Decompiles Overlay_DoRelocation (#149)

* decompile Overlay_DoRelocation * add non-matching comments
2024-11-29 03:34:07 +00:00 · 2020-05-20 07:53:42 -05:00 · 2020-05-20 07:53:42 -05:00 · 9a478a96ec
commit 9a478a96ec
parent 43dfaa7518
2 changed files with 129 additions and 3 deletions
--- a/src/code/relocation.c
+++ b/src/code/relocation.c
@ -1,3 +1,129 @@
 #include <global.h>

+#ifdef NON_MATCHING
+void Overlay_DoRelocation(void* allocatedVRamAddress, OverlayRelocationSection* overlayInfo, void* vRamAddress) {
+    // mostly regalloc, more specific issues described below.
+    u32 sections[4];
+    u32 unrelocatedAddress;
+    u32 dbg;
+    u32 relocatedValue;
+    u32 relocOffset;
+    u32 relocatedAddress;
+    u32 i;
+    u32* relocDataP;
+    u32* luiRefs[32];
+    u32 luiVals[32];
+    u32 relocData;
+    u32 reloc;
+    u32 vaddr;
+    u32* luiInstRef;
+    u32 addrToLoad;
+    u32 luiInst;
+    u32* regValP;
+    u32 isLoNeg;
+
+    relocOffset = 0;
+    relocatedValue = 0;
+    unrelocatedAddress = 0;
+    relocatedAddress = 0;
+
+    if (gOverlayLogSeverity >= 3) {
+        osSyncPrintf("DoRelocation(%08x, %08x, %08x)\n", allocatedVRamAddress, overlayInfo, vRamAddress);
+        osSyncPrintf("text=%08x, data=%08x, rodata=%08x, bss=%08x\n", overlayInfo->textSize, overlayInfo->dataSize,
+                     overlayInfo->rodataSize, overlayInfo->bssSize);
+    }
+
+    sections[0] = 0;
+    sections[1] = (u32)allocatedVRamAddress;
+    sections[2] = sections[1] + overlayInfo->textSize;
+    sections[3] = sections[2] + overlayInfo->dataSize;
+
+    for (i = 0; i < overlayInfo->nRelocations; i++) {
+        reloc = overlayInfo->relocations[i];
+        relocDataP = (u32*)(sections[reloc >> 0x1E] + (reloc & 0xFFFFFF));
+        relocData = *relocDataP;
+        switch (reloc & 0x3F000000) {
+            case 0x2000000:
+                /* R_MIPS_32
+                 * handles 32-bit address relocation.  Used in things such as
+                 * jump tables.
+                 */
+                if ((*relocDataP & 0xF000000) == 0) {
+                    relocOffset = *relocDataP - (u32)vRamAddress;
+                    relocatedAddress = relocOffset + (u32)allocatedVRamAddress;
+                    relocatedValue = relocatedAddress;
+                    unrelocatedAddress = relocData;
+                    *relocDataP = relocatedAddress;
+                }
+                break;
+            case 0x4000000:
+                /* R_MIPS_26
+                 * handles 26-bit address relocation, used for jumps and jals
+                 */
+                unrelocatedAddress = ((*relocDataP & 0x3FFFFFF) << 2) | 0x80000000;
+                relocOffset = unrelocatedAddress - (u32)vRamAddress;
+                relocatedValue =
+                    (*relocDataP & 0xFC000000) | ((((u32)allocatedVRamAddress + relocOffset) & 0xFFFFFFF) >> 2);
+                relocatedAddress = ((relocatedValue & 0x3FFFFFF) << 4) | 0x80000000;
+                *relocDataP = relocatedValue;
+                break;
+            case 0x5000000:
+                /* R_MIPS_HI16
+                 * Handles relocation for a lui instruciton, we just store the reference to
+                 * the instruction, and will update it in the R_MIPS_LO16 section.
+                 */
+                luiRefs[(*relocDataP >> 0x10) & 0x1F] = relocDataP;
+                luiVals[(*relocDataP >> 0x10) & 0x1F] = *relocDataP;
+                break;
+            case 0x6000000:
+                /* R_MIPS_LO16
+                 * here we will update the LUI instruction to reflect the relocated address.
+                 * The full address is calculated from the LUI and lo parts, and then updated.
+                 * if the lo part is negative, we make sure to add 1 to the lui.
+                 */
+                regValP = &luiVals[((*relocDataP >> 0x15) & 0x1F)];
+                vaddr = (*regValP << 0x10) + (s16)*relocDataP;
+                luiInstRef = luiRefs[((*relocDataP >> 0x15) & 0x1F)];
+                if ((vaddr & 0xF000000) == 0) {
+                    relocOffset = vaddr - (u32)vRamAddress;
+                    addrToLoad = relocOffset + (u32)allocatedVRamAddress;
+                    isLoNeg = ((addrToLoad & 0x8000) ? 1 : 0);
+                    luiInst = *luiInstRef;
+                    *luiInstRef = (luiInst & 0xFFFF0000) | (((addrToLoad >> 0x10) & 0xFFFF) + isLoNeg);
+                    unrelocatedAddress = (luiInst << 0x10) + (((s16)relocData) & (0xFFFFFFFFFFFFFFFFu));
+                    relocatedValue = (*relocDataP & 0xFFFF0000) | (addrToLoad & 0xFFFF);
+
+                    // The conversion of relocatedAddress to s16 is wrapped around the OR operation of
+                    // relocated value
+                    relocatedAddress = (*luiInstRef << 0x10) + (s16)relocatedValue;
+                    *relocDataP = relocatedValue;
+                }
+                break;
+        }
+
+        if (1) {
+            dbg = 0x10;
+            switch (reloc & 0x3F000000) {
+                case 0x2000000:
+                    dbg = 0x16;
+                case 0x4000000:
+                    dbg += 0xA;
+                case 0x6000000:
+                    if (gOverlayLogSeverity >= 3) {
+                        osSyncPrintf("%02d %08x %08x %08x ", dbg, relocDataP, relocatedValue, relocatedAddress);
+                        osSyncPrintf(" %08x %08x %08x %08x\n",
+                                     ((u32)relocDataP + (u32)vRamAddress) - (u32)allocatedVRamAddress, relocData,
+                                     unrelocatedAddress, relocOffset);
+                    }
+                    break;
+                default:
+                    continue;
+            }
+        }
+        // The loop seems to be incremented, then checked, but the conditional is a likely vs non, so it could
+        // potentially resolve itself.
+    }
+}
+#else
 #pragma GLOBAL_ASM("asm/non_matchings/code/relocation/Overlay_DoRelocation.s")
+#endif