I'm having a look at windows booting process, what is Windows kernel's required drivers and BOOT_Start drivers, any example?

1. PreBoot process: The PC's firmware initiates a power-on self test (POST) and loads firmware settings. This process ends when the firmware detects a valid system disk.
   
   • When a BIOS-based computer enters this phase, the firmware loads the master boot record (MBR) into memory, and then starts Windows Boot Manager.
   • When a UEFI-based computer enters this phase, the firmware loads and starts the Windows Boot Manager EFI application.
2. Windows Boot Manager: Windows Boot Manager finds the Windows loader (Winload.exe) on the Windows boot partition, and then starts it.
3. Windows operating system loader: The Windows Loader loads the Windows kernel's required drivers, and then starts the kernel.
4. Windows NT OS Kernel: The kernel loads the system registry hive into memory. It also loads other drivers that are marked as BOOT_START.
   
   The kernel passes control to the session manager process (Smss.exe). This process initializes the system session, and then loads and starts the devices and drivers that aren't marked as BOOT_START.

Here's a corrected and more accurate version with consistent terminology and the missing winload.efi reference added:

1. PreBoot process:The PC's firmware performs a power-on self-test (POST) and initializes the hardware and firmware settings. This phase ends when the firmware locates a valid boot device.
   • On a BIOS-based computer, the firmware loads the master boot record (MBR) into memory, which eventually starts Windows Boot Manager.
   • On a UEFI-based computer, the firmware loads and starts the Windows Boot Manager EFI application (Bootmgfw.efi).
2. Windows Boot Manager: Windows Boot Manager locates and starts the Windows operating system loader. On BIOS-based systems, this is Winload.exe. On UEFI-based systems, this is Winload.efi.
3. Windows operating system loader: The Windows operating system loader (Winload.exe or Winload.efi) loads the Windows kernel (Ntoskrnl.exe), the hardware abstraction layer (HAL), and the boot-start drivers required to initialize the operating system. It then transfers control to the Windows kernel.
4. Windows NT operating system kernel: The Windows kernel initializes the executive subsystem and loads the SYSTEM registry hive into memory. It also initializes the remaining drivers that are configured to start during the boot process. Finally, the kernel passes control to the Session Manager process (Smss.exe), which creates the system session and starts the Windows initialization processes and services.

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Here are concise answers to OP's questions, with a bit of context.

1. What are the Windows kernel's required drivers and BOOT_START drivers? Are there examples?​

The "Windows kernel's required drivers" are the components that Winload.exe/Winload.efi must load before the kernel can begin executing. These include:

• The Windows kernel (Ntoskrnl.exe)
• The Hardware Abstraction Layer (Hal.dll)
• Drivers whose Start value is BOOT_START (Start = 0)

BOOT_START drivers are drivers that are essential for the operating system to access the boot device and initialize core hardware. Because Windows cannot continue booting without them, they are loaded by the Windows operating system loader before control is transferred to the kernel.

Examples of BOOT_START drivers include:

• disk.sys – Disk driver
• partmgr.sys – Partition manager
• volmgr.sys – Volume manager
• volsnap.sys – Volume Snapshot driver
• CLASSPNP.SYS – SCSI/Class driver
• storport.sys – Storage port driver
• stornvme.sys – NVMe storage driver (on NVMe systems)
• iaStorAC.sys or similar vendor storage drivers (if required to access the boot disk)

The exact set depends on the hardware and how Windows is installed. For example, a system booting from an NVMe SSD loads different storage drivers than one booting from a SATA AHCI controller.

After the kernel starts, it continues initializing the system and loads drivers according to their configured start types (such as SYSTEM_START, AUTO_START, and DEMAND_START).

2. Are USB 3.0 drivers not loaded early in the boot process?​

It depends on whether they are needed to boot Windows.

• If the boot device is connected via USB 3.0, then the necessary USB host controller, USB hub, and USB storage drivers are loaded as BOOT_START drivers so Windows can access the boot volume.
• If Windows is booting from an internal SATA or NVMe drive, USB 3.0 drivers are generally not required during the earliest stages of boot. They are initialized later by the kernel during Plug and Play device enumeration.

So USB 3.0 drivers are not inherently late-loading. They are loaded early only when they are necessary to access the boot device.

For example:

• Windows installed on an internal NVMe SSD: USB 3.0 drivers are typically initialized later.
• Windows To Go or another Windows installation booting from a USB 3.0 SSD: USB 3.0 controller and storage drivers must be loaded during the boot loader phase so the operating system can continue loading from the USB device.

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Celery said:

ChatGPT:

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trinhanhduc said:

Well, I don't think Chatgpt is reliable for topics like this

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OAT said:

How do you know if you don't use it?
The answer is actually pretty good for the boot process.

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trinhanhduc said:

No, like I'm afraid that it will make up its answer

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