add heap alloc function

Physically contiguous memory

boot/Makefile

@@ -5,7 +5,7 @@ PROG = boot
 SRCS = srt0.S gdt.S boot.c
 OBJS = srt0.o gdt.o boot.o
 
-ESRCS = pccon.c sricon.c print.c fmt.c a20.c time.c mem.c cpu.c
+ESRCS = pccon.c sricon.c print.c fmt.c a20.c time.c mem.c cpu.c alloc.c
 OBJS += $(ESRCS:.c=.o)
 
 include $(SDIR)/Makefile.inc

boot/alloc.c

@@ -0,0 +1,67 @@
+#include <u.h>
+#include "dat.h"
+#include "fn.h"
+
+// only for booting
+
+typedef struct FreeList FreeList;
+static struct FreeList{
+	uint size;
+	FreeList *next;
+} *freed;
+
+extern char end[];
+static char *top = end;
+
+static void
+putfreed(FreeList *p)
+{
+	p->next = nil;
+	if(freed){
+		p->next = freed;
+		freed = p;
+	}else
+		freed = p;
+}
+
+static FreeList*
+getfreed(uint n)
+{
+	for(FreeList *p=freed,*l=freed; p; p=p->next){
+		if(p->size >= n){
+			l->next = p->next;
+			if(p == freed)
+				freed = nil;
+			return p;
+		}
+		l = p;
+	}
+	return nil;
+}
+
+void*
+alloc(uint n)
+{
+	FreeList *p;
+
+	p = getfreed(n);
+	if(p == nil){
+		p = (FreeList*)top;
+		p->size = n;
+		p->next = nil;
+		memset(p+sizeof(*p), 0, n);
+		top += n + sizeof(*p);
+	}
+if(debug) print("alloc %x %ud\n", &p[1], n);
+	return &p[1];
+}
+
+void
+free(void *src)
+{
+	FreeList *p;
+
+	p = (FreeList*)((char*)src-sizeof(FreeList));
+if(debug) print("free %x %ud\n", src, p->size);
+	putfreed(p);
+}

boot/boot.c

@@ -36,6 +36,7 @@ ConDev contab[CON_END] = {
 ConDev *con = &contab[0];
 BIOSmmap biosmmap[64];
 uint cnvmem, extmem;
+int debug = BOOT_DEBUG;
 
 static void
 coninit(void)
@@ -96,7 +97,8 @@ done:
 void
 boot(int bootdev)
 {
-	print("\n\n===> Hello world <===\n\tBooted on disk 0x%x\n", bootdev);
+	print("\n===> Hello world <===\n\t"
+		"Booted on disk 0x%x debug:%d\n\t", bootdev, debug);
 	machdep();	
 
 	for(;;){

boot/dat.h

@@ -3,6 +3,9 @@
 // 0x64	Read	Status Register
 // 0x64	Write	Command Register
 #define TABWIDTH 8
+#ifndef BOOT_DEBUG
+#define BOOT_DEBUG 1
+#endif
 
 enum{
 	CON_PC,
@@ -64,3 +67,4 @@ extern BIOSmmap biosmmap[64];
 extern ConDev contab[CON_END];
 extern ConDev *con;
 extern uint cnvmem, extmem;
+extern int debug;

boot/fn.h

@@ -35,6 +35,13 @@ void cpuidprobe(void);
 // time.c
 long getsecs(void);
 
+// alloc.c
+void *alloc(uint);
+void free(void*);
+
+// util
+void* memset(void *dst, int v, int l);
+
 static __inline int
 major(int x)
 {