Messages in this thread | | | Date | Sat, 3 Mar 2007 20:38:34 +0300 | From | Oleg Nesterov <> | Subject | Re: + fully-honor-vdso_enabled.patch added to -mm tree |
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On 03/02, John Reiser wrote: > > Oleg Nesterov wrote: > > > Still, I don't understand why we don't pass NEW_AUX_ENT(AT_SYSINFO) when > > vdso_enabled == 0. We don't need linux-gate.so to use __kernel_vsyscall, > > we have FIX_VDSO. In that case we should s/PAGE_KERNEL_RO/PAGE_READONLY/ > > of course. I guess the reason is some magic in glibc. > > In the past there were problems where user code could not single-step > (or even read the code of) such system calls. Can these two operations > be performed today with what you propose, particularly if FIX_VDSO is > near 0xfffff000 ?
No, we can't COW the gate page, it lives in swapper_pg_dir. I am not sure why we could not read it, we have gate_vma for that.
So, the reason is debugger. Thanks.
Oleg.
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