[Minios-devel] [UNIKRAFT PATCH v3 3/3] lib/posix-user: Add more group file related functions

[stefanl.teodorescu@xxxxxxxxx]

From: Costin Lupu <costin.lupu@xxxxxxxxx>

This patch introduces the changes needed for iterating through the
"/etc/groups" file. But because we currently provide only a single hardcoded
group, we will return just one single entry. This can be extended easily,
either by adding more hardcoded groups or by using the actual "/etc/groups".
However, the latter option is subject to future work, when we will need a more
consistent analysis regarding user management and permissions on Unikraft.

The groups iterator is thread safe, therefore we also introduce the `__uk_tls`,
qualifier which depends on `CONFIG_HAVE_SCHED`, and mark the users iterator as
TLS as well. Another minor change revisits this library constructor by marking
it as a Unikraft constructor.

Signed-off-by: Costin Lupu <costin.lupu@xxxxxxxxx>
Reviewed-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
---
 include/uk/essentials.h |  6 ++++
 lib/posix-user/user.c   | 72 +++++++++++++++++++++++++++++++++++++++--
 2 files changed, 75 insertions(+), 3 deletions(-)

diff --git a/include/uk/essentials.h b/include/uk/essentials.h
index e8264c5f..a6d969e7 100644
--- a/include/uk/essentials.h
+++ b/include/uk/essentials.h
@@ -124,6 +124,12 @@ extern "C" {
 #define __constructor_prio(lvl) __attribute__ ((constructor (lvl)))
 #endif
 
+#ifdef CONFIG_HAVE_SCHED
+#define __uk_tls __thread
+#else
+#define __uk_tls
+#endif
+
 #else
 /* TO BE DEFINED */
 #endif /* __GNUC__ */
diff --git a/lib/posix-user/user.c b/lib/posix-user/user.c
index 0d6ca3fb..715c4cef 100644
--- a/lib/posix-user/user.c
+++ b/lib/posix-user/user.c
@@ -41,6 +41,7 @@
 #include <sys/types.h>
 #include <uk/essentials.h>
 #include <uk/list.h>
+#include <uk/ctors.h>
 #include <uk/print.h>
 #include <uk/user.h>
 
@@ -50,7 +51,7 @@
 #define UK_DEFAULT_GROUP  "root"
 #define UK_DEFAULT_PASS   "x"
 
-static struct passwd_entry {
+static __uk_tls struct passwd_entry {
        struct passwd *passwd;
 
        UK_SLIST_ENTRY(struct passwd_entry) entries;
@@ -60,7 +61,13 @@ UK_SLIST_HEAD(uk_entry_list, struct passwd_entry);
 
 static struct uk_entry_list passwds;
 
-void __constructor init_ukunistd()
+static void init_groups(void);
+
+/*
+ * TODO make passwd management consistent with group management
+ */
+
+static void init_posix_user(void)
 {
        static struct passwd_entry p1;
        static struct passwd passwd = {
@@ -77,7 +84,10 @@ void __constructor init_ukunistd()
 
        UK_SLIST_INIT(&passwds);
        UK_SLIST_INSERT_HEAD(&passwds, &p1, entries);
+
+       init_groups();
 }
+UK_CTOR_FUNC(2, init_posix_user);
 
 uid_t getuid(void)
 {
@@ -169,7 +179,7 @@ int getpwuid_r(uid_t uid __unused, struct passwd *pwd 
__unused,
 struct passwd *getpwent(void)
 {
        struct passwd *pwd;
-       
+
        if (iter == NULL)
                return NULL;
 
@@ -328,3 +338,59 @@ int getgrnam_r(const char *name, struct group *grp,
 
        return 0;
 }
+
+struct group *getgrgid(gid_t gid)
+{
+       struct group *res;
+
+       if (gid == g__.gr_gid)
+               res = &g__;
+       else {
+               res = NULL;
+               errno = ENOENT;
+       }
+
+       return res;
+}
+
+static __uk_tls struct group_entry {
+       struct group *group;
+       UK_SLIST_ENTRY(struct group_entry) entries;
+} *groups_iter;
+
+UK_SLIST_HEAD(uk_group_entry_list, struct group_entry);
+
+static struct uk_group_entry_list groups;
+
+static void init_groups(void)
+{
+       static struct group_entry ge;
+
+       ge.group = &g__;
+       UK_SLIST_INIT(&groups);
+       UK_SLIST_INSERT_HEAD(&groups, &ge, entries);
+}
+
+void setgrent(void)
+{
+       groups_iter = UK_SLIST_FIRST(&groups);
+}
+
+void endgrent(void)
+{
+       setgrent();
+}
+
+struct group *getgrent(void)
+{
+       struct group *res;
+
+       if (groups_iter) {
+               res = groups_iter->group;
+               groups_iter = UK_SLIST_NEXT(groups_iter, entries);
+       } else
+               res = NULL;
+
+       return res;
+
+}
-- 
2.25.0


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