Commit e9a970a8 authored by Peter Maydell's avatar Peter Maydell Committed by Riku Voipio
Browse files

linux-user/syscall.c: Don't warn about unimplemented get_robust_list 



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: default avatarPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: default avatarRichard Henderson <rth@twiddle.net>
Signed-off-by: default avatarRiku Voipio <riku.voipio@linaro.org>
parent a94b4987

linux-user/syscall.c

+14 −1
Original line number Diff line number Diff line
@@ -8631,6 +8631,19 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, 


#ifdef TARGET_NR_set_robust_list

    case TARGET_NR_set_robust_list:

    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