[lld] a4c5db3 - [ELF] Remove redundant fillTrap and memset(*, 0, *). NFC

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2022-01-16T22:37:31-08:00
New Revision: a4c5db30be4e216834b44e31b47304ea1b92635f

URL: https://github.com/llvm/llvm-project/commit/a4c5db30be4e216834b44e31b47304ea1b92635f
DIFF: https://github.com/llvm/llvm-project/commit/a4c5db30be4e216834b44e31b47304ea1b92635f.diff

LOG: [ELF] Remove redundant fillTrap and memset(*, 0, *). NFC

The new tests in build-id.s would catch problems if we made a mistake here.

Added: 
    

Modified: 
    lld/ELF/SyntheticSections.cpp
    lld/ELF/Writer.cpp

Removed: 
    


################################################################################
diff  --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
index 2bb94b54bc1e..6069c603bacb 100644
--- a/lld/ELF/SyntheticSections.cpp
+++ b/lld/ELF/SyntheticSections.cpp
@@ -2398,11 +2398,6 @@ void GnuHashTableSection::finalizeContents() {
 }
 
 void GnuHashTableSection::writeTo(uint8_t *buf) {
-  // The output buffer is not guaranteed to be zero-cleared because we pre-
-  // fill executable sections with trap instructions. This is a precaution
-  // for that case, which happens only when --no-rosegment is given.
-  memset(buf, 0, size);
-
   // Write a header.
   write32(buf, nBuckets);
   write32(buf + 4, getPartition().dynSymTab->getNumSymbols() - symbols.size());
@@ -2515,10 +2510,6 @@ void HashTableSection::finalizeContents() {
 
 void HashTableSection::writeTo(uint8_t *buf) {
   SymbolTableBaseSection *symTab = getPartition().dynSymTab.get();
-
-  // See comment in GnuHashTableSection::writeTo.
-  memset(buf, 0, size);
-
   unsigned numSymbols = symTab->getNumSymbols();
 
   uint32_t *p = reinterpret_cast<uint32_t *>(buf);

diff  --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 737863bb4208..ba69189eeccd 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -2851,8 +2851,8 @@ template <class ELFT> void Writer<ELFT>::writeTrapInstr() {
     // Fill the last page.
     for (PhdrEntry *p : part.phdrs)
       if (p->p_type == PT_LOAD && (p->p_flags & PF_X))
-        fillTrap(Out::bufferStart + alignDown(p->firstSec->offset + p->p_filesz,
-                                              config->maxPageSize),
+        fillTrap(Out::bufferStart +
+                     alignDown(p->firstSec->offset + p->p_filesz, 4),
                  Out::bufferStart + alignTo(p->firstSec->offset + p->p_filesz,
                                             config->maxPageSize));