[PATCH] D65722: [ELF] Expand regions for gaps due to explicit address

[Gabriel Smith via Phabricator via llvm-commits]

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

If the dot gets moved by an explicit section address, an empty gap between sections could be created. The encompassing region for the section being parsed needs to be expanded to include the gap.


Repository:
  rL LLVM

https://reviews.llvm.org/D65722

Files:
  lld/ELF/LinkerScript.cpp
  lld/test/ELF/linkerscript/section-gap-explicit-expr.test


Index: lld/test/ELF/linkerscript/section-gap-explicit-expr.test
===================================================================
--- /dev/null
+++ lld/test/ELF/linkerscript/section-gap-explicit-expr.test
@@ -0,0 +1,25 @@
+# REQUIRES: x86
+
+# RUN: echo ".section .aaa, \"a\"; .quad 0; .section .bbb, \"a\"; .quad 0;" \
+# RUN:   | llvm-mc -filetype=obj -triple=x86_64-pc-linux - -o %t
+# RUN: ld.lld %t --script %s -o %t2
+
+# RUN: llvm-objdump -section-headers %t2 | FileCheck %s
+# CHECK: .aaa_s 00000008 0000000000000000 DATA
+# CHECK: .bbb_s 00000008 0000000000000014 DATA
+
+MEMORY {
+  REGION (rwx) : ORIGIN = 0x0000, LENGTH = 0x100
+}
+
+SECTIONS {
+  .aaa_s ORIGIN(REGION) :
+  {
+    *(.aaa)
+  } > REGION
+
+  .bbb_s ORIGIN(REGION) + 0x14 :
+  {
+    *(.bbb)
+  } > REGION
+}
Index: lld/ELF/LinkerScript.cpp
===================================================================
--- lld/ELF/LinkerScript.cpp
+++ lld/ELF/LinkerScript.cpp
@@ -772,6 +772,15 @@
   if ((sec->flags & SHF_ALLOC) && sec->addrExpr)
     setDot(sec->addrExpr, sec->location, false);
 
+  // If the address of the section has been moved forward by an explicit
+  // expression so that it now starts past the current curPos of the enclosing
+  // region, we need to expand the current region to account for the space
+  // between the previous section, if any, and the start of this section.
+  if (ctx->memRegion && ctx->memRegion->curPos < dot) {
+    expandMemoryRegion(ctx->memRegion, dot - ctx->memRegion->curPos,
+                       ctx->memRegion->name, sec->name);
+  }
+
   switchTo(sec);
 
   if (sec->lmaExpr)


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