[PATCH] D43284: [ELF] Simplify handling of AT section attribute.

[Igor Kudrin via Phabricator via llvm-commits]

ikudrin updated this revision to Diff 134376.
ikudrin added a comment.

Update according to Rafael's comments:

- Replace `!FirstLoadSection` with `Load->LastSec != Out::ProgramHeaders`.
- Add a corresponding comment.


https://reviews.llvm.org/D43284

Files:
  ELF/Writer.cpp
  ELF/Writer.h
  test/ELF/linkerscript/at5.s


Index: test/ELF/linkerscript/at5.s
===================================================================
--- /dev/null
+++ test/ELF/linkerscript/at5.s
@@ -0,0 +1,36 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: echo "SECTIONS { \
+# RUN:  . = 0x1000; \
+# RUN:  .aaa : { *(.aaa) } \
+# RUN:  .bbb : AT(0x2008) { *(.bbb) } \
+# RUN:  .ccc : { *(.ccc) } \
+# RUN: }" > %t.script
+# RUN: ld.lld %t --script %t.script -o %t2
+# RUN: llvm-readobj -program-headers %t2 | FileCheck %s
+
+# CHECK:        Type: PT_LOAD
+# CHECK-NEXT:     Offset: 0x1000
+# CHECK-NEXT:     VirtualAddress: 0x1000
+# CHECK-NEXT:     PhysicalAddress: 0x1000
+# CHECK-NEXT:     FileSize: 8
+# CHECK-NEXT:     MemSize: 8
+# CHECK:        Type: PT_LOAD
+# CHECK-NEXT:     Offset: 0x1008
+# CHECK-NEXT:     VirtualAddress: 0x1008
+# CHECK-NEXT:     PhysicalAddress: 0x2008
+# CHECK-NEXT:     FileSize: 17
+# CHECK-NEXT:     MemSize: 17
+
+.global _start
+_start:
+ nop
+
+.section .aaa, "a"
+.quad 0
+
+.section .bbb, "a"
+.quad 0
+
+.section .ccc, "a"
+.quad 0
Index: ELF/Writer.h
===================================================================
--- ELF/Writer.h
+++ ELF/Writer.h
@@ -45,11 +45,6 @@
   OutputSection *LastSec = nullptr;
   bool HasLMA = false;
 
-  // True if one of the sections in this program header has a LMA specified via
-  // linker script: AT(addr). We never allow 2 or more sections with LMA in the
-  // same program header.
-  bool ASectionHasLMA = false;
-
   uint64_t LMAOffset = 0;
 };
 
Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -821,8 +821,6 @@
   p_align = std::max(p_align, Sec->Alignment);
   if (p_type == PT_LOAD)
     Sec->PtLoad = this;
-  if (Sec->LMAExpr)
-    ASectionHasLMA = true;
 }
 
 // The beginning and the ending of .rel[a].plt section are marked
@@ -1697,9 +1695,11 @@
     // (e.g. executable or writable). There is one phdr for each segment.
     // Therefore, we need to create a new phdr when the next section has
     // different flags or is loaded at a discontiguous address using AT linker
-    // script command.
+    // script command. At the same time, we don't want to create a separate
+    // load segment for the headers, even if the first output section has
+    // an AT attribute.
     uint64_t NewFlags = computeFlags(Sec->getPhdrFlags());
-    if ((Sec->LMAExpr && Load->ASectionHasLMA) ||
+    if ((Sec->LMAExpr && Load->LastSec != Out::ProgramHeaders) ||
         Sec->MemRegion != Load->FirstSec->MemRegion || Flags != NewFlags) {
 
       Load = AddHdr(PT_LOAD, NewFlags);


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