memory.c: add wc_ConstantCompare wrapper.

[philljj]

Description

Add a public wc_ConstantCompare wrapper, similar to the existing wc_ForceZero wrapper. Other project integrations regularly reuse wc_ForceZero, but then reimplement their own ConstantCompare if they don't include misc.c.

The wc_ConstantCompare is guarded by #ifndef WOLFSSL_NO_CONST_CMP.

Update linuxkm to use wc_ForceZero and wc_ConstantCompare where it wasn't. linuxkm and bsdkm were already using wc_ForceZero in a few spots.

Testing

Tested with bsdkm, linuxkm, and all-c89-clang-tidy.

[Copilot]

Pull request overview

This PR introduces a new public wolfCrypt API wrapper wc_ConstantCompare() (patterned after the existing wc_ForceZero() wrapper) and updates Linux kernel module glue code to prefer the public wc_ wrappers over internal ForceZero() / ConstantCompare().

Changes:

• Add public wc_ConstantCompare() declaration to wolfssl/wolfcrypt/memory.h.
• Implement wc_ConstantCompare() in wolfcrypt/src/memory.c as a thin wrapper around ConstantCompare().
• Update several linuxkm/*_glue.c call sites to use wc_ForceZero() and wc_ConstantCompare().

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
wolfssl/wolfcrypt/memory.h	Exposes new public wc_ConstantCompare() API (guarded by WOLFSSL_NO_CONST_CMP).
wolfcrypt/src/memory.c	Implements wc_ConstantCompare() wrapper calling ConstantCompare().
linuxkm/lkcapi_sha_glue.c	Switches sensitive-buffer clearing to wc_ForceZero().
linuxkm/lkcapi_rsa_glue.c	Switches buffer clearing to wc_ForceZero() and signature comparisons to wc_ConstantCompare().
linuxkm/lkcapi_ecdh_glue.c	Switches shared-secret clearing to wc_ForceZero().
linuxkm/lkcapi_dh_glue.c	Switches key/shared-secret clearing to wc_ForceZero().
linuxkm/lkcapi_aes_glue.c	Switches temp buffer clearing to wc_ForceZero().

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[github-actions]

MemBrowse Memory Report

gcc-arm-cortex-m0plus

• FLASH: .text +28 B (+0.0%, 64,183 B / 262,144 B, total: 24% used)

gcc-arm-cortex-m3

• FLASH: .text +24 B (+0.0%, 122,473 B / 262,144 B, total: 47% used)

gcc-arm-cortex-m4-baremetal

• FLASH: .text +64 B (+0.1%, 66,827 B / 262,144 B, total: 25% used)

gcc-arm-cortex-m4-openssl-compat

• FLASH: .text +64 B (+0.0%, 770,828 B / 1,048,576 B, total: 74% used)

gcc-arm-cortex-m4-pq

• FLASH: .text +64 B (+0.0%, 279,300 B / 1,048,576 B, total: 27% used)

gcc-arm-cortex-m4-tls13

• FLASH: .text +64 B (+0.0%, 235,982 B / 262,144 B, total: 90% used)

gcc-arm-cortex-m7

• FLASH: .text +64 B (+0.0%, 200,284 B / 262,144 B, total: 76% used)

gcc-arm-cortex-m7-pq

• FLASH: .text +64 B (+0.0%, 279,876 B / 1,048,576 B, total: 27% used)

linuxkm-pie

• Data: __patchable_function_entries +8 B (+0.0%, 25,520 B)

linuxkm-standard

• Data: __patchable_function_entries +8 B (+0.0%, 48,168 B)
  No memory changes detected for:
• gcc-arm-cortex-m4
• gcc-arm-cortex-m4-crypto-only
• gcc-arm-cortex-m4-dtls13
• gcc-arm-cortex-m4-min-ecc
• gcc-arm-cortex-m4-pkcs7
• gcc-arm-cortex-m4-rsa-only
• gcc-arm-cortex-m4-sp-math
• gcc-arm-cortex-m4-tls12
• gcc-arm-cortex-m7-tls13
• stm32-sim-stm32h753

[philljj]

No Malloc Tests failure will be fixed here:

• Time-Stamping Protocol testing: fix CI loop static-memory #10868

[douzzer]

We want the fast inline version, ForceZero, in the linuxkm glue layer -- it's faster and avoids some a little stack burden.