Memory Allocation + Deallocation implementation (#19)

* update README

* [FIX] fix param name in gettime

* [UPDATE] updated printf param to const

* [ADD] kernel halt and panic for unexpected behaviors

* refactor + added discard commands + reserve spaces for page table

* [REFACTOR] consolidate irq files to interrupt file

* [refactor] updated the way we handled irq testing

* update function documentation

* [ADD] custom division operation

* added more macros + moved the irq handlers from irq file to interrupt file

* added mapping file for  linker instruction address mapping

* fix documentation mismatch + add .data init

* move the attribute noreturn order

* updated panic to use more modern C standard (C23)

* Updated stack start and end + added proper heap start and end

* enforce std=C23

* update mapping with no debu mode

* updated doc with updated stack name

* Updated header documentation for Doxygen auto generated docs

* Updated implementation documentation for Doxygen auto generated documentation.

* Added config file for Doxygen.

* remove MAN generated documentation from Doxygen config

* Added Doxygen documentation generator to makefile

* added README as main page

* update formatting

* init implementation of kernel malloc

* added init of kernel malloc to main kernel

* added docs to gitignore

* refactor codebase structure to move kernel/ and user/ directories to src/ directory

* Switch ifndef to pragam once

* added easy open documentation

* updated variables

* Added testing for memory

* Refactor printf file by simplifiying printf parameters handling

* Added documentation for doxygen + FSM for printf function

* Added testing for printf

* mapp update

* remove map_file.map do VC

* Added debugging make command to makefile

* Added todo for printf file to refactor the file

* added more testing for malloc on kernel.c

* added structure definition for linked list kmalloc

* Move from linear kmalloc to dynamic kmalloc using linked list.

Also added kfree first implementation with some testing

* Added doxygen docs deployement badge to readme

* refatored kmalloc to separate the split block + added doxygem

* added todo comment for memory file testing section

Author: chrisdedman

.gitignore

@@ -1,3 +1,4 @@
 /build
 .DS_Store
-/docs
+/docs
+map_file.map

Makefile

@@ -68,4 +68,7 @@ docs:
 doc:
 	open "docs/html/index.html"
 
+debug:
+	make KFLAGS="-DUSE_KTESTS"
+
 .PHONY: all clean qemu docker docs

README.md

@@ -1,6 +1,7 @@
 # AstraKernel ~ A minimal ARM kernel for QEMU
 
 [![GitHub release (including pre-releases)](https://img.shields.io/github/v/release/sandbox-science/AstraKernel?include_prereleases)](https://github.com/sandbox-science/AstraKernel/releases)
+[![Doxygen Docs](https://github.com/sandbox-science/AstraKernel/actions/workflows/static.yml/badge.svg?branch=main)](https://github.com/sandbox-science/AstraKernel/actions/workflows/static.yml)
 
 AstraKernel is a minimal experimental kernel written in modern C and ARM assembly, designed to run on
 **QEMU’s Versatile AB/PB board with a Cortex‑A8 CPU override (-cpu cortex-a8)**. This setup keeps the

include/memory.h

@@ -7,11 +7,37 @@
 extern "C"
 {
 #endif
+    /**
+     * @enum block_state
+     * @brief Enumeration of block states in the memory allocator.
+     *
+     * This enum defines the possible states of a memory block in the
+     * kernel memory allocator.
+     */
+    enum block_state {
+        BLOCK_FREE = 0, /**< Block is free and available for allocation. */
+        BLOCK_USED      /**< Block is currently allocated and in use. */
+    };
 
-    void  kmalloc_init(void *start, void *limit);
-    void* kmalloc(size_t size);
-    size_t kmalloc_remaining(void);
+    /**
+     * @brief Header structure for memory blocks in the allocator.
+     *
+     * Each allocated or free block in the kernel memory allocator is
+     * preceded by a header that contains metadata about the block.
+     */
+    struct header {
+        size_t           size;     /**< Size of the memory block (excluding header). */
+        enum block_state state;    /**< State of the block (free or used). */
+        struct header    *next;    /**< Pointer to the next block in the linked list. */
+        struct header    *prev;    /**< Pointer to the previous block in the linked list. */
+    };
 
+    struct header *kmalloc_get_head(void);
+
+    void   kmalloc_init(void *start, void *limit);
+    void*  kmalloc(size_t size);
+    void   kfree(void *block);
+    int    kmalloc_test(void);
 #ifdef __cplusplus
 }
 #endif

src/kernel/kernel.c

@@ -71,6 +71,11 @@ void not_main(void)
     void *p2 = kmalloc(48);
     printf("kmalloc(10) addr: %p\n", p);
     printf("kmalloc(48) addr: %p\n", p2);
+    struct header *h = (struct header *)p - 1;
+    struct header *h2 = (struct header *)p2 - 1;
+    printf("size of kmalloc(10) %d\nsize of kmalloc(48) %d\n", h->size, h2->size);
+    kfree(p);
+    kfree(p2);
 
     char *buf = kmalloc(1);
     if (buf)
@@ -114,20 +119,21 @@ void not_main(void)
 #define     TIMER_TICK_TEST     not_main()
 #define     SANITY_CHECK        irq_sanity_check()
 #define     CALL_SVC_0          __asm__ volatile ("svc #0")
+#define     KMALLOC_TEST        kmalloc_test()
 
 // Entry point for the kernel
 void kernel_main(void)
 {
     clear();
     kmalloc_init(&__heap_start__, &__heap_end__);
-    kmalloc_remaining();
 
     /* TESTS */
-    #ifdef USE_KTESTS 
-        SANITY_CHECK;
-        CALL_SVC_0;
-        TIMER_TICK_TEST;
-    #endif
+#ifdef USE_KTESTS 
+    SANITY_CHECK;
+    CALL_SVC_0;
+    KMALLOC_TEST;
+    TIMER_TICK_TEST;
+#endif
 
     /* Back to normal operations */
     init_message();