Today I want to share my experience implementing a custom memory allocator for a resource-constrained embedded system. When working with devices that have limited RAM, the standard malloc/free implementations are often too heavy and inefficient.

The key requirements were:

• Deterministic allocation times
• Low fragmentation
• Small memory overhead

Here's the core implementation of the block allocation strategy:

typedef struct block_meta {
    size_t size;
    struct block_meta *next;
    int free;
} block_meta_t;

#define META_SIZE sizeof(block_meta_t)

static block_meta_t *global_base = NULL;

// Find a free block of sufficient size
block_meta_t *find_free_block(block_meta_t **last, size_t size) {
    block_meta_t *current = global_base;
    while (current && !(current->free && current->size >= size)) {
        *last = current;
        current = current->next;
    }
    return current;
}

The main challenge was handling fragmentation efficiently while maintaining real-time constraints. I ended up implementing a hybrid approach using fixed-size blocks for common allocations and a more dynamic approach for larger requests.

I recently explored hardware security techniques involving exposed UART debug ports on IoT devices. Here's what I discovered about gaining shell access through these debug interfaces:

First, I identified the UART pins on the PCB using a logic analyzer:

After analyzing the boot sequence, I discovered a timing vulnerability in the authentication routine that could be exploited to bypass security measures entirely.

I've been struggling with a frustrating issue on my Linux laptop where network interfaces would occasionally disappear after resuming from suspend. After much debugging, I finally found the root cause and solution.

The Problem:

After resuming from suspend, both WiFi and Ethernet interfaces would be missing. Running ip link would show no network devices except for loopback. This made the laptop essentially unusable until a full reboot was performed.

Through careful investigation of system logs and kernel behavior, I discovered that this was related to power management issues with the specific network hardware in my laptop.