docs: Add FIPS documentation to BUILDING.md and README.md

BUILDING.md

@@ -238,6 +238,10 @@ mechanism is ignored.
 Snapshots taken on active hosts can potentially be unsafe to use.
 See "Snapshot Safety Prerequisites" here: https://lkml.org/lkml/2021/3/8/677
 
+# FIPS Mode
+
+For more details on building AWS-LC in FIPS mode, see the [crypto/fipsmodule/FIPS.md](crypto/fipsmodule/FIPS.md).
+
 # Data Independent Timing on AArch64
 
 The functions described in this section are still experimental.

README.md

@@ -116,6 +116,10 @@ that improve the experience for consumers on these platforms.
 | OpenBSD   | x86-64      |
 | FreeBSD   | x86-64      |
 
+### FIPS Compliance
+
+For information about FIPS compliance, building AWS-LC in FIPS mode, and platform limitations, see [crypto/fipsmodule/FIPS.md](crypto/fipsmodule/FIPS.md).
+
 ### Post-Quantum Cryptography
 
 Details on the post-quantum algorithms supported by AWS-LC can be found at [PQREADME](https://github.com/aws/aws-lc/tree/main/crypto/fipsmodule/PQREADME.md).
@@ -188,5 +192,3 @@ Security via our
 Please do **not** create a public GitHub issue.
 
 If you package or distribute AWS-LC, or use AWS-LC as part of a large multi-user service, you may be eligible for pre-notification of future AWS-LC releases. Please contact aws-lc-pre-notifications@amazon.com.
-
-

crypto/fipsmodule/FIPS.md

@@ -14,6 +14,14 @@ NIST has also awarded SP 800-90B validation certificate for our CPU Jitter Entro
 
 1. 2023-09-14: entropy certificate [#E77](https://csrc.nist.gov/projects/cryptographic-module-validation-program/entropy-validations/certificate/77), [public use document](https://csrc.nist.gov/CSRC/media/projects/cryptographic-module-validation-program/documents/entropy/E77_PublicUse.pdf)
 
+## Platform Limitations
+
+When building AWS-LC in FIPS mode, please be aware of the following platform limitations:
+
+- Static FIPS builds are only supported on Linux platforms
+- Shared library FIPS builds are supported on both Linux and Windows
+- Windows Debug builds are not supported with FIPS
+
 ### Modules in Process
 
 The modules below have been tested by an accredited lab and have been submitted to NIST for FIPS 140-3 validation.
@@ -180,4 +188,3 @@ Initially the known-good value will be incorrect. Another script (`inject_hash.g
 The utility in `util/fipstools/break-hash.go` can be used to corrupt the FIPS module inside a binary and thus trigger a failure of the integrity test. Note that the binary must not be stripped, otherwise the utility will not be able to find the FIPS module.
 
 ![build process](./intcheck2.png)
-