[FreeBSD] Mark __stack_chk_guard dso_local except for PPC64

[justincady]

Adjust logic of 1cb9f37 to match freebsd/freebsd-src@9a4d48a645a7a.

D113443 is the original attempt to bring this FreeBSD patch to llvm-project,
but it never landed. This change is required to build FreeBSD kernel modules
with -fstack-protector using a standard LLVM toolchain. The FreeBSD kernel
loader does not handle R_X86_64_REX_GOTPCRELX relocations.

Fixes #50932.

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: Justin Cady (justincady)

Changes

Adjust logic of 1cb9f37 to match freebsd/freebsd-src@9a4d48a645a7a.

D113443 is the original attempt to bring this FreeBSD patch to llvm-project,
but it never landed. This change is required to build FreeBSD kernel modules
with -fstack-protector using a standard LLVM toolchain. The FreeBSD kernel
loader does not handle R_X86_64_REX_GOTPCRELX relocations.

Fixes #50932.

---

Full diff: https://github.com/llvm/llvm-project/pull/86665.diff

2 Files Affected:

• (modified) llvm/lib/CodeGen/TargetLoweringBase.cpp (+2-1)
• (modified) llvm/test/CodeGen/X86/stack-protector.ll (+9)

diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index 9990556f89ed8b..b16e78daf58614 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -2073,7 +2073,8 @@ void TargetLoweringBase::insertSSPDeclarations(Module &M) const {
     // FreeBSD has "__stack_chk_guard" defined externally on libc.so
     if (M.getDirectAccessExternalData() &&
         !TM.getTargetTriple().isWindowsGNUEnvironment() &&
-        !TM.getTargetTriple().isOSFreeBSD() &&
+        !(TM.getTargetTriple().isPPC64() &&
+          TM.getTargetTriple().isOSFreeBSD()) &&
         (!TM.getTargetTriple().isOSDarwin() ||
          TM.getRelocationModel() == Reloc::Static))
       GV->setDSOLocal(true);
diff --git a/llvm/test/CodeGen/X86/stack-protector.ll b/llvm/test/CodeGen/X86/stack-protector.ll
index a277f9f862ab26..f4f3ae4f55f2ee 100644
--- a/llvm/test/CodeGen/X86/stack-protector.ll
+++ b/llvm/test/CodeGen/X86/stack-protector.ll
@@ -1,6 +1,7 @@
 ; RUN: llc -mtriple=i386-pc-linux-gnu < %s -o - | FileCheck --check-prefix=LINUX-I386 %s
 ; RUN: llc -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck --check-prefix=LINUX-X64 %s
 ; RUN: llc -code-model=kernel -mtriple=x86_64-pc-linux-gnu < %s -o - | FileCheck --check-prefix=LINUX-KERNEL-X64 %s
+; RUN: llc -code-model=kernel -mtriple=x86_64-unknown-freebsd < %s -o - | FileCheck --check-prefix=FREEBSD-KERNEL-X64 %s
 ; RUN: llc -mtriple=x86_64-apple-darwin < %s -o - | FileCheck --check-prefix=DARWIN-X64 %s
 ; RUN: llc -mtriple=amd64-pc-openbsd < %s -o - | FileCheck --check-prefix=OPENBSD-AMD64 %s
 ; RUN: llc -mtriple=i386-pc-windows-msvc < %s -o - | FileCheck -check-prefix=MSVC-I386 %s
@@ -75,6 +76,10 @@ entry:
 ; LINUX-X64: mov{{l|q}} %fs:
 ; LINUX-X64: callq __stack_chk_fail
 
+; FREEBSD-KERNEL-X64-LABEL: test1b:
+; FREEBSD-KERNEL-X64-NOT: mov{{l|q}} __stack_chk_guard@GOTPCREL
+; FREEBSD-KERNEL-X64: callq __stack_chk_fail
+
 ; LINUX-KERNEL-X64-LABEL: test1b:
 ; LINUX-KERNEL-X64: mov{{l|q}} %gs:
 ; LINUX-KERNEL-X64: callq __stack_chk_fail
@@ -118,6 +123,10 @@ entry:
 ; LINUX-X64: mov{{l|q}} %fs:
 ; LINUX-X64: callq __stack_chk_fail
 
+; FREEBSD-KERNEL-X64-LABEL: test1c:
+; FREEBSD-KERNEL-X64: mov{{l|q}} __stack_chk_guard(%rip)
+; FREEBSD-KERNEL-X64: callq __stack_chk_fail
+
 ; LINUX-KERNEL-X64-LABEL: test1c:
 ; LINUX-KERNEL-X64: mov{{l|q}} %gs:
 ; LINUX-KERNEL-X64: callq __stack_chk_fail

[MaskRay]

We should have a powerpc64 freebsd test as well, if we haven't yet.

[DimitryAndric]

Yes, this is handy to reduce the amount of diffs we have in FreeBSD. :)

[justincady]

We should have a powerpc64 freebsd test as well, if we haven't yet.

Good news: I believe this case is covered by llvm/test/CodeGen/PowerPC/stack-protector.ll. I tested it by deleting the !(TM.getTargetTriple().isPPC64() && TM.getTargetTriple().isOSFreeBSD()) conditional entirely, which caused that test to fail.