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[Qemu-devel] [PATCH 11/11] linux-user/syscall.c: Don't warn about unimpl
From: |
riku . voipio |
Subject: |
[Qemu-devel] [PATCH 11/11] linux-user/syscall.c: Don't warn about unimplemented get_robust_list |
Date: |
Mon, 11 Mar 2013 21:27:48 +0200 |
From: Peter Maydell <address@hidden>
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 <address@hidden>
Reviewed-by: Richard Henderson <address@hidden>
Signed-off-by: Riku Voipio <address@hidden>
---
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
- [Qemu-devel] [PATCH 05/11] linux-user: Support setgroups syscall with no groups, (continued)
- [Qemu-devel] [PATCH 05/11] linux-user: Support setgroups syscall with no groups, riku . voipio, 2013/03/11
- [Qemu-devel] [PATCH 02/11] linux-user: improve print_fcntl(), riku . voipio, 2013/03/11
- [Qemu-devel] [PATCH 03/11] linux-user/syscall.c: handle FUTEX_WAIT_BITSET in do_futex, riku . voipio, 2013/03/11
- [Qemu-devel] [PATCH 04/11] linux-user: fix futex strace of FUTEX_CLOCK_REALTIME, riku . voipio, 2013/03/11
- [Qemu-devel] [PATCH 09/11] linux-user: Implement sendfile and sendfile64, riku . voipio, 2013/03/11
- [Qemu-devel] [PATCH 06/11] linux-user: Add more sparc syscall numbers, riku . voipio, 2013/03/11
- [Qemu-devel] [PATCH 10/11] linux-user: Implement accept4, riku . voipio, 2013/03/11
- [Qemu-devel] [PATCH 01/11] linux-user: Add Alpha socket constants, riku . voipio, 2013/03/11
- [Qemu-devel] [PATCH 07/11] linux-user: Fix layout of usage table to account for option text, riku . voipio, 2013/03/11
- [Qemu-devel] [PATCH 08/11] linux-user: make bogus negative iovec lengths fail EINVAL, riku . voipio, 2013/03/11
- [Qemu-devel] [PATCH 11/11] linux-user/syscall.c: Don't warn about unimplemented get_robust_list,
riku . voipio <=
- Re: [Qemu-devel] [PULL] linux-user updates, Peter Maydell, 2013/03/11
- Re: [Qemu-devel] [PULL] linux-user updates, Anthony Liguori, 2013/03/15