Add /proc/mm and a /bin/mm utility that just dumps it.

This shows some info about the MM. Right now it's just the zone count
and the number of free physical pages. Lots more can be added.

Also added "exit" to sh so we can nest shells and exit from them.

I also noticed that we were leaking all the physical pages, so fixed that.

Userland/.gitignore

@@ -13,3 +13,4 @@ cat
 uname
 clear
 tst
+mm

Userland/Makefile

@@ -12,7 +12,8 @@ OBJS = \
        cat.o \
        uname.o \
        clear.o \
-       tst.o
+       tst.o \
+       mm.o
 
 APPS = \
        id \
@@ -28,7 +29,8 @@ APPS = \
        cat \
        uname \
        clear \
-       tst
+       tst \
+       mm
 
 ARCH_FLAGS =
 STANDARD_FLAGS = -std=c++17 -nostdinc++ -nostdlib
@@ -90,6 +92,9 @@ clear: clear.o
 tst: tst.o
 	$(LD) -o $@ $(LDFLAGS) $< ../LibC/LibC.a
 
+mm: mm.o
+	$(LD) -o $@ $(LDFLAGS) $< ../LibC/LibC.a
+
 .cpp.o:
 	@echo "CXX $<"; $(CXX) $(CXXFLAGS) -o $@ -c $<
 

Userland/mm.cpp

@@ -0,0 +1,25 @@
+#include <LibC/stdio.h>
+#include <LibC/unistd.h>
+
+int main(int c, char** v)
+{
+    int fd = open("/proc/mm");
+    if (fd == -1) {
+        perror("failed to open /proc/mm");
+        return 1;
+    }
+    for (;;) {
+        char buf[128];
+        ssize_t nread = read(fd, buf, sizeof(buf));
+        if (nread == 0)
+            break;
+        if (nread < 0) {
+            perror("failed to read");
+            return 2;
+        }
+        for (ssize_t i = 0; i < nread; ++i) {
+            putchar(buf[i]);
+        }
+    }
+    return 0;
+}

Userland/ps.cpp

@@ -5,7 +5,7 @@ int main(int c, char** v)
 {
     int fd = open("/proc/summary");
     if (fd == -1) {
-        printf("failed to open /proc/summary :(\n");
+        perror("failed to open /proc/summary");
         return 1;
     }
     for (;;) {
@@ -14,7 +14,7 @@ int main(int c, char** v)
         if (nread == 0)
             break;
         if (nread < 0) {
-            printf("failed to read :(\n");
+            perror("failed to read");
             return 2;
         }
         for (ssize_t i = 0; i < nread; ++i) {

Userland/sh.cpp

@@ -26,6 +26,13 @@ static int sh_pwd(int, const char**)
     return 0;
 }
 
+static int sh_exit(int, const char**)
+{
+    printf("Good-bye!\n");
+    exit(0);
+    return 0;
+}
+
 static int sh_cd(int argc, const char** argv)
 {
     if (argc == 1) {
@@ -77,6 +84,10 @@ static bool handle_builtin(int argc, const char** argv, int& retval)
         retval = sh_pwd(argc, argv);
         return true;
     }
+    if (!strcmp(argv[0], "exit")) {
+        retval = sh_exit(argc, argv);
+        return true;
+    }
     return false;
 }