[Qemu-devel] [PATCH] linux-user: improve fake /proc/self/stat making `ps` not segfault.

[Fabio Erculiani <lxnay@sabayon.org>]

With the current fake /proc/self/stat implementation `ps` is
segfaulting because it expects to read PID and argv[0] as first and
second field respectively, with the latter being enclosed between
backets.

Reproducing is as easy as running: `ps` inside qemu-user chroot
with /proc mounted.

Signed-off-by: Fabio Erculiani <lxnay@sabayon.org>
---
 linux-user/syscall.c |   20 +++++++++++++++-----
 1 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 9ba51bf..f2af5d5 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4678,14 +4678,24 @@ static int open_self_stat(void *cpu_env, int fd)
       int len;
       uint64_t val = 0;
 
-      if (i == 27) {
-          /* stack bottom */
-          val = start_stack;
+      if (i == 0) {
+        /* pid */
+        snprintf(buf, sizeof(buf), "%"PRId64 " ", getpid());
+      } else if (i == 1) {
+        /* app name */
+        snprintf(buf, sizeof(buf), "(%s) ", ts->bprm->argv[0]);
+      } else if (i == 27) {
+        /* stack bottom */
+        val = start_stack;
+        snprintf(buf, sizeof(buf), "%"PRId64 " ", val);
+      } else {
+        /* for the rest, there is MasterCard */
+        snprintf(buf, sizeof(buf), "0%c", i == 43 ? '\n' : ' ');
       }
-      snprintf(buf, sizeof(buf), "%"PRId64 "%c", val, i == 43 ? '\n' : ' ');
+
       len = strlen(buf);
       if (write(fd, buf, len) != len) {
-          return -1;
+        return -1;
       }
     }
 
-- 
1.7.7