[Buildroot] [PATCH 1/1] package/ibm-sw-tpm2: fix build with gcc-15.x

* [Buildroot] [PATCH 1/1] package/ibm-sw-tpm2: fix build with gcc-15.x
@ 2026-09-16 23:12 Bernd Kuhls
  2026-09-17  6:37 ` Thomas Petazzoni via buildroot
  2026-09-25 14:46 ` Raphaël Mélotte via buildroot
  0 siblings, 2 replies; 3+ messages in thread
From: Bernd Kuhls @ 2026-09-16 23:12 UTC (permalink / raw)
  To: buildroot; +Cc: Philippe Reynes

Fixes:
https://autobuild.buildroot.net/results/d43/d4364f6e3636c696471bf8cba6d308439130e53a/

In function 'MakeIv',
    inlined from 'TestSymmetricAlgorithm' at AlgorithmTests.c:197:25:
AlgorithmTests.c:181:23: error: writing 32 bytes into a region of size
 16 [-Werror=stringop-overflow=]

The build error occurs with gcc 15.x on some platforms, gcc 14.x is not
affected.

These defconfigs build without this patch:

BR2_x86_64=y
BR2_GCC_VERSION_14_X=y
BR2_PACKAGE_IBM_SW_TPM2=y

BR2_x86_64=y
BR2_x86_x86_64_v4=y
BR2_GCC_VERSION_14_X=y
BR2_PACKAGE_IBM_SW_TPM2=y

BR2_x86_64=y
BR2_PACKAGE_IBM_SW_TPM2=y

This gcc-15 based defconfig is broken:

BR2_x86_64=y
BR2_x86_x86_64_v4=y
BR2_PACKAGE_IBM_SW_TPM2=y

The build error is not related to the recent bump of the package from
rev183-2024-03-27 to rev183-2026-08-26 because no changes were committed
upstream to AlgorithmTests.c since rev183-2024-03-27:
https://github.com/kgoldman/ibmswtpm2/commits/master/src/AlgorithmTests.c

Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
---
 ...15-stringop-overflow-error-in-MakeIv.patch | 45 +++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 package/ibm-sw-tpm2/0003-tpm2-fix-GCC-15-stringop-overflow-error-in-MakeIv.patch

diff --git a/package/ibm-sw-tpm2/0003-tpm2-fix-GCC-15-stringop-overflow-error-in-MakeIv.patch b/package/ibm-sw-tpm2/0003-tpm2-fix-GCC-15-stringop-overflow-error-in-MakeIv.patch
new file mode 100644
index 0000000000..9b22522b36
--- /dev/null
+++ b/package/ibm-sw-tpm2/0003-tpm2-fix-GCC-15-stringop-overflow-error-in-MakeIv.patch
@@ -0,0 +1,45 @@
+From b35faee1224f5bccf759464e69f724a03421c8a9 Mon Sep 17 00:00:00 2001
+From: Arthur Gautier <arthur.gautier@arista.com>
+Date: Tue, 9 Jun 2026 21:52:07 -0700
+Subject: [PATCH] tpm2: fix GCC 15 stringop-overflow error in MakeIv
+
+When compiling with GCC 15 using `CFLAGS=-march=x86-64-v4`, the compiler's
+aggressively optimized vectorizer triggers a false-positive
+-Wstringop-overflow error. Because x86-64-v4 enables wide AVX-512 registers,
+the compiler misinterprets the loop unrolling and warns that a 64-byte
+vector write is overflowing the destination buffer:
+```
+  tpm2/TPMCmd/tpm/src/crypt/AlgorithmTests.c:158:17: error:
+  writing 64 bytes into a region of size 15 [-Werror=stringop-overflow=]
+    158 |             *iv = i;
+```
+
+This fixes the warning by marking the `iv` output pointer parameter as
+`volatile`. This inhibits the over-aggressive loop vectorization on this
+specific buffer, silencing the compiler error without changing the
+underlying logic.
+
+Signed-off-by: Arthur Gautier <arthur.gautier@arista.com>
+
+Source: https://github.com/stefanberger/libtpms/commit/2d9b00c4e42677cd0a9b67344f4d873ddc409a21
+Upstream: https://github.com/kgoldman/ibmswtpm2/pull/25
+
+[Bernd: rebased for ibm-sw-tpm2 package]
+Signed-off-by: Bernd Kuhls <bernd@kuhls.net>
+---
+ src/AlgorithmTests.c | 6 +++---
+ 1 file changed, 3 insertions(+), 3 deletions(-)
+
+diff --git a/src/AlgorithmTests.c b/src/AlgorithmTests.c
+index e8549adca..28d8e780a 100644
+--- a/src/AlgorithmTests.c
++++ b/src/AlgorithmTests.c
+@@ -162,7 +162,7 @@
+ // Internal function to make the appropriate IV depending on the mode.
+ static UINT32 MakeIv(TPM_ALG_ID mode,  // IN: symmetric mode
+ 		     UINT32     size,  // IN: block size of the algorithm
+-		     BYTE*      iv     // OUT: IV to fill in
++		     volatile BYTE*      iv     // OUT: IV to fill in
+ 		     )
+ {
+     BYTE i;
-- 
2.47.3

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