TLSF and the Temple of Corrupted Memory

[DrZlo13]

What's new

• [ Describe changes here ]

Verification

• [ Describe how to verify changes ]

Checklist (For Reviewer)

• PR has description of feature/bug or link to Confluence/Jira task
• Description contains actions to verify feature/bugfix
• I've built this code, uploaded it to the device and verified feature/bugfix

[github-actions]

Compiled f7 firmware for commit 9b15e05e:

• 📦 Update package
• 📥 DFU file
• ☁️ Web/App updater
• 📊 Size report

[CookiePLMonster]

Regarding the 8-byte alignment, GCC indeed appears to make that assumption, with or without -Os.

This code:

int32_t align_test_app(void* p) {
    UNUSED(p);
    FURI_LOG_I("TEST", "Hello world");
    FURI_LOG_I("TEST", "I'm align_test!");

    void* b = malloc(4);

    uintptr_t valB = (uintptr_t)b;
    return (valB & 7) == 0;
}

compiled into:

So it's a very good idea to guarantee proper alignment, at least for malloc and realloc.

[github-actions]

PVS-Studio report for commit 7d50f4b5:

• Report

[DrZlo13]

I disabled all dolphin animations and ran some tests:

tlsf

: free
Free heap size: 141416
Total heap size: 185560
Minimum heap size: 137696
Maximum heap block: 140328
Aux pool total free: 2752
Aux pool max free block: 2644

: free
Free heap size: 141304
Total heap size: 185560
Minimum heap size: 125768
Maximum heap block: 132512
Aux pool total free: 2752
Aux pool max free block: 2644

heap4

: free
Free heap size: 146200
Total heap size: 185544
Minimum heap size: 142512
Maximum heap block: 145136
Pool free: 1464
Maximum pool block: 1348

: free
Free heap size: 146136
Total heap size: 185544
Minimum heap size: 142440
Maximum heap block: 145296
Pool free: 1464
Maximum pool block: 1348

It looks like in the current version tlsf has no meaning except for the correct implementation of realloc.

[CookiePLMonster]

Suggestion - if this goes through, consider exposing tlsf_memalign_offs as a non-standard aligned_offset_alloc(size_t alignment, size_t size, size_t offset) function, much like MSVC does:
https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/aligned-offset-malloc

It may be handy for cases where a nested object or class field requires alignment, but the rest of the structure does not.