feat(elfpatcher): add dt_runpath libs/ support with configurable --rpath flag

README.md

@@ -4,8 +4,7 @@ Converter for native execution of PlayStation 5 ELF binaries on Linux through bi
 
 ## Status
 
-Output ELF is accepted by the Linux kernel and handed to ld.so. Crashes during ld.so startup:
-e_entry contains a file offset instead of a virtual address, causing an invalid jump at loader handoff.
+Loader startup works: execution reaches `_start` and runs normally up to the first call into an external library function (from test `.prx` stubs).
 
 ## Disclaimer
 

core/elfpatcher/include/elfpatcher/general/ElfConstants.hpp

@@ -87,6 +87,7 @@ inline constexpr std::int64_t DT_STRSZ = 10;
 inline constexpr std::int64_t DT_SYMENT = 11;
 inline constexpr std::int64_t DT_PLTREL = 20;
 inline constexpr std::int64_t DT_JMPREL = 23;
+inline constexpr std::int64_t DT_RUNPATH = 29;
 
 inline constexpr std::uint32_t SHT_NULL = 0;
 inline constexpr std::uint32_t SHT_PROGBITS = 1;

core/elfpatcher/include/elfpatcher/general/IElfPatcher.hpp

@@ -3,6 +3,7 @@
 
 #include <domain/Types.hpp>
 #include <cstdint>
+#include <string>
 #include <vector>
 
 namespace Elfpatcher {
@@ -15,7 +16,8 @@ public:
         const std::vector<std::uint8_t>& sourceElf,
         const std::vector<Domain::ProgramHeader>& originalHeaders,
         const Domain::SysVDynamicSection& dynamicSection,
-        std::uint64_t originalPltGotVaddr
+        std::uint64_t originalPltGotVaddr,
+        const std::string& runPath
     ) = 0;
 };
 

core/elfpatcher/include/elfpatcher/linux/LinuxElfPatcher.hpp

@@ -7,6 +7,7 @@
 #include <elfpatcher/general/ISectionHeaderTableBuilder.hpp>
 #include <io/IByteWriter.hpp>
 #include <memory>
+#include <string>
 
 namespace Elfpatcher::Linux {
 
@@ -23,7 +24,8 @@ public:
         const std::vector<std::uint8_t>& sourceElf,
         const std::vector<Domain::ProgramHeader>& originalHeaders,
         const Domain::SysVDynamicSection& dynamicSection,
-        std::uint64_t originalPltGotVaddr
+        std::uint64_t originalPltGotVaddr,
+        const std::string& runPath
     ) override;
 
 private:

core/elfpatcher/include/elfpatcher/windows/WindowsElfPatcher.hpp

@@ -7,6 +7,7 @@
 #include <elfpatcher/general/ISectionHeaderTableBuilder.hpp>
 #include <io/IByteWriter.hpp>
 #include <memory>
+#include <string>
 
 namespace Elfpatcher::Windows {
 
@@ -23,7 +24,8 @@ public:
         const std::vector<std::uint8_t>& sourceElf,
         const std::vector<Domain::ProgramHeader>& originalHeaders,
         const Domain::SysVDynamicSection& dynamicSection,
-        std::uint64_t originalPltGotVaddr
+        std::uint64_t originalPltGotVaddr,
+        const std::string& runPath
     ) override;
 
 private:

core/elfpatcher/src/linux/LinuxElfPatcher.cpp

@@ -2,6 +2,7 @@
 #include <elfpatcher/general/ElfConstants.hpp>
 #include <elfpatcher/general/ProgramHeaderLayoutRequest.hpp>
 #include <elfpatcher/general/SectionHeaderTableRequest.hpp>
+#include <string>
 
 namespace Elfpatcher::Linux {
 
@@ -27,7 +28,8 @@ std::vector<std::uint8_t> LinuxElfPatcher::Patch(
     const std::vector<std::uint8_t>& sourceElf,
     const std::vector<Domain::ProgramHeader>& originalHeaders,
     const Domain::SysVDynamicSection& dynSection,
-    const std::uint64_t originalPltGotVaddr)
+    const std::uint64_t originalPltGotVaddr,
+    const std::string& runPath)
 {
     std::vector<std::uint8_t> buf = sourceElf;
 
@@ -51,6 +53,10 @@ std::vector<std::uint8_t> LinuxElfPatcher::Patch(
     const auto dynStrOff = static_cast<std::uint64_t>(buf.size());
     for (std::uint8_t b : dynSection.DynStrData)
         buf.push_back(b);
+    const std::uint64_t runPathStrOff = static_cast<std::uint64_t>(buf.size()) - dynStrOff;
+    for (char c : runPath)
+        buf.push_back(static_cast<std::uint8_t>(c));
+    buf.push_back(0);
     alignBuf(buf, kDynStrAlignment);
 
     const auto dynSymOff = static_cast<std::uint64_t>(buf.size());
@@ -95,6 +101,7 @@ std::vector<std::uint8_t> LinuxElfPatcher::Patch(
         _appendDynEntry(dynSegBuf, DT_PLTREL, static_cast<std::uint64_t>(DT_RELA));
         _appendDynEntry(dynSegBuf, DT_PLTGOT, originalPltGotVaddr);
     }
+    _appendDynEntry(dynSegBuf, DT_RUNPATH, runPathStrOff);
     _appendDynEntry(dynSegBuf, DT_NULL, 0);
 
     const auto dynSegOff = static_cast<std::uint64_t>(buf.size());

core/elfpatcher/src/windows/WindowsElfPatcher.cpp

@@ -20,7 +20,8 @@ std::vector<std::uint8_t> WindowsElfPatcher::Patch(
     const std::vector<std::uint8_t>& sourceElf,
     const std::vector<Domain::ProgramHeader>& originalHeaders,
     const Domain::SysVDynamicSection& dynamicSection,
-    std::uint64_t originalPltGotVaddr)
+    std::uint64_t originalPltGotVaddr,
+    const std::string& runPath)
 {
     throw Domain::RelinkerException("Not implemented");
 }

core/main.cpp

@@ -15,6 +15,7 @@
 #include <relinker/output/CallRegistryWriter.hpp>
 #include <relinker/pipeline/RelinkerPipeline.hpp>
 #include <codegen/IAmd64OnlyConverter.hpp>
+#include <filesystem>
 #include <iostream>
 #include <memory>
 #include <string>
@@ -26,6 +27,7 @@ int main(const int argc, char* argv[]) {
     std::string inputPath;
     std::string outputElfPath;
     std::optional<std::string> registryPath;
+    std::string runPath = "$ORIGIN/libs";
 
     for (int i = 1; i < argc; ++i) {
         const std::string arg = argv[i];
@@ -33,6 +35,12 @@ int main(const int argc, char* argv[]) {
             skipSyscallCheck = true;
         } else if (arg == "--to-intel") {
             toIntel = true;
+        } else if (arg == "--rpath") {
+            if (i + 1 >= argc) {
+                std::cerr << "FAIL: --rpath requires a value\n";
+                return 1;
+            }
+            runPath = argv[++i];
         } else if (inputPath.empty()) {
             inputPath = arg;
         } else if (outputElfPath.empty()) {
@@ -43,10 +51,17 @@ int main(const int argc, char* argv[]) {
     }
 
     if (inputPath.empty() || outputElfPath.empty()) {
-        std::cerr << "Usage: relinker [--skip-syscall-check] [--to-intel] <input.elf> <output.elf> [output_registry.json]\n";
+        std::cerr << "Usage: relinker [--skip-syscall-check] [--to-intel] [--rpath <path>] <input.elf> <output.elf> [output_registry.json]\n";
         return 1;
     }
 
+    const std::filesystem::path outputElfFsPath(outputElfPath);
+    const std::filesystem::path outputDir = outputElfFsPath.parent_path() / (outputElfFsPath.stem().string() + "_out");
+    std::filesystem::create_directories(outputDir);
+    outputElfPath = (outputDir / outputElfFsPath.filename()).string();
+    if (registryPath.has_value())
+        registryPath = (outputDir / std::filesystem::path(*registryPath).filename()).string();
+
     try {
         Io::FileReader fileReader;
         Io::FileWriter fileWriter;
@@ -93,7 +108,7 @@ int main(const int argc, char* argv[]) {
             std::make_shared<Elfpatcher::SectionHeaderTableBuilder>(byteWriter),
             byteWriter
         );
-        auto patchedElf = elfPatcher.Patch(sourceBytes, result.OriginalHeaders, result.DynamicSection, result.OriginalPltGotVaddr);
+        auto patchedElf = elfPatcher.Patch(sourceBytes, result.OriginalHeaders, result.DynamicSection, result.OriginalPltGotVaddr, runPath);
         fileWriter.Write(outputElfPath, patchedElf);
 
     } catch (const Domain::RelinkerException& e) {