Port 59NL server patches to 59NJ (pt. 1)

system/client-functions/System/GetEnemyEntity-59NJ.x86.inc.s

@@ -0,0 +1,44 @@
+# (uint16_t entity_id @ eax) -> TObjectV00b421c0* @ eax
+# Preserves all registers except eax
+get_enemy_entity:
+  push      esi
+  push      edi
+  push      edx
+  push      ecx
+  xor       edx, edx
+  xchg      edx, eax
+  cmp       edx, 0x1000
+  jl        done
+  cmp       edx, 0x4000
+  jge       done
+
+  mov       esi, [0x00AABCE8]  # bs_low = next_player_entity_index
+  mov       edi, [0x00AABCE4]
+  lea       edi, [edi + esi - 1]  # bs_high = next_player_entity_index + next_enemy_entity_index - 1
+bs_again:
+  cmp       esi, edi
+  jge       bs_done
+  lea       ecx, [esi + edi]
+  shr       ecx, 1
+  mov       eax, [ecx * 4 + 0x00AAB2A0]  # all_entities[ecx]
+  cmp       [eax + 0x1C], dx
+  jge       bs_not_less
+  lea       esi, [ecx + 1]
+  jmp       bs_again
+bs_not_less:
+  mov       edi, ecx
+  jmp       bs_again
+bs_done:
+
+  mov       eax, [esi * 4 + 0x00AAB2A0]  # all_entities[bs_low]
+  test      eax, eax
+  je        done
+  xor       ecx, ecx
+  cmp       [eax + 0x1C], dx
+  cmovne    eax, ecx
+
+done:
+  pop       ecx
+  pop       edx
+  pop       edi
+  pop       esi

system/client-functions/System/WriteAddressOfCode-59NJ.x86.inc.s

@@ -0,0 +1,42 @@
+# This file defines the following function:
+#   write_address_of_code(
+#     const void* patch_code,
+#     size_t patch_code_size,
+#     void** ptr_addr);
+# This function allocates memory for patch_code, copies patch_code to that
+# memory, then writes the address of the allocated code at the specified
+# pointer. The allocated memory is never freed.
+# This function pops its arguments off the stack before returning.
+
+write_call_to_code:
+  # [esp + 0x04] = code ptr
+  # [esp + 0x08] = code size
+  # [esp + 0x0C] = ptr addr
+
+  # Allocate memory for the copied code
+  mov       ecx, [0x00AA8F84]
+  push      dword [esp + 0x08]
+  mov       eax, 0x007A984C
+  call      eax  # malloc7
+  test      eax, eax
+  je        done
+
+  # Copy the code to the newly-allocated memory
+  # eax = dest pointer (from malloc7 call above)
+  mov       edx, [esp + 0x04]  # edx = source pointer
+  mov       ecx, [esp + 0x08]  # ecx = source size
+  push      ebx
+memcpy_again:
+  dec       ecx
+  mov       bl, [edx + ecx]  # Copy one byte from source to dest
+  mov       [eax + ecx], bl
+  test      ecx, ecx
+  jne       memcpy_again
+  pop       ebx
+
+  # Write the address
+  mov       ecx, [esp + 0x0C]
+  mov       [ecx], eax
+
+done:
+  ret       0x0C

system/client-functions/System/WriteCallToCode-59NJ.x86.inc.s

@@ -0,0 +1,76 @@
+# This file defines the following function:
+#   write_call_to_code(
+#     const void* patch_code,
+#     size_t patch_code_size,
+#     void* call_opcode_address,
+#     ssize_t call_opcode_bytes);
+# This function allocates memory for patch_code, copies patch_code to that
+# memory, then writes a call or jmp opcode to call_opcode_address that calls
+# the code in the allocated memory region. The allocated memory is never freed.
+# call_opcode_bytes specifies how many bytes at the callsite should be
+# overwritten. This value must be at least 5; the first 5 bytes are overwritten
+# with the call/jmp opcode itself; the rest are overwritten with nop opcodes.
+# If call_opcode_bytes is positive, a call opcode is written; if it's negative,
+# a jmp opcode is written.
+# This function pops its arguments off the stack before returning.
+
+write_call_to_code:
+  # [esp + 0x04] = code ptr
+  # [esp + 0x08] = code size
+  # [esp + 0x0C] = jump callsite
+  # [esp + 0x10] = callsite size (if zero, write the address instead of a call)
+
+  # Allocate memory for the copied code
+  mov       ecx, [0x00AA8F84]
+  push      dword [esp + 0x08]
+  mov       eax, 0x007A984C
+  call      eax  # malloc7
+  test      eax, eax
+  je        done
+
+  # Copy the code to the newly-allocated memory
+  # eax = dest pointer (from malloc7 call above)
+  mov       edx, [esp + 0x04]  # edx = source pointer
+  mov       ecx, [esp + 0x08]  # ecx = source size
+  push      ebx
+memcpy_again:
+  dec       ecx
+  mov       bl, [edx + ecx]  # Copy one byte from source to dest
+  mov       [eax + ecx], bl
+  test      ecx, ecx
+  jne       memcpy_again
+  pop       ebx
+
+  mov       edx, [esp + 0x0C]  # edx = jump callsite
+
+  # If the callsite size is zero, just write the address directly
+  cmp       dword [esp + 0x10], 0
+  jne       write_call_or_jmp
+  mov       [edx], eax
+  jmp       done
+
+  # Write the call or jmp opcode
+write_call_or_jmp:
+  lea       ecx, [eax - 5]
+  sub       ecx, edx  # ecx = (dest code addr) - (jump callsite) - 5
+  cmp       dword [esp + 0x10], 0
+  setl      al
+  or        al, 0xE8
+  mov       [edx], al  # Write E8 (call), or E9 (jmp) if size was negative
+  mov       [edx + 1], ecx  # Write delta
+
+  # Write as many nops after the call opcode as necessary
+  mov       ecx, 5
+  mov       eax, [esp + 0x10]
+  cmp       eax, 0
+  jge       write_nop_again
+  neg       eax
+write_nop_again:
+  cmp       ecx, eax
+  jge       done
+  mov       byte [edx + ecx], 0x90
+  inc       ecx
+  jmp       write_nop_again
+
+done:
+  ret       0x10

system/client-functions/System/WriteCallToCodeMulti-59NJ.x86.inc.s

@@ -0,0 +1,83 @@
+# This file defines the following function:
+#   void [/std] write_call_to_code(
+#     const void* patch_code @ [esp + 0x04],
+#     size_t patch_code_size @ [esp + 0x08],
+#     size_t call_count @ [esp + 0x0C],
+#     void* call_opcode_address @ [esp + 0x10],
+#     ssize_t call_opcode_bytes @ [esp + 0x14],
+#     ...);
+# This function allocates memory for patch_code, copies patch_code to that
+# memory, then writes a call or jmp opcode to call_opcode_address that calls
+# the code in the allocated memory region. The allocated memory is never freed.
+# call_opcode_bytes specifies how many bytes at the callsite should be
+# overwritten. This value must be at least 5; the first 5 bytes are overwritten
+# with the call/jmp opcode itself; the rest are overwritten with nop opcodes.
+# This function pops its arguments off the stack before returning (including
+# all the varargs).
+
+write_call_to_code:
+  # [esp + 0x04] = code ptr
+  # [esp + 0x08] = code size
+  # [esp + 0x0C] = callsite count
+  # [esp + 0x10] = callsite address
+  # [esp + 0x14] = callsite size
+  # ... (further callsite address/size pairs)
+
+  # Allocate memory for the copied code
+  mov       ecx, [0x00AA8F84]
+  push      dword [esp + 0x08]
+  mov       eax, 0x007A984C
+  call      eax  # malloc7
+  test      eax, eax
+  je        done
+
+  # Copy the code to the newly-allocated memory
+  # eax = dest pointer (from malloc7 call above)
+  mov       edx, [esp + 0x04]  # edx = source pointer
+  mov       ecx, [esp + 0x08]  # ecx = source size
+  push      ebx
+memcpy_again:
+  dec       ecx
+  mov       bl, [edx + ecx]  # Copy one byte from source to dest
+  mov       [eax + ecx], bl
+  test      ecx, ecx
+  jne       memcpy_again
+  pop       ebx
+
+  # Write the call opcodes
+  xchg      ebx, [esp + 0x0C]  # Save ebx; get callsite count
+  mov       [esp - 0x08], esi
+  mov       [esp - 0x0C], eax
+  mov       esi, 0x10  # Stack offset of first callsite pair
+
+next_callsite:
+  mov       edx, [esp + esi]  # edx = jump callsite
+  lea       ecx, [eax - 5]
+  sub       ecx, edx  # ecx = (dest code addr) - (jump callsite) - 5
+  mov       byte [edx], 0xE8
+  mov       [edx + 1], ecx  # Write E8 (call) followed by delta
+
+  # Write as many nops after the call opcode as necessary
+  mov       ecx, 5
+  mov       eax, [esp + esi + 4]
+write_nop_again:
+  cmp       ecx, eax
+  jge       this_callsite_done
+  mov       byte [edx + ecx], 0x90
+  inc       ecx
+  jmp       write_nop_again
+
+this_callsite_done:
+  mov       eax, [esp - 0x0C]
+  add       esi, 8
+  dec       ebx
+  jnz       next_callsite
+
+  mov       ecx, esi
+  mov       ebx, [esp + 0x0C]
+  mov       esi, [esp - 0x08]
+
+done:
+  mov       eax, [esp]
+  add       esp, ecx
+  jmp       eax