linux-user: Add generic env variable handling

Adds support for qemu to modify target process environment
variables using -E and -U commandline switches. This replaces
eventually the -drop-ld-preload flag.

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Riku Voipio <riku.voipio@iki.fi>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6484 c046a42c-6fe2-441c-8c8c-71466251a162

linux-user/envlist.c

@@ -0,0 +1,247 @@
+#include <sys/queue.h>
+
+#include <assert.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "envlist.h"
+
+struct envlist_entry {
+	const char *ev_var;			/* actual env value */
+	LIST_ENTRY(envlist_entry) ev_link;
+};
+
+struct envlist {
+	LIST_HEAD(, envlist_entry) el_entries;	/* actual entries */
+	size_t el_count;			/* number of entries */
+};
+
+static int envlist_parse(envlist_t *envlist,
+    const char *env, int (*)(envlist_t *, const char *));
+
+/*
+ * Allocates new envlist and returns pointer to that or
+ * NULL in case of error.
+ */
+envlist_t *
+envlist_create(void)
+{
+	envlist_t *envlist;
+
+	if ((envlist = malloc(sizeof (*envlist))) == NULL)
+		return (NULL);
+
+	LIST_INIT(&envlist->el_entries);
+	envlist->el_count = 0;
+
+	return (envlist);
+}
+
+/*
+ * Releases given envlist and its entries.
+ */
+void
+envlist_free(envlist_t *envlist)
+{
+	struct envlist_entry *entry;
+
+	assert(envlist != NULL);
+
+	while (envlist->el_entries.lh_first != NULL) {
+		entry = envlist->el_entries.lh_first;
+		LIST_REMOVE(entry, ev_link);
+
+		free((char *)entry->ev_var);
+		free(entry);
+	}
+	free(envlist);
+}
+
+/*
+ * Parses comma separated list of set/modify environment
+ * variable entries and updates given enlist accordingly.
+ *
+ * For example:
+ *     envlist_parse(el, "HOME=foo,SHELL=/bin/sh");
+ *
+ * inserts/sets environment variables HOME and SHELL.
+ *
+ * Returns 0 on success, errno otherwise.
+ */
+int
+envlist_parse_set(envlist_t *envlist, const char *env)
+{
+	return (envlist_parse(envlist, env, &envlist_setenv));
+}
+
+/*
+ * Parses comma separated list of unset environment variable
+ * entries and removes given variables from given envlist.
+ *
+ * Returns 0 on success, errno otherwise.
+ */
+int
+envlist_parse_unset(envlist_t *envlist, const char *env)
+{
+	return (envlist_parse(envlist, env, &envlist_unsetenv));
+}
+
+/*
+ * Parses comma separated list of set, modify or unset entries
+ * and calls given callback for each entry.
+ *
+ * Returns 0 in case of success, errno otherwise.
+ */
+static int
+envlist_parse(envlist_t *envlist, const char *env,
+    int (*callback)(envlist_t *, const char *))
+{
+	char *tmpenv, *envvar;
+	char *envsave = NULL;
+
+	assert(callback != NULL);
+
+	if ((envlist == NULL) || (env == NULL))
+		return (EINVAL);
+
+	/*
+	 * We need to make temporary copy of the env string
+	 * as strtok_r(3) modifies it while it tokenizes.
+	 */
+	if ((tmpenv = strdup(env)) == NULL)
+		return (errno);
+
+	envvar = strtok_r(tmpenv, ",", &envsave);
+	while (envvar != NULL) {
+		if ((*callback)(envlist, envvar) != 0) {
+			free(tmpenv);
+			return (errno);
+		}
+		envvar = strtok_r(NULL, ",", &envsave);
+	}
+
+	free(tmpenv);
+	return (0);
+}
+
+/*
+ * Sets environment value to envlist in similar manner
+ * than putenv(3).
+ *
+ * Returns 0 in success, errno otherwise.
+ */
+int
+envlist_setenv(envlist_t *envlist, const char *env)
+{
+	struct envlist_entry *entry = NULL;
+	const char *eq_sign;
+	size_t envname_len;
+
+	if ((envlist == NULL) || (env == NULL))
+		return (EINVAL);
+
+	/* find out first equals sign in given env */
+	if ((eq_sign = strchr(env, '=')) == NULL)
+		return (EINVAL);
+	envname_len = eq_sign - env + 1;
+
+	/*
+	 * If there already exists variable with given name
+	 * we remove and release it before allocating a whole
+	 * new entry.
+	 */
+	for (entry = envlist->el_entries.lh_first; entry != NULL;
+	    entry = entry->ev_link.le_next) {
+		if (strncmp(entry->ev_var, env, envname_len) == 0)
+			break;
+	}
+
+	if (entry != NULL) {
+		LIST_REMOVE(entry, ev_link);
+		free((char *)entry->ev_var);
+		free(entry);
+	} else {
+		envlist->el_count++;
+	}
+
+	if ((entry = malloc(sizeof (*entry))) == NULL)
+		return (errno);
+	if ((entry->ev_var = strdup(env)) == NULL) {
+		free(entry);
+		return (errno);
+	}
+	LIST_INSERT_HEAD(&envlist->el_entries, entry, ev_link);
+
+	return (0);
+}
+
+/*
+ * Removes given env value from envlist in similar manner
+ * than unsetenv(3).  Returns 0 in success, errno otherwise.
+ */
+int
+envlist_unsetenv(envlist_t *envlist, const char *env)
+{
+	struct envlist_entry *entry;
+	size_t envname_len;
+
+	if ((envlist == NULL) || (env == NULL))
+		return (EINVAL);
+
+	/* env is not allowed to contain '=' */
+	if (strchr(env, '=') != NULL)
+		return (EINVAL);
+
+	/*
+	 * Find out the requested entry and remove
+	 * it from the list.
+	 */
+	envname_len = strlen(env);
+	for (entry = envlist->el_entries.lh_first; entry != NULL;
+	    entry = entry->ev_link.le_next) {
+		if (strncmp(entry->ev_var, env, envname_len) == 0)
+			break;
+	}
+	if (entry != NULL) {
+		LIST_REMOVE(entry, ev_link);
+		free((char *)entry->ev_var);
+		free(entry);
+
+		envlist->el_count--;
+	}
+	return (0);
+}
+
+/*
+ * Returns given envlist as array of strings (in same form that
+ * global variable environ is).  Caller must free returned memory
+ * by calling free(3) for each element and for the array.  Returned
+ * array and given envlist are not related (no common references).
+ *
+ * If caller provides count pointer, number of items in array is
+ * stored there.  In case of error, NULL is returned and no memory
+ * is allocated.
+ */
+char **
+envlist_to_environ(const envlist_t *envlist, size_t *count)
+{
+	struct envlist_entry *entry;
+	char **env, **penv;
+
+	penv = env = malloc((envlist->el_count + 1) * sizeof (char *));
+	if (env == NULL)
+		return (NULL);
+
+	for (entry = envlist->el_entries.lh_first; entry != NULL;
+	    entry = entry->ev_link.le_next) {
+		*(penv++) = strdup(entry->ev_var);
+	}
+	*penv = NULL; /* NULL terminate the list */
+
+	if (count != NULL)
+		*count = envlist->el_count;
+
+	return (env);
+}