[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Qemu-stable] [PATCH 36/37] linux-user/syscall.c: Don't warn about unimp

From: Michael Roth
Subject: [Qemu-stable] [PATCH 36/37] linux-user/syscall.c: Don't warn about unimplemented get_robust_list
Date: Tue, 2 Apr 2013 16:45:41 -0500

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>
(cherry picked from commit e9a970a8316f9f86a6c800a9a90175bd593f862c)

Signed-off-by: Michael Roth <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 b682357..4e43a58 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8551,7 +8551,20 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
 #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;
 #if defined(TARGET_NR_utimensat) && defined(__NR_utimensat)

reply via email to

[Prev in Thread] Current Thread [Next in Thread]