[edk2-devel] [PATCH v3 1/1] MdePkg: Add PCD to disable safe string constraint assertions

[Yao, Jiewen]

In BaseLib.h, we have below comments in each safe string function header.
===============
  If an error would be returned, then the function will also ASSERT().
===============

As I mentioned earlier, the original purpose is to let the caller guarantee the correctness of the input. Similar to Microsoft Visual Studio strcpy_s() behavior.


If we decide to change the purpose and change the design, I recommend we add clarification in the function header as well.

For example:
===============================
The PcdAssertOnSafeStringConstraints is used to control the behavior of the runtime violation.
When PcdAssertOnSafeStringConstraints is TRUE, if an error would be returned, then the function will also ASSERT().
When PcdAssertOnSafeStringConstraints is FALSE, if an error would be returned, then the function will NOT ASSERT().
===============================


Hi Michael D Kinney
Do you have some comment?

Thank you
Yao Jiewen


> -----Original Message-----
> From: devel at edk2.groups.io <devel at edk2.groups.io> On Behalf Of Vitaly
> Cheptsov via Groups.Io
> Sent: Tuesday, October 22, 2019 3:20 PM
> To: devel at edk2.groups.io
> Subject: [edk2-devel] [PATCH v3 1/1] MdePkg: Add PCD to disable safe string
> constraint assertions
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2054
> 
> Runtime data checks are not meant to cause debug assertions
> unless explicitly needed by some debug code (thus the PCD)
> as this breaks debug builds validating data with BaseLib.
> 
> Signed-off-by: Vitaly Cheptsov <vit9696 at protonmail.com>>
> ---
>  MdePkg/MdePkg.dec                   |  6 ++++++
>  MdePkg/Library/BaseLib/BaseLib.inf  | 11 ++++++-----
>  MdePkg/Library/BaseLib/SafeString.c |  4 +++-
>  MdePkg/MdePkg.uni                   |  6 ++++++
>  4 files changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/MdePkg/MdePkg.dec b/MdePkg/MdePkg.dec
> index 3fd7d1634c..c1671333f6 100644
> --- a/MdePkg/MdePkg.dec
> +++ b/MdePkg/MdePkg.dec
> @@ -2221,6 +2221,12 @@ [PcdsFixedAtBuild,PcdsPatchableInModule]
>    # @Prompt Memory Address of GuidedExtractHandler Table.
> 
> gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress|0x1000000
> |UINT64|0x30001015
> 
> +  ## Indicates if safe string constraint violation should assert.<BR><BR>
> +  #   TRUE  - Safe string constraint violation causes assertion.<BR>
> +  #   FALSE - Safe string constraint violation does not cause assertion.<BR>
> +  # @Prompt Enable safe string constraint violation assertions.
> +
> gEfiMdePkgTokenSpaceGuid.PcdAssertOnSafeStringConstraints|TRUE|BOOLEA
> N|0x0000002e
> +
>  [PcdsFixedAtBuild, PcdsPatchableInModule, PcdsDynamic, PcdsDynamicEx]
>    ## This value is used to set the base address of PCI express hierarchy.
>    # @Prompt PCI Express Base Address.
> diff --git a/MdePkg/Library/BaseLib/BaseLib.inf
> b/MdePkg/Library/BaseLib/BaseLib.inf
> index 3586beb0ab..bc98bc6134 100644
> --- a/MdePkg/Library/BaseLib/BaseLib.inf
> +++ b/MdePkg/Library/BaseLib/BaseLib.inf
> @@ -390,11 +390,12 @@ [LibraryClasses]
>    BaseMemoryLib
> 
>  [Pcd]
> -  gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength      ##
> SOMETIMES_CONSUMES
> -  gEfiMdePkgTokenSpaceGuid.PcdMaximumAsciiStringLength     ##
> SOMETIMES_CONSUMES
> -  gEfiMdePkgTokenSpaceGuid.PcdMaximumUnicodeStringLength   ##
> SOMETIMES_CONSUMES
> -  gEfiMdePkgTokenSpaceGuid.PcdControlFlowEnforcementPropertyMask   ##
> SOMETIMES_CONSUMES
> -  gEfiMdePkgTokenSpaceGuid.PcdSpeculationBarrierType       ##
> SOMETIMES_CONSUMES
> +  gEfiMdePkgTokenSpaceGuid.PcdAssertOnSafeStringConstraints       ##
> SOMETIMES_CONSUMES
> +  gEfiMdePkgTokenSpaceGuid.PcdMaximumLinkedListLength             ##
> SOMETIMES_CONSUMES
> +  gEfiMdePkgTokenSpaceGuid.PcdMaximumAsciiStringLength            ##
> SOMETIMES_CONSUMES
> +  gEfiMdePkgTokenSpaceGuid.PcdMaximumUnicodeStringLength          ##
> SOMETIMES_CONSUMES
> +  gEfiMdePkgTokenSpaceGuid.PcdControlFlowEnforcementPropertyMask  ##
> SOMETIMES_CONSUMES
> +  gEfiMdePkgTokenSpaceGuid.PcdSpeculationBarrierType              ##
> SOMETIMES_CONSUMES
> 
>  [FeaturePcd]
>    gEfiMdePkgTokenSpaceGuid.PcdVerifyNodeInList  ## CONSUMES
> diff --git a/MdePkg/Library/BaseLib/SafeString.c
> b/MdePkg/Library/BaseLib/SafeString.c
> index 7dc03d2caa..56b5e34a8d 100644
> --- a/MdePkg/Library/BaseLib/SafeString.c
> +++ b/MdePkg/Library/BaseLib/SafeString.c
> @@ -14,7 +14,9 @@
> 
>  #define SAFE_STRING_CONSTRAINT_CHECK(Expression, Status)  \
>    do { \
> -    ASSERT (Expression); \
> +    if (PcdGetBool (PcdAssertOnSafeStringConstraints)) { \
> +      ASSERT (Expression); \
> +    } \
>      if (!(Expression)) { \
>        return Status; \
>      } \
> diff --git a/MdePkg/MdePkg.uni b/MdePkg/MdePkg.uni
> index 5c1fa24065..425b66bb43 100644
> --- a/MdePkg/MdePkg.uni
> +++ b/MdePkg/MdePkg.uni
> @@ -287,6 +287,12 @@
> 
>  #string
> STR_gEfiMdePkgTokenSpaceGuid_PcdGuidedExtractHandlerTableAddress_HELP
> #language en-US "This value is used to set the available memory address to
> store Guided Extract Handlers. The required memory space is decided by the
> value of PcdMaximumGuidedExtractHandler."
> 
> +#string
> STR_gEfiMdePkgTokenSpaceGuid_PcdAssertOnSafeStringConstraints_PROMPT
> #language en-US "Enable safe string constraint violation assertions"
> +
> +#string
> STR_gEfiMdePkgTokenSpaceGuid_PcdAssertOnSafeStringConstraints_HELP
> #language en-US "Indicates if safe string constraint violation should
> assert.<BR><BR>\n"
> +                                                                                   "TRUE  - Safe string constraint
> violation causes assertion.<BR>\n"
> +                                                                                   "FALSE - Safe string constraint
> violation does not cause assertion.<BR>"
> +
>  #string STR_gEfiMdePkgTokenSpaceGuid_PcdPciExpressBaseAddress_PROMPT
> #language en-US "PCI Express Base Address"
> 
>  #string STR_gEfiMdePkgTokenSpaceGuid_PcdPciExpressBaseAddress_HELP
> #language en-US "This value is used to set the base address of PCI express
> hierarchy."
> --
> 2.21.0 (Apple Git-122)
> 
> 
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