7f9761b915
Key updates: - README: comprehensive distro comparison table (spaetzle vs dumpling-wayland) - Recommend dumpling-wayland (glibc) for Qt/GUI applications - spaetzle (musl) explicitly blocks Qt: SKIP_RECIPE[tq-image-qt6] - Both distros are 2038-safe (glibc 2.39 and musl 1.2+ both use 64-bit time_t) - Updated 2038 analysis to cover both C library options - Updated license tables with both glibc and musl entries - Fixed remaining config references (imx → mainline) - Added image availability matrix per distro - Corrected package versions to match Scarthgap 5.0.11
106 lines
3.5 KiB
Markdown
106 lines
3.5 KiB
Markdown
# 2038 Compliance Analysis – TQMa6UL
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## Overview
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The Year 2038 problem (Y2K38) occurs when a signed 32-bit integer used for
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Unix timestamps overflows on **2038-01-19 03:14:07 UTC**. This affects all
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32-bit ARM systems using traditional 32-bit `time_t`.
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## Architecture
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```
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┌─────────────────────────────────────┐
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│ Application Layer │
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│ (all userspace uses 64-bit t) │
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├─────────────────────────────────────┤
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│ C Library │
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│ glibc 2.39: 64-bit time_t (Y2038) │
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│ musl 1.2+: 64-bit time_t (Y2038) │
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├─────────────────────────────────────┤
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│ Linux Kernel (Mainline 6.x) │
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│ 64-bit time syscalls on ARM32 │
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├─────────────────────────────────────┤
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│ i.MX6 UltraLite (Cortex-A7) │
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└─────────────────────────────────────┘
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```
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## C Library Options
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### Option 1: glibc (recommended for Qt/GUI)
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**Distro:** `dumpling-wayland`
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**Target triplet:** `arm-tq-linux-gnueabi`
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glibc provides 64-bit `time_t` on 32-bit ARM since version 2.34, when built
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with `_TIME_BITS=64` (which Yocto Scarthgap enables by default). The BSP
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includes glibc 2.39.
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Advantages:
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- Full compatibility with third-party software
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- Qt5/Qt6 support
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- Broader library ecosystem
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### Option 2: musl (for minimal/headless)
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**Distro:** `spaetzle`
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**Target triplet:** `arm-tq-linux-musleabi`
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musl has provided 64-bit `time_t` unconditionally on all 32-bit architectures
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since version 1.2.0 (February 2020).
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Advantages:
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- Smaller footprint
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- Simpler, no locale overhead
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Limitations:
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- Qt is blocked (`SKIP_RECIPE`)
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- Some third-party software may not build
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## Kernel Support
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The mainline kernel (6.x) provides:
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- 64-bit time variants of all relevant syscalls (`clock_gettime64`,
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`futex_time64`, etc.)
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- `CONFIG_COMPAT_32BIT_TIME=y` for backwards compatibility
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- ext4 timestamps beyond 2038
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## Compliance Matrix
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| Component | glibc (dumpling) | musl (spaetzle) | 2038-safe? |
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|-----------|-----------------|-----------------|-----------|
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| Kernel | Mainline 6.x | Mainline 6.x | ✅ |
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| C Library | glibc 2.39 | musl 1.2+ | ✅ |
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| Userspace | 64-bit time_t | 64-bit time_t | ✅ |
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| U-Boot | Mainline | Mainline | ✅ |
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| Qt6 | ✅ supported | ❌ blocked | ✅ (glibc) |
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## Verification
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After building, verify on the target:
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```bash
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# Check time_t size (should print 8)
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cat << 'C' > /tmp/check_time.c
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#include <stdio.h>
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#include <time.h>
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int main() { printf("sizeof(time_t) = %zu\n", sizeof(time_t)); return 0; }
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C
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$CC /tmp/check_time.c -o /tmp/check_time && /tmp/check_time
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```
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## Risk Assessment
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| Risk | Severity | Status |
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|------|----------|--------|
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| time_t overflow | Critical | ✅ Mitigated (both libc options) |
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| Filesystem timestamps | Medium | ✅ ext4 supports >2038 |
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| Network protocols (NTP) | Low | ✅ 64-bit aware |
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| Third-party binaries | Medium | ⚠️ Must verify pre-built binaries |
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| Qt5 compatibility | Medium | ⚠️ meta-qt5 not included, add manually |
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## References
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- [glibc Y2038 Design](https://sourceware.org/glibc/wiki/Y2038ProofnessDesign)
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- [musl time64](https://musl.libc.org/time64.html)
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- [Kernel Y2038 work](https://kernelnewbies.org/y2038)
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