[ELF] - Fix calculation of memory region offset.

[grimar]

Summary

This is PR33714.

Previously for each input section offset of memory region
was incremented on a size of output section.

That resulted in a wrong error message saying about
overflow. Patch fixes that.

[meadori]

Thanks for fixing this. I had recently ran into as well. LGTM.

[ruiu]

LGTM

ELF/LinkerScript.cpp

uint64_t LinkerScript::advance(uint64_t Size, unsigned Align) {
   if (IsTbss)
     CurAddressState->ThreadBssOffset = End - Dot;
   else
     Dot = End;
   return End;
 }
 
 void LinkerScript::output(InputSection *S) {
+  uint64_t Before = advance(0, 1);
   uint64_t Pos = advance(S->getSize(), S->Alignment);
   S->OutSecOff = Pos - S->getSize() - CurAddressState->OutSec->Addr;
 
   // Update output section size after adding each section. This is so that
   // SIZEOF works correctly in the case below:
   // .foo { *(.aaa) a = SIZEOF(.foo); *(.bbb) }
   CurAddressState->OutSec->Size = Pos - CurAddressState->OutSec->Addr;
 
   // If there is a memory region associated with this input section, then
   // place the section in that region and update the region index.
   if (CurAddressState->MemRegion) {
     uint64_t &CurOffset =
         CurAddressState->MemRegionOffset[CurAddressState->MemRegion];
-    CurOffset += CurAddressState->OutSec->Size;
+    CurOffset += Pos - Before;
     uint64_t CurSize = CurOffset - CurAddressState->MemRegion->Origin;
     if (CurSize > CurAddressState->MemRegion->Length) {
       uint64_t OverflowAmt = CurSize - CurAddressState->MemRegion->Length;
       error("section '" + CurAddressState->OutSec->Name +
             "' will not fit in region '" + CurAddressState->MemRegion->Name +
             "': overflowed by " + Twine(OverflowAmt) + " bytes");
     }
   }

test/ELF/linkerscript/memory2.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: echo "MEMORY { ram (rwx) : ORIGIN = 0, LENGTH = 2K } \
+# RUN: SECTIONS { .text : { *(.text*) } > ram }" > %t.script
+# RUN: ld.lld -o %t2 --script %t.script %t
+
+.text
+.global _start
+_start:
+  .zero 1024
+
+.section .text.foo,"ax",%progbits
+foo:
+  nop