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SubjectRe: [PATCH] uprobes: Shift ->readpage check from __copy_insn() to uprobe_register()
* Oleg Nesterov <oleg@redhat.com> [2014-05-19 20:40:54]:

> Sorry for double-posting, but it seems that this patch didn't reach
> lkml. Let me resend it just on case. Plus another patch in reply, on
> top of this change.
>
> -------------------------------------------------------------------------------
> Subject: [PATCH] uprobes: Shift ->readpage check from __copy_insn() to uprobe_register()
>
> copy_insn() fails with -EIO if ->readpage == NULL, but this error
> is not propagated unless uprobe_register() path finds ->mm which
> already mmaps this file. In this case (say) "perf record" does not
> actually install the probe, but the user can't know about this.
>
> Move this check into uprobe_register() so that this problem can be
> detected earlier and reported to user.
>
> Note: this is still not perfect,
>
> - copy_insn() and arch_uprobe_analyze_insn() should be called
> by uprobe_register() but this is not simple, we need vm_file
> for read_mapping_page() (although perhaps we can pass NULL),
> and we need ->mm for is_64bit_mm() (although this logic is
> broken anyway).
>
> - uprobe_register() should be called by create_trace_uprobe(),
> not by probe_event_enable(), so that an error can be detected
> at "perf probe -x" time. This also needs more changes in the
> core uprobe code, uprobe register/unregister interface was
> poorly designed from the very beginning.
>
> Reported-by: Denys Vlasenko <dvlasenk@redhat.com>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

--
Thanks and Regards
Srikar Dronamraju



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