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From:   Maxim Levitsky <mlevitsk@redhat.com>
To:     kvm@vger.kernel.org
Cc:     Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        linux-kernel@vger.kernel.org, Wanpeng Li <wanpengli@tencent.com>,
        Maxim Levitsky <mlevitsk@redhat.com>,
        Ingo Molnar <mingo@redhat.com>,
        Sean Christopherson <seanjc@google.com>, x86@kernel.org,
        Jim Mattson <jmattson@google.com>,
        Kees Cook <keescook@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Joerg Roedel <joro@8bytes.org>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Subject: [PATCH v3 01/13] bug: introduce ASSERT_STRUCT_OFFSET
Date:   Wed,  3 Aug 2022 18:49:59 +0300
Message-Id: <20220803155011.43721-2-mlevitsk@redhat.com>
In-Reply-To: <20220803155011.43721-1-mlevitsk@redhat.com>
References: <20220803155011.43721-1-mlevitsk@redhat.com>
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ASSERT_STRUCT_OFFSET allows to assert during the build of
the kernel that a field in a struct have an expected offset.

KVM used to have such macro, but there is almost nothing KVM specific
in it so move it to build_bug.h, so that it can be used in other
places in KVM.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/vmx/vmcs12.h | 5 ++---
 include/linux/build_bug.h | 9 +++++++++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmcs12.h b/arch/x86/kvm/vmx/vmcs12.h
index 746129ddd5ae02..01936013428b5c 100644
--- a/arch/x86/kvm/vmx/vmcs12.h
+++ b/arch/x86/kvm/vmx/vmcs12.h
@@ -208,9 +208,8 @@ struct __packed vmcs12 {
 /*
  * For save/restore compatibility, the vmcs12 field offsets must not change.
  */
-#define CHECK_OFFSET(field, loc)				\
-	BUILD_BUG_ON_MSG(offsetof(struct vmcs12, field) != (loc),	\
-		"Offset of " #field " in struct vmcs12 has changed.")
+#define CHECK_OFFSET(field, loc) \
+	ASSERT_STRUCT_OFFSET(struct vmcs12, field, loc)
 
 static inline void vmx_check_vmcs12_offsets(void)
 {
diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
index e3a0be2c90ad98..3aa3640f8c181f 100644
--- a/include/linux/build_bug.h
+++ b/include/linux/build_bug.h
@@ -77,4 +77,13 @@
 #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
 #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
 
+
+/*
+ * Compile time check that field has an expected offset
+ */
+#define ASSERT_STRUCT_OFFSET(type, field, expected_offset)	\
+	BUILD_BUG_ON_MSG(offsetof(type, field) != (expected_offset),	\
+		"Offset of " #field " in " #type " has changed.")
+
+
 #endif	/* _LINUX_BUILD_BUG_H */
-- 
2.26.3