Fix: #1351

Don't attempt to apply relocations to sections that aren't loaded into memory.
uxmal · Aug 21, 2024 · 72a6b8f · 72a6b8f
1 parent df5c4a5
commit 72a6b8f
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Showing 10 changed files with 82 additions and 26 deletions.
diff --git a/src/Core/Hll/C/CParser.cs b/src/Core/Hll/C/CParser.cs
@@ -1577,7 +1577,7 @@ private static (int?, int?) infixBindingPower(CTokenType tokenType)
         //Expr       = AssignExpr {','  AssignExpr}.
         public CExpression Parse_Expr()
         {
-            return this.expr_bp(0);
+            //return this.expr_bp(0);
 
             var left = Parse_AssignExpr();
             while (PeekThenDiscard(CTokenType.Comma))

diff --git a/src/ImageLoaders/Elf/ElfImageLoader.cs b/src/ImageLoaders/Elf/ElfImageLoader.cs
@@ -25,6 +25,7 @@
 using Reko.Core.Loading;
 using Reko.Core.Memory;
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 
 namespace Reko.ImageLoaders.Elf
@@ -81,9 +82,11 @@ public override Program LoadProgram(Address? addrLoad)
             innerLoader.LoadSymbolsFromSections();
             //innerLoader.Dump();           // This spews a lot into the unit test output.
             Program program;
+            Dictionary<ElfSymbol, Address> plt;
             if (cHeaders > 0)
             {
                 program = innerLoader.LoadImage(platform, RawImage);
+                plt = new Dictionary<ElfSymbol, Address>();
             }
             else
             {
@@ -97,8 +100,9 @@ public override Program LoadProgram(Address? addrLoad)
                 // linked before we can load it.
                 var linker = innerLoader.CreateLinker();
                 program = linker.LinkObject(platform, addrLoad, RawImage);
+                plt = linker.PltEntries;
             }
-            innerLoader!.Relocate(program, addrLoad!);
+            innerLoader!.Relocate(program, addrLoad!, plt);
             return program;
         }
 

diff --git a/src/ImageLoaders/Elf/ElfLoader.cs b/src/ImageLoaders/Elf/ElfLoader.cs
@@ -456,7 +456,10 @@ public IPlatform LoadPlatform(byte osAbi, IProcessorArchitecture arch)
             return platform;
         }
 
-        public virtual ElfRelocator CreateRelocator(ElfMachine machine, SortedList<Address, ImageSymbol> symbols)
+        public virtual ElfRelocator CreateRelocator(
+            ElfMachine machine,
+            SortedList<Address, ImageSymbol> symbols,
+            Dictionary<ElfSymbol, Address> plt)
         {
             throw new NotSupportedException($"Relocator for architecture {machine} not implemented yet.");
         }
@@ -836,10 +839,10 @@ public string ReadAsciiString(ulong fileOffset)
             return Encoding.ASCII.GetString(bytes, (int) fileOffset, u - (int) fileOffset);
         }
 
-        public void Relocate(Program program, Address addrLoad)
+        public void Relocate(Program program, Address addrLoad, Dictionary<ElfSymbol, Address> plt)
         {
             var symbols = CreateSymbolDictionaries(IsExecutableFile);
-            var relocator = CreateRelocator(this.Machine, symbols);
+            var relocator = CreateRelocator(this.Machine, symbols, plt);
             relocator.Relocate(program);
             relocator.LocateGotPointers(program, symbols);
             symbols = symbols.Values.Select(relocator.AdjustImageSymbol).ToSortedList(s => s.Address!);

diff --git a/src/ImageLoaders/Elf/ElfLoader32.cs b/src/ImageLoaders/Elf/ElfLoader32.cs
@@ -160,7 +160,10 @@ public override ElfObjectLinker CreateLinker()
             return new ElfObjectLinker32(this, Architecture, rawImage);
         }
 
-        public override ElfRelocator CreateRelocator(ElfMachine machine, SortedList<Address, ImageSymbol> imageSymbols)
+        public override ElfRelocator CreateRelocator(
+            ElfMachine machine, 
+            SortedList<Address, ImageSymbol> imageSymbols,
+            Dictionary<ElfSymbol, Address> plt)
         {
             switch (machine)
             {
@@ -191,7 +194,7 @@ public override ElfRelocator CreateRelocator(ElfMachine machine, SortedList<Addr
             case ElfMachine.EM_ALTERA_NIOS2: return new Nios2Relocator(this, imageSymbols);
             case ElfMachine.EM_TC32: return new TC32Relocator(this, imageSymbols);
             }
-            return base.CreateRelocator(machine, imageSymbols);
+            return base.CreateRelocator(machine, imageSymbols, plt);
         }
 
         public ImageSegmentRenderer? CreateRenderer(ElfSection shdr, ElfMachine machine)

diff --git a/src/ImageLoaders/Elf/ElfLoader64.cs b/src/ImageLoaders/Elf/ElfLoader64.cs
@@ -139,12 +139,15 @@ public override ElfObjectLinker CreateLinker()
             }
         }
 
-        public override ElfRelocator CreateRelocator(ElfMachine machine, SortedList<Address, ImageSymbol> symbols)
+        public override ElfRelocator CreateRelocator(
+            ElfMachine machine, 
+            SortedList<Address, ImageSymbol> symbols,
+            Dictionary<ElfSymbol, Address> plt)
         {
             switch (machine)
             {
             case ElfMachine.EM_AARCH64: return new Arm64Relocator(this, symbols);
-            case ElfMachine.EM_X86_64: return new x86_64Relocator(this, symbols);
+            case ElfMachine.EM_X86_64: return new x86_64Relocator(this, symbols, plt);
             case ElfMachine.EM_PPC64: return new PpcRelocator64(this, symbols);
             case ElfMachine.EM_MIPS: return new MipsRelocator64(this, symbols);
             case ElfMachine.EM_RISCV: return new RiscVRelocator64(this, symbols);
@@ -154,7 +157,7 @@ public override ElfRelocator CreateRelocator(ElfMachine machine, SortedList<Addr
             case ElfMachine.EM_SPARCV9: return new Sparc64Relocator(this, symbols);
             case ElfMachine.EM_IA_64: return new Ia64Relocator(this, symbols);
             }
-            return base.CreateRelocator(machine, symbols);
+            return base.CreateRelocator(machine, symbols, plt);
         }
 
         public override void Dump(Address addrLoad, TextWriter writer)

diff --git a/src/ImageLoaders/Elf/ElfObjectLinker.cs b/src/ImageLoaders/Elf/ElfObjectLinker.cs
@@ -39,6 +39,10 @@ public abstract class ElfObjectLinker
         protected readonly IProcessorArchitecture arch;
         private readonly ElfLoader loader;
         protected byte[] rawImage;
+
+        /// <summary>
+        /// Section used to simulate the presence of external functions.
+        /// </summary>
         protected readonly ElfSection rekoExtfn;
         protected readonly List<ElfSymbol> unresolvedSymbols;
 
@@ -58,16 +62,24 @@ public ElfObjectLinker(ElfLoader loader, IProcessorArchitecture arch, byte[] raw
                 Alignment = 0x10,
             };
             this.unresolvedSymbols = new List<ElfSymbol>();
+            this.PltEntries = new Dictionary<ElfSymbol, Address>();
         }
 
+        public Dictionary<ElfSymbol, Address> PltEntries { get; }
+
         public abstract Program LinkObject(IPlatform platform, Address? addrLoad, byte[] rawImage);
 
         protected Address? ComputeBaseAddressFromSections(IEnumerable<ElfSection> sections)
         {
-            return sections.Where(s => s.Address != null && (s.Flags & ElfLoader.SHF_ALLOC) != 0)
+            var address = sections.Where(s => s.Address != null && (s.Flags & ElfLoader.SHF_ALLOC) != 0)
                 .OrderBy(s => s.Address)
                 .Select(s => s.Address)
-                .First();
+                .FirstOrDefault();
+            if (address is null)
+                return loader.CreateAddress(0x1000);
+            if (address.Offset == 0)
+                address += 0x1000;
+            return address;
         }
 
         /// <summary>
@@ -88,6 +100,7 @@ public void LoadExternalProcedures(Dictionary<Address, ExternalProcedure> interc
                 //$TODO: try guessing the signature based on the symbol name.
                 var sig = new FunctionType();
                 interceptedCalls.Add(addr, new ExternalProcedure(sym.Name, sig));
+                PltEntries[sym] = addr;
             }
         }
     }
@@ -105,7 +118,9 @@ protected ElfObjectLinker(TLoader loader, IProcessorArchitecture arch, byte[] im
 
         public override Program LinkObject(IPlatform platform, Address? addrLoad, byte[] rawImage)
         {
-            var addrBase = addrLoad ?? ComputeBaseAddressFromSections(loader.Sections)!;
+            var addrBase = addrLoad is not null && addrLoad.Offset != 0
+                ? addrLoad
+                : ComputeBaseAddressFromSections(loader.Sections)!;
             CollectCommonSymbolsIntoSection();
             CollectUndefinedSymbolsIntoSection();
             var segments = ComputeSegmentSizes();

diff --git a/src/ImageLoaders/Elf/Relocators/ElfRelocator.cs b/src/ImageLoaders/Elf/Relocators/ElfRelocator.cs
@@ -35,7 +35,7 @@ namespace Reko.ImageLoaders.Elf.Relocators
 {
     public abstract class ElfRelocator
     {
-        private readonly SortedList<Address, ImageSymbol> imageSymbols;
+        protected readonly SortedList<Address, ImageSymbol> imageSymbols;
 
         public ElfRelocator(SortedList<Address, ImageSymbol> syms)
         {
@@ -188,7 +188,7 @@ public List<ElfSymbol> RelocateDynamicSymbols(Program program)
                         throw new BadImageFormatException("ELF dynamic segment lacks the size of relocation table entries.");
                     relTable = new RelaTable(this, rela.UValue, relasz.UValue);
                 }
-                else if (rel != null)
+                else if (rel is { })
                 {
                     if (relsz is null)
                         throw new BadImageFormatException("ELF dynamic segment lacks the size of the relocation table.");
@@ -421,12 +421,10 @@ public virtual void LocateGotPointers(Program program, SortedList<Address, Image
     public abstract class ElfRelocator32 : ElfRelocator
     {
         protected ElfLoader32 loader;
-        protected SortedList<Address, ImageSymbol> imageSymbols;
 
         public ElfRelocator32(ElfLoader32 loader, SortedList<Address, ImageSymbol> imageSymbols) : base(imageSymbols)
         {
             this.loader = loader;
-            this.imageSymbols = imageSymbols;
         }
 
         public override ElfLoader Loader => loader;
@@ -534,12 +532,11 @@ protected void DumpRela32(ElfLoader32 loader)
     public abstract class ElfRelocator64 : ElfRelocator
     {
         protected ElfLoader64 loader;
-        protected SortedList<Address, ImageSymbol> imageSymbols;
 
-        public ElfRelocator64(ElfLoader64 loader, SortedList<Address, ImageSymbol> imageSymbols) : base(imageSymbols)
+        public ElfRelocator64(ElfLoader64 loader, SortedList<Address, ImageSymbol> imageSymbols) 
+            : base(imageSymbols)
         {
             this.loader = loader;
-            this.imageSymbols = imageSymbols;
         }
 
         public override ElfLoader Loader => loader;
@@ -565,6 +562,8 @@ public override void Relocate(Program program)
 
             foreach (var relSection in loader.Sections.Where(s => s.Type == SectionHeaderType.SHT_RELA))
             {
+                if (relSection.RelocatedSection?.Address is null)
+                    continue;
                 var symbols = loader.Symbols[relSection.LinkedSection!.FileOffset];
                 var referringSection = relSection.RelocatedSection;
                 var rdr = loader.CreateReader(relSection.FileOffset);

diff --git a/src/ImageLoaders/Elf/Relocators/x86_64Relocator.cs b/src/ImageLoaders/Elf/Relocators/x86_64Relocator.cs
@@ -32,10 +32,15 @@ namespace Reko.ImageLoaders.Elf.Relocators
     public class x86_64Relocator : ElfRelocator64
     {
         private Dictionary<Address, ImportReference>? importReferences;
+        private Dictionary<ElfSymbol, Address> plt;
 
-        public x86_64Relocator(ElfLoader64 loader, SortedList<Address, ImageSymbol> imageSymbols) : base(loader, imageSymbols)
+        public x86_64Relocator(
+            ElfLoader64 loader,
+            SortedList<Address, ImageSymbol> imageSymbols,
+            Dictionary<ElfSymbol, Address> plt) : base(loader, imageSymbols)
         {
             this.loader = loader;
+            this.plt = plt;
         }
 
         /// <remarks>
@@ -83,6 +88,8 @@ private void LoadImportReferencesFromRelaPlt()
 
         public override (Address?, ElfSymbol?) RelocateEntry(Program program, ElfSymbol sym, ElfSection? referringSection, ElfRelocation rela)
         {
+            if (rela.Offset == 0x540)
+                _ = this; //$DEBUG
             var rt = (x86_64Rt)(rela.Info & 0xFF);
             if (loader.Sections.Count <= sym.SectionIndex)
                 return (null, null);
@@ -103,6 +110,8 @@ public override (Address?, ElfSymbol?) RelocateEntry(Program program, ElfSymbol
             if (sym.SectionIndex != 0)
             {
                 var symSection = loader.Sections[(int) sym.SectionIndex];
+                if (symSection.Address is null)
+                    return (null, null);
                 S = (ulong) sym.Value + symSection.Address!.ToLinear();
             }
             long A = 0;
@@ -130,6 +139,20 @@ public override (Address?, ElfSymbol?) RelocateEntry(Program program, ElfSymbol
                 break;
             case x86_64Rt.R_X86_64_COPY:
                 break;
+            case x86_64Rt.R_X86_64_PC32:
+                relW.WriteUInt32(
+                       (uint)(S + (ulong) rela.Addend!.Value - P));
+                return (addr, null);
+            case x86_64Rt.R_X86_64_PLT32:
+                if (!plt.TryGetValue(sym, out var L))
+                {
+                    Debug.Print("ELF external symbol {0} not present in PLT", sym);
+                    return (null, null);
+                }
+                relW.WriteUInt32(
+                       (uint) (L.Offset + (ulong) rela.Addend!.Value - P));
+                return (addr, null);
+
             default:
                 Debug.Print("x86_64 ELF relocation type {0} not implemented yet.",
                     rt);
@@ -138,7 +161,7 @@ public override (Address?, ElfSymbol?) RelocateEntry(Program program, ElfSymbol
                 //    "x86_64 ELF relocation type {0} not implemented yet.",
                 //    rt));
             }
-            if (relR != null)
+            if (relR is not null)
             {
                 var w = relR.ReadUInt64();
                 w += ((ulong)(S + (ulong)A + P) >> sh) & mask;

diff --git a/src/UnitTests/Arch/Avr/Avr32RewriterTests.cs b/src/UnitTests/Arch/Avr/Avr32RewriterTests.cs
@@ -585,7 +585,7 @@ public void Avr32Rw_muls_d()
             Given_HexString("F6080444");
             AssertCode(     // muls.d	r4,r11,r8
                 "0|L--|00100000(4): 1 instructions",
-                "1|L--|r5_r4 = r11 *s r8");
+                "1|L--|r5_r4 = r11 *s64 r8");
         }
 
         [Test]
@@ -605,7 +605,7 @@ public void Avr32Rw_mulu_d()
             Given_HexString("F6080644");
             AssertCode(     // mulu.d	r4,r11,r8
                 "0|L--|00100000(4): 1 instructions",
-                "1|L--|r5_r4 = r11 *u r8");
+                "1|L--|r5_r4 = r11 *u64 r8");
         }
 
         [Test]

diff --git a/subjects/regression.log b/subjects/regression.log