[lld] 8412915 - [lld][WebAssembly] Fix memory size in dylink section for -pie exectuables

[Sam Clegg via llvm-commits]

Author: Sam Clegg
Date: 2020-10-27T16:05:52-07:00
New Revision: 84129150ce82894e185c084f2eaec05f4c03dd4c

URL: https://github.com/llvm/llvm-project/commit/84129150ce82894e185c084f2eaec05f4c03dd4c
DIFF: https://github.com/llvm/llvm-project/commit/84129150ce82894e185c084f2eaec05f4c03dd4c.diff

LOG: [lld][WebAssembly] Fix memory size in dylink section for -pie exectuables

This field to represents the amount of static data needed by
an dynamic library or executable it should not include things
like heap or stack areas, which in the case of `-pie` are
not determined until runtime (e.g. __stack_pointer is imported).

Differential Revision: https://reviews.llvm.org/D90261

Added: 
    

Modified: 
    lld/test/wasm/pie.ll
    lld/wasm/Writer.cpp

Removed: 
    


################################################################################
diff  --git a/lld/test/wasm/pie.ll b/lld/test/wasm/pie.ll
index 13d30ffe51c3..9dfee4537609 100644
--- a/lld/test/wasm/pie.ll
+++ b/lld/test/wasm/pie.ll
@@ -1,5 +1,5 @@
 ; RUN: llc -relocation-model=pic -mattr=+mutable-globals -filetype=obj %s -o %t.o
-; RUN: wasm-ld --no-gc-sections --allow-undefined -pie -o %t.wasm %t.o
+; RUN: wasm-ld --no-gc-sections --allow-undefined --experimental-pic -pie -o %t.wasm %t.o
 ; RUN: obj2yaml %t.wasm | FileCheck %s
 
 target triple = "wasm32-unknown-emscripten"
@@ -30,6 +30,15 @@ define void @_start() {
   ret void
 }
 
+;      CHECK: Sections:
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            dylink
+; CHECK-NEXT:     MemorySize:      16
+; CHECK-NEXT:     MemoryAlignment: 2
+; CHECK-NEXT:     TableSize:       1
+; CHECK-NEXT:     TableAlignment:  0
+; CHECK-NEXT:     Needed:          []
+
 ; CHECK:        - Type:            IMPORT
 ; CHECK-NEXT:     Imports:
 ; CHECK-NEXT:       - Module:          env

diff  --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp
index aaa29744c326..975f173c500c 100644
--- a/lld/wasm/Writer.cpp
+++ b/lld/wasm/Writer.cpp
@@ -293,10 +293,10 @@ void Writer::layoutMemory() {
   if (WasmSym::dataEnd)
     WasmSym::dataEnd->setVirtualAddress(memoryPtr);
 
-  log("mem: static data = " + Twine(memoryPtr - dataStart));
-
-  if (config->shared) {
-    out.dylinkSec->memSize = memoryPtr;
+  uint64_t staticDataSize = memoryPtr - dataStart;
+  log("mem: static data = " + Twine(staticDataSize));
+  if (config->isPic) {
+    out.dylinkSec->memSize = staticDataSize;
     return;
   }
 
@@ -323,7 +323,6 @@ void Writer::layoutMemory() {
             Twine(maxMemorySetting));
     memoryPtr = config->initialMemory;
   }
-  out.dylinkSec->memSize = memoryPtr;
   out.memorySec->numMemoryPages =
       alignTo(memoryPtr, WasmPageSize) / WasmPageSize;
   log("mem: total pages = " + Twine(out.memorySec->numMemoryPages));