Messages in this thread | | | Date | Fri, 29 Feb 2008 16:52:07 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86_64 ia32 syscall restart fix |
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* Roland McGrath <roland@redhat.com> wrote:
> The code to restart syscalls after signals depends on checking for a > negative orig_ax, and for particular negative -ERESTART* values in ax. > These fields are 64 bits and for a 32-bit task they get zero-extended. > The syscall restart behavior is lost, a regression from a native > 32-bit kernel and from 64-bit tasks' behavior. This patch fixes the > problem by doing sign-extension where it matters. For orig_ax, the > only time the value should be -1 but winds up as 0x0ffffffff is via a > 32-bit ptrace call. So the patch changes ptrace to sign-extend the > 32-bit orig_eax value when it's stored; it doesn't change the checks > on orig_ax, though it uses the new current_syscall() inline to better > document the subtle importance of the used of signedness there. The > ax value is stored a lot of ways and it seems hard to get them all > sign-extended at their origins. So for that, we use the > current_syscall_ret() to sign-extend it only for 32-bit tasks at the > time of the -ERESTART* comparisons.
thanks, applied.
Ingo
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