Development

[assembler-0]

Summary by CodeRabbit

• New Features
  • Added support for running a.out executables.
• Bug Fixes
  • Strengthened stack canary installation and verification to prevent misconfiguration and improve reliability.
  • Ensured terminated processes are always cleaned up to avoid lingering metadata.
• Documentation
  • Updated version badges and architecture docs to v0.0.2-rc2.
• Chores
  • Bumped project version to v0.0.2-rc2.
  • Enabled stack protection in the build configuration.

[coderabbitai]

Caution

Review failed

The pull request is closed.

Walkthrough

Version bumped to v0.0.2-rc2 across docs, banners, and build. Added a.out executable format support with new loader module and ExecLoader integration. Enabled Cerberus stack protection and reworked stack canary placement/verification. Made procinfo auto-cleanup unconditional in MLFQ. StackGuard now uses a fixed canary value.

Changes

Cohort / File(s)	Summary of Changes
Version strings and build config README.md, docs/ARCHITECTURE.md, kernel/core/Kernel.c, kernel/etc/Shell.c, meson.build	Bump version to v0.0.2-rc2 in docs and kernel/shell banners; update Meson project version; add a.out include/src; enable CERBERUS_STACK_PROTECTION; comment out PROCINFO_AUTO_CLEANUP.
Exec format integration kernel/execf/ExecLoader.c, kernel/execf/ExecLoader.h	Add EXEC_FORMAT_AOUT detection and handling path; include a.out loader header; route loads to CreateProcessFromAout with defaulted AoutLoadOptions; add enum member and trailing comma.
A.out loader module kernel/execf/aout/AoutLoader.h, kernel/execf/aout/AoutLoader.c	New API and implementation for validating and loading a.out binaries, memory checks, segment copying, entry computation, and process creation; define header struct, magic constants, options struct, and loader functions.
Scheduler cleanup behavior kernel/sched/MLFQ.c	Remove VF_CONFIG_PROCINFO_AUTO_CLEANUP guard; always compute cleanup path and delete procinfo for terminated processes.
Stack canary behavior mm/StackGuard.c, mm/security/Cerberus.c	StackGuardInit sets fixed STACK_CANARY_VALUE and logs; Cerberus moves canary near stack top, adds bounds/map/writeability checks, validates/unmaps handling, and updates mismatch reporting.

Sequence Diagram(s)

sequenceDiagram
  autonumber
  participant User as User
  participant Shell as Shell
  participant Exec as ExecLoader
  participant FS as VFS
  participant AOUT as AoutLoader
  participant Sched as MLFQ

  User->>Shell: exec "prog"
  Shell->>Exec: LoadExecutable("prog", options)
  Exec->>FS: Read first bytes
  FS-->>Exec: Magic
  alt Format == A.OUT (new)
    Exec->>AOUT: CreateProcessFromAout("prog", AoutLoadOptions)
    AOUT->>FS: VfsGetFileSize / VfsReadFile
    AOUT->>AOUT: ValidateAoutFile()
    AOUT->>AOUT: Allocate process memory, copy text/data, zero bss
    AOUT->>Sched: MLFQCreateProcess(entry, name, priv)
    Sched-->>AOUT: pid
    AOUT-->>Exec: pid
  else Other formats
    Exec->>Exec: Existing loaders (ELF/PE/etc.)
  end
  Exec-->>Shell: pid or error
  Shell-->>User: Report result
  note over Exec,AOUT: New A.OUT detection and loader path

Loading

sequenceDiagram
  autonumber
  participant Kernel as Kernel
  participant Cerb as Cerberus
  participant VMem as VMem
  participant Proc as Process

  rect rgb(235,245,255)
  note right of Kernel: Install phase (on process creation)
  Kernel->>Cerb: CerberusInstallStackCanary(pid, stack_top, stack_size)
  Cerb->>Cerb: Validate pid and min stack size
  Cerb->>VMem: VMemGetPhysAddr(canary_addr=stack_top-0x100)
  alt mapped and writable
    Cerb->>VMem: Test write/read at canary_addr
    Cerb->>Proc: Store STACK_CANARY_VALUE at canary_addr
  else invalid
    Cerb-->>Kernel: -1
  end
  end

  rect rgb(245,235,255)
  note right of Kernel: Check phase (on preemption/trap)
  Kernel->>Cerb: CerberusCheckStackCanary(pid)
  Cerb->>VMem: Ensure canary address mapped
  Cerb->>Proc: Read canary (volatile)
  alt mismatch
    Cerb-->>Kernel: 1 (violation)
  else ok
    Cerb-->>Kernel: 0
  end
  end

Loading

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Possibly related PRs

• Development #104 — Both touch Cerberus and build flags; this PR enables Cerberus stack protection and updates Cerberus/StackGuard logic.
• Development #115 — Overlaps on version string updates across README, docs, Kernel.c, Shell.c, and meson.build.
• Development #118 — Similar version/branding updates in the same files and build configuration.

Poem

Hop, hop—new loader on the trail,
A.out sails where bytes prevail.
Cerberus guards with steady glare,
A fixed canary in the air.
Schedulers sweep without a pause,
rc2 stamped—applause, applause!
(_/) ⭐ (•_•) ⭐ />🍪

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between a4d8180 and 30c9456.

📒 Files selected for processing (12)

• README.md (2 hunks)
• docs/ARCHITECTURE.md (1 hunks)
• kernel/core/Kernel.c (1 hunks)
• kernel/etc/Shell.c (2 hunks)
• kernel/execf/ExecLoader.c (3 hunks)
• kernel/execf/ExecLoader.h (1 hunks)
• kernel/execf/aout/AoutLoader.c (1 hunks)
• kernel/execf/aout/AoutLoader.h (1 hunks)
• kernel/sched/MLFQ.c (0 hunks)
• meson.build (4 hunks)
• mm/StackGuard.c (1 hunks)
• mm/security/Cerberus.c (3 hunks)

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