From 70bf449665545c34d7db0154bbcbacf990565ce0 Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@linux.intel.com>
Date: Sat, 27 Dec 2014 15:12:17 +0000
Subject: [PATCH] init: remove use of the malloc package

We can sbrk up our own environment strings and that cuts init down to about
9K. Way more than it should be, but most of what it drags in now needs
fixing in the libraries instead.
---
 Applications/util/init.c | 68 ++++++++++++++++++++++++++--------------
 1 file changed, 45 insertions(+), 23 deletions(-)

diff --git a/Applications/util/init.c b/Applications/util/init.c
index 148e1caf..8ae13010 100644
--- a/Applications/util/init.c
+++ b/Applications/util/init.c
@@ -10,8 +10,6 @@
 #include <fcntl.h>
 #include <pwd.h>
 
-extern char **environ;
-
 char *argp[] = { "sh", NULL };
 
 #define crlf   write(1, "\n", 1)
@@ -47,10 +45,7 @@ int main(int argc, char *argv[])
     close(2);
     dup(fdtty1);
 
-    /* start with a clean environment */
-    environ = 0;
-
-    putstr("init version 0.8\n");
+    putstr("init version 0.8.1ac\n");
     
     /* then call the login procedure on it */
 
@@ -70,6 +65,43 @@ int main(int argc, char *argv[])
     }
 }
 
+static char *env[10];
+static int envn;
+#if 1
+static char hex(char *av, int b)
+{
+    unsigned int x = (unsigned int)av;
+    x >>= b;
+    x &= 15;
+    if (x < 10)
+        x += '0';
+    else
+        x += 'A' - 10;
+    return (char)x;
+}
+#endif
+static void envset(char *a, char *b)
+{
+    int al = strlen(a);
+    static char hptr[5];
+    char *tp = sbrk(al + strlen(b) + 2);
+    if (tp == (char *)-1) {
+        putstr("out of memory.\n");
+        return;
+    }
+    strcpy(tp, a);
+    tp[al]='=';
+    strcpy(tp + al + 1, b);
+    env[envn++] = tp;
+#if 0    
+    hptr[0] = hex(tp,12);
+    hptr[1] = hex(tp,8);
+    hptr[2] = hex(tp,4);
+    hptr[3] = hex(tp,0);
+    putstr(hptr);
+#endif    
+}
+
 int login(char *ttyname)
 {
     int  fdtty, pid;
@@ -91,11 +123,8 @@ int login(char *ttyname)
             }
             
             /* here we are inside child's context of execution */
-            
-            putenv("PATH=:/bin:/usr/bin");
-            strcpy(buf, "CTTY=");
-            strcat(buf, ttyname);
-            putenv(strdup(buf));
+            envset("PATH", "/bin:/usr/bin");     
+            envset("CTTY", ttyname);
 
             /* make stdin, stdout and stderr point to fdtty */
 
@@ -153,17 +182,9 @@ void spawn(struct passwd *pwd)
 
     /* setup user environment variables */
 
-    strcpy(buf, "LOGNAME=");
-    strcat(buf, pwd->pw_name);
-    putenv(strdup(buf));
-
-    strcpy(buf, "HOME=");
-    strcat(buf, pwd->pw_dir);
-    putenv(strdup(buf));
-
-    strcpy(buf, "SHELL=");
-    strcat(buf, pwd->pw_shell);
-    putenv(strdup(buf));
+    envset("LOGNAME", pwd->pw_name);
+    envset("HOME", pwd->pw_dir);
+    envset("SHELL", pwd->pw_shell);
 
     /*chdir(pwd->pw_dir);*/
 
@@ -182,7 +203,8 @@ void spawn(struct passwd *pwd)
     argp[0] = buf;
     argp[1] = NULL;
 
-    execve(pwd->pw_shell, argp, environ);
+    putstr(pwd->pw_shell);
+    execve(pwd->pw_shell, argp, env);
     putstr("login: can't execute shell\n");
     exit(1);
 }
-- 
2.34.1