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 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 ASSERT_STRUCT_OFFSET allows to assert during the build of
  10 the kernel that a field in a struct have an expected offset.
  11
  12 KVM used to have such macro, but there is almost nothing KVM specific
  13 in it so move it to build_bug.h, so that it can be used in other
  14 places in KVM.
  15
  16 Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
  17 Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  18 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  19 ---
  20  arch/x86/kvm/vmx/vmcs12.h | 5 ++---
  21  include/linux/build_bug.h | 9 +++++++++
  22  2 files changed, 11 insertions(+), 3 deletions(-)
  23
  24 diff --git a/arch/x86/kvm/vmx/vmcs12.h b/arch/x86/kvm/vmx/vmcs12.h
  25 index 746129ddd5ae..01936013428b 100644
  26 --- a/arch/x86/kvm/vmx/vmcs12.h
  27 +++ b/arch/x86/kvm/vmx/vmcs12.h
  28 @@ -208,9 +208,8 @@ struct __packed vmcs12 {
  29  /*
  30   * For save/restore compatibility, the vmcs12 field offsets must not change.
  31   */
  32 -#define CHECK_OFFSET(field, loc)                               \
  33 -       BUILD_BUG_ON_MSG(offsetof(struct vmcs12, field) != (loc),       \
  34 -               "Offset of " #field " in struct vmcs12 has changed.")
  35 +#define CHECK_OFFSET(field, loc) \
  36 +       ASSERT_STRUCT_OFFSET(struct vmcs12, field, loc)
  37
  38  static inline void vmx_check_vmcs12_offsets(void)
  39  {
  40 diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
  41 index e3a0be2c90ad..3aa3640f8c18 100644
  42 --- a/include/linux/build_bug.h
  43 +++ b/include/linux/build_bug.h
  44 @@ -77,4 +77,13 @@
  45  #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
  46  #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
  47
  48 +
  49 +/*
  50 + * Compile time check that field has an expected offset
  51 + */
  52 +#define ASSERT_STRUCT_OFFSET(type, field, expected_offset)     \
  53 +       BUILD_BUG_ON_MSG(offsetof(type, field) != (expected_offset),    \
  54 +               "Offset of " #field " in " #type " has changed.")
  55 +
  56 +
  57  #endif /* _LINUX_BUILD_BUG_H */