[PATCH] D64516: [WebAssembly] Import __stack_pointer when building -pie binaries

[Sam Clegg via Phabricator via llvm-commits]

sbc100 created this revision.
Herald added subscribers: llvm-commits, sunfish, aheejin, jgravelle-google, dschuff.
Herald added a project: LLVM.

The -pie binary doesn't know that layout ahead of time so needs to
import the stack pointer from the embedder, just like we do already
for shared libraries.

cleanup


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D64516

Files:
  lld/test/wasm/pie.ll
  lld/wasm/Driver.cpp
  lld/wasm/Writer.cpp


Index: lld/wasm/Writer.cpp
===================================================================
--- lld/wasm/Writer.cpp
+++ lld/wasm/Writer.cpp
@@ -204,7 +204,7 @@
   uint32_t MemoryPtr = 0;
 
   auto PlaceStack = [&]() {
-    if (Config->Relocatable || Config->Shared)
+    if (Config->Relocatable || Config->Pie)
       return;
     MemoryPtr = alignTo(MemoryPtr, StackAlignment);
     if (Config->ZStackSize != alignTo(Config->ZStackSize, StackAlignment))
Index: lld/wasm/Driver.cpp
===================================================================
--- lld/wasm/Driver.cpp
+++ lld/wasm/Driver.cpp
@@ -482,11 +482,22 @@
     }
   }
 
-  // The __stack_pointer is imported in the shared library case, and exported
-  // in the non-shared (executable) case.
-  if (Config->Shared) {
+  if (!Config->Shared)
+    WasmSym::DataEnd = Symtab->addOptionalDataSymbol("__data_end");
+
+  if (Config->Pic) {
     WasmSym::StackPointer =
         createUndefinedGlobal("__stack_pointer", &MutableGlobalTypeI32);
+    // For PIC code, we import two global variables (__memory_base and
+    // __table_base) from the environment and use these as the offset at
+    // which to load our static data and function table.
+    // See:
+    // https://github.com/WebAssembly/tool-conventions/blob/master/DynamicLinking.md
+    WasmSym::MemoryBase =
+        createUndefinedGlobal("__memory_base", &GlobalTypeI32);
+    WasmSym::TableBase = createUndefinedGlobal("__table_base", &GlobalTypeI32);
+    WasmSym::MemoryBase->markLive();
+    WasmSym::TableBase->markLive();
   } else {
     llvm::wasm::WasmGlobal Global;
     Global.Type = {WASM_TYPE_I32, true};
@@ -501,24 +512,10 @@
     // See: https://github.com/WebAssembly/mutable-global
     WasmSym::StackPointer = Symtab->addSyntheticGlobal(
         "__stack_pointer", WASM_SYMBOL_VISIBILITY_HIDDEN, StackPointer);
-    WasmSym::DataEnd = Symtab->addOptionalDataSymbol("__data_end");
     WasmSym::GlobalBase = Symtab->addOptionalDataSymbol("__global_base");
     WasmSym::HeapBase = Symtab->addOptionalDataSymbol("__heap_base");
   }
 
-  if (Config->Pic) {
-    // For PIC code, we import two global variables (__memory_base and
-    // __table_base) from the environment and use these as the offset at
-    // which to load our static data and function table.
-    // See:
-    // https://github.com/WebAssembly/tool-conventions/blob/master/DynamicLinking.md
-    WasmSym::MemoryBase =
-        createUndefinedGlobal("__memory_base", &GlobalTypeI32);
-    WasmSym::TableBase = createUndefinedGlobal("__table_base", &GlobalTypeI32);
-    WasmSym::MemoryBase->markLive();
-    WasmSym::TableBase->markLive();
-  }
-
   WasmSym::DsoHandle = Symtab->addSyntheticDataSymbol(
       "__dso_handle", WASM_SYMBOL_VISIBILITY_HIDDEN);
 }
Index: lld/test/wasm/pie.ll
===================================================================
--- lld/test/wasm/pie.ll
+++ lld/test/wasm/pie.ll
@@ -40,6 +40,11 @@
 ; CHECK-NEXT:           Limits:
 ; CHECK-NEXT:             Initial:         0x00000001
 ; CHECK-NEXT:       - Module:          env
+; CHECK-NEXT:         Field:           __stack_pointer
+; CHECK-NEXT:         Kind:            GLOBAL
+; CHECK-NEXT:         GlobalType:      I32
+; CHECK-NEXT:         GlobalMutable:   true
+; CHECK-NEXT:       - Module:          env
 ; CHECK-NEXT:         Field:           __memory_base
 ; CHECK-NEXT:         Kind:            GLOBAL
 ; CHECK-NEXT:         GlobalType:      I32


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