kernel: implement syscall 0x83 FindAddress + unit tests (#93)

ps2xRuntime/src/lib/ps2_syscalls.cpp

@@ -286,6 +286,9 @@ namespace ps2_syscalls
         case static_cast<uint32_t>(-0x78):
             ps2_stubs::sceSifSetDChain(rdram, ctx, runtime);
             return true;
+        case 0x83:
+            FindAddress(rdram, ctx, runtime);
+            return true;
         case 0x85:
             SetMemoryMode(rdram, ctx, runtime);
             return true;

ps2xRuntime/src/lib/syscalls/ps2_syscalls_system.inl

@@ -355,6 +355,59 @@ void GetMemorySize(uint8_t *rdram, R5900Context *ctx, PS2Runtime *runtime)
     setReturnU32(ctx, PS2_RAM_SIZE);
 }
 
+static inline uint32_t normalizeKernelAlias(uint32_t addr)
+{
+    if (addr >= 0x80000000u && addr < 0xC0000000u)
+    {
+        return addr & 0x1FFFFFFFu;
+    }
+    return addr;
+}
+
+// 0x83 FindAddress:
+// - a0: table start (inclusive)
+// - a1: table end (exclusive)
+// - a2: target address to locate inside the table (word entries)
+// Returns the guest address of the matching word entry, or 0 if not found.
+void FindAddress(uint8_t *rdram, R5900Context *ctx, PS2Runtime *runtime)
+{
+    (void)runtime;
+
+    uint32_t start = getRegU32(ctx, 4);
+    uint32_t end = getRegU32(ctx, 5);
+    const uint32_t target = getRegU32(ctx, 6);
+    const uint32_t targetNorm = normalizeKernelAlias(target);
+
+    // Word-scan semantics: align the search window to uint32 boundaries.
+    start = (start + 3u) & ~0x3u;
+    end &= ~0x3u;
+
+    if (start >= end)
+    {
+        setReturnU32(ctx, 0u);
+        return;
+    }
+
+    for (uint32_t addr = start; addr < end; addr += sizeof(uint32_t))
+    {
+        const uint8_t *entryPtr = getConstMemPtr(rdram, addr);
+        if (!entryPtr)
+        {
+            break;
+        }
+
+        uint32_t entry = 0;
+        std::memcpy(&entry, entryPtr, sizeof(entry));
+        if (entry == target || normalizeKernelAlias(entry) == targetNorm)
+        {
+            setReturnU32(ctx, addr);
+            return;
+        }
+    }
+
+    setReturnU32(ctx, 0u);
+}
+
 void Deci2Call(uint8_t *rdram, R5900Context *ctx, PS2Runtime *runtime)
 {
     (void)rdram;

ps2xTest/src/ps2_runtime_kernel_tests.cpp

@@ -386,5 +386,72 @@ void register_ps2_runtime_kernel_tests()
             const uint32_t setupSp = static_cast<uint32_t>(getRegS32(env.ctx, 2));
             t.Equals(setupSp & 0xFu, 0u, "SetupThread should always return a 16-byte aligned stack pointer");
         });
+
+        tc.Run("numeric syscall 0x83 finds matching table entry", [](TestCase &t)
+        {
+            TestEnv env;
+            constexpr uint32_t kTableBase = 0x00002000u;
+            constexpr uint32_t kValues[] = {
+                0x11111111u,
+                0x11223344u,
+                0x55555555u,
+                0x89ABCDEFu
+            };
+
+            writeGuestWords(env.rdram.data(), kTableBase, kValues, std::size(kValues));
+            setRegU32(env.ctx, 4, kTableBase);
+            setRegU32(env.ctx, 5, kTableBase + static_cast<uint32_t>(sizeof(kValues)));
+            setRegU32(env.ctx, 6, 0x11223344u);
+
+            t.IsTrue(callSyscall(0x83u, env.rdram.data(), &env.ctx, &env.runtime),
+                     "syscall 0x83 should dispatch");
+            t.Equals(static_cast<uint32_t>(getRegS32(env.ctx, 2)),
+                     kTableBase + 4u,
+                     "FindAddress should return address of first matching word");
+        });
+
+        tc.Run("numeric syscall 0x83 supports KSEG aliases", [](TestCase &t)
+        {
+            TestEnv env;
+            constexpr uint32_t kTableBasePhys = 0x00003000u;
+            constexpr uint32_t kTableBaseKseg = 0x80003000u;
+            constexpr uint32_t kValues[] = {
+                0x00123456u,
+                0x8000AAAAu
+            };
+
+            writeGuestWords(env.rdram.data(), kTableBasePhys, kValues, std::size(kValues));
+            setRegU32(env.ctx, 4, kTableBaseKseg);
+            setRegU32(env.ctx, 5, kTableBaseKseg + static_cast<uint32_t>(sizeof(kValues)));
+            setRegU32(env.ctx, 6, 0x80123456u); // Alias of first table value
+
+            t.IsTrue(callSyscall(0x83u, env.rdram.data(), &env.ctx, &env.runtime),
+                     "syscall 0x83 should dispatch");
+            t.Equals(static_cast<uint32_t>(getRegS32(env.ctx, 2)),
+                     kTableBaseKseg,
+                     "FindAddress should match KSEG aliases and preserve guest segment in return value");
+        });
+
+        tc.Run("numeric syscall 0x83 returns 0 when entry is absent", [](TestCase &t)
+        {
+            TestEnv env;
+            constexpr uint32_t kTableBase = 0x00004000u;
+            constexpr uint32_t kValues[] = {
+                0x00000001u,
+                0x00000002u,
+                0x00000003u
+            };
+
+            writeGuestWords(env.rdram.data(), kTableBase, kValues, std::size(kValues));
+            setRegU32(env.ctx, 4, kTableBase);
+            setRegU32(env.ctx, 5, kTableBase + static_cast<uint32_t>(sizeof(kValues)));
+            setRegU32(env.ctx, 6, 0xDEADBEEFu);
+
+            t.IsTrue(callSyscall(0x83u, env.rdram.data(), &env.ctx, &env.runtime),
+                     "syscall 0x83 should dispatch");
+            t.Equals(static_cast<uint32_t>(getRegS32(env.ctx, 2)),
+                     0u,
+                     "FindAddress should return 0 when no matching word exists");
+        });
     });
 }