From ebbafc3cec890183ed9b73e58f313aa139176913 Mon Sep 17 00:00:00 2001
From: Michael Kubacki <michael.kubacki@microsoft.com>
Date: Wed, 1 Mar 2023 11:59:34 -0500
Subject: [PATCH] [CHERRY-PICK] MdePkg/BaseMemoryLib: Prevent VS2022 (17.5)
 linker failure (#290)

Fixes #291

After updating from Visual Studio 17.4 to 17.5, a large number of
linker failures began to appear in several modules because `memset`
is an unresolved symbol.

It was found that the following functions in BaseMemoryLib/MemLibGeneric.c
were having their loop pattern replaced with the `memset` intrinsic
function:

- `InternalMemSetMem16()`
- `InternalMemSetMem32()`
- `InternalMemSetMem64()`

An example of an error related to `InternalMemSetMem64()` in
VariableSmmRuntimeDxe is shown below:

```
INFO - BaseMemoryLib.lib(MemLibGeneric.obj) : error LNK2001:
         unresolved external symbol memset
INFO - <...>\VariableSmmRuntimeDxe.dll : fatal error LNK1120:
         1 unresolved externals
```

This was reproduced in several environments including:

- Public VM image:
  https://github.com/actions/runner-images/blob/win22/20230226.1/images/win/Windows2022-Readme.md

- Locally when updating from 17.4.4 to 17.5.1

> Note: The previous public VM image (with 17.4) did not have this issue
  https://github.com/actions/runner-images/blob/win22/20230219.1/images/win/Windows2022-Readme.md

This change updates the type cast for the destination buffer to be
a pointer to `volatile` data to prevent this optimization and introduce
a minimum delta to prior implementation.

---

- [ ] Impacts functionality?
  - **Functionality** - Does the change ultimately impact how firmware functions?
  - Examples: Add a new library, publish a new PPI, update an algorithm, ...
- [ ] Impacts security?
  - **Security** - Does the change have a direct security impact on an application,
    flow, or firmware?
  - Examples: Crypto algorithm change, buffer overflow fix, parameter
    validation improvement, ...
- [ ] Breaking change?
  - **Breaking change** - Will anyone consuming this change experience a break
    in build or boot behavior?
  - Examples: Add a new library class, move a module to a different repo, call
    a function in a new library class in a pre-existing module, ...
- [ ] Includes tests?
  - **Tests** - Does the change include any explicit test code?
  - Examples: Unit tests, integration tests, robot tests, ...
- [ ] Includes documentation?
  - **Documentation** - Does the change contain explicit documentation additions
    outside direct code modifications (and comments)?
  - Examples: Update readme file, add feature readme file, link to documentation
    on an a separate Web page, ...

Built several times with and without the change on Visual Studio 17.5.1
locally and on CI agents.

Include this change if building with the 17.5.1. It is currently the latest
release in most recent Windows VM images.

Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
---
 MdePkg/Library/BaseMemoryLib/MemLibGeneric.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/MdePkg/Library/BaseMemoryLib/MemLibGeneric.c b/MdePkg/Library/BaseMemoryLib/MemLibGeneric.c
index 086eb2966b..1de6b31225 100644
--- a/MdePkg/Library/BaseMemoryLib/MemLibGeneric.c
+++ b/MdePkg/Library/BaseMemoryLib/MemLibGeneric.c
@@ -32,7 +32,9 @@ InternalMemSetMem16 (
   )
 {
   for ( ; Length != 0; Length--) {
-    ((UINT16 *)Buffer)[Length - 1] = Value;
+    // MU_CHANGE use a pointer to volatile data to prevent Visual Studio 17.5 (VS2022)
+    // from replacing the assignment with a `memset()` intrinsic
+    ((volatile UINT16 *)Buffer)[Length - 1] = Value;
   }
 
   return Buffer;
@@ -57,7 +59,9 @@ InternalMemSetMem32 (
   )
 {
   for ( ; Length != 0; Length--) {
-    ((UINT32 *)Buffer)[Length - 1] = Value;
+    // MU_CHANGE use a pointer to volatile data to prevent Visual Studio 17.5 (VS2022)
+    // from replacing the assignment with a `memset()` intrinsic
+    ((volatile UINT32 *)Buffer)[Length - 1] = Value;
   }
 
   return Buffer;
@@ -82,7 +86,9 @@ InternalMemSetMem64 (
   )
 {
   for ( ; Length != 0; Length--) {
-    ((UINT64 *)Buffer)[Length - 1] = Value;
+    // MU_CHANGE use a pointer to volatile data to prevent Visual Studio 17.5 (VS2022)
+    // from replacing the assignment with a `memset()` intrinsic
+    ((volatile UINT64 *)Buffer)[Length - 1] = Value;
   }
 
   return Buffer;