Changes

The IPC subsystem can temporarily map a whole buffer of the sender's memory into the receiver's memory space. This is useful for large buffers, for which the overhead of copying static buffer data around would be too expensive.

The IPC subsystem can temporarily map a whole buffer of the sender's memory into the receiver's memory space. This is useful for large buffers, for which the overhead of copying static buffer data around would be too expensive.

This kind of translation is enabled by setting bit3 in the translation descriptor. The other two bits of what's documented as the translation type above are used to specify buffer access permissions of the receiving process.

This kind of translation is enabled by setting bit3 in the translation descriptor. The other two bits of what's documented as the translation type above are used to specify buffer access permissions of the source process.

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. 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.

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. 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-. 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 memory mapped at 0x04000000+ is a copy of the source data, allocated in the BASE memregion. With descriptor 0x0000000C at least, only the first and last pages of the buffer at 0x04000000+ are under BASE, 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). 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 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).

{| class="wikitable" border="1"

{| class="wikitable" border="1"

| 0x0000000C <nowiki>|</nowiki> (size<<4)

| 0x0000000C <nowiki>|</nowiki> (size<<4)

<ptr>

<ptr>

| The corresponding value contains a ptr to a buffer of said size. The buffer specified by the source process must have write permission. Used for output buffers. In the destination process with the buffer mapped at 0x04000000+, that buffer has same content as the buffer from the source buffer(like descriptor 0x0000000A). The 0x04000000+ buffer for this has memory permissions RW-.

| The corresponding value contains a ptr to a buffer of said size. The buffer specified by the source process must have write permission. Used for output buffers. In the destination process with the buffer mapped at 0x04000000+, that buffer has same content as the buffer from the source buffer(like descriptor 0x0000000A).

|-

|-

| 0x0000000E <nowiki>|</nowiki> (size<<4)

| 0x0000000E <nowiki>|</nowiki> (size<<4)

<ptr>

<ptr>

| The corresponding value contains a ptr to a buffer of said size. The buffer specified by the source process must have read+write permission.

| The corresponding value contains a ptr to a buffer of said size. The buffer specified by the source process must have read+write permission. This isn't known to be used by any processes.

|}

|}