linux-user/elfload: check PR_GET_DUMPABLE before creating coredump

A process can opt-out of coredump creation by calling
prctl(PR_SET_DUMPABLE, 0).
linux-user passes this call from the guest through to the
operating system.
From there it can be read back again to avoid creating coredumps from
qemu-user itself if the guest chose so.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
Message-Id: <20240120-qemu-user-dumpable-v3-2-6aa410c933f1@t-8ch.de>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

linux-user/elfload.c

@@ -2,6 +2,7 @@
 #include "qemu/osdep.h"
 #include <sys/param.h>
 
+#include <sys/prctl.h>
 #include <sys/resource.h>
 #include <sys/shm.h>
 
@@ -4667,6 +4668,11 @@ static int elf_core_dump(int signr, const CPUArchState *env)
     init_note_info(&info);
 
     errno = 0;
+
+    if (prctl(PR_GET_DUMPABLE) == 0) {
+        return 0;
+    }
+
     if (getrlimit(RLIMIT_CORE, &dumpsize) == 0 && dumpsize.rlim_cur == 0) {
         return 0;
     }