| Message ID | 1360334094-1991-1-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | Accepted |
| Commit | e9a970a8316f9f86a6c800a9a90175bd593f862c |
| Headers | show |
On 2013-02-08 06:34, Peter Maydell wrote: > 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<peter.maydell@linaro.org> > --- > linux-user/syscall.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) Reviewed-by: Richard Henderson <rth@twiddle.net> r~
diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 9e31ea7..cd0389b 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -8550,7 +8550,20 @@ 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)
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 <peter.maydell@linaro.org> --- linux-user/syscall.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)