linux-user: remove all traces of qemu from /proc/self/cmdline

Instead of post-processing the real contents use the remembered target
argv.  That removes all traces of qemu, including command line options,
and handles QEMU_ARGV0.
Signed-off-by: NAndreas Schwab <schwab@suse.de>
Signed-off-by: NRiku Voipio <riku.voipio@linaro.org>

linux-user/syscall.c

@@ -7358,52 +7358,19 @@ int host_to_target_waitstatus(int 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;
-    }
+    CPUState *cpu = ENV_GET_CPU((CPUArchState *)cpu_env);
+    struct linux_binprm *bprm = ((TaskState *)cpu->opaque)->bprm;
+    int i;
 
-    while (true) {
-        ssize_t nb_read;
-        char buf[128];
-        char *cp_buf = buf;
+    for (i = 0; i < bprm->argc; i++) {
+        size_t len = strlen(bprm->argv[i]) + 1;
 
-        nb_read = read(fd_orig, buf, sizeof(buf));
-        if (nb_read < 0) {
-            int e = errno;
-            fd_orig = close(fd_orig);
-            errno = e;
+        if (write(fd, bprm->argv[i], len) != len) {
             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, nb_read);
-            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) {
-                int e = errno;
-                close(fd_orig);
-                errno = e;
-                return -1;
-            }
         }
     }
 
-    return close(fd_orig);
+    return 0;
 }
 
 static int open_self_maps(void *cpu_env, int fd)