[ELF] - Check that output sections fit in address space.

[grimar]

Summary

I suggest to add checks to test that we do not produce
output where VA of sections overruns available address space.

[jhenderson]

Seems reasonable to me. A few nit comments though.

ELF/Writer.cpp

1986

addresses -> address

1991–1992

This comment looks like it's wrapped early?

2003–2004

Ditto comment wrapping. Also "Any" -> "any".

[grimar]

• Addressed comments. Thanks, James !

[grimar]

Do we want it?

[• espindola]

LGTM with nits.

ELF/Writer.cpp

1995

This is templated on ELFT, may as well use it.

It might be cleaner to write this as one check
(OS->Addr + OS->Size < OS->Addr) || (!ELF::Is64Bits && OS->Addr + OS->Size > UINT32_MAX)

[ruiu]

ELF/Writer.cpp

1991–1992

You should have changed the name of this function because it does more than checking section overlaps.

[grimar]

ELF/Writer.cpp

1991–1992

I renamed it to checkSections, it matches the command line option name. Does it sound fine?

ELF/Writer.cpp

for (auto *Other : ArrayRef<OutputSection *>(Sections).slice(I + 1)) {
                   " range overlaps with " + Other->Name + "\n>>> " + Sec->Name +
                   " range is " + rangeToString(Start, Sec->Size) + "\n>>> " +
                   Other->Name + " range is " +
                   rangeToString(GetStart(Other), Other->Size));
     }
   }
 }
 
-// Check for overlapping sections
+// Check for overlapping sections and address overflows.
 //
 // In this function we check that none of the output sections have overlapping
 // file offsets. For SHF_ALLOC sections we also check that the load address
 // ranges and the virtual address ranges don't overlap
 template <class ELFT> void Writer<ELFT>::checkNoOverlappingSections() {
-  // First 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 the file so Sec->Offset + Sec->Size can overlap with others.
-  // If --oformat binary is specified only add SHF_ALLOC sections are added to
-  // the output file so we skip any non-allocated sections in that case.
+  // First, check that section's VAs fit in available address space for target.
+  for (OutputSection *OS : OutputSections) {
+    bool Overflow = OS->Addr + OS->Size < OS->Addr;
+    if (!Config->Is64)
+      Overflow |= OS->Addr + OS->Size > UINT32_MAX;
+    if (Overflow)
+      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
+  // the file so Sec->Offset + Sec->Size can overlap with others. If --oformat
+  // binary is specified only add SHF_ALLOC sections are added to the output
+  // file so we skip any non-allocated sections in that case.
   checkForSectionOverlap(
       OutputSections, "file", [](const OutputSection *Sec) { return Sec->Offset; },
       [](const OutputSection *Sec) {
         return Sec->Type == SHT_NOBITS ||
                (Config->OFormatBinary && (Sec->Flags & SHF_ALLOC) == 0);
       });
 
   // When linking with -r there is no need to check for overlapping virtual/load

test/ELF/linkerscript/i386-sections-max-va-overflow.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=i386-pc-linux %s -o %t.o
+
+# RUN: echo "SECTIONS { . = 0xfffffff1;" > %t.script
+# RUN: echo "           .bar : { *(.bar*) } }" >> %t.script
+# RUN: not ld.lld -o %t.so --script %t.script %t.o 2>&1 | FileCheck %s -check-prefix=ERR
+
+## .bar section has data in [0xfffffff1, 0xfffffff1 + 0x10] == [0xffffff1, 0x1]. 
+## Check we can catch this overflow.
+# ERR: error: section .bar at 0xFFFFFFF1 of size 0x10 exceeds available address space
+
+.section .bar,"ax",@progbits
+.zero 0x10

test/ELF/linkerscript/output-too-large.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=i686-unknown-linux %s -o %t.o
 # RUN: echo "SECTIONS { .text : { . = 0xffffffff; *(.text*); } }" > %t.script
-# RUN: not ld.lld --script %t.script %t.o -o %t 2>&1 | FileCheck %s
+# RUN: not ld.lld --no-check-sections --script %t.script %t.o -o %t 2>&1 | FileCheck %s
 # CHECK: error: output file too large
 
 .global _start
 _start:
   nop

test/ELF/linkerscript/sections-max-va-overflow.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+
+# RUN: echo "SECTIONS { . = 0xfffffffffffffff1;" > %t.script
+# RUN: echo "           .bar : { *(.bar*) } }" >> %t.script
+# RUN: not ld.lld -o %t.so --script %t.script %t.o 2>&1 | FileCheck %s -check-prefix=ERR
+
+## .bar section has data in [0xfffffffffffffff1, 0xfffffffffffffff1 + 0x10] ==
+## [0xfffffffffffffff1, 0x1]. Check we can catch this overflow.
+# ERR: error: section .bar at 0xFFFFFFFFFFFFFFF1 of size 0x10 exceeds available address space
+
+.section .bar,"ax",@progbits
+.zero 0x10