citra/src/core/hle/kernel/ipc.cpp

// Copyright 2017 Citra Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.

#include "common/alignment.h"
#include "core/hle/ipc.h"
#include "core/hle/kernel/handle_table.h"
#include "core/hle/kernel/ipc.h"
#include "core/hle/kernel/kernel.h"
#include "core/hle/kernel/memory.h"
#include "core/hle/kernel/process.h"
#include "core/hle/kernel/thread.h"
#include "core/memory.h"

namespace Kernel {

ResultCode TranslateCommandBuffer(SharedPtr<Thread> src_thread, SharedPtr<Thread> dst_thread,
                                  VAddr src_address, VAddr dst_address, bool reply) {

    auto& src_process = src_thread->owner_process;
    auto& dst_process = dst_thread->owner_process;

    IPC::Header header;
    // TODO(Subv): Replace by Memory::Read32 when possible.
    Memory::ReadBlock(*src_process, src_address, &header.raw, sizeof(header.raw));

    size_t untranslated_size = 1u + header.normal_params_size;
    size_t command_size = untranslated_size + header.translate_params_size;

    // Note: The real kernel does not check that the command length fits into the IPC buffer area.
    ASSERT(command_size <= IPC::COMMAND_BUFFER_LENGTH);

    std::array<u32, IPC::COMMAND_BUFFER_LENGTH> cmd_buf;
    Memory::ReadBlock(*src_process, src_address, cmd_buf.data(), command_size * sizeof(u32));

    size_t i = untranslated_size;
    while (i < command_size) {
        u32 descriptor = cmd_buf[i];
        i += 1;

        switch (IPC::GetDescriptorType(descriptor)) {
        case IPC::DescriptorType::CopyHandle:
        case IPC::DescriptorType::MoveHandle: {
            u32 num_handles = IPC::HandleNumberFromDesc(descriptor);
            // Note: The real kernel does not check that the number of handles fits into the command
            // buffer before writing them, only after finishing.
            if (i + num_handles > command_size) {
                return ResultCode(ErrCodes::CommandTooLarge, ErrorModule::OS,
                                  ErrorSummary::InvalidState, ErrorLevel::Status);
            }

            for (u32 j = 0; j < num_handles; ++j) {
                Handle handle = cmd_buf[i];
                SharedPtr<Object> object = nullptr;
                // Perform pseudo-handle detection here because by the time this function is called,
                // the current thread and process are no longer the ones which created this IPC
                // request, but the ones that are handling it.
                if (handle == CurrentThread) {
                    object = src_thread;
                } else if (handle == CurrentProcess) {
                    object = src_process;
                } else if (handle != 0) {
                    object = g_handle_table.GetGeneric(handle);
                    if (descriptor == IPC::DescriptorType::MoveHandle) {
                        g_handle_table.Close(handle);
                    }
                }

                if (object == nullptr) {
                    // Note: The real kernel sets invalid translated handles to 0 in the target
                    // command buffer.
                    cmd_buf[i++] = 0;
                    continue;
                }

                auto result = g_handle_table.Create(std::move(object));
                cmd_buf[i++] = result.ValueOr(0);
            }
            break;
        }
        case IPC::DescriptorType::CallingPid: {
            cmd_buf[i++] = src_process->process_id;
            break;
        }
        case IPC::DescriptorType::StaticBuffer: {
            IPC::StaticBufferDescInfo bufferInfo{descriptor};
            VAddr static_buffer_src_address = cmd_buf[i];

            std::vector<u8> data(bufferInfo.size);
            Memory::ReadBlock(*src_process, static_buffer_src_address, data.data(), data.size());

            // Grab the address that the target thread set up to receive the response static buffer
            // and write our data there. The static buffers area is located right after the command
            // buffer area.
            struct StaticBuffer {
                IPC::StaticBufferDescInfo descriptor;
                VAddr address;
            };

            static_assert(sizeof(StaticBuffer) == 8, "StaticBuffer struct has incorrect size.");

            StaticBuffer target_buffer;

            u32 static_buffer_offset = IPC::COMMAND_BUFFER_LENGTH * sizeof(u32) +
                                       sizeof(StaticBuffer) * bufferInfo.buffer_id;
            Memory::ReadBlock(*dst_process, dst_address + static_buffer_offset, &target_buffer,
                              sizeof(target_buffer));

            // Note: The real kernel doesn't seem to have any error recovery mechanisms for this
            // case.
            ASSERT_MSG(target_buffer.descriptor.size >= data.size(),
                       "Static buffer data is too big");

            Memory::WriteBlock(*dst_process, target_buffer.address, data.data(), data.size());

            cmd_buf[i++] = target_buffer.address;
            break;
        }
        case IPC::DescriptorType::MappedBuffer: {
            IPC::MappedBufferDescInfo descInfo{descriptor};
            VAddr source_address = cmd_buf[i];

            size_t size = descInfo.size;
            IPC::MappedBufferPermissions permissions = descInfo.perms;

            VAddr page_start = Common::AlignDown(source_address, Memory::PAGE_SIZE);
            u32 page_offset = source_address - page_start;
            u32 num_pages =
                Common::AlignUp(page_offset + size, Memory::PAGE_SIZE) >> Memory::PAGE_BITS;

            ASSERT(num_pages >= 1);

            if (reply) {
                // TODO(Subv): Scan the target's command buffer to make sure that there was a
                // MappedBuffer descriptor in the original request. The real kernel panics if you
                // try to reply with an unsolicited MappedBuffer.

                // Unmap the buffers. Readonly buffers do not need to be copied over to the target
                // process again because they were (presumably) not modified. This behavior is
                // consistent with the real kernel.
                if (permissions == IPC::MappedBufferPermissions::R) {
                    ResultCode result = src_process->vm_manager.UnmapRange(
                        page_start, num_pages * Memory::PAGE_SIZE);
                    ASSERT(result == RESULT_SUCCESS);
                }

                ASSERT_MSG(permissions == IPC::MappedBufferPermissions::R,
                           "Unmapping Write MappedBuffers is unimplemented");
                i += 1;
                break;
            }

            VAddr target_address = 0;

            auto IsPageAligned = [](VAddr address) -> bool {
                return (address & Memory::PAGE_MASK) == 0;
            };

            // TODO(Subv): Support more than 1 page and aligned page mappings
            ASSERT_MSG(
                num_pages == 1 &&
                    (!IsPageAligned(source_address) || !IsPageAligned(source_address + size)),
                "MappedBuffers of more than one page or aligned transfers are not implemented");

            // TODO(Subv): Perform permission checks.

            // TODO(Subv): Leave a page of Reserved memory before the first page and after the last
            // page.

            if (!IsPageAligned(source_address) ||
                (num_pages == 1 && !IsPageAligned(source_address + size))) {
                // If the address of the source buffer is not page-aligned or if the buffer doesn't
                // fill an entire page, then we have to allocate a page of memory in the target
                // process and copy over the data from the input buffer. This allocated buffer will
                // be copied back to the source process and deallocated when the server replies to
                // the request via ReplyAndReceive.

                auto buffer = std::make_shared<std::vector<u8>>(Memory::PAGE_SIZE);

                // Number of bytes until the next page.
                size_t difference_to_page =
                    Common::AlignUp(source_address, Memory::PAGE_SIZE) - source_address;
                // If the data fits in one page we can just copy the required size instead of the
                // entire page.
                size_t read_size = num_pages == 1 ? size : difference_to_page;

                Memory::ReadBlock(*src_process, source_address, buffer->data() + page_offset,
                                  read_size);

                // Map the page into the target process' address space.
                target_address = dst_process->vm_manager
                                     .MapMemoryBlockToBase(
                                         Memory::IPC_MAPPING_VADDR, Memory::IPC_MAPPING_SIZE,
                                         buffer, 0, buffer->size(), Kernel::MemoryState::Shared)
                                     .Unwrap();
            }

            cmd_buf[i++] = target_address + page_offset;
            break;
        }
        default:
            UNIMPLEMENTED_MSG("Unsupported handle translation: {:#X}", descriptor);
        }
    }

    Memory::WriteBlock(*dst_process, dst_address, cmd_buf.data(), command_size * sizeof(u32));

    return RESULT_SUCCESS;
}
} // namespace Kernel