kernel: Preserve TLS key in kernel_reset() after force-rewind

[JoyciAkira]

Summary

Fix critical bug where kernel_reset() was destroying the TLS key created by syscalls_init() during Asyncify force-rewind, causing all subsequent syscalls to fail with ENOMEM (-12).

Problem

After Asyncify force-rewind, the kernel becomes unusable:

• tls_get() returns NULL
• new_host_task() fails
• All syscalls return -12 (ENOMEM)

Root Cause

1. Force-rewind calls init() → syscalls_init() → tls_alloc() (Key Prepare website #1)
2. kernel_reset() frees Key Prepare website #1 and allocates Key Syscall porting is incomplete #2
3. Kernel threads created with Key Prepare website #1 now have invalid TLS
4. tls_get() returns NULL, breaking all syscalls

Solution

• Preserve existing task_key instead of freeing it
• Only allocate new key as fallback if none exists
• Don't recreate idle_host_task_loop if already exists
• Update host0 and set TLS on existing key

Testing

Tested with Zeronode project (https://github.com/zeronode/zeronode):

• CERT_300_2_STRICT certification gate
• Boot succeeds with nominal mount after force-rewind
• No regression in normal boot path

Impact

• Fixes ENOMEM bug blocking LKL-WASM Asyncify support
• Benefits all projects using LKL-WASM with Asyncify
• No regression in normal boot path

Code Changes

• arch/lkl/kernel/syscalls.c: Modified kernel_reset() function
  • Commented out tls_free(task_key) call
  • Added conditional TLS initialization
  • Added conditional idle_host_task_loop creation

References

• Technical analysis: Zeronode docs/issues/300.2-enomem-tls-root-cause.md
• Related issue: Asyncify force-rewind ENOMEM failure

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Co-authored-by: Daniele Corrao danicorrao87@gmail.com
Signed-off-by: Daniele Corrao danicorrao87@gmail.com