aganea created this revision.
aganea added reviewers: amccarth, craig.topper, hans, rnk, stefan_reinalter.
Herald added subscribers: ormris, dexonsmith, dang, pengfei, hiraditya.
aganea requested review of this revision.
Herald added projects: clang, LLVM.
Herald added subscribers: llvm-commits, cfe-commits.
This patch adds support for the /HOTPATCH flag:
https://docs.microsoft.com/sv-se/cpp/build/reference/hotpatch-create-hotpatchable-image?view=msvc-170&viewFallbackFrom=vs-2019
The flag is translated to a new `-fhotpatch` cc1 flag, which in turn adds a
`patchable-function` attribute for each function in the TU. This is then picked
up by the `PatchableFunction` pass which would generate a
`TargetOpcode::PATCHABLE_OP` of minsize = 2 (which means the target instruction
must resolve to at least two bytes). Currently `TargetOpcode::PATCHABLE_OP` is
only implemented for x86/x64.
Additionally we generate a 'hot patchable' flag in the CodeView debug stream,
in the `S_COMPILE3` record. This flag is then picked up by LLD (or link.exe)
and is used in conjunction with the linker `/FUNCTIONPADMIN` flag to generate
extraneous space before each function, to accommodate for live patching. Please
see:
https://github.com/llvm/llvm-project/blob/d703b922961e0d02a5effdd4bfbb23ad50a3cc9f/lld/COFF/Writer.cpp#L1298
The end result is that one can finally use Live++
<https://molecular-matters.com/> or Recode <http://www.indefiant.com/> along
with clang-cl.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D116511
Files:
clang/include/clang/Basic/CodeGenOptions.def
clang/include/clang/Driver/Options.td
clang/lib/CodeGen/BackendUtil.cpp
clang/lib/CodeGen/CodeGenFunction.cpp
clang/lib/Driver/ToolChains/Clang.cpp
clang/test/CodeGen/patchable-function-entry.c
clang/test/CodeGenCXX/debug-info-hotpatch.cpp
clang/test/Driver/cl-options.c
llvm/include/llvm/Target/TargetOptions.h
llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
Index: llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
+++ llvm/lib/CodeGen/AsmPrinter/CodeViewDebug.cpp
@@ -843,6 +843,8 @@
if (MMI->getModule()->getProfileSummary(/*IsCS*/ false) != nullptr) {
Flags |= static_cast<uint32_t>(CompileSym3Flags::PGO);
}
+ if (Asm->TM.Options.Hotpatch)
+ Flags |= static_cast<uint32_t>(CompileSym3Flags::HotPatch);
OS.AddComment("Flags and language");
OS.emitInt32(Flags);
Index: llvm/include/llvm/Target/TargetOptions.h
===================================================================
--- llvm/include/llvm/Target/TargetOptions.h
+++ llvm/include/llvm/Target/TargetOptions.h
@@ -140,9 +140,9 @@
EnableMachineFunctionSplitter(false), SupportsDefaultOutlining(false),
EmitAddrsig(false), EmitCallSiteInfo(false),
SupportsDebugEntryValues(false), EnableDebugEntryValues(false),
- ValueTrackingVariableLocations(false),
- ForceDwarfFrameSection(false), XRayOmitFunctionIndex(false),
- DebugStrictDwarf(false),
+ ValueTrackingVariableLocations(false), ForceDwarfFrameSection(false),
+ XRayOmitFunctionIndex(false), DebugStrictDwarf(false),
+ Hotpatch(false),
FPDenormalMode(DenormalMode::IEEE, DenormalMode::IEEE) {}
/// DisableFramePointerElim - This returns true if frame pointer elimination
@@ -342,6 +342,9 @@
/// By default, it is set to false.
unsigned DebugStrictDwarf : 1;
+ /// Emit the hotpatch flag in CodeView debug.
+ unsigned Hotpatch : 1;
+
/// Name of the stack usage file (i.e., .su file) if user passes
/// -fstack-usage. If empty, it can be implied that -fstack-usage is not
/// passed on the command line.
Index: clang/test/Driver/cl-options.c
===================================================================
--- clang/test/Driver/cl-options.c
+++ clang/test/Driver/cl-options.c
@@ -118,6 +118,9 @@
// RUN: %clang_cl /Gw /Gw- -### -- %s 2>&1 | FileCheck -check-prefix=Gw_ %s
// Gw_-NOT: -fdata-sections
+// RUN: %clang_cl /hotpatch -### -- %s 2>&1 | FileCheck -check-prefix=hotpatch %s
+// hotpatch: -fhotpatchable
+
// RUN: %clang_cl /Imyincludedir -### -- %s 2>&1 | FileCheck -check-prefix=SLASH_I %s
// RUN: %clang_cl /I myincludedir -### -- %s 2>&1 | FileCheck -check-prefix=SLASH_I %s
// SLASH_I: "-I" "myincludedir"
Index: clang/test/CodeGenCXX/debug-info-hotpatch.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/debug-info-hotpatch.cpp
@@ -0,0 +1,13 @@
+// REQUIRES: x86-registered-target
+// RUN: %clang_cl --target=x86_64-windows-msvc /c /hotpatch /Z7 %s -o %t.obj
+// RUN: llvm-pdbutil dump -symbols %t.obj | FileCheck %s
+// RUN: %clang_cl --target=x86_64-windows-msvc /c /Z7 %s -o %t.obj
+// RUN: llvm-pdbutil dump -symbols %t.obj | FileCheck %s --check-prefix=NOHOTPATCH
+
+int main() {
+ return 0;
+}
+
+// CHECK: S_COMPILE3 [size = [[#]]] sig=0, `{{.+}}main.obj`
+// CHECK: flags = hot patchable
+// NOHOTPATCH-NOT: flags = hot patchable
Index: clang/test/CodeGen/patchable-function-entry.c
===================================================================
--- clang/test/CodeGen/patchable-function-entry.c
+++ clang/test/CodeGen/patchable-function-entry.c
@@ -1,5 +1,6 @@
// RUN: %clang_cc1 -triple aarch64 -emit-llvm %s -o - | FileCheck %s
// RUN: %clang_cc1 -triple x86_64 -emit-llvm %s -fpatchable-function-entry=1 -o - | FileCheck --check-prefixes=CHECK,OPT %s
+// RUN: %clang_cc1 -triple x86_64 -emit-llvm %s -fhotpatchable -o - | FileCheck --check-prefixes=HOTPATCH %s
// CHECK: define{{.*}} void @f0() #0
__attribute__((patchable_function_entry(0))) void f0() {}
@@ -34,3 +35,7 @@
// CHECK: attributes #2 = { {{.*}} "patchable-function-entry"="0" "patchable-function-prefix"="4"
// CHECK: attributes #3 = { {{.*}} "patchable-function-entry"="3" "patchable-function-prefix"="2"
// OPT: attributes #4 = { {{.*}} "patchable-function-entry"="1"
+// HOTPATCH: attributes #0 = { {{.*}} "patchable-function"="prologue-short-redirect"
+// HOTPATCH: attributes #1 = { {{.*}} "patchable-function"="prologue-short-redirect"
+// HOTPATCH: attributes #2 = { {{.*}} "patchable-function"="prologue-short-redirect"
+// HOTPATCH: attributes #3 = { {{.*}} "patchable-function"="prologue-short-redirect"
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -5994,6 +5994,7 @@
"-fpatchable-function-entry-offset=" + Twine(Offset)));
}
}
+ Args.AddLastArg(CmdArgs, options::OPT_fhotpatch);
if (TC.SupportsProfiling()) {
Args.AddLastArg(CmdArgs, options::OPT_pg);
Index: clang/lib/CodeGen/CodeGenFunction.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenFunction.cpp
+++ clang/lib/CodeGen/CodeGenFunction.cpp
@@ -882,6 +882,8 @@
if (Offset)
Fn->addFnAttr("patchable-function-prefix", std::to_string(Offset));
}
+ if (CGM.getCodeGenOpts().HotPatch)
+ Fn->addFnAttr("patchable-function", "prologue-short-redirect");
// Add no-jump-tables value.
if (CGM.getCodeGenOpts().NoUseJumpTables)
Index: clang/lib/CodeGen/BackendUtil.cpp
===================================================================
--- clang/lib/CodeGen/BackendUtil.cpp
+++ clang/lib/CodeGen/BackendUtil.cpp
@@ -645,6 +645,7 @@
Options.MCOptions.CommandLineArgs = CodeGenOpts.CommandLineArgs;
Options.DebugStrictDwarf = CodeGenOpts.DebugStrictDwarf;
Options.ObjectFilenameForDebug = CodeGenOpts.ObjectFilenameForDebug;
+ Options.Hotpatch = CodeGenOpts.HotPatch;
return true;
}
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -2490,6 +2490,9 @@
def fpatchable_function_entry_EQ : Joined<["-"], "fpatchable-function-entry=">, Group<f_Group>, Flags<[CC1Option]>,
MetaVarName<"<N,M>">, HelpText<"Generate M NOPs before function entry and N-M NOPs after function entry">,
MarshallingInfoInt<CodeGenOpts<"PatchableFunctionEntryCount">>;
+def fhotpatch : Flag<["-"], "fhotpatch">, Group<f_Group>, Flags<[CC1Option]>,
+ HelpText<"Ensure that all functions can be hotpatched at runtime">,
+ MarshallingInfoFlag<CodeGenOpts<"HotPatch">>;
def fpcc_struct_return : Flag<["-"], "fpcc-struct-return">, Group<f_Group>, Flags<[CC1Option]>,
HelpText<"Override the default ABI to return all structs on the stack">;
def fpch_preprocess : Flag<["-"], "fpch-preprocess">, Group<f_Group>;
@@ -6114,6 +6117,8 @@
def _SLASH_help : CLFlag<"help">, Alias<help>,
HelpText<"Display available options">;
def _SLASH_HELP : CLFlag<"HELP">, Alias<help>;
+def _SLASH_hotpatch : CLFlag<"hotpatch">, Alias<fhotpatch>,
+ HelpText<"Create hotpatchable image">;
def _SLASH_I : CLJoinedOrSeparate<"I">,
HelpText<"Add directory to include search path">, MetaVarName<"<dir>">,
Alias<I>;
@@ -6470,7 +6475,6 @@
def _SLASH_headerUnitAngle : CLJoinedOrSeparate<"headerUnit:angle">;
def _SLASH_headerUnitQuote : CLJoinedOrSeparate<"headerUnit:quote">;
def _SLASH_homeparams : CLFlag<"homeparams">;
-def _SLASH_hotpatch : CLFlag<"hotpatch">;
def _SLASH_kernel : CLFlag<"kernel">;
def _SLASH_LN : CLFlag<"LN">;
def _SLASH_MP : CLJoined<"MP">;
Index: clang/include/clang/Basic/CodeGenOptions.def
===================================================================
--- clang/include/clang/Basic/CodeGenOptions.def
+++ clang/include/clang/Basic/CodeGenOptions.def
@@ -139,6 +139,9 @@
VALUE_CODEGENOPT(PatchableFunctionEntryCount , 32, 0) ///< Number of NOPs at function entry
VALUE_CODEGENOPT(PatchableFunctionEntryOffset , 32, 0)
+CODEGENOPT(HotPatch, 1, 0) ///< Supports the Microsoft /HOTPATCH flag and would
+ ///< generate a 'patchable-function' attribute.
+
CODEGENOPT(InstrumentForProfiling , 1, 0) ///< Set when -pg is enabled.
CODEGENOPT(CallFEntry , 1, 0) ///< Set when -mfentry is enabled.
CODEGENOPT(MNopMCount , 1, 0) ///< Set when -mnop-mcount is enabled.
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