[PATCH] D67211: [ELF] Initialize PhdrEntry::p_align to maxPageSize for PT_LOAD

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: grimar, peter.smith, ruiu.
Herald added subscribers: llvm-commits, arichardson, emaste.
Herald added a reviewer: espindola.
Herald added a project: LLVM.

  Writer<ELFT>::run
    assignFileOffsets
      setFileOffset
        computeFileOffset
          os->ptLoad->p_align may be smaller than config->maxPageSize
    setPhdrs
      p_align = max(p_align, config->maxPageSize)

If we move the config->maxPageSize logic to the constructor of
PhdrEntry, computeFileOffset can be simplified.


Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D67211

Files:
  ELF/Writer.cpp
  ELF/Writer.h


Index: ELF/Writer.h
===================================================================
--- ELF/Writer.h
+++ ELF/Writer.h
@@ -9,6 +9,7 @@
 #ifndef LLD_ELF_WRITER_H
 #define LLD_ELF_WRITER_H
 
+#include "Config.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/StringRef.h"
 #include <cstdint>
@@ -28,7 +29,9 @@
 // Each contains type, access flags and range of output sections that will be
 // placed in it.
 struct PhdrEntry {
-  PhdrEntry(unsigned type, unsigned flags) : p_type(type), p_flags(flags) {}
+  PhdrEntry(unsigned type, unsigned flags)
+      : p_align(type == llvm::ELF::PT_LOAD ? config->maxPageSize : 0),
+        p_type(type), p_flags(flags) {}
   void add(OutputSection *sec);
 
   uint64_t p_paddr = 0;
Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -2270,12 +2270,9 @@
 // load executables without any address adjustment.
 static uint64_t computeFileOffset(OutputSection *os, uint64_t off) {
   // The first section in a PT_LOAD has to have congruent offset and address
-  // module the page size.
-  if (os->ptLoad && os->ptLoad->firstSec == os) {
-    uint64_t alignment =
-        std::max<uint64_t>(os->ptLoad->p_align, config->maxPageSize);
-    return alignTo(off, alignment, os->addr);
-  }
+  // modulo the maximum page size.
+  if (os->ptLoad && os->ptLoad->firstSec == os)
+    return alignTo(off, os->ptLoad->p_align, os->addr);
 
   // File offsets are not significant for .bss sections other than the first one
   // in a PT_LOAD. By convention, we keep section offsets monotonically
@@ -2385,9 +2382,7 @@
         p->p_paddr = first->getLMA();
     }
 
-    if (p->p_type == PT_LOAD) {
-      p->p_align = std::max<uint64_t>(p->p_align, config->maxPageSize);
-    } else if (p->p_type == PT_GNU_RELRO) {
+    if (p->p_type == PT_GNU_RELRO) {
       p->p_align = 1;
       // musl/glibc ld.so rounds the size down, so we need to round up
       // to protect the last page. This is a no-op on FreeBSD which always


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D67211.218841.patch
Type: text/x-patch
Size: 2037 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20190905/c9fd2f9a/attachment.bin>