SchOS/tools/crashshot.ps1

# Boot SchOS, crash it on purpose, and capture the crash screen as an image.
#
# The crash screen is the one part of the system you cannot look at by using
# the system, so it is the one part that quietly rots. This drives it through
# /proc/sysrq and takes a picture, which turns "does the panic screen still
# render" into something answerable in thirty seconds.
#
# QEMU's monitor is on its own socket so the serial console stays free for the
# shell. screendump writes a PPM; the PNG conversion is optional and skipped if
# ImageMagick is not around.
#
#   tools/crashshot.ps1              crash the ramdisk-root build

param(
    [int]$BootSeconds = 20,
    [string]$Out = "build/crashscreen.ppm",
    [string]$Qemu = (Find-Qemu)
)

# QEMU, on whichever host this is.
#
# PowerShell 7 runs on Linux, macOS and the BSDs as well as Windows, so these
# scripts are usable from all of them -- but the old default was a hardcoded
# scoop path under $env:USERPROFILE, which exists on exactly one of those. PATH
# first, because a package-managed qemu is on it everywhere; the scoop location
# is only a fallback for the Windows install that does not add itself to PATH.
function Find-Qemu {
    $exe = if ($IsWindows -or $env:OS -eq 'Windows_NT') { 'qemu-system-x86_64.exe' }
           else { 'qemu-system-x86_64' }
    $onPath = Get-Command $exe -ErrorAction SilentlyContinue
    if ($onPath) { return $onPath.Source }
    if ($env:USERPROFILE) {
        $scoop = Join-Path (Join-Path $env:USERPROFILE 'scoop/apps/qemu/current') $exe
        if (Test-Path $scoop) { return $scoop }
    }
    foreach ($p in @('/usr/bin', '/usr/local/bin', '/opt/homebrew/bin')) {
        $c = Join-Path $p $exe
        if (Test-Path $c) { return $c }
    }
    throw "qemu-system-x86_64 not found on PATH. Install QEMU, or pass -Qemu <path>."
}

$ErrorActionPreference = 'Stop'
$root = Split-Path $PSScriptRoot -Parent
$hda  = Join-Path $root 'schos.img'
# The root filesystem. SchFS is the only root there is: the kernel mounts
# device 1 in forkret() and panics if it is not a SchFS volume, so this is
# not a choice and there is no -SchFS switch any more. It used to default to
# build/fs.img, which stopped being bootable the moment SchFS became root.
$hdb  = Join-Path $root 'build/schfs.img'
$log  = Join-Path $root 'build/crashshot.log'
$ppm  = Join-Path $root $Out
$mon  = Join-Path $root 'build/qemu-mon.sock'

Remove-Item -Force $log, $ppm -ErrorAction SilentlyContinue

# The monitor goes to a TCP port rather than a unix socket: PowerShell can open
# a TCP client without any extra machinery, and QEMU on Windows has no unix
# sockets anyway.
$monPort = 55555

$psi = New-Object System.Diagnostics.ProcessStartInfo
$psi.FileName = $Qemu
$psi.Arguments = @(
    "-drive file=`"$hda`",format=raw,index=0,media=disk"
    "-drive file=`"$hdb`",format=raw,index=1,media=disk"
    '-m 1G -smp 1 -cpu qemu64,+rdtscp -machine pc-i440fx-9.2'
    '-display none'
    "-chardev stdio,id=c0,logfile=`"$log`""
    '-serial chardev:c0'
    "-monitor tcp:127.0.0.1:$monPort,server,nowait"
) -join ' '
$psi.RedirectStandardInput = $true
$psi.UseShellExecute       = $false

Write-Host "==> booting" -ForegroundColor Cyan
$p = [System.Diagnostics.Process]::Start($psi)

function Send-Line($text) {
    foreach ($ch in ($text + "`n").ToCharArray()) {
        $p.StandardInput.Write($ch)
        $p.StandardInput.Flush()
        Start-Sleep -Milliseconds 30    # serial has no flow control
    }
}

try {
    Start-Sleep -Seconds $BootSeconds

    # Put something on the display first. The whole design of the crash screen
    # is that it dims what was there rather than clearing it, so a blank screen
    # underneath would prove nothing.
    Write-Host "  > filling the screen with normal output" -ForegroundColor DarkGray
    Send-Line 'ls /bin'
    Start-Sleep -Seconds 3
    Send-Line 'cat /proc/cpuinfo'
    Start-Sleep -Seconds 2

    Write-Host "  > echo c > /proc/sysrq" -ForegroundColor DarkGray
    Send-Line 'echo c > /proc/sysrq'
    Start-Sleep -Seconds 4

    Write-Host "==> capturing the framebuffer" -ForegroundColor Cyan
    $client = New-Object System.Net.Sockets.TcpClient('127.0.0.1', $monPort)
    $stream = $client.GetStream()
    $writer = New-Object System.IO.StreamWriter($stream)
    $writer.AutoFlush = $true
    Start-Sleep -Milliseconds 500
    # QEMU on Windows wants a native path here, not the one PowerShell shows.
    $writer.WriteLine("screendump $ppm")
    Start-Sleep -Seconds 2
    $writer.WriteLine('quit')
    Start-Sleep -Milliseconds 500
    $client.Close()
} finally {
    if (-not $p.HasExited) { $p.Kill() }
    Start-Sleep -Milliseconds 800
}

if (Test-Path $log) {
    $text = Get-Content $log -Raw
    Write-Host "==> serial transcript" -ForegroundColor Cyan
    # Only the crash report, not the whole boot.
    $idx = $text.IndexOf('SchOS stopped')
    if ($idx -ge 0) { Write-Host $text.Substring($idx) } else { Write-Host $text }
}

if (Test-Path $ppm) {
    $size = (Get-Item $ppm).Length
    Write-Host "==> $ppm ($size bytes)" -ForegroundColor Green
    $png = [System.IO.Path]::ChangeExtension($ppm, '.png')
    $magick = Get-Command magick -ErrorAction SilentlyContinue
    if ($magick) {
        & magick $ppm $png
        Write-Host "==> $png" -ForegroundColor Green
    }
} else {
    Write-Host "FAIL: no screendump was produced" -ForegroundColor Red
    exit 1
}