo;
> EFI_PEI_HOB_POINTERS Hob;
> IA32_CR0 Cr0;
> @@ -563,11 +564,10 @@ MemoryDiscoveredPpiNotifyCallback (
> // initialization later will not contain paging information and then fail
> // the task switch (for the sake of stack switch).
> //
> - InitStackGuard = FALSE;
> - Hob.Raw = NULL;
> + Hob.Raw = NULL;
> if (IsIa32PaeSupported ()) {
> - Hob.Raw = GetFirstGuidHob (&gEdkiiMigratedFvInfoGuid);
> - InitStackGuard = PcdGetBool (PcdCpuStackGuard);
> + Hob.Raw = GetFirstGuidHob (&gEdkiiMigratedFvInfoGuid);
> + mInitStackGuard = TRUE;
> }
>
> //
> @@ -575,7 +575,7 @@ MemoryDiscoveredPpiNotifyCallback (
> // is to enable paging if it is not enabled (only in 32bit mode).
> //
> Cr0.UintN = AsmReadCr0 ();
> - if ((Cr0.Bits.PG == 0) && (InitStackGuard || (Hob.Raw != NULL))) {
> + if ((Cr0.Bits.PG == 0) && (mInitStackGuard || (Hob.Raw != NULL))) {
> ASSERT (sizeof (UINTN) == sizeof (UINT32));
>
> Status = EnablePaePageTable ();
> @@ -588,7 +588,7 @@ MemoryDiscoveredPpiNotifyCallback (
> Status = InitializeCpuMpWorker ((CONST EFI_PEI_SERVICES **)PeiServices);
> ASSERT_EFI_ERROR (Status);
>
> - if (InitStackGuard) {
> + if (mInitStackGuard) {
> SetupStackGuardPage ();
> }
>
> diff --git a/UefiCpuPkg/CpuMpPei/CpuMpPei.h b/UefiCpuPkg/CpuMpPei/CpuMpPei.h
> index 1b9a94e18fdf..d0db4e480e13 100644
> --- a/UefiCpuPkg/CpuMpPei/CpuMpPei.h
> +++ b/UefiCpuPkg/CpuMpPei/CpuMpPei.h
> @@ -31,6 +31,7 @@
> #include <Library/CpuPageTableLib.h>
>
> extern EFI_PEI_PPI_DESCRIPTOR mPeiCpuMpPpiDesc;
> +extern BOOLEAN mInitStackGuard;
>
> /**
> This service retrieves the number of logical processor in the platform
> @@ -426,7 +427,7 @@ InitializeCpuMpWorker (
> );
>
> /**
> - Enable/setup stack guard for each processor if PcdCpuStackGuard is set to TRUE.
> + Enable/setup stack guard for each processor.
>
> Doing this in the memory-discovered callback is to make sure the Stack Guard
> feature to cover as most PEI code as possible.
> diff --git a/UefiCpuPkg/CpuMpPei/CpuMpPei.inf b/UefiCpuPkg/CpuMpPei/CpuMpPei.inf
> index 865be5627e85..6a987754120a 100644
> --- a/UefiCpuPkg/CpuMpPei/CpuMpPei.inf
> +++ b/UefiCpuPkg/CpuMpPei/CpuMpPei.inf
> @@ -64,7 +64,6 @@ [Ppis]
>
> [Pcd]
> gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask ## CONSUMES
> - gEfiMdeModulePkgTokenSpaceGuid.PcdCpuStackGuard ## CONSUMES
> gUefiCpuPkgTokenSpaceGuid.PcdCpuStackSwitchExceptionList ## SOMETIMES_CONSUMES
> gUefiCpuPkgTokenSpaceGuid.PcdCpuKnownGoodStackSize ## SOMETIMES_CONSUMES
> gUefiCpuPkgTokenSpaceGuid.PcdCpuApStackSize ## SOMETIMES_CONSUMES
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