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[Qemu-devel] [PATCH] linux-user/syscall.c: Don't warn about unimplemente
From: |
Peter Maydell |
Subject: |
[Qemu-devel] [PATCH] linux-user/syscall.c: Don't warn about unimplemented get_robust_list |
Date: |
Fri, 8 Feb 2013 14:34:54 +0000 |
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>
---
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 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)
--
1.7.9.5
- [Qemu-devel] [PATCH] linux-user/syscall.c: Don't warn about unimplemented get_robust_list,
Peter Maydell <=