feat: Bochs VBE linear framebuffer support

[GloriousAlpaca]

I'm currently working on porting Doom to Hermit and needed a feature to directly write pixel data into the Bochs Graphics Adaptor as Hermit currently only has support for VGA in textmode.

The feature currently adds standard BGA preparation (Link to OSDev) with a hardcoded resolution (640x400), bpp (32) and a systemcall (sys_get_framebuffer) to receive the address of the framebuffer.
The systemcall falls back to 0 if there was a failure in initializing the framebuffer (e.g. if pci is missing, or the bga feature is not enabled).

I have currently only tested this feature with c programs on a mac using Qemu. The feature is also only available on the x86_64 architecture.

[github-actions]

Benchmark Results

Details

Benchmark	Current: ff8a16b	Previous: 2e23902	Performance Ratio
startup_benchmark Build Time	124.40 s	80.34 s	1.55 ❗
startup_benchmark File Size	0.77 MB	0.80 MB	0.97 ❗
Startup Time - 1 core	0.95 s (±0.04 s)	0.75 s (±0.02 s)	1.27 ❗
Startup Time - 2 cores	0.99 s (±0.04 s)	0.74 s (±0.02 s)	1.35 ❗
Startup Time - 4 cores	0.98 s (±0.04 s)	0.74 s (±0.02 s)	1.32 ❗
multithreaded_benchmark Build Time	130.95 s	82.11 s	1.59 ❗
multithreaded_benchmark File Size	0.83 MB	0.86 MB	0.97 ❗
Multithreaded Pi Efficiency - 2 Threads	65.26 % (±8.55 %)	85.89 % (±6.61 %)	0.76 ❗
Multithreaded Pi Efficiency - 4 Threads	36.50 % (±3.88 %)	43.43 % (±2.56 %)	0.84 ❗
Multithreaded Pi Efficiency - 8 Threads	21.60 % (±1.97 %)	25.76 % (±1.53 %)	0.84 ❗
micro_benchmarks Build Time	127.17 s	80.40 s	1.58 ❗
micro_benchmarks File Size	0.83 MB	0.86 MB	0.97 ❗
Scheduling time - 1 thread	76.25 ticks (±2.60 ticks)	62.65 ticks (±4.06 ticks)	1.22 ❗
Scheduling time - 2 threads	51.92 ticks (±17.13 ticks)	34.08 ticks (±4.10 ticks)	1.52 ❗
Micro - Time for syscall (getpid)	4.25 ticks (±0.30 ticks)	3.45 ticks (±0.58 ticks)	1.23 ❗
Memcpy speed - (built_in) block size 4096	56753.93 MByte/s (±39495.32 MByte/s)	82448.38 MByte/s (±56997.13 MByte/s)	0.69
Memcpy speed - (built_in) block size 1048576	29525.56 MByte/s (±24027.90 MByte/s)	30585.98 MByte/s (±24707.84 MByte/s)	0.97
Memcpy speed - (built_in) block size 16777216	27134.26 MByte/s (±22418.82 MByte/s)	26340.06 MByte/s (±21720.96 MByte/s)	1.03
Memset speed - (built_in) block size 4096	57157.63 MByte/s (±39780.19 MByte/s)	82292.76 MByte/s (±56891.50 MByte/s)	0.69
Memset speed - (built_in) block size 1048576	30260.29 MByte/s (±24451.10 MByte/s)	31323.85 MByte/s (±25145.86 MByte/s)	0.97
Memset speed - (built_in) block size 16777216	27892.32 MByte/s (±22875.70 MByte/s)	27104.68 MByte/s (±22209.94 MByte/s)	1.03
Memcpy speed - (rust) block size 4096	51521.06 MByte/s (±36342.87 MByte/s)	74097.96 MByte/s (±51811.44 MByte/s)	0.70
Memcpy speed - (rust) block size 1048576	29443.93 MByte/s (±23985.96 MByte/s)	30361.60 MByte/s (±24602.37 MByte/s)	0.97
Memcpy speed - (rust) block size 16777216	26881.00 MByte/s (±22172.02 MByte/s)	27625.34 MByte/s (±22806.88 MByte/s)	0.97
Memset speed - (rust) block size 4096	52144.26 MByte/s (±36783.49 MByte/s)	74373.47 MByte/s (±51976.48 MByte/s)	0.70
Memset speed - (rust) block size 1048576	30186.75 MByte/s (±24416.22 MByte/s)	31110.89 MByte/s (±25033.24 MByte/s)	0.97
Memset speed - (rust) block size 16777216	27635.24 MByte/s (±22629.49 MByte/s)	28386.93 MByte/s (±23265.03 MByte/s)	0.97
alloc_benchmarks Build Time	122.13 s	74.76 s	1.63 ❗
alloc_benchmarks File Size	0.85 MB	0.87 MB	0.97 ❗
Allocations - Allocation success	91.35 %	91.31 %	1.00 ❗
Allocations - Deallocation success	100.00 %	100.00 %	1
Allocations - Pre-fail Allocations	61.55 %	61.44 %	1.00 ❗
Allocations - Average Allocation time	3004.23 Ticks (±1413.56 Ticks)	5860.58 Ticks (±98.43 Ticks)	0.51 ❗
Allocations - Average Allocation time (no fail)	4013.56 Ticks (±1190.84 Ticks)	6554.81 Ticks (±92.86 Ticks)	0.61 ❗
Allocations - Average Deallocation time	855.34 Ticks (±379.13 Ticks)	1805.01 Ticks (±250.35 Ticks)	0.47 ❗
mutex_benchmark Build Time	124.76 s	79.82 s	1.56 ❗
mutex_benchmark File Size	0.83 MB	0.86 MB	0.97 ❗
Mutex Stress Test Average Time per Iteration - 1 Threads	14.98 ns (±0.62 ns)	12.10 ns (±0.41 ns)	1.24 ❗
Mutex Stress Test Average Time per Iteration - 2 Threads	26.24 ns (±9.05 ns)	40.26 ns (±1.68 ns)	0.65 ❗

This comment was automatically generated by workflow using github-action-benchmark.

[mkroening]

Thanks for the PR! :)

This is great! First I was wondering why we should use BGA instead of UEFI's GOP, which would also work on real machines, but I guess BGA is just easier at the moment. Since it is not that invasive, this is fine with me.

I am a bit confused regarding naming; maybe you could clear that up in a doc comment of the module or even the feature documentation. If I understand correctly, BGA is the Bochs Graphics Adapter, which we talk to via the VESA BIOS Extensions (VBE) API. But instead of talking to the BIOS via interrupts, we can just talk to the VBE API through the special BGA ports, right? In that case, the module names, feature names, and constant names make sense to me now.

[mkroening]

Ah, please also ensure that your PR does not include merge commits. Please rebase instead.

[GloriousAlpaca]

Thanks a lot for the feedback! I have pushed a commit, where I've addressed the feedback you've given. I have actually implemented the systemcall a bit differently than I've written before. Please do have a look if this is a good way to design it. I have also used structs instead of enums to consolidate the constants. Let me know if this is alright with you.

[github-actions]

LLM review

The BGA driver implementation has several critical issues that need to be addressed, particularly around unsafe operations, error handling, and potential race conditions.

[jounathaen]

Suggested change

	/// Returns the framebuffer information for the BGA device, if it has been initialized. Returns 0
	/// on success, or -1 if the BGA device has not been initialized.
	#[cfg(all(target_arch = "x86_64", feature = "bga"))]
	#[hermit_macro::system]
	#[unsafe(no_mangle)]
	pub unsafe extern "C" fn sys_get_bga_info(info: *mut FramebufferInfo) -> c_int {
	/// Returns the framebuffer information for the video output device.
	/// Returns 0 on success, or -1 if the BGA device has not yet been initialized.
	#[cfg(all(target_arch = "x86_64", feature = "bga"))]
	#[hermit_macro::system]
	#[unsafe(no_mangle)]
	pub unsafe extern "C" fn sys_get_framebuffer_info(info: *mut FramebufferInfo) -> c_int {

[jounathaen]

Suggested change

	pub unsafe extern "C" fn sys_set_bga_resolution(width: u16, height: u16, bpp: u16) -> c_int {
	pub unsafe extern "C" fn sys_set_resolution(width: u16, height: u16, bpp: u16) -> c_int {