[PULL 4/9] linux-user: Implement pivot_root

[Laurent Vivier <laurent@vivier.eu>]

From: YAMAMOTO Takashi <yamamoto@midokura.com>

Used by runc.

Signed-off-by: YAMAMOTO Takashi <yamamoto@midokura.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210531055019.10149-6-yamamoto@midokura.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 linux-user/syscall.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 54037db8d66d..723cb02d2a00 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8257,6 +8257,10 @@ static int host_to_target_cpu_mask(const unsigned long *host_mask,
     return 0;
 }
 
+#if defined(TARGET_NR_pivot_root) && defined(__NR_pivot_root)
+_syscall2(int, pivot_root, const char *, new_root, const char *, put_old)
+#endif
+
 /* This is an internal helper for do_syscall so that it is easier
  * to have a single return point, so that actions, such as logging
  * of syscall results, can be performed.
@@ -13220,6 +13224,23 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
         return ret;
 #endif
 
+#if defined(TARGET_NR_pivot_root)
+    case TARGET_NR_pivot_root:
+        {
+            void *p2;
+            p = lock_user_string(arg1); /* new_root */
+            p2 = lock_user_string(arg2); /* put_old */
+            if (!p || !p2) {
+                ret = -TARGET_EFAULT;
+            } else {
+                ret = get_errno(pivot_root(p, p2));
+            }
+            unlock_user(p2, arg2, 0);
+            unlock_user(p, arg1, 0);
+        }
+        return ret;
+#endif
+
     default:
         qemu_log_mask(LOG_UNIMP, "Unsupported syscall: %d\n", num);
         return -TARGET_ENOSYS;
-- 
2.31.1