[llvm] d10110a - [StackProtector] attribute __stack_chk_fail as NoReturn

[Nick Desaulniers via llvm-commits]

Author: Nick Desaulniers
Date: 2023-03-23T12:45:40-07:00
New Revision: d10110a8a60137d430f7a75051d0794293982ef6

URL: https://github.com/llvm/llvm-project/commit/d10110a8a60137d430f7a75051d0794293982ef6
DIFF: https://github.com/llvm/llvm-project/commit/d10110a8a60137d430f7a75051d0794293982ef6.diff

LOG: [StackProtector] attribute __stack_chk_fail as NoReturn

When GCC added support for stack smashing protections, it was defined
that:

> This hook returns a CALL_EXPR that alerts the runtime that the stack
> protect guard variable has been modified. This expression should
> involve a call to a noreturn function.
> The default version of this hook invokes a function called
> ‘__stack_chk_fail’, taking no arguments.

Do so as well for __stack_smash_handler for OpenBSD.

Every libc implementation I could find has __stack_chk_fail marked
noreturn, or the implementation calls abort, exit, or panic (which
themselves are noreturn).

Glibc: https://sourceware.org/git/?p=glibc.git;a=blob;f=debug/stack_chk_fail.c
Musl: https://git.musl-libc.org/cgit/musl/tree/src/env/__stack_chk_fail.c
Bionic: https://android.googlesource.com/platform/bionic/+/refs/heads/master/libc/bionic/__stack_chk_fail.cpp
FreeBSD: https://cgit.freebsd.org/src/tree/lib/libc/secure/stack_protector.c
OpenBSD: https://github.com/openbsd/src/blob/master/lib/libc/sys/stack_protector.c
NetBSD: https://github.com/NetBSD/src/blob/trunk/lib/libc/misc/stack_protector.c
Linux Kernel: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/panic.c
Apple: https://opensource.apple.com/source/Libc/Libc-1439.40.11/sys/OpenBSD/stack_protector.c.auto.html

Link: https://gcc.gnu.org/onlinedocs/gccint/Stack-Smashing-Protection.html#Stack-Smashing-Protection

This will later help us diagnose functions that fall through to other
functions vs end in calls to functions that are noreturn.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D146339

Added: 
    

Modified: 
    llvm/lib/CodeGen/StackProtector.cpp
    llvm/test/CodeGen/X86/2009-04-14-IllegalRegs.ll
    llvm/test/CodeGen/X86/stack-protector-weight.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/StackProtector.cpp b/llvm/lib/CodeGen/StackProtector.cpp
index aa92dcb386560..05ac176461a5c 100644
--- a/llvm/lib/CodeGen/StackProtector.cpp
+++ b/llvm/lib/CodeGen/StackProtector.cpp
@@ -15,6 +15,7 @@
 
 #include "llvm/CodeGen/StackProtector.h"
 #include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/BranchProbabilityInfo.h"
 #include "llvm/Analysis/MemoryLocation.h"
@@ -620,18 +621,19 @@ BasicBlock *StackProtector::CreateFailBB() {
   if (F->getSubprogram())
     B.SetCurrentDebugLocation(
         DILocation::get(Context, 0, 0, F->getSubprogram()));
+  FunctionCallee StackChkFail;
+  SmallVector<Value *, 1> Args;
   if (Trip.isOSOpenBSD()) {
-    FunctionCallee StackChkFail = M->getOrInsertFunction(
-        "__stack_smash_handler", Type::getVoidTy(Context),
-        Type::getInt8PtrTy(Context));
-
-    B.CreateCall(StackChkFail, B.CreateGlobalStringPtr(F->getName(), "SSH"));
+    StackChkFail = M->getOrInsertFunction("__stack_smash_handler",
+                                          Type::getVoidTy(Context),
+                                          Type::getInt8PtrTy(Context));
+    Args.push_back(B.CreateGlobalStringPtr(F->getName(), "SSH"));
   } else {
-    FunctionCallee StackChkFail =
+    StackChkFail =
         M->getOrInsertFunction("__stack_chk_fail", Type::getVoidTy(Context));
-
-    B.CreateCall(StackChkFail, {});
   }
+  cast<Function>(StackChkFail.getCallee())->addFnAttr(Attribute::NoReturn);
+  B.CreateCall(StackChkFail, Args);
   B.CreateUnreachable();
   return FailBB;
 }

diff  --git a/llvm/test/CodeGen/X86/2009-04-14-IllegalRegs.ll b/llvm/test/CodeGen/X86/2009-04-14-IllegalRegs.ll
index 5e3bea0a83c24..da8e7b16a0cef 100644
--- a/llvm/test/CodeGen/X86/2009-04-14-IllegalRegs.ll
+++ b/llvm/test/CodeGen/X86/2009-04-14-IllegalRegs.ll
@@ -53,7 +53,6 @@ define i32 @z() nounwind ssp {
 ; CHECK-NEXT:    retl
 ; CHECK-NEXT:  LBB0_3: ## %CallStackCheckFailBlk
 ; CHECK-NEXT:    calll ___stack_chk_fail
-; CHECK-NEXT:    ud2
 entry:
 	%retval = alloca i32		; <ptr> [#uses=2]
 	%xxx = alloca %struct.X		; <ptr> [#uses=6]

diff  --git a/llvm/test/CodeGen/X86/stack-protector-weight.ll b/llvm/test/CodeGen/X86/stack-protector-weight.ll
index 0b7620fdee657..862b130bfa4c6 100644
--- a/llvm/test/CodeGen/X86/stack-protector-weight.ll
+++ b/llvm/test/CodeGen/X86/stack-protector-weight.ll
@@ -10,7 +10,7 @@
 ; DARWIN-SELDAG: bb.[[SUCCESS]]{{[0-9a-zA-Z_.]+}}:
 
 ; DARWIN-IR: # Machine code for function test_branch_weights:
-; DARWIN-IR: successors: %bb.[[SUCCESS:[0-9]+]](0x7fffffff), %bb.[[FAILURE:[0-9]+]]
+; DARWIN-IR: successors: %bb.[[SUCCESS:[0-9]+]](0x7ffff800), %bb.[[FAILURE:[0-9]+]]
 ; DARWIN-IR: bb.[[SUCCESS]]{{[0-9a-zA-Z_.]+}}:
 ; DARWIN-IR: bb.[[FAILURE]]{{[0-9a-zA-Z_.]+}}:
 ; DARWIN-IR: CALL64pcrel32 @__stack_chk_fail