# This function is required for loading DOLs. If it's not present, newserv can't # serve DOL files to GameCube clients. # This is also the file I've chosen to document how to write code for newserv's # functions subsystem. There are three kinds of functions: includes, patches, # and general functions. This file, WriteMemory, is a general function. It # writes a variable-length block of data to a specified address in the client's # memory. # Includes are snippets of code that are intended to be used as part of other # functions and patches. These files' names end with .inc.s. These can be used # with the .include directive; there is an example of this in the code below. # Patches are functions that are available to run upon client request. They can # be made available in the Patches menu or via the $patch command. Patches # should be named like PATCHNAME.VXLS.patch.s, where V, X, L, and S denote which # specific game version the patch is for. Specifically: # V should be 3 for PSO GameCube, 4 for PSO Xbox, 5 for PSO BB # X should be O for GC Episodes 1 & 2, S for GC Episode 3, 0 for Xbox # L should be E, J, or P for USA, Japanese, or Europe # S should be 0, 1, 2, etc. for the GC disc version (0 = 1.0, 1 = 1.1, etc.) # On Xbox, S is B (beta), D (disc), or U (title update) # (For the curious, these four-character version codes directly match the # values returned by the VersionDetectGC or VersionDetectXB functions; see # those files for more details.) For example, the patch that gives the player a # VIP card in Episode 3 USA is in the file VIPCard.3SE0.patch.s. (If there were # a Japanese version of that patch, it would be in VIPCard.3SJ0.patch.s.) # For example, to use this function to write the bytes 38 00 00 05 to the # address 8010521C, send_function_call could be called like this: # auto fn = s->function_code_index->name_to_function.at("WriteMemory"); # unordered_map label_writes( # {{"dest_addr", 0x8010521C}, {"size", 4}}); # string suffix("\x38\x00\x00\x05", 4); # send_function_call( # c, // Client to send function call to # fn, // The function's code # label_writes, // Variables to pass in to the function's code # suffix); // Data to append after the code (not all functions use this) # The meanings of label_writes and suffix are described in the comments below. # Note that there is no way to specify label_writes or suffix for patches # requested by the client, so those features should only be used in general # functions. # These directives tell newserv what to show to the player in the Patches menu. # Neither of them is required; if the name is omitted, the filename is used # instead. .meta name="Write memory" .meta description="Writes data to any location in memory" # The .meta index directive tells newserv what value to use in the flag field # when sending the B2 command. This is needed if the server needs to do # something when the B3 response is received. If specified, the index must be in # the range 01-FF. The DOL loading functionality, which this function is a part # of, uses indexes E0, E1, and E2, but the WriteMemory function can also be used # for other purposes. .meta index=E1 # To hide a patch from the Patches menu (so it can only be used with the $patch # command), this directive can be used. This has no effect if used in includes # or general functions. # .meta hide_from_patches_menu # The entry_ptr label is required for all functions. It should point to a # .offsetof directive that itself points to the actual entrypoint. entry_ptr: # All labels starting with reloc signify that the following PPC word (big-endian # 32-bit value) is to be relocated at runtime. That is, when the code runs on # the client, the PPC word will contain the actual memory address relative to # the running code instead of the offset that it holds at assembly time. The # entry_ptr label should almost always have a reloc label next to it. reloc0: .offsetof start start: mflr r12 bl get_block_ptr mr r6, r3 # r6 = address of dest_addr label copy_block: lwz r3, [r6] # r3 = dest ptr subi r3, r3, 1 # subtract 1 so we can use stbu lwz r5, [r6 + 4] # r5 = size (bytes remaining) add r5, r5, r3 # r5 = dest end ptr (last byte to be written) addi r4, r6, 7 # r4 = src ptr (starting at -1 so we can use lbzu) copy_block__again: lbzu r0, [r4 + 1] stbu [r3 + 1], r0 cmp r3, r5 bne copy_block__again # Flush the data cache and clear the instruction cache at the written region lwz r3, [r6] # r3 = dest ptr lwz r4, [r6 + 4] # r4 = size # A .include directive essentially pastes in the code from the referenced # file. Here, we use the code from the file FlushCachedCode.inc.s. .include FlushCachedCode # Return the address after the last byte written. The value returned in r3 # from the function is sent back to the server in a B3 command. newserv uses # the return value during DOL loading to know which section of the DOL file to # send next, or to send the RunDOL function if all sections have been loaded. lwz r3, [r6] # r3 = dest ptr lwz r4, [r6 + 4] # r4 = size add r3, r3, r4 mtlr r12 blr get_block_ptr__ret: mflr r3 mtlr r10 blr get_block_ptr: # We use a trick here to get the address of the dest_addr label: since bl puts # the immediately-following address into the link register, we "call" # get_block_ptr__ret and get the dest_addr pointer out of the LR. We then put # r10 back into the LR so get_block_ptr__ret returns to the caller. mflr r10 bl get_block_ptr__ret # These fields are filled in right before the command is sent to the client. # Specifically, the label_writes argument to send_function_call is responsible # for this. The label_writes argument is a map of label name to value, and # send_function_call simply writes the given values after the given labels. This # is a way to pass arbitrary arguments to a function at call time. dest_addr: .zero size: .zero # Finally, we use the suffix argument to instruct send_function_call to append # the data we want to write to memory immediately after the assembled code. # (The data_to_write label here is for documentation purposes only; the suffix # argument always appends data after the end of all the assembled code.) data_to_write: