patches/kernel/0007-bug-introduce-ASSERT_STRUCT_OFFSET.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Maxim Levitsky <mlevitsk@redhat.com>
   3 Date: Wed, 3 Aug 2022 18:49:59 +0300
   4 Subject: [PATCH] bug: introduce ASSERT_STRUCT_OFFSET
   5
   6 ASSERT_STRUCT_OFFSET allows to assert during the build of
   7 the kernel that a field in a struct have an expected offset.
   8
   9 KVM used to have such macro, but there is almost nothing KVM specific
  10 in it so move it to build_bug.h, so that it can be used in other
  11 places in KVM.
  12
  13 Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
  14 Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  15 ---
  16  arch/x86/kvm/vmx/vmcs12.h | 5 ++---
  17  include/linux/build_bug.h | 9 +++++++++
  18  2 files changed, 11 insertions(+), 3 deletions(-)
  19
  20 diff --git a/arch/x86/kvm/vmx/vmcs12.h b/arch/x86/kvm/vmx/vmcs12.h
  21 index 746129ddd5ae..01936013428b 100644
  22 --- a/arch/x86/kvm/vmx/vmcs12.h
  23 +++ b/arch/x86/kvm/vmx/vmcs12.h
  24 @@ -208,9 +208,8 @@ struct __packed vmcs12 {
  25  /*
  26   * For save/restore compatibility, the vmcs12 field offsets must not change.
  27   */
  28 -#define CHECK_OFFSET(field, loc)                               \
  29 -       BUILD_BUG_ON_MSG(offsetof(struct vmcs12, field) != (loc),       \
  30 -               "Offset of " #field " in struct vmcs12 has changed.")
  31 +#define CHECK_OFFSET(field, loc) \
  32 +       ASSERT_STRUCT_OFFSET(struct vmcs12, field, loc)
  33
  34  static inline void vmx_check_vmcs12_offsets(void)
  35  {
  36 diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
  37 index e3a0be2c90ad..3aa3640f8c18 100644
  38 --- a/include/linux/build_bug.h
  39 +++ b/include/linux/build_bug.h
  40 @@ -77,4 +77,13 @@
  41  #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
  42  #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
  43
  44 +
  45 +/*
  46 + * Compile time check that field has an expected offset
  47 + */
  48 +#define ASSERT_STRUCT_OFFSET(type, field, expected_offset)     \
  49 +       BUILD_BUG_ON_MSG(offsetof(type, field) != (expected_offset),    \
  50 +               "Offset of " #field " in " #type " has changed.")
  51 +
  52 +
  53  #endif /* _LINUX_BUILD_BUG_H */