linux-user: added fake open() for /proc/self/cmdline

Signed-off-by: Wim Vander Schelden <wim@fixnum.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

linux-user/syscall.c

@@ -4949,6 +4949,51 @@ int host_to_target_waitstatus(int status)
     return status;
 }
 
+static int open_self_cmdline(void *cpu_env, int fd)
+{
+    int fd_orig = -1;
+    bool word_skipped = false;
+
+    fd_orig = open("/proc/self/cmdline", O_RDONLY);
+    if (fd_orig < 0) {
+        return fd_orig;
+    }
+
+    while (true) {
+        ssize_t nb_read;
+        char buf[128];
+        char *cp_buf = buf;
+
+        nb_read = read(fd_orig, buf, sizeof(buf));
+        if (nb_read < 0) {
+            fd_orig = close(fd_orig);
+            return -1;
+        } else if (nb_read == 0) {
+            break;
+        }
+
+        if (!word_skipped) {
+            /* Skip the first string, which is the path to qemu-*-static
+               instead of the actual command. */
+            cp_buf = memchr(buf, 0, sizeof(buf));
+            if (cp_buf) {
+                /* Null byte found, skip one string */
+                cp_buf++;
+                nb_read -= cp_buf - buf;
+                word_skipped = true;
+            }
+        }
+
+        if (word_skipped) {
+            if (write(fd, cp_buf, nb_read) != nb_read) {
+                return -1;
+            }
+        }
+    }
+
+    return close(fd_orig);
+}
+
 static int open_self_maps(void *cpu_env, int fd)
 {
 #if defined(TARGET_ARM) || defined(TARGET_M68K) || defined(TARGET_UNICORE32)
@@ -5150,6 +5195,7 @@ static int do_open(void *cpu_env, const char *pathname, int flags, mode_t mode)
         { "maps", open_self_maps, is_proc_myself },
         { "stat", open_self_stat, is_proc_myself },
         { "auxv", open_self_auxv, is_proc_myself },
+        { "cmdline", open_self_cmdline, is_proc_myself },
 #if defined(HOST_WORDS_BIGENDIAN) != defined(TARGET_WORDS_BIGENDIAN)
         { "/proc/net/route", open_net_route, is_proc },
 #endif