fix(relinker): hand the guest the real argv on Linux

The Linux entry stub built a copy of the entry parameter block holding
argc and a pointer to the host argv array, so the guest read that pointer
as argv[0] and uninitialised stack as argv[1..]. The process stack at
entry already has the guest's layout (argc as a qword, then the argv
pointers and a null), so pass rsp itself.

Test: linux_entry_argv relinks a fixture whose entry checks argc and
argv and runs the output on Linux x86-64.

core/relinker/CMakeLists.txt

@@ -180,6 +180,8 @@ if(BUILD_TESTING)
             ${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_tls_function_coverage.py $<TARGET_FILE:relinker>)
         add_test(NAME linux_load_alignment COMMAND ${Python3_EXECUTABLE}
             ${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_linux_load_alignment.py $<TARGET_FILE:relinker>)
+        add_test(NAME linux_entry_argv COMMAND ${Python3_EXECUTABLE}
+            ${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_linux_entry_argv.py $<TARGET_FILE:relinker>)
         add_test(NAME windows_gui COMMAND ${Python3_EXECUTABLE}
             ${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_windows_gui.py $<TARGET_FILE:relinker>)
         add_test(NAME guest_intel_trampolines COMMAND ${Python3_EXECUTABLE}

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

@@ -115,12 +115,7 @@ inline constexpr std::uint32_t kDynSymInfoFirstGlobal = 1;
 inline constexpr std::uint64_t kDynSymAlign = 8;
 inline constexpr std::uint32_t kDynamicLinkToStrTab = 2;
 
-inline constexpr std::uint8_t kStubOpPopRax = 0x58;
-inline constexpr std::uint8_t kStubOpMovRbxRsp[] = {0x48, 0x89, 0xe3};
-inline constexpr std::uint8_t kStubOpSubRsp0x30[] = {0x48, 0x83, 0xec, 0x30};
 inline constexpr std::uint8_t kStubOpAndRsp0xf0[] = {0x48, 0x83, 0xe4, 0xf0};
-inline constexpr std::uint8_t kStubOpMovDwordPtrRsp[] = {0x89, 0x04, 0x24};
-inline constexpr std::uint8_t kStubOpMovQwordPtrRsp8Rbx[] = {0x48, 0x89, 0x5c, 0x24, 0x08};
 inline constexpr std::uint8_t kStubOpMovRdiRsp[] = {0x48, 0x89, 0xe7};
 inline constexpr std::uint8_t kStubOpXorRsiRsi[] = {0x48, 0x31, 0xf6};
 inline constexpr std::uint8_t kStubOpCallRel32 = 0xe8;

core/relinker/elfpatcher/src/general/EntryStubBuilder.cpp

@@ -15,13 +15,8 @@ std::vector<std::uint8_t> EntryStubBuilder::BuildEntryStub(
     const std::uint64_t realEntryVaddr
 ) const {
     std::vector<std::uint8_t> s;
-    s.push_back(kStubOpPopRax);
-    _appendBytes(s, kStubOpMovRbxRsp, sizeof(kStubOpMovRbxRsp));
-    _appendBytes(s, kStubOpSubRsp0x30, sizeof(kStubOpSubRsp0x30));
-    _appendBytes(s, kStubOpAndRsp0xf0, sizeof(kStubOpAndRsp0xf0));
-    _appendBytes(s, kStubOpMovDwordPtrRsp, sizeof(kStubOpMovDwordPtrRsp));
-    _appendBytes(s, kStubOpMovQwordPtrRsp8Rbx, sizeof(kStubOpMovQwordPtrRsp8Rbx));
     _appendBytes(s, kStubOpMovRdiRsp, sizeof(kStubOpMovRdiRsp));
+    _appendBytes(s, kStubOpAndRsp0xf0, sizeof(kStubOpAndRsp0xf0));
     _appendBytes(s, kStubOpXorRsiRsi, sizeof(kStubOpXorRsiRsi));
     const std::uint64_t callInsnVaddr = stubVaddr + s.size();
     const std::uint64_t callNextVaddr = callInsnVaddr + kStubCallInstructionSize;

core/relinker/relinker/tests/test_linux_entry_argv.py

@@ -0,0 +1,50 @@
+"""Check that a Linux relink hands the guest entry the process argc and inline argv array."""
+
+from pathlib import Path
+import platform
+import signal
+import struct
+import subprocess
+import sys
+import tempfile
+
+from test_linux_load_alignment import fixture
+
+ENTRY = 0x10
+ARGV_CHECK = bytes.fromhex(
+    "833f02" "751e"
+    "48837f0800" "7417"
+    "488b4710"
+    "80385a" "750e"
+    "80780100" "7508"
+    "48837f1800" "7501"
+    "cc"
+    "0f0b")
+
+
+def argv_fixture():
+    image = fixture()
+    struct.pack_into("<Q", image, 24, ENTRY)
+    image[0x4000 + ENTRY:0x4000 + ENTRY + len(ARGV_CHECK)] = ARGV_CHECK
+    return image
+
+
+def main():
+    relinker = Path(sys.argv[1]).resolve()
+    with tempfile.TemporaryDirectory(prefix="anyps5-argv-") as directory:
+        source = Path(directory) / "input.elf"
+        output = Path(directory) / "output.elf"
+        source.write_bytes(argv_fixture())
+        result = subprocess.run([str(relinker), "--skip-sce-module", str(source), str(output)],
+                                capture_output=True, text=True, timeout=20)
+        assert result.returncode == 0, (result.stdout, result.stderr)
+        if sys.platform.startswith("linux") and platform.machine() in ("x86_64", "AMD64"):
+            output.chmod(0o755)
+            for arguments, expected in ((["Z"], -signal.SIGTRAP), (["Z", "extra"], -signal.SIGILL)):
+                executed = subprocess.run([str(output), *arguments], capture_output=True, timeout=20)
+                assert executed.returncode == expected, (arguments, executed.returncode)
+    print("Linux entry argv test passed")
+
+
+if __name__ == "__main__":
+    main()