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→Buffer Mapping Translation
Buffers will get mapped at virtual address 0x04000000+ in the destination process. When this translation descriptor is submitted to the kernel through svcReplyAndReceive, the given buffer will be unmapped from the sending process(otherwise the buffer will be left mapped after the cmd-reply is finished). Regardless of the descriptor used here, the MMU-table entries for the source-process(from svcSendSyncRequest) buffers are not changed: memory permissions are left at the original while commands are being processed. The memory permissions for buffers at 0x04000000+ is always RW-, regardless of the actual memory permissions for the source-process buffer. Bitmask 0xFFF(low 12-bits) of the start address of each buffer for 0x04000000+ is the same as bitmask 0xFFF from the source-process buffer address.
Buffers will get mapped at virtual address 0x04000000+ in the destination process. When this translation descriptor is submitted to the kernel through svcReplyAndReceive, the given buffer will be unmapped from the sending process(otherwise the buffer will be left mapped after the cmd-reply is finished). Regardless of the descriptor used here, the MMU-table entries for the source-process(from svcSendSyncRequest) buffers are not changed: memory permissions are left at the original while commands are being processed. The memory permissions for buffers at 0x04000000+ is always RW-, regardless of the actual memory permissions for the source-process buffer. Bitmask 0xFFF(low 12-bits) of the start address of each buffer for 0x04000000+ is the same as bitmask 0xFFF from the source-process buffer address.
The buffer address written into the destination cmdbuf by the kernel with svcSendSyncRequest is the allocated 0x04000000+ buffer. When doing the same with svcSendSyncRequest, the buffer address is the same one from the source cmdbuf(0x04000000+).
The first and last pages of the buffer at 0x04000000+ are allocated under the BASE memregion(with data being copied to/from the original source-process buffer as needed), with the rest being mapped to the original buffer physmem. When the source-process buffer is 0x1000-byte aligned, the first page for 0x04000000+ is mapped directly into the original buffer physmem instead of allocating BASE memory(likewise for the last page when the buffer size is 0x1000-byte aligned).
The first and last pages of the buffer at 0x04000000+ are allocated under the BASE memregion(with data being copied to/from the original source-process buffer as needed), with the rest being mapped to the original buffer physmem. When the source-process buffer is 0x1000-byte aligned, the first page for 0x04000000+ is mapped directly into the original buffer physmem instead of allocating BASE memory(likewise for the last page when the buffer size is 0x1000-byte aligned).