uprobes: Shift ->readpage check from __copy_insn() to uprobe_register()
authorOleg Nesterov <oleg@redhat.com>
Mon, 19 May 2014 18:40:54 +0000 (20:40 +0200)
committerIngo Molnar <mingo@kernel.org>
Thu, 5 Jun 2014 10:30:07 +0000 (12:30 +0200)
commit41ccba029e9492dd0fc1bf5c23b72c6322a6dfe9
treed12da7b78672c157b26a32b2d8a9067f6fe9d6e7
parentc184c980de30dc5f6fec4b281928aa6743708da9
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>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140519184054.GA6750@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
kernel/events/uprobes.c