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[BPF] use base lvalue type for preserve_{struct,union}_access_index metadata 

Linux commit
  1cf5b23988 (diff-289313b9fec99c6f0acfea19d9cfd949)
uses "#pragma clang attribute push (__attribute__((preserve_access_index)),
      apply_to = record)"
to apply CO-RE relocations to all records including the following pattern:
  #pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)
  typedef struct {
    int a;
  } __t;
  #pragma clang attribute pop
  int test(__t *arg) { return arg->a; }

The current approach to use struct type in the relocation record will
result in an anonymous struct, which make later type matching difficult
    in bpf loader. In fact, current BPF backend will fail the above program
with assertion:
  clang: ../lib/Target/BPF/BPFAbstractMemberAccess.cpp:796: ...
     Assertion `TypeName.size()' failed.

The patch use the base lvalue type for the "base" value to annotate
preservee_{struct,union}_access_index intrinsics. In the above example,
the type will be "__t" which preserved the type name.

Differential Revision: https://reviews.llvm.org/D73900
This commit is contained in:
Yonghong Song 2020-02-02 14:54:16 -08:00
parent 2eaa9d991d
commit 9271cab270
2 changed files with 32 additions and 8 deletions

16
clang/lib/CodeGen/CGExpr.cpp
View File

@ -4024,17 +4024,17 @@ static Address emitAddrOfFieldStorage(CodeGenFunction &CGF, Address base,
return CGF.Builder.CreateStructGEP(base, idx, field->getName());
}
static Address emitPreserveStructAccess(CodeGenFunction &CGF, Address base,
const FieldDecl *field) {
static Address emitPreserveStructAccess(CodeGenFunction &CGF, LValue base,
Address addr, const FieldDecl *field) {
const RecordDecl *rec = field->getParent();
llvm::DIType *DbgInfo = CGF.getDebugInfo()->getOrCreateRecordType(
CGF.getContext().getRecordType(rec), rec->getLocation());
llvm::DIType *DbgInfo = CGF.getDebugInfo()->getOrCreateStandaloneType(
base.getType(), rec->getLocation());
unsigned idx =
CGF.CGM.getTypes().getCGRecordLayout(rec).getLLVMFieldNo(field);
return CGF.Builder.CreatePreserveStructAccessIndex(
base, idx, CGF.getDebugInfoFIndex(rec, field->getFieldIndex()), DbgInfo);
addr, idx, CGF.getDebugInfoFIndex(rec, field->getFieldIndex()), DbgInfo);
}
static bool hasAnyVptr(const QualType Type, const ASTContext &Context) {
@ -4158,8 +4158,8 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
if (IsInPreservedAIRegion ||
(getDebugInfo() && rec->hasAttr<BPFPreserveAccessIndexAttr>())) {
// Remember the original union field index
llvm::DIType *DbgInfo = getDebugInfo()->getOrCreateRecordType(
getContext().getRecordType(rec), rec->getLocation());
llvm::DIType *DbgInfo = getDebugInfo()->getOrCreateStandaloneType(base.getType(),
rec->getLocation());
addr = Address(
Builder.CreatePreserveUnionAccessIndex(
addr.getPointer(), getDebugInfoFIndex(rec, field->getFieldIndex()), DbgInfo),
@ -4176,7 +4176,7 @@ LValue CodeGenFunction::EmitLValueForField(LValue base,
addr = emitAddrOfFieldStorage(*this, addr, field);
else
// Remember the original struct field index
addr = emitPreserveStructAccess(*this, addr, field);
addr = emitPreserveStructAccess(*this, base, addr, field);
}
// If this is a reference field, load the reference right now.

24
clang/test/CodeGen/builtin-preserve-access-index-typedef.c Normal file
View File

@ -0,0 +1,24 @@
// REQUIRES: bpf-registered-target
// RUN: %clang -target bpf -emit-llvm -S -g %s -o - | FileCheck %s
#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)
typedef struct {
int a;
} __t;
typedef union {
int b;
} __u;
#pragma clang attribute pop
int test1(__t *arg) { return arg->a; }
int test2(const __u *arg) { return arg->b; }
// CHECK: define dso_local i32 @test1
// CHECK: call i32* @llvm.preserve.struct.access.index.p0i32.p0s_struct.__ts(%struct.__t* %{{[0-9a-z]+}}, i32 0, i32 0), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[TYPEDEF_STRUCT:[0-9]+]]
// CHECK: define dso_local i32 @test2
// CHECK: call %union.__u* @llvm.preserve.union.access.index.p0s_union.__us.p0s_union.__us(%union.__u* %{{[0-9a-z]+}}, i32 0), !dbg !{{[0-9]+}}, !llvm.preserve.access.index ![[CONST_TYPEDEF:[0-9]+]]
//
// CHECK: ![[TYPEDEF_STRUCT]] = !DIDerivedType(tag: DW_TAG_typedef, name: "__t"
// CHECK: ![[CONST_TYPEDEF]] = !DIDerivedType(tag: DW_TAG_const_type, baseType: ![[TYPEDEF_UNION:[0-9]+]]
// CHECK: ![[TYPEDEF_UNION]] = !DIDerivedType(tag: DW_TAG_typedef, name: "__u"