[UBsan] add -fsanitize-handler-preserve-all-regs flag

[fmayer]

This is currently a no op.
This will be supported for the minimal runtime in a follow up. This allows
to improve codegen for fsanitize-recover by compiling the handlers with
[[clang::preserve_all]]. This makes sure that the caller does not need
to spill any registers. We do not expect this function to be called
frequently, so this is beneficial for code size.

[llvmbot]

@llvm/pr-subscribers-clang-driver

@llvm/pr-subscribers-clang

Author: Florian Mayer (fmayer)

Changes

This is currently a no op.

This will be supported for the minimal runtime in a follow up. This allows
to improve codegen for fsanitize-recover by compiling the handlers with
[[clang::preserve_all]]. This makes sure that the caller does not need
to spill any registers. We do not expect this function to be called
frequently, so this is beneficial for code size.

---

Full diff: https://github.com/llvm/llvm-project/pull/168644.diff

5 Files Affected:

• (modified) clang/include/clang/Basic/CodeGenOptions.def (+2)
• (modified) clang/include/clang/Driver/SanitizerArgs.h (+1)
• (modified) clang/include/clang/Options/Options.td (+5)
• (modified) clang/lib/Driver/SanitizerArgs.cpp (+6)
• (modified) clang/test/Driver/fsanitize.c (+5)

diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
index 52360b67b306c..3c9cdf5545c1f 100644
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -270,6 +270,8 @@ CODEGENOPT(SanitizeMemoryUseAfterDtor, 1, 0, Benign) ///< Enable use-after-delet
 CODEGENOPT(SanitizeCfiCrossDso, 1, 0, Benign) ///< Enable cross-dso support in CFI.
 CODEGENOPT(SanitizeMinimalRuntime, 1, 0, Benign) ///< Use "_minimal" sanitizer runtime for
                                                  ///< diagnostics.
+CODEGENOPT(SanitizePreserveRuntime, 1, 0, Benign) ///< Use "_preserve" sanitizer runtime for
+                                                 ///< diagnostics.
 CODEGENOPT(SanitizeCfiICallGeneralizePointers, 1, 0, Benign) ///< Generalize pointer types in
                                                              ///< CFI icall function signatures
 CODEGENOPT(SanitizeCfiICallNormalizeIntegers, 1, 0, Benign) ///< Normalize integer types in
diff --git a/clang/include/clang/Driver/SanitizerArgs.h b/clang/include/clang/Driver/SanitizerArgs.h
index eea7897e96afd..eef482cb577a9 100644
--- a/clang/include/clang/Driver/SanitizerArgs.h
+++ b/clang/include/clang/Driver/SanitizerArgs.h
@@ -67,6 +67,7 @@ class SanitizerArgs {
   bool TsanFuncEntryExit = true;
   bool TsanAtomics = true;
   bool MinimalRuntime = false;
+  bool PreserveRuntime = false;
   // True if cross-dso CFI support if provided by the system (i.e. Android).
   bool ImplicitCfiRuntime = false;
   bool NeedsMemProfRt = false;
diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td
index 2f7434d8afe11..a3e0566d9763d 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -2656,6 +2656,11 @@ defm sanitize_minimal_runtime : BoolOption<"f", "sanitize-minimal-runtime",
   PosFlag<SetTrue>,
   NegFlag<SetFalse>>,
   Group<f_clang_Group>;
+defm sanitize_preserve_runtime
+    : BoolOption<"f", "sanitize-preserve-runtime",
+                 CodeGenOpts<"SanitizePreserveRuntime">, DefaultFalse,
+                 PosFlag<SetTrue>, NegFlag<SetFalse>>,
+      Group<f_clang_Group>;
 def fsanitize_link_runtime : Flag<["-"], "fsanitize-link-runtime">,
                            Group<f_clang_Group>;
 def fno_sanitize_link_runtime : Flag<["-"], "fno-sanitize-link-runtime">,
diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
index 420c4cddbc8dd..c5ef3018b2455 100644
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -423,6 +423,9 @@ SanitizerArgs::SanitizerArgs(const ToolChain &TC,
   MinimalRuntime =
       Args.hasFlag(options::OPT_fsanitize_minimal_runtime,
                    options::OPT_fno_sanitize_minimal_runtime, MinimalRuntime);
+  PreserveRuntime =
+      Args.hasFlag(options::OPT_fsanitize_preserve_runtime,
+                   options::OPT_fno_sanitize_preserve_runtime, PreserveRuntime);
 
   // The object size sanitizer should not be enabled at -O0.
   Arg *OptLevel = Args.getLastArg(options::OPT_O_Group);
@@ -1469,6 +1472,9 @@ void SanitizerArgs::addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
   if (MinimalRuntime)
     CmdArgs.push_back("-fsanitize-minimal-runtime");
 
+  if (PreserveRuntime)
+    CmdArgs.push_back("-fsanitize-preserve-runtime");
+
   if (AsanFieldPadding)
     CmdArgs.push_back(Args.MakeArgString("-fsanitize-address-field-padding=" +
                                          Twine(AsanFieldPadding)));
diff --git a/clang/test/Driver/fsanitize.c b/clang/test/Driver/fsanitize.c
index 263301ad4466a..03241c2fcf91a 100644
--- a/clang/test/Driver/fsanitize.c
+++ b/clang/test/Driver/fsanitize.c
@@ -984,6 +984,11 @@
 // CHECK-UBSAN-MINIMAL: "-fsanitize={{((signed-integer-overflow|integer-divide-by-zero|shift-base|shift-exponent|unreachable|return|vla-bound|alignment|null|pointer-overflow|float-cast-overflow|array-bounds|enum|bool|builtin|returns-nonnull-attribute|nonnull-attribute|function),?){18}"}}
 // CHECK-UBSAN-MINIMAL: "-fsanitize-minimal-runtime"
 
+// RUN: %clang --target=x86_64-linux-gnu -fsanitize=undefined -fsanitize-minimal-runtime -fsanitize-preserve-runtime %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-UBSAN-MINIMAL-PRESERVE
+// CHECK-UBSAN-MINIMAL-PRESERVE: "-fsanitize={{((signed-integer-overflow|integer-divide-by-zero|shift-base|shift-exponent|unreachable|return|vla-bound|alignment|null|pointer-overflow|float-cast-overflow|array-bounds|enum|bool|builtin|returns-nonnull-attribute|nonnull-attribute|function),?){18}"}}
+// CHECK-UBSAN-MINIMAL-PRESERVE: "-fsanitize-minimal-runtime"
+// CHECK-UBSAN-MINIMAL-PRESERVE: "-fsanitize-preserve-runtime"
+
 // RUN: %clang --target=x86_64-linux-gnu -fsanitize=integer -fsanitize-trap=integer %s -### 2>&1 | FileCheck %s --check-prefix=CHECK-INTSAN-TRAP
 // CHECK-INTSAN-TRAP: "-fsanitize-trap=integer-divide-by-zero,shift-base,shift-exponent,signed-integer-overflow,unsigned-integer-overflow,unsigned-shift-base,implicit-unsigned-integer-truncation,implicit-signed-integer-truncation,implicit-integer-sign-change"
 

[vitalybuka]

HelpText<>?

[fmayer]

OK

[github-actions]

🐧 Linux x64 Test Results

• 111346 tests passed
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