[PATCH] D132592: [Clang] Implement function attribute nouwtable

[Yuanfang Chen via Phabricator via cfe-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG70248bfdea6c: [Clang] Implement function attribute nouwtable 
(authored by ychen).

Changed prior to commit:
  https://reviews.llvm.org/D132592?vs=456403&id=456433#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132592/new/

https://reviews.llvm.org/D132592

Files:
  clang/docs/ReleaseNotes.rst
  clang/include/clang/Basic/Attr.td
  clang/include/clang/Basic/AttrDocs.td
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/test/CodeGen/attr-nouwtable.c
  clang/test/Misc/pragma-attribute-supported-attributes-list.test


Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -115,6 +115,7 @@
 // CHECK-NEXT: NoStackProtector (SubjectMatchRule_function)
 // CHECK-NEXT: NoThreadSafetyAnalysis (SubjectMatchRule_function)
 // CHECK-NEXT: NoThrow (SubjectMatchRule_hasType_functionType)
+// CHECK-NEXT: NoUwtable (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: NotTailCalled (SubjectMatchRule_function)
 // CHECK-NEXT: OSConsumed (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: OSReturnsNotRetained (SubjectMatchRule_function, 
SubjectMatchRule_objc_method, SubjectMatchRule_objc_property, 
SubjectMatchRule_variable_is_parameter)
Index: clang/test/CodeGen/attr-nouwtable.c
===
--- /dev/null
+++ clang/test/CodeGen/attr-nouwtable.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -funwind-tables=2 -S -emit-llvm %s -o - | FileCheck %s
+
+__attribute__((nouwtable))
+int test1(void) { return 0; }
+
+// CHECK: @test1{{.*}}[[ATTR1:#[0-9]+]]
+// CHECK: attributes [[ATTR1]] = {
+// CHECK-NOT: uwtable
+// CHECK: }
Index: clang/lib/CodeGen/CodeGenModule.cpp
===
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -1963,7 +1963,7 @@
llvm::Function *F) {
   llvm::AttrBuilder B(F->getContext());
 
-  if (CodeGenOpts.UnwindTables)
+  if ((!D || !D->hasAttr()) && CodeGenOpts.UnwindTables)
 B.addUWTableAttr(llvm::UWTableKind(CodeGenOpts.UnwindTables));
 
   if (CodeGenOpts.StackClashProtector)
Index: clang/include/clang/Basic/AttrDocs.td
===
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -4537,6 +4537,16 @@
 }];
 }
 
+def NoUwtableDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+Clang supports the ``nouwtable`` attribute which skips emitting
+the unwind table entry for the specified function. This attribute is useful for
+selectively emitting the unwind table entry on some functions when building 
with
+``-funwind-tables`` compiler option.
+}];
+}
+
 def InternalLinkageDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
Index: clang/include/clang/Basic/Attr.td
===
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -2092,6 +2092,13 @@
   let Documentation = [NoThrowDocs];
 }
 
+def NoUwtable : InheritableAttr {
+  let Spellings = [Clang<"nouwtable">];
+  let Subjects = SubjectList<[FunctionLike]>;
+  let Documentation = [NoUwtableDocs];
+  let SimpleHandler = 1;
+}
+
 def NvWeak : IgnoredAttr {
   // No Declspec spelling of this attribute; the CUDA headers use
   // __attribute__((nv_weak)) unconditionally. Does not receive an [[]]
Index: clang/docs/ReleaseNotes.rst
===
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -149,6 +149,9 @@
   using the MinGW environment. This attribute is only available for Windows
   targets.
 
+- Introduced a new function attribute ``__attribute__((nouwtable))`` to 
suppress
+  LLVM IR ``uwtable`` function attribute.
+
 Windows Support
 ---
 


Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -115,6 +115,7 @@
 // CHECK-NEXT: NoStackProtector (SubjectMatchRule_function)
 // CHECK-NEXT: NoThreadSafetyAnalysis (SubjectMatchRule_function)
 // CHECK-NEXT: NoThrow (SubjectMatchRule_hasType_functionType)
+// CHECK-NEXT: NoUwtable (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: NotTailCalled (SubjectMatchRule_function)
 // CHECK-NEXT: OSConsumed (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: OSReturnsNo

[PATCH] D132592: [Clang] Implement function attribute nouwtable

[Yuanfang Chen via Phabricator via cfe-commits]

ychen updated this revision to Diff 456403.
ychen added a comment.

- add a release note.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132592/new/

https://reviews.llvm.org/D132592

Files:
  clang/docs/ReleaseNotes.rst
  clang/include/clang/Basic/Attr.td
  clang/include/clang/Basic/AttrDocs.td
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/test/CodeGen/attr-nouwtable.c
  clang/test/Misc/pragma-attribute-supported-attributes-list.test


Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -114,6 +114,7 @@
 // CHECK-NEXT: NoStackProtector (SubjectMatchRule_function)
 // CHECK-NEXT: NoThreadSafetyAnalysis (SubjectMatchRule_function)
 // CHECK-NEXT: NoThrow (SubjectMatchRule_hasType_functionType)
+// CHECK-NEXT: NoUwtable (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: NotTailCalled (SubjectMatchRule_function)
 // CHECK-NEXT: OSConsumed (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: OSReturnsNotRetained (SubjectMatchRule_function, 
SubjectMatchRule_objc_method, SubjectMatchRule_objc_property, 
SubjectMatchRule_variable_is_parameter)
Index: clang/test/CodeGen/attr-nouwtable.c
===
--- /dev/null
+++ clang/test/CodeGen/attr-nouwtable.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -funwind-tables=2 -S -emit-llvm %s -o - | FileCheck %s
+
+__attribute__((nouwtable))
+int test1(void) { return 0; }
+
+// CHECK: @test1{{.*}}[[ATTR1:#[0-9]+]]
+// CHECK: attributes [[ATTR1]] = {
+// CHECK-NOT: uwtable
+// CHECK: }
Index: clang/lib/CodeGen/CodeGenModule.cpp
===
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -1942,7 +1942,7 @@
llvm::Function *F) {
   llvm::AttrBuilder B(F->getContext());
 
-  if (CodeGenOpts.UnwindTables)
+  if ((!D || !D->hasAttr()) && CodeGenOpts.UnwindTables)
 B.addUWTableAttr(llvm::UWTableKind(CodeGenOpts.UnwindTables));
 
   if (CodeGenOpts.StackClashProtector)
Index: clang/include/clang/Basic/AttrDocs.td
===
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -4537,6 +4537,16 @@
 }];
 }
 
+def NoUwtableDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+Clang supports the ``nouwtable`` attribute which skips emitting
+the unwind table entry for the specified function. This attribute is useful for
+selectively emitting the unwind table entry on some functions when building 
with
+``-funwind-tables`` compiler option.
+}];
+}
+
 def InternalLinkageDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
Index: clang/include/clang/Basic/Attr.td
===
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -2086,6 +2086,13 @@
   let Documentation = [NoThrowDocs];
 }
 
+def NoUwtable : InheritableAttr {
+  let Spellings = [Clang<"nouwtable">];
+  let Subjects = SubjectList<[FunctionLike]>;
+  let Documentation = [NoUwtableDocs];
+  let SimpleHandler = 1;
+}
+
 def NvWeak : IgnoredAttr {
   // No Declspec spelling of this attribute; the CUDA headers use
   // __attribute__((nv_weak)) unconditionally. Does not receive an [[]]
Index: clang/docs/ReleaseNotes.rst
===
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -129,6 +129,9 @@
 Attribute Changes in Clang
 --
 
+- Introduced a new function attribute ``__attribute__((nouwtable))`` to 
suppress
+  LLVM IR ``uwtable`` function attribute.
+
 Windows Support
 ---
 


Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -114,6 +114,7 @@
 // CHECK-NEXT: NoStackProtector (SubjectMatchRule_function)
 // CHECK-NEXT: NoThreadSafetyAnalysis (SubjectMatchRule_function)
 // CHECK-NEXT: NoThrow (SubjectMatchRule_hasType_functionType)
+// CHECK-NEXT: NoUwtable (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: NotTailCalled (SubjectMatchRule_function)
 // CHECK-NEXT: OSConsumed (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: OSReturnsNotRetained (SubjectMatchRule_function, SubjectMatchRule_objc_method, SubjectMatchRule_objc_property, SubjectMatchRule_variable_is_parameter)
Index: clang/test/CodeGen/attr-nouwtable.c
===
--- /dev

[PATCH] D132592: [Clang] Implement function attribute nouwtable

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman accepted this revision.
aaron.ballman added a comment.
This revision is now accepted and ready to land.

LGTM, though please add a release note for the new attribute.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132592/new/

https://reviews.llvm.org/D132592

___
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

[PATCH] D132592: [Clang] Implement function attribute nouwtable

[Yuanfang Chen via Phabricator via cfe-commits]

ychen added a comment.

In D132592#3751561 , @aaron.ballman 
wrote:

> In D132592#3749567 , @ychen wrote:
>
>> Thanks for taking a look!
>>
>> In D132592#3749261 , 
>> @aaron.ballman wrote:
>>
>>> Do we have any evidence that users need this level of control or will 
>>> understand how to properly use the attribute? The command line option makes 
>>> sense to me because it's an all-or-nothing flag, but I'm not certain I 
>>> understand the need for per-function control.
>>
>> https://github.com/llvm/llvm-project/blob/064a08cd955019da9130f1109bfa534e79b8ec7c/llvm/include/llvm/IR/Function.h#L639-L641,
>>  per-function unwind table entry depends on both nounwind and uwtable. We 
>> have nothrow attribute for nounwind but not nouwtable for uwtable. With 
>> this, a user could use function attributes to control unwind table entry 
>> generation which could only be achieved by inline assembly or writing 
>> assembly files directly. I'd consider this a companion of nothrow. So making 
>> them both per-function attribute seems natural?
>>
>>> Also, if a user gets this wrong (applies the attribute where they 
>>> shouldn't), what is the failure mode (does it introduce any exploitable 
>>> behavior)?
>>
>> The flag may only suppress unwind table emission instead of causing more, 
>> the lack of unwind table may only stop control flow rather than giving it 
>> more freedom. So I think this is safe from a security perspective. Using it 
>> wrong may cause unnecessary crashes just like any other memory bugs, but not 
>> a malicious binary.
>
> Thank you for the explanations, that helped. :-)
>
> You're missing all of the semantic tests (that the attr takes no arguments, 
> only applies to function-like things, etc). Also, the subject you picked is 
> `FunctionLike` so you should have some test coverage showing how this works 
> when calling through a function pointer with the attribute (or you should 
> pick a more appropriate subject if that one is wrong).

Yes, `Function` is more proper than `FunctionLike`.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132592/new/

https://reviews.llvm.org/D132592

___
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

[PATCH] D132592: [Clang] Implement function attribute nouwtable

[Yuanfang Chen via Phabricator via cfe-commits]

ychen updated this revision to Diff 456069.
ychen added a comment.

- change from `FunctionLike` to `Function`
- add a Sema test
- update doc


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132592/new/

https://reviews.llvm.org/D132592

Files:
  clang/include/clang/Basic/Attr.td
  clang/include/clang/Basic/AttrDocs.td
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/test/CodeGen/attr-nouwtable.c
  clang/test/Misc/pragma-attribute-supported-attributes-list.test
  clang/test/Sema/attr-nouwtable.c


Index: clang/test/Sema/attr-nouwtable.c
===
--- /dev/null
+++ clang/test/Sema/attr-nouwtable.c
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void *t1() __attribute__((nouwtable(1))); // expected-error {{'nouwtable' 
attribute takes no arguments}}
+
+typedef void (*F)(void);
+__attribute__((nouwtable)) F f; // expected-warning {{'nouwtable' attribute 
only applies to functions}}
Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -114,6 +114,7 @@
 // CHECK-NEXT: NoStackProtector (SubjectMatchRule_function)
 // CHECK-NEXT: NoThreadSafetyAnalysis (SubjectMatchRule_function)
 // CHECK-NEXT: NoThrow (SubjectMatchRule_hasType_functionType)
+// CHECK-NEXT: NoUwtable (SubjectMatchRule_function)
 // CHECK-NEXT: NotTailCalled (SubjectMatchRule_function)
 // CHECK-NEXT: OSConsumed (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: OSReturnsNotRetained (SubjectMatchRule_function, 
SubjectMatchRule_objc_method, SubjectMatchRule_objc_property, 
SubjectMatchRule_variable_is_parameter)
Index: clang/test/CodeGen/attr-nouwtable.c
===
--- /dev/null
+++ clang/test/CodeGen/attr-nouwtable.c
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -funwind-tables=2 -S -emit-llvm %s -o - | FileCheck %s
+
+void t1(void) {}
+
+void t2(void) __attribute__((nouwtable));
+void t2(void) {}
+
+// CHECK: @t1{{.*}}[[ATTR1:#[0-9]+]]
+// CHECK: @t2{{.*}}[[ATTR2:#[0-9]+]]
+
+// CHECK: attributes [[ATTR1]] = {{{.*}}uwtable{{.*}}}
+// CHECK: attributes [[ATTR2]] = {
+// CHECK-NOT: uwtable
+// CHECK: }
Index: clang/lib/CodeGen/CodeGenModule.cpp
===
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -1942,7 +1942,7 @@
llvm::Function *F) {
   llvm::AttrBuilder B(F->getContext());
 
-  if (CodeGenOpts.UnwindTables)
+  if ((!D || !D->hasAttr()) && CodeGenOpts.UnwindTables)
 B.addUWTableAttr(llvm::UWTableKind(CodeGenOpts.UnwindTables));
 
   if (CodeGenOpts.StackClashProtector)
Index: clang/include/clang/Basic/AttrDocs.td
===
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -4537,6 +4537,16 @@
 }];
 }
 
+def NoUwtableDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+Clang supports the ``nouwtable`` attribute which skips emitting
+the unwind table entry for the specified function. This attribute is useful for
+selectively suppressing the unwind table entry on some functions when building
+with the ``-funwind-tables`` compiler option.
+}];
+}
+
 def InternalLinkageDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
Index: clang/include/clang/Basic/Attr.td
===
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -2086,6 +2086,13 @@
   let Documentation = [NoThrowDocs];
 }
 
+def NoUwtable : InheritableAttr {
+  let Spellings = [Clang<"nouwtable">];
+  let Subjects = SubjectList<[Function]>;
+  let Documentation = [NoUwtableDocs];
+  let SimpleHandler = 1;
+}
+
 def NvWeak : IgnoredAttr {
   // No Declspec spelling of this attribute; the CUDA headers use
   // __attribute__((nv_weak)) unconditionally. Does not receive an [[]]


Index: clang/test/Sema/attr-nouwtable.c
===
--- /dev/null
+++ clang/test/Sema/attr-nouwtable.c
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void *t1() __attribute__((nouwtable(1))); // expected-error {{'nouwtable' attribute takes no arguments}}
+
+typedef void (*F)(void);
+__attribute__((nouwtable)) F f; // expected-warning {{'nouwtable' attribute only applies to functions}}
Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -114,6 +1

[PATCH] D132592: [Clang] Implement function attribute nouwtable

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

In D132592#3749567 , @ychen wrote:

> Thanks for taking a look!
>
> In D132592#3749261 , @aaron.ballman 
> wrote:
>
>> Do we have any evidence that users need this level of control or will 
>> understand how to properly use the attribute? The command line option makes 
>> sense to me because it's an all-or-nothing flag, but I'm not certain I 
>> understand the need for per-function control.
>
> https://github.com/llvm/llvm-project/blob/064a08cd955019da9130f1109bfa534e79b8ec7c/llvm/include/llvm/IR/Function.h#L639-L641,
>  per-function unwind table entry depends on both nounwind and uwtable. We 
> have nothrow attribute for nounwind but not nouwtable for uwtable. With this, 
> a user could use function attributes to control unwind table entry generation 
> which could only be achieved by inline assembly or writing assembly files 
> directly. I'd consider this a companion of nothrow. So making them both 
> per-function attribute seems natural?
>
>> Also, if a user gets this wrong (applies the attribute where they 
>> shouldn't), what is the failure mode (does it introduce any exploitable 
>> behavior)?
>
> The flag may only suppress unwind table emission instead of causing more, the 
> lack of unwind table may only stop control flow rather than giving it more 
> freedom. So I think this is safe from a security perspective. Using it wrong 
> may cause unnecessary crashes just like any other memory bugs, but not a 
> malicious binary.

Thank you for the explanations, that helped. :-)

You're missing all of the semantic tests (that the attr takes no arguments, 
only applies to function-like things, etc). Also, the subject you picked is 
`FunctionLike` so you should have some test coverage showing how this works 
when calling through a function pointer with the attribute (or you should pick 
a more appropriate subject if that one is wrong).




Comment at: clang/include/clang/Basic/AttrDocs.td:4545-4546
+the unwind table entry for the specified function. This attribute is useful for
+selectively emitting the unwind table entry on some functions when building 
with
+``-funwind-tables`` compiler option.
+}];




Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132592/new/

https://reviews.llvm.org/D132592

___
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

[PATCH] D132592: [Clang] Implement function attribute nouwtable

[Yuanfang Chen via Phabricator via cfe-commits]

ychen added a comment.

Thanks for taking a look!

In D132592#3749261 , @aaron.ballman 
wrote:

> Do we have any evidence that users need this level of control or will 
> understand how to properly use the attribute? The command line option makes 
> sense to me because it's an all-or-nothing flag, but I'm not certain I 
> understand the need for per-function control.

https://github.com/llvm/llvm-project/blob/064a08cd955019da9130f1109bfa534e79b8ec7c/llvm/include/llvm/IR/Function.h#L639-L641,
 per-function unwind table entry depends on both nounwind and uwtable. We have 
nothrow attribute for nounwind but not nouwtable for uwtable. With this, a user 
could use function attributes to control unwind table entry generation which 
could only be achieved by inline assembly or writing assembly files directly. 
I'd consider this a companion of nothrow. So making them both per-function 
attribute seems natural?

> Also, if a user gets this wrong (applies the attribute where they shouldn't), 
> what is the failure mode (does it introduce any exploitable behavior)?

The flag may only suppress unwind table emission instead of causing more, the 
lack of unwind table may only stop control flow rather than giving it more 
freedom. So I think this is safe from a security perspective. Using it wrong 
may cause unnecessary crashes just like any other memory bugs, but not a 
malicious binary.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132592/new/

https://reviews.llvm.org/D132592

___
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

[PATCH] D132592: [Clang] Implement function attribute nouwtable

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added a comment.

Do we have any evidence that users need this level of control or will 
understand how to properly use the attribute? The command line option makes 
sense to me because it's an all-or-nothing flag, but I'm not certain I 
understand the need for per-function control. Also, if a user gets this wrong 
(applies the attribute where they shouldn't), what is the failure mode (does it 
introduce any exploitable behavior)?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132592/new/

https://reviews.llvm.org/D132592

___
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits

[PATCH] D132592: [Clang] Implement function attribute nouwtable

[Yuanfang Chen via Phabricator via cfe-commits]

ychen updated this revision to Diff 455395.
ychen added a comment.
Herald added a subscriber: jdoerfert.

- update test


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132592/new/

https://reviews.llvm.org/D132592

Files:
  clang/include/clang/Basic/Attr.td
  clang/include/clang/Basic/AttrDocs.td
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/test/CodeGen/attr-nouwtable.c
  clang/test/Misc/pragma-attribute-supported-attributes-list.test


Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -114,6 +114,7 @@
 // CHECK-NEXT: NoStackProtector (SubjectMatchRule_function)
 // CHECK-NEXT: NoThreadSafetyAnalysis (SubjectMatchRule_function)
 // CHECK-NEXT: NoThrow (SubjectMatchRule_hasType_functionType)
+// CHECK-NEXT: NoUwtable (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: NotTailCalled (SubjectMatchRule_function)
 // CHECK-NEXT: OSConsumed (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: OSReturnsNotRetained (SubjectMatchRule_function, 
SubjectMatchRule_objc_method, SubjectMatchRule_objc_property, 
SubjectMatchRule_variable_is_parameter)
Index: clang/test/CodeGen/attr-nouwtable.c
===
--- /dev/null
+++ clang/test/CodeGen/attr-nouwtable.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -funwind-tables=2 -S -emit-llvm %s -o - | FileCheck %s
+
+__attribute__((nouwtable))
+int test1(void) { return 0; }
+
+// CHECK: @test1{{.*}}[[ATTR1:#[0-9]+]]
+// CHECK: attributes [[ATTR1]] = {
+// CHECK-NOT: uwtable
+// CHECK: }
Index: clang/lib/CodeGen/CodeGenModule.cpp
===
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -1942,7 +1942,7 @@
llvm::Function *F) {
   llvm::AttrBuilder B(F->getContext());
 
-  if (CodeGenOpts.UnwindTables)
+  if ((!D || !D->hasAttr()) && CodeGenOpts.UnwindTables)
 B.addUWTableAttr(llvm::UWTableKind(CodeGenOpts.UnwindTables));
 
   if (CodeGenOpts.StackClashProtector)
Index: clang/include/clang/Basic/AttrDocs.td
===
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -4537,6 +4537,16 @@
 }];
 }
 
+def NoUwtableDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+Clang supports the ``nouwtable`` attribute which skips emitting
+the unwind table entry for the specified function. This attribute is useful for
+selectively emitting the unwind table entry on some functions when building 
with
+``-funwind-tables`` compiler option.
+}];
+}
+
 def InternalLinkageDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
Index: clang/include/clang/Basic/Attr.td
===
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -2086,6 +2086,13 @@
   let Documentation = [NoThrowDocs];
 }
 
+def NoUwtable : InheritableAttr {
+  let Spellings = [Clang<"nouwtable">];
+  let Subjects = SubjectList<[FunctionLike]>;
+  let Documentation = [NoUwtableDocs];
+  let SimpleHandler = 1;
+}
+
 def NvWeak : IgnoredAttr {
   // No Declspec spelling of this attribute; the CUDA headers use
   // __attribute__((nv_weak)) unconditionally. Does not receive an [[]]


Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -114,6 +114,7 @@
 // CHECK-NEXT: NoStackProtector (SubjectMatchRule_function)
 // CHECK-NEXT: NoThreadSafetyAnalysis (SubjectMatchRule_function)
 // CHECK-NEXT: NoThrow (SubjectMatchRule_hasType_functionType)
+// CHECK-NEXT: NoUwtable (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: NotTailCalled (SubjectMatchRule_function)
 // CHECK-NEXT: OSConsumed (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: OSReturnsNotRetained (SubjectMatchRule_function, SubjectMatchRule_objc_method, SubjectMatchRule_objc_property, SubjectMatchRule_variable_is_parameter)
Index: clang/test/CodeGen/attr-nouwtable.c
===
--- /dev/null
+++ clang/test/CodeGen/attr-nouwtable.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -funwind-tables=2 -S -emit-llvm %s -o - | FileCheck %s
+
+__attribute__((nouwtable))
+int test1(void) { return 0; }
+
+// CHECK: @test1{{.*}}[[ATTR1:#[0-9]+]]
+// CHECK: attributes [[ATTR1]] = {
+// CHECK-NOT: uwtable
+// CHECK: }
Index: clang/lib/CodeGen/CodeGenModule.cpp
=

[PATCH] D132592: Clang] Implement function attribute nouwtable

[Yuanfang Chen via Phabricator via cfe-commits]

ychen created this revision.
ychen added reviewers: aaron.ballman, rnk, rsmith.
Herald added a project: All.
ychen requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

To have finer control of IR uwtable attribute generation. For target code 
generation,
IR nounwind and uwtable may have some interaction. However, for frontend, there 
are
no semantic interactions so the this new `nouwtable` is marked "SimpleHandler = 
1".


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D132592

Files:
  clang/include/clang/Basic/Attr.td
  clang/include/clang/Basic/AttrDocs.td
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/test/CodeGen/attr-nouwtable.c


Index: clang/test/CodeGen/attr-nouwtable.c
===
--- /dev/null
+++ clang/test/CodeGen/attr-nouwtable.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -funwind-tables=2 -S -emit-llvm %s -o - | FileCheck %s
+
+__attribute__((nouwtable))
+int test1(void) { return 0; }
+
+// CHECK: @test1{{.*}}[[ATTR1:#[0-9]+]]
+// CHECK: attributes [[ATTR1]] = {
+// CHECK-NOT: uwtable
+// CHECK: }
Index: clang/lib/CodeGen/CodeGenModule.cpp
===
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -1942,7 +1942,7 @@
llvm::Function *F) {
   llvm::AttrBuilder B(F->getContext());
 
-  if (CodeGenOpts.UnwindTables)
+  if ((!D || !D->hasAttr()) && CodeGenOpts.UnwindTables)
 B.addUWTableAttr(llvm::UWTableKind(CodeGenOpts.UnwindTables));
 
   if (CodeGenOpts.StackClashProtector)
Index: clang/include/clang/Basic/AttrDocs.td
===
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -4537,6 +4537,16 @@
 }];
 }
 
+def NoUwtableDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+Clang supports the ``nouwtable`` attribute which skips emitting
+the unwind table entry for the specified function. This attribute is useful for
+selectively emitting the unwind table entry on some functions when building 
with
+``-funwind-tables`` compiler option.
+}];
+}
+
 def InternalLinkageDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
Index: clang/include/clang/Basic/Attr.td
===
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -2086,6 +2086,13 @@
   let Documentation = [NoThrowDocs];
 }
 
+def NoUwtable : InheritableAttr {
+  let Spellings = [Clang<"nouwtable">];
+  let Subjects = SubjectList<[FunctionLike]>;
+  let Documentation = [NoUwtableDocs];
+  let SimpleHandler = 1;
+}
+
 def NvWeak : IgnoredAttr {
   // No Declspec spelling of this attribute; the CUDA headers use
   // __attribute__((nv_weak)) unconditionally. Does not receive an [[]]


Index: clang/test/CodeGen/attr-nouwtable.c
===
--- /dev/null
+++ clang/test/CodeGen/attr-nouwtable.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -funwind-tables=2 -S -emit-llvm %s -o - | FileCheck %s
+
+__attribute__((nouwtable))
+int test1(void) { return 0; }
+
+// CHECK: @test1{{.*}}[[ATTR1:#[0-9]+]]
+// CHECK: attributes [[ATTR1]] = {
+// CHECK-NOT: uwtable
+// CHECK: }
Index: clang/lib/CodeGen/CodeGenModule.cpp
===
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -1942,7 +1942,7 @@
llvm::Function *F) {
   llvm::AttrBuilder B(F->getContext());
 
-  if (CodeGenOpts.UnwindTables)
+  if ((!D || !D->hasAttr()) && CodeGenOpts.UnwindTables)
 B.addUWTableAttr(llvm::UWTableKind(CodeGenOpts.UnwindTables));
 
   if (CodeGenOpts.StackClashProtector)
Index: clang/include/clang/Basic/AttrDocs.td
===
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -4537,6 +4537,16 @@
 }];
 }
 
+def NoUwtableDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+Clang supports the ``nouwtable`` attribute which skips emitting
+the unwind table entry for the specified function. This attribute is useful for
+selectively emitting the unwind table entry on some functions when building with
+``-funwind-tables`` compiler option.
+}];
+}
+
 def InternalLinkageDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
Index: clang/include/clang/Basic/Attr.td
===
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -2086,6 +2086,13 @@
   let Documentation = [NoThrowDocs];
 }
 
+def NoUwtable : InheritableAttr {
+  let Spellings = [Clang<"nouwtable">