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https://github.com/LNH-team/pico-loader.git
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a648d4c4a9
Replaces static helper functions in
Sdk5DsiSdCardRedirectPatch.cpp
LastWindowCrcPatch.h
CardiTryReadCardDmaPatch.cpp
36 lines
1.7 KiB
C++
36 lines
1.7 KiB
C++
#pragma once
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#include "../Patch.h"
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/// @brief Arm9 patch for intercepting calls to SVC_GetCRC16 in The Last Window: The Secret of Cape West
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/// @details
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/// This game has DS Protect 1.27, which is patched by the regular DS Protect patches, but also has
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/// an extra layer of CRC checks that must match or the game will fail to boot.
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///
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/// It first runs DS Protect NotA1 at startup, and then does a CRC of most of DS Protect. This can
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/// tell which DS Protect functions were run, because at decrypt-run-encrypt, the key gets changed.
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/// So the CRC is sensitive not only to code modifications, but also to which encrypted functions
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/// were run, and how many times they were run.
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///
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/// The current DS Protect patch modifies NotA1, causes one of its subfunction to run twice, and
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/// the other subfunction to not be run, which obviously breaks the CRC.
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///
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/// Another region is also CRCed, from 0202DB34 to 02030334. What resides here is unknown, it does not
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/// contain any commonly modified functions such as AP or card reading.
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///
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/// To make things more annoying, the memory location of the correct CRC is randomized, and the code
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/// that checks the CRC resides in a compressed overlay which is loaded into ITCM. This same function
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/// also receives several dummy checks that are expected to fail, and so cannot be patched to always
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/// report the CRC matches.
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///
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/// Instead, the function call that calculates the CRC is shimmed and if its arguments match
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/// a problematic CRC calculation, the expected answer is returned instead.
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class LastWindowCrcPatch : public Patch
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{
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public:
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bool FindPatchTarget(PatchContext& patchContext) override;
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void ApplyPatch(PatchContext& patchContext) override;
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private:
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u32* _getCrc16 = nullptr;
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};
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