[PATCH] D111871: [ELF] Let sections reach the end of the address space

[Hristo Venev via Phabricator via llvm-commits]

hvenev created this revision.
hvenev added reviewers: MaskRay, psmith.
Herald added subscribers: arichardson, emaste.
hvenev requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

This is permitted by the GNU linker.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D111871

Files:
  lld/ELF/Writer.cpp
  lld/test/ELF/linkerscript/i386-sections-until-end-of-va.s
  lld/test/ELF/linkerscript/sections-until-end-of-va.s


Index: lld/test/ELF/linkerscript/sections-until-end-of-va.s
===================================================================
--- /dev/null
+++ lld/test/ELF/linkerscript/sections-until-end-of-va.s
@@ -0,0 +1,12 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+
+# RUN: echo "SECTIONS { . = 0xfffffffffffffff0;" > %t.script
+# RUN: echo "           .bar : { *(.bar*) } }" >> %t.script
+# RUN: ld.lld -o /dev/null --script %t.script %t.o 2>&1
+
+## .bar section has data in [0xfffffffffffffff0, 0xfffffffffffffff0 + 0x10] ==
+## [0xfffffffffffffff0, 0]. There is no overflow.
+
+.section .bar,"ax", at progbits
+.zero 0x10
Index: lld/test/ELF/linkerscript/i386-sections-until-end-of-va.s
===================================================================
--- /dev/null
+++ lld/test/ELF/linkerscript/i386-sections-until-end-of-va.s
@@ -0,0 +1,12 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=i386-unknown-linux %s -o %t.o
+
+# RUN: echo "SECTIONS { . = 0xfffffff0;" > %t.script
+# RUN: echo "           .bar : { *(.bar*) } }" >> %t.script
+# RUN: ld.lld -o /dev/null --script %t.script %t.o 2>&1
+
+## .bar section has data in [0xfffffff0, 0xfffffff0 + 0x10] ==
+## [0xfffffff0, 0]. There is no overflow.
+
+.section .bar,"ax", at progbits
+.zero 0x10
Index: lld/ELF/Writer.cpp
===================================================================
--- lld/ELF/Writer.cpp
+++ lld/ELF/Writer.cpp
@@ -2782,12 +2782,15 @@
 // ranges and the virtual address ranges don't overlap
 template <class ELFT> void Writer<ELFT>::checkSections() {
   // First, check that section's VAs fit in available address space for target.
-  for (OutputSection *os : outputSections)
-    if ((os->addr + os->size < os->addr) ||
-        (!ELFT::Is64Bits && os->addr + os->size > UINT32_MAX))
+  for (OutputSection *os : outputSections) {
+    if (os->size == 0)
+      continue;
+    uint64_t lastByte = os->addr + (os->size - 1);
+    if ((lastByte < os->addr) || (!ELFT::Is64Bits && lastByte > UINT32_MAX))
       errorOrWarn("section " + os->name + " at 0x" + utohexstr(os->addr) +
                   " of size 0x" + utohexstr(os->size) +
                   " exceeds available address space");
+  }
 
   // Check for overlapping file offsets. In this case we need to skip any
   // section marked as SHT_NOBITS. These sections don't actually occupy space in


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