From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:52447) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UF8OH-0007vb-D5 for qemu-devel@nongnu.org; Mon, 11 Mar 2013 15:28:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UF8O2-00032O-G0 for qemu-devel@nongnu.org; Mon, 11 Mar 2013 15:28:09 -0400 Received: from afflict.kos.to ([92.243.29.197]:34986) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UF8O2-00032A-52 for qemu-devel@nongnu.org; Mon, 11 Mar 2013 15:27:54 -0400 Received: from kos.to (a91-156-58-157.elisa-laajakaista.fi [91.156.58.157]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by afflict.kos.to (Postfix) with ESMTPSA id EC27E26552 for ; Mon, 11 Mar 2013 20:27:52 +0100 (CET) From: riku.voipio@linaro.org Date: Mon, 11 Mar 2013 21:27:48 +0200 Message-Id: In-Reply-To: References: Subject: [Qemu-devel] [PATCH 11/11] linux-user/syscall.c: Don't warn about unimplemented get_robust_list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Peter Maydell From: Peter Maydell The nature of the kernel ABI for the get_robust_list and set_robust_list syscalls means we cannot implement them in QEMU. Make get_robust_list silently return ENOSYS rather than using the default "print message and then fail ENOSYS" code path, in the same way we already do for set_robust_list, and add a comment documenting why we do this. This silences warnings which were being produced for emulating even trivial programs like 'ls' in x86-64-on-x86-64. Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Signed-off-by: Riku Voipio --- linux-user/syscall.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 6182a27..ee82a2d 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -8631,7 +8631,20 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, #ifdef TARGET_NR_set_robust_list case TARGET_NR_set_robust_list: - goto unimplemented_nowarn; + case TARGET_NR_get_robust_list: + /* The ABI for supporting robust futexes has userspace pass + * the kernel a pointer to a linked list which is updated by + * userspace after the syscall; the list is walked by the kernel + * when the thread exits. Since the linked list in QEMU guest + * memory isn't a valid linked list for the host and we have + * no way to reliably intercept the thread-death event, we can't + * support these. Silently return ENOSYS so that guest userspace + * falls back to a non-robust futex implementation (which should + * be OK except in the corner case of the guest crashing while + * holding a mutex that is shared with another process via + * shared memory). + */ + goto unimplemented_nowarn; #endif #if defined(TARGET_NR_utimensat) && defined(__NR_utimensat) -- 1.7.10.4