Author: Yonghong Song Date: 2023-05-08T07:41:27-07:00 New Revision: 3060304906f08f933672f0a30cc57d5f09766444
URL: https://github.com/llvm/llvm-project/commit/3060304906f08f933672f0a30cc57d5f09766444 DIFF: https://github.com/llvm/llvm-project/commit/3060304906f08f933672f0a30cc57d5f09766444.diff LOG: [Clang][BPF] Type print btf_type_tag properly When running bcc tool execsnoop ([1]) which is built with latest llvm, I hit the following error: $ sudo ./execsnoop.py /virtual/main.c:99:157: error: expected ')' data.ppid = ({ typeof(pid_t) _val; __builtin_memset(&_val, 0, sizeof(_val)); bpf_probe_read(&_val, sizeof(_val), (void *)&({ typeof(struct task_struct btf_type_tag(rcu)*) _val; __builtin_memset(&_val, 0, sizeof(_val)); ^ bpf_probe_read(&_val, sizeof(_val), (void *)&task->real_parent); _val; })->tgid); _val; }); The failure reason is due to that the bcc rewriter printed type like struct task_struct btf_type_tag(rcu)* where the compiler cannot recognize what 'btf_type_tag(rcu)' is. The above type is printed in [2] by UnaryOperator->getType().getAsString() (from clang) in function ProbeVisitor::VisitUnaryOperator. The original source type looks like ([3]) struct task_struct { ... struct task_struct __rcu *real_parent; ... } where '__rcu' is a macro expanding to '__attribute__((btf_type_tag("rcu")))'. Let us print btf_type_tag properly in clang so bcc tools and broader type printing will work properly. With this patch, the above rewrited source code looks like data.ppid = ({ typeof(pid_t) _val; __builtin_memset(&_val, 0, sizeof(_val)); bpf_probe_read(&_val, sizeof(_val), (void *)&({ typeof(struct task_struct __attribute__((btf_type_tag("rcu")))*) _val; __builtin_memset(&_val, 0, sizeof(_val)); bpf_probe_read(&_val, sizeof(_val), (void *)&task->real_parent); _val; })->tgid); _val; }); and execsnoop.py tool can run properly. [1] https://github.com/iovisor/bcc/blob/master/tools/exitsnoop.py [2] https://github.com/iovisor/bcc/blob/master/src/cc/frontends/clang/b_frontend_action.cc [3] https://github.com/torvalds/linux/blob/master/include/linux/sched.h Differential Revision: https://reviews.llvm.org/D150017 Added: clang/test/AST/ast-dump-bpf-attr.c Modified: clang/lib/AST/TypePrinter.cpp clang/test/Sema/attr-btf_type_tag.c clang/test/SemaCXX/sugar-common-types.cpp Removed: ################################################################################ diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp index 408c7caa16c93..02e0793f5cb16 100644 --- a/clang/lib/AST/TypePrinter.cpp +++ b/clang/lib/AST/TypePrinter.cpp @@ -1845,7 +1845,7 @@ void TypePrinter::printAttributedAfter(const AttributedType *T, void TypePrinter::printBTFTagAttributedBefore(const BTFTagAttributedType *T, raw_ostream &OS) { printBefore(T->getWrappedType(), OS); - OS << " btf_type_tag(" << T->getAttr()->getBTFTypeTag() << ")"; + OS << " __attribute__((btf_type_tag(\"" << T->getAttr()->getBTFTypeTag() << "\")))"; } void TypePrinter::printBTFTagAttributedAfter(const BTFTagAttributedType *T, diff --git a/clang/test/AST/ast-dump-bpf-attr.c b/clang/test/AST/ast-dump-bpf-attr.c new file mode 100644 index 0000000000000..8899cecbb6e9f --- /dev/null +++ b/clang/test/AST/ast-dump-bpf-attr.c @@ -0,0 +1,5 @@ +// RUN: %clang_cc1 -triple bpf-pc-linux-gnu -ast-dump %s \ +// RUN: | FileCheck --strict-whitespace %s + +int __attribute__((btf_type_tag("rcu"))) * g; +// CHECK: VarDecl{{.*}}g 'int __attribute__((btf_type_tag("rcu")))*' diff --git a/clang/test/Sema/attr-btf_type_tag.c b/clang/test/Sema/attr-btf_type_tag.c index f7ba29b0aa657..a3ef404f38238 100644 --- a/clang/test/Sema/attr-btf_type_tag.c +++ b/clang/test/Sema/attr-btf_type_tag.c @@ -28,8 +28,8 @@ int __tag4 * __tag5 * __tag6 *foo1(struct t __tag1 * __tag2 * __tag3 *a1) { int g1 = _Generic((int *)0, int __tag1 *: 0); int g2 = _Generic((int __tag1 *)0, int *: 0); int g3 = _Generic(0, - int __tag1 * : 0, // expected-note {{compatible type 'int btf_type_tag(tag1)*' (aka 'int *') specified here}} - int * : 0, // expected-error {{type 'int *' in generic association compatible with previously specified type 'int btf_type_tag(tag1)*' (aka 'int *')}} + int __tag1 * : 0, // expected-note {{compatible type 'int __attribute__((btf_type_tag("tag1")))*' (aka 'int *') specified here}} + int * : 0, // expected-error {{type 'int *' in generic association compatible with previously specified type 'int __attribute__((btf_type_tag("tag1")))*' (aka 'int *')}} default : 0); // The btf_type_tag attribute will be ignored during overloadable type matching diff --git a/clang/test/SemaCXX/sugar-common-types.cpp b/clang/test/SemaCXX/sugar-common-types.cpp index f4e545bb9bceb..4a8ff2addb663 100644 --- a/clang/test/SemaCXX/sugar-common-types.cpp +++ b/clang/test/SemaCXX/sugar-common-types.cpp @@ -95,7 +95,7 @@ using SBTF2 = ::SS1 [[clang::btf_type_tag("1")]]; using SBTF3 = ::SS1 [[clang::btf_type_tag("2")]]; N t21 = 0 ? (SBTF1){} : (SBTF3){}; // expected-error {{from 'SS1'}} -N t22 = 0 ? (SBTF1){} : (SBTF2){}; // expected-error {{from 'SS1 btf_type_tag(1)' (aka 'SS1')}} +N t22 = 0 ? (SBTF1){} : (SBTF2){}; // expected-error {{from 'SS1 __attribute__((btf_type_tag("1")))' (aka 'SS1')}} using QX = const SB1 *; using QY = const ::SB1 *; _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits