kernel: add basic modules: arch, mem, rt

6 files changed, 158 insertions, 0 deletions

diff --git a/mem/README b/mem/README
new file mode 100644
index 0000000..bb27b25
--- /dev/null
+++ b/mem/README
@@ -0,0 +1,2 @@
+The [mem] module maintains abstraction and facilities aiming
+to manipulate memory and allocators.
\ No newline at end of file
diff --git a/mem/allocator.c b/mem/allocator.c
new file mode 100644
index 0000000..b4d9068
--- /dev/null
+++ b/mem/allocator.c
@@ -0,0 +1,23 @@
+#include "allocator.h"
+
+/* Dispatches the alloc call */
+void *mem_alloc(MemAllocator *self, usize n) {
+	if (self->alloc)
+		return self->alloc(self, n);
+	
+	return nil;
+}
+
+/* Dispatches the realloc call */
+void *mem_realloc(MemAllocator *self, void *ptr, usize n) {
+	if (self->realloc)
+		return self->realloc(self, ptr, n);
+	
+	return nil;
+}
+
+/* Dispatches the free call */
+void mem_free(MemAllocator *self, void *ptr) {
+	if (self->free)
+		self->free(self, ptr);
+}
\ No newline at end of file
diff --git a/mem/allocator.h b/mem/allocator.h
new file mode 100644
index 0000000..535965a
--- /dev/null
+++ b/mem/allocator.h
@@ -0,0 +1,23 @@
+#ifndef MEM_ALLOCATOR_H
+#define MEM_ALLOCATOR_H
+
+#include <rt.h>
+
+typedef struct mem_allocator MemAllocator;
+
+typedef void *(*MemAlloc)(MemAllocator *, usize);
+typedef void *(*MemRealloc)(MemAllocator *, void *, usize);
+typedef void (*MemFree)(MemAllocator *, void *);
+
+/* Abstract object representing an allocator */
+struct mem_allocator {
+	MemAlloc alloc;
+	MemRealloc realloc;
+	MemFree free;
+};
+
+void *mem_alloc(MemAllocator *self, usize n);
+void *mem_realloc(MemAllocator *self, void *ptr, usize n);
+void mem_free(MemAllocator *self, void *ptr);
+
+#endif
\ No newline at end of file
diff --git a/mem/framer.c b/mem/framer.c
new file mode 100644
index 0000000..9a66feb
--- /dev/null
+++ b/mem/framer.c
@@ -0,0 +1,63 @@
+#include "framer.h"
+
+/* Installs a MemFramer at the specified address */
+MemFramer *mem_framer_install(void *addr, usize end, uint blksz) {
+	MemFramer *self = addr;
+	usize selfend = (usize)(self + 1);
+	usize next = ALIGN_UP(selfend, blksz);
+
+	*self = (MemFramer) {
+		.allocator = (MemAllocator) {
+			.alloc = mem_framer_alloc,
+			.free = mem_framer_free
+		},
+		.next = next,
+		.end = end,
+		.blksz = blksz
+	};
+
+	return self;
+}
+
+/* Allocates a frame */
+void *mem_framer_alloc(MemAllocator *inner, usize n) {
+	/* When allocating a frame, we have two paths:
+	      1. The freelist is not empty: give away
+		     the last freed frame
+		  2. The freelist is empty: bump away the next
+		     frame (pointed at by the next member)
+	   The alloc must fail the freelist is empty and that
+	   the next is beyond the end of the region */
+	
+	MemFramer *self = (MemFramer*)inner;
+
+	/* The implementation does not support more than
+	   one frame */
+	if (n == 0 || n > self->blksz)
+		return nil;
+
+	void *ptr = nil;
+
+	if (self->free) {
+		ptr = self->free;
+		self->free = self->free->next;
+	} else if (self->next + self->blksz <= self->end) {
+		ptr = (void*)self->next;
+		self->next += self->blksz;
+	}
+
+	return ptr;
+}
+
+/* Frees a frame */
+void mem_framer_free(MemAllocator *inner, void *ptr) {
+	/* NOTE: this implementation does make the assumption
+	         that the given pointer is the base of the allocated
+			 region without correction */
+
+	MemFramer *self = (MemFramer*)inner;
+
+	MemFramerFreed *freed = ptr;
+	freed->next = self->free;
+	self->free = freed;
+}
\ No newline at end of file
diff --git a/mem/framer.h b/mem/framer.h
new file mode 100644
index 0000000..6d7034b
--- /dev/null
+++ b/mem/framer.h
@@ -0,0 +1,39 @@
+#ifndef MEM_FRAMER_H
+#define MEM_FRAMER_H
+
+#include <rt.h>
+
+#include "allocator.h"
+
+typedef struct mem_framer_freed {
+	struct mem_framer_freed *next;
+} MemFramerFreed;
+
+/* Allocator for frames: aligned regions of memory of same size */
+typedef struct mem_framer {
+	MemAllocator allocator;
+
+	/* The next frame to be given off to the caller
+	   in case the freelist is empty */
+	usize next;
+
+	/* The end of the region covered by the memory allocator */
+	usize end;
+
+	/* The address of the last frame that has been added in
+	   the freelist
+	   NOTE: the freelist is a singly-linked list comprising
+	         all frames that have been previously allocated
+			 and then freed */ 
+	MemFramerFreed *free;
+
+	/* The size of a frame. This value also defines the alignment
+	   that the frames must respect */
+	uint blksz;
+} MemFramer;
+
+MemFramer *mem_framer_install(void *addr, usize end, uint blksz);
+void *mem_framer_alloc(MemAllocator *self, usize n);
+void mem_framer_free(MemAllocator *self, void *ptr);
+
+#endif
\ No newline at end of file
diff --git a/mem/meson.build b/mem/meson.build
new file mode 100644
index 0000000..ec4a984
--- /dev/null
+++ b/mem/meson.build
@@ -0,0 +1,8 @@
+mem_src = [
+	'allocator.c',
+	'framer.c'
+]
+
+mem = static_library('mem', mem_src, include_directories: kernel_inc)
+
+kernel_mod += mem
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