1 files changed, 164 insertions, 0 deletions
diff --git a/sys/src/cmd/upas/fs/seg.c b/sys/src/cmd/upas/fs/seg.c
new file mode 100644
index 000000000..394b66ad3
--- /dev/null
+++ b/sys/src/cmd/upas/fs/seg.c
@@ -0,0 +1,164 @@
+#include "common.h"
+#include <libsec.h>
+#include "dat.h"
+
+/*
+ * unnatural acts with virtual memory
+ */
+
+typedef struct{
+	int	ref;
+	char	*va;
+	long	sz;
+}S;
+
+static S		s[15];		/* 386 only gives 4 */
+static int		nstab = nelem(s);
+static long	ssem = 1;
+//static ulong	thresh = 10*1024*1024;
+static ulong	thresh = 1024;
+
+void*
+segmalloc(ulong sz)
+{
+	int i, j;
+	void *va;
+
+	if(sz < thresh)
+		return emalloc(sz);
+	semacquire(&ssem, 1);
+	for(i = 0; i < nstab; i++)
+		if(s[i].ref == 0)
+			goto found;
+notfound:
+	/* errstr not informative; assume we hit seg limit */
+	for(j = nstab - 1; j >= i; j--)
+		if(s[j].ref)
+			break;
+	nstab = j;
+	semrelease(&ssem, 1);
+	return emalloc(sz);
+found:
+	/*
+	 * the system doesn't leave any room for expansion
+	 */
+	va = segattach(SG_CEXEC, "memory", 0, sz + sz/10 + 4096);
+	if(va == 0)
+		goto notfound;
+	s[i].ref++;
+	s[i].va = va;
+	s[i].sz = sz;
+	semrelease(&ssem, 1);
+	memset(va, 0, sz);
+	return va;
+}
+
+void
+segmfree(void *va)
+{
+	char *a;
+	int i;
+
+	a = va;
+	for(i = 0; i < nstab; i++)
+		if(s[i].va == a)
+			goto found;
+	free(va);
+	return;
+found:
+	semacquire(&ssem, 1);
+	s[i].ref--;
+	s[i].va = 0;
+	s[i].sz = 0;
+	semrelease(&ssem, 1);
+}
+
+void*
+segreallocfixup(int i, ulong sz)
+{
+	char buf[ERRMAX];
+	void *va, *ova;
+
+	rerrstr(buf, sizeof buf);
+	if(strstr(buf, "segments overlap") == 0)
+		sysfatal("segibrk: %r");
+	va = segattach(SG_CEXEC, "memory", 0, sz);
+	if(va == 0)
+		sysfatal("segattach: %r");
+	ova = s[i].va;
+fprint(2, "fix memcpy(%p, %p, %lud)\n", va, ova, s[i].sz);
+	memcpy(va, ova, s[i].sz);
+	s[i].va = va;
+	s[i].sz = sz;
+	segdetach(ova);
+	return va;
+}
+
+void*
+segrealloc(void *va, ulong sz)
+{
+	char *a;
+	int i;
+	ulong sz0;
+
+fprint(2, "segrealloc %p %lud\n", va, sz);
+	if(va == 0)
+		return segmalloc(sz);
+	a = va;
+	for(i = 0; i < nstab; i++)
+		if(s[i].va == a)
+			goto found;
+	if(sz >= thresh)
+	if(a = segmalloc(sz)){
+		sz0 = msize(va);
+		memcpy(a, va, sz0);
+fprint(2, "memset(%p, 0, %lud)\n", a + sz0, sz - sz0);
+		memset(a + sz0, 0, sz - sz0);
+		return a;
+	}
+	return realloc(va, sz);
+found:
+	sz0 = s[i].sz;
+fprint(2, "segbrk(%p, %p)\n", s[i].va, s[i].va + sz);
+	va = segbrk(s[i].va, s[i].va + sz);
+	if(va == (void*)-1 || va < end)
+		return segreallocfixup(i, sz);
+	a = va;
+	if(sz > sz0)
+{
+fprint(2, "memset(%p, 0, %lud)\n", a + sz0, sz - sz0);
+		memset(a + sz0, 0, sz - sz0);
+}
+	s[i].va = va;
+	s[i].sz = sz;
+	return va;
+}
+
+void*
+emalloc(ulong n)
+{
+	void *p;
+fprint(2, "emalloc %lud\n", n);
+	p = mallocz(n, 1);
+	if(!p)
+		sysfatal("malloc %lud: %r", n);
+	setmalloctag(p, getcallerpc(&n));
+	return p;
+}
+
+void
+main(void)
+{
+	char *p;
+	int i;
+	ulong sz;
+
+	p = 0;
+	for(i = 0; i < 6; i++){
+		sz = i*512;
+		p = segrealloc(p, sz);
+		memset(p, 0, sz);
+	}
+	segmfree(p);
+	exits("");
+}