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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
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D150017
Files:
clang/lib/AST/TypePrinter.cpp
clang/test/AST/ast-dump-bpf-attr.c
clang/test/Sema/attr-btf_type_tag.c
clang/test/SemaCXX/sugar-common-types.cpp
Index: clang/test/SemaCXX/sugar-common-types.cpp
===================================================================
--- clang/test/SemaCXX/sugar-common-types.cpp
+++ clang/test/SemaCXX/sugar-common-types.cpp
@@ -95,7 +95,7 @@
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 *;
Index: clang/test/Sema/attr-btf_type_tag.c
===================================================================
--- clang/test/Sema/attr-btf_type_tag.c
+++ clang/test/Sema/attr-btf_type_tag.c
@@ -28,8 +28,8 @@
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
Index: clang/test/AST/ast-dump-bpf-attr.c
===================================================================
--- /dev/null
+++ 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")))*'
Index: clang/lib/AST/TypePrinter.cpp
===================================================================
--- clang/lib/AST/TypePrinter.cpp
+++ clang/lib/AST/TypePrinter.cpp
@@ -1845,7 +1845,7 @@
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,
Index: clang/test/SemaCXX/sugar-common-types.cpp
===================================================================
--- clang/test/SemaCXX/sugar-common-types.cpp
+++ clang/test/SemaCXX/sugar-common-types.cpp
@@ -95,7 +95,7 @@
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 *;
Index: clang/test/Sema/attr-btf_type_tag.c
===================================================================
--- clang/test/Sema/attr-btf_type_tag.c
+++ clang/test/Sema/attr-btf_type_tag.c
@@ -28,8 +28,8 @@
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
Index: clang/test/AST/ast-dump-bpf-attr.c
===================================================================
--- /dev/null
+++ 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")))*'
Index: clang/lib/AST/TypePrinter.cpp
===================================================================
--- clang/lib/AST/TypePrinter.cpp
+++ clang/lib/AST/TypePrinter.cpp
@@ -1845,7 +1845,7 @@
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,
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