Re: [edk2-devel] [PATCH] CryptoPkg/FltUsedLib: Add FltUsedLib for float.

["Guomin Jiang" <guomin.jiang@intel.com>]

The size comparation between with _fltused and without _fltused, use OvmfPkgX64 as build target
OvmfX64  EFI_FV_TAKEN_SIZE  |   Without _fltused       | With _fltused
DXEFV                                             |  0x46bbe0                     | 0x46bbc0
FVMAIN_COMPACT                     |  0x12c8a0                      | 0x12c7f0
PEIFV                                              |  0x4cae8                         | 0x4ca68
From the result, it will occupy less size rather than more size.

Code Change as below and build command is ```build -p OvmfPkg/OvmfPkgX64 -b DEBUG -t VS2019 -a X64 -DTPM_ENABLE=TRUE```

diff --git a/CryptoPkg/Library/IntrinsicLib/MemoryIntrinsics.c b/CryptoPkg/Library/IntrinsicLib/MemoryIntrinsics.c
index 94fe341bec..c4136916d0 100644
--- a/CryptoPkg/Library/IntrinsicLib/MemoryIntrinsics.c
+++ b/CryptoPkg/Library/IntrinsicLib/MemoryIntrinsics.c
@@ -2,7 +2,7 @@
   Intrinsic Memory Routines Wrapper Implementation for OpenSSL-based
   Cryptographic Library.

-Copyright (c) 2010 - 2019, Intel Corporation. All rights reserved.<BR>
+Copyright (c) 2010 - 2020, Intel Corporation. All rights reserved.<BR>
 SPDX-License-Identifier: BSD-2-Clause-Patent

 **/
@@ -13,16 +13,6 @@ SPDX-License-Identifier: BSD-2-Clause-Patent

 typedef UINTN  size_t;

-#if defined(__GNUC__) || defined(__clang__)
-  #define GLOBAL_USED __attribute__((used))
-#else
-  #define GLOBAL_USED
-#endif
-
-/* OpenSSL will use floating point support, and C compiler produces the _fltused
-   symbol by default. Simply define this symbol here to satisfy the linker. */
-int  GLOBAL_USED _fltused = 1;
-
 /* Sets buffers to a specified character */
 void * memset (void *dest, int ch, size_t count)
 {
diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf
index 3586beb0ab..bab31c07c7 100644
--- a/MdePkg/Library/BaseLib/BaseLib.inf
+++ b/MdePkg/Library/BaseLib/BaseLib.inf
@@ -1,7 +1,7 @@
 ## @file
 #  Base Library implementation.
 #
-#  Copyright (c) 2007 - 2019, Intel Corporation. All rights reserved.<BR>
+#  Copyright (c) 2007 - 2020, Intel Corporation. All rights reserved.<BR>
 #  Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
 #  Portions copyright (c) 2011 - 2013, ARM Ltd. All rights reserved.<BR>
 #
@@ -60,6 +60,7 @@
   String.c
   FilePaths.c
   BaseLibInternals.h
+  FltUsed.c               | MSFT

 [Sources.Ia32]
   Ia32/WriteTr.nasm
diff --git a/MdePkg/Library/BaseLib/FltUsed.c b/MdePkg/Library/BaseLib/FltUsed.c
new file mode 100644
index 0000000000..c065594266
--- /dev/null
+++ b/MdePkg/Library/BaseLib/FltUsed.c
@@ -0,0 +1,14 @@
+/** @file
+  Declare _fltused symbol for MSVC
+
+  MSVC need this symbol for float, andd it here to feed MSVC. it may remove
+  if MSVC not need it any more.
+
+  Copyright (c) 2020 - 2020, Intel Corporation. All rights reserved.<BR>
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+//
+// Just for MSVC float
+//
+int _fltused = 0x1;

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Guomin
> Jiang
> Sent: Tuesday, April 14, 2020 3:01 PM
> To: devel@edk2.groups.io; Ni, Ray <ray.ni@intel.com>; Kinney, Michael D
> <michael.d.kinney@intel.com>; ard.biesheuvel@linaro.org
> Cc: lersek@redhat.com; macarl@microsoft.com
> Subject: Re: [edk2-devel] [PATCH] CryptoPkg/FltUsedLib: Add FltUsedLib for
> float.
> 
> Summarize current status:
> 
> Problem Statement:
> Openssl require _fltused to be defined as a constant anywhere floating point
> is used.
> It may use float out of edk2 tree and need _fltused, for example, Microsoft’s
> OnScreenKeyboard and UiToolKit.
> 
> Current Proposal as below:
> 
> Proposal 1: Add FltUsed.c into exist library
> Detail: Add FltUsed.c into EntryPointLib(PEIM, DXE).
> Recommend: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Approve: Laszlo Ersek lersek@redhat.com
> Netual: Michael D Kinney <michael.d.kinney@intel.com>
> Benefit: Doesn’t need modify every .dsc description file.
> Defection: I test that it will fail because of /GL option, the error show fatal
> error LNK1237: during code generation, compiler introduced reference to
> symbol '_fltused' defined in module
> 'UefiApplicationEntryPoint.lib(FltUsed.obj)' compiled with /GL
> 
> Proposal 2: Define NULL library
> Recommend: Michael D Kinney michael.d.kinney@intel.com
> Oppose: Sean sean.brogan=microsoft.com@groups.io , Ard Biesheuvel
> <ard.biesheuvel@linaro.org>
> Benefit: I test it and prove that it is executable.
> Defection: It is required that modify every description file.
> Defection: It need be very careful that it should only apply some module
> type(PEIM, DXE_DRIVER, UEFI_APPLICATION) rather than all.
> Defection: Build break up.
> Action Required: Need evaluate the affection on size.
> Consideration: Add PCD to control the feature
> 
> Proposal 3: Define FltUsedLib
> Detail: Define FltUsedLib and add dependence
> Oppose: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Benefit: Doesn’t need care that which module will use it, we will explicitly
> point it in component file.
> Defection: More complex, It is required that modify every description file
> and modify component meanwhile.
> Defection: Build breakup
> 
> Thanks
> guomin
> 
> > -----Original Message-----
> > From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Ni,
> Ray
> > Sent: Tuesday, April 14, 2020 1:03 PM
> > To: devel@edk2.groups.io; Kinney, Michael D
> > <michael.d.kinney@intel.com>; ard.biesheuvel@linaro.org; Kinney,
> > Michael D <michael.d.kinney@intel.com>
> > Cc: lersek@redhat.com; macarl@microsoft.com
> > Subject: Re: [edk2-devel] [PATCH] CryptoPkg/FltUsedLib: Add FltUsedLib
> > for float.
> >
> > UEFI spec allows using float operation so asking module developers
> > avoid using float may not make sense. Even
> > UefiCpuPkg\Library\BaseUefiCpuLib\
> > provides routine to initialize float support for X86.
> >
> > Given ARM already uses NULL library class mechanism to supply the
> > compiler stub, I prefer X86 aligns to the ARM style.
> >
> > The only unsure thing is the size impact when a module is not using
> > float. We expect there is no size impact when a module is not using float.
> >
> > Thanks,
> > Ray
> >
> > > -----Original Message-----
> > > From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of
> > Michael
> > > D Kinney
> > > Sent: Thursday, April 2, 2020 12:38 AM
> > > To: devel@edk2.groups.io; ard.biesheuvel@linaro.org; Kinney, Michael
> > > D <michael.d.kinney@intel.com>
> > > Cc: lersek@redhat.com; macarl@microsoft.com
> > > Subject: Re: [edk2-devel] [PATCH] CryptoPkg/FltUsedLib: Add
> > > FltUsedLib for float.
> > >
> > > Hi Ard,
> > >
> > > I think adding a dependency in the module entry point libs is also
> > > good way to guarantee an intrinsic lib is available.  I agree that
> > > it can provide module type and arch specific mappings.  The NULL lib
> > > instance can do the same if the NULL instance is listed in the
> > > module/arch specific library classes sections. a few example section
> > > names.
> > >
> > > [LibraryClasses.ARM.PEIM, LibraryClasses.AARCH64.PEIM]
> > >
> > > [LibraryClasses.IA32.UEFI_DRIVER]
> > >
> > > [LibraryClasses.X64.DXE_DRIVER]
> > >
> > > So either way, the DSC files need to provide the library mapping.
> > > The only difference between these
> > > 2 approaches is that adding a dependency to the module entry point
> > > libs uses a formally defined library class name for the intrinsic
> > > functions vs.
> > > the un-named NULL library instance.  A formally defined library
> > > class name is better supported for things like unit tests from the
> > > UnitTestFrameworkPkg.
> > >
> > > The fltused issue would not go away of we removed the float usage
> > > for OpenSSL.  One or more other libs or the module could use
> > > float/double types and this issue would pop up again.  I do agree it
> > > would be cleaner if we could use OpenSSL without floating point.
> > >
> > > I think adding an intrinsic lib for IA32/X64 for VS20xx generation
> > > of intrinsic functions would address fltused and other common C
> > > implementation styles that generate intrinsic functions (e.g. 64-bit
> > > int math on 32-bit, structure variable assignments, and loops that
> > > fill a buffer with a const value) by VS20xx compilers.  An intrinsic
> > > lib for GCC would also help with these same common C implementation
> > > styles that generate intrinsic functions.
> > >
> > > Mike
> > >
> > > > -----Original Message-----
> > > > From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of
> Ard
> > > > Biesheuvel
> > > > Sent: Tuesday, March 31, 2020 11:43 PM
> > > > To: Kinney, Michael D <michael.d.kinney@intel.com>
> > > > Cc: devel@edk2.groups.io; lersek@redhat.com; macarl@microsoft.com
> > > > Subject: Re: [edk2-devel] [PATCH] CryptoPkg/FltUsedLib:
> > > > Add FltUsedLib for float.
> > > >
> > > > On Tue, 31 Mar 2020 at 16:36, Kinney, Michael D
> > > > <michael.d.kinney@intel.com> wrote:
> > > > >
> > > > > ARM and AARCH64 have a compiler intrinsic lib that is
> > > > linked against all modules.
> > > > >
> > > > > [LibraryClasses.ARM, LibraryClasses.AARCH64]
> > > > >   #
> > > > >   # It is not possible to prevent ARM compiler calls to
> > > > generic intrinsic functions.
> > > > >   # This library provides the instrinsic functions
> > > > generated by a given compiler.
> > > > >   # [LibraryClasses.ARM] and NULL mean link this
> > > > library into all ARM images.
> > > > >   #
> > > > >
> > > > NULL|ArmPkg/Library/CompilerIntrinsicsLib/CompilerIntrins
> > > > icsLib.inf
> > > > >
> > > > > Can we use this same technique for IA32/X64 VS builds?
> > > > >
> > > >
> > > > In my opinion, having these intrinsics libraries added via NULL
> > > > library class resolution was a mistake to begin with.
> > > >
> > > > Every component that we build incorporates some kind of startup
> > > > code library that defines the _ModuleEntryPoint symbol, and it
> > > > would be much better to make those libraries include an
> > > > IntrinsicsLibrary dependency that can be satisfied by arch
> > > > specific versions that also encapsulate the toolchain dependencies
> > > > (such as this _fltused symbol, or memcpy/memset on ARM/GCC).
> > > >
> > > > On another note, it is still deeply disappointing that we need to
> > > > jump through all of these hoops because the *only* single use of
> > > > floating point in OpenSSL is the entropy estimate of an RNG, which
> > > > is in the range of 0..1023 to begin with [IIRC). Remember that we
> > > > also have a softfloat submodule for 32-bit ARM, for the same
> > > > stupid reason. If we could stop pulling in that part of the code
> > > > (or replace it with an
> > > > UINT16 when building for the UEFI target), the whole floating
> > > > point issue would mostly go away AFAICT.
> > > >
> > > >
> > >
> > >
> > >
> >
> >
> >
> 
> 
>