I found couple of events using al, bl, cl and dl registers for argument.
These are not directly accepted by uprobe_events and thus needs to be
mapped to ax, bx, cx and dx respectively.

Few ex,

  /usr/bin/qemu-system-s390x
    css_adapter_interrupt: 1@%bl
    css_chpid_add: 1@%cl 1@%sil 1@%dl
    dma_bdrv_io: 8@%rbx 8@%rbp -8@%r14 1@%al

  /usr/bin/postgres
    buffer__read__done: ... -1@-bash -1@%al
    buffer__read__start: ... -1@%al

I don't find any sdt events using ah, bh,... registers. But I also don't
see any reason to not use them, so there might be rare events using
these registers, and if so, perf should have a renaming logic for them
too.
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexis Berlemont <alexis.berlemont@gmail.com>
Cc: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170328094754.3156-2-ravi.bangoria@linux.vnet.ibm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>