This process was added in firmware version 4.0.0.

Safemode can be launched by a button combo at boot and has the task of performing any pending system updates.

Initialization

It calls GetServiceDiscoveryControlSettings to check if IsChangeEnvironmentIdentifierDisabled is set. If not, it calls RebootSystem, otherwise the process continues.

It creates and starts a new thread with the sole purpose of setting up the display and showing a progress bar using raw graphics data embedded in the sysmodule's binary.

The display is configured as follows:

*(u32 *)DC_CMD_DISPLAY_WINDOW_HEADER = 0x00000040;    // WINDOW_C_SELECT
*(u32 *)DC_WIN_WIN_OPTIONS = 0x00000000;              // NO_OPTIONS
*(u32 *)DC_CMD_DISPLAY_WINDOW_HEADER = 0x00000020;    // WINDOW_B_SELECT
*(u32 *)DC_WIN_WIN_OPTIONS = 0x00000000;              // NO_OPTIONS
*(u32 *)DC_CMD_DISPLAY_WINDOW_HEADER = 0x00000010;    // WINDOW_A_SELECT
*(u32 *)DC_WIN_WIN_OPTIONS = 0x00000000;              // NO_OPTIONS
*(u32 *)DC_DISP_DISP_WIN_OPTIONS = 0x20000000;        // DSI_ENABLE
*(u32 *)DC_WIN_COLOR_DEPTH = 0x0000000D;              // WIN_COLOR_DEPTH_R8G8B8A8
*(u32 *)DC_WIN_WIN_OPTIONS = 0x00000000;              // NO_OPTIONS
*(u32 *)DC_WIN_WIN_OPTIONS = 0x00000000;              // NO_OPTIONS
*(u32 *)DC_WIN_POSITION = 0x00000000;
*(u32 *)DC_WIN_H_INITIAL_DDA = 0x00000000;
*(u32 *)DC_WIN_V_INITIAL_DDA = 0x00000000;
*(u32 *)DC_WIN_PRESCALED_SIZE = 0x05000B40;           // H_PRESCALED_SIZE=1280, V_PRESCALED_SIZE=2880
*(u32 *)DC_WIN_DDA_INCREMENT = 0x10001000;            // H_DDA_INC=0x1000, V_DDA_INC=0x1000
*(u32 *)DC_WIN_SIZE = 0x050002D0;                     // H_SIZE=1280, V_SIZE=720
*(u32 *)DC_WIN_LINE_STRIDE = 0x06000C00;              // UV_LINE_STRIDE=0x600, LINE_STRIDE=0xC00
*(u32 *)DC_WIN_BUFFER_CONTROL = 0x00000000;           // BUFFER_CONTROL_HOST
*(u32 *)DC_WIN_BUFFER_SURFACE_KIND = 0x00000000;      // DC_WIN_BUFFER_SURFACE_PITCH
*(u32 *)DC_WINBUF_START_ADDR = 0xC0000000;
*(u32 *)DC_WINBUF_ADDR_H_OFFSET = 0x00000000;
*(u32 *)DC_WINBUF_ADDR_V_OFFSET = 0x00000000;
*(u32 *)DC_WIN_WIN_OPTIONS = 0x00000000;              // NO_OPTIONS
*(u32 *)DC_DISP_DISP_WIN_OPTIONS = 0x20000000;        // DSI_ENABLE
*(u32 *)DC_WIN_WIN_OPTIONS = 0x00000000;              // NO_OPTIONS
*(u32 *)DC_DISP_DISP_WIN_OPTIONS = 0x20000000;        // DSI_ENABLE
*(u32 *)DC_WIN_WIN_OPTIONS = 0x00000000;              // NO_OPTIONS
*(u32 *)DC_DISP_DISP_WIN_OPTIONS = 0x20000000;        // DSI_ENABLE
*(u32 *)DC_WIN_WIN_OPTIONS = 0x40000000;              // WIN_ENABLE
*(u32 *)DC_CMD_DISPLAY_COMMAND = 0x00000020;          // DISP_CTRL_MODE_C_DISPLAY
*(u32 *)DC_CMD_STATE_CONTROL = 0x00000300;            // GENERAL_UPDATE | WIN_A_UPDATE
*(u32 *)DC_CMD_STATE_CONTROL = 0x00000003;            // GENERAL_ACT_REQ | WIN_A_ACT_REQ

While this thread is running, safemode proceeds with the actual update process.

System update

Safemode sets up service sessions for ns:su and nifm:u.

It calls CreateRequest with request_id 0x02.

Then calls GetSystemEventReadableHandles on the returned IRequest and creates an event object.

It uses GetRequestState and GetResult for synchronizing with the request object, calls Submit on the request and waits for it to finish.

After submitting the first request, safemode repeats the request process again and waits for it to finish. If the request fails to finish at this point, RebootSystem is called.

It calls OpenSystemUpdateControl and creates a system update event by calling:

GetClientId to obtain the current client's ID;
IsAnyInternetRequestAccepted with the returned client ID (if no request was accepted, error 0x2A810 is returned);
RequestDownloadLatestUpdate.

After this, an event object is created and safemode loops waiting on it while calling GetDownloadProgress.

When the system update event is signalled, safemode calls GetBackgroundNetworkUpdateState and if this fails, RebootSystem is called.

Finally, ApplyDownloadedUpdate is called and the process exits.