[PATCH 2/2 v2] perf tools: Enable bpf prologue for arm64

On Thu, Jan 26, 2017 at 10:49:16AM +0900, Masami Hiramatsu wrote:

On Wed, 25 Jan 2017 13:32:01 +0000
Will Deacon [off-list ref] wrote:

quoted

On Wed, Jan 25, 2017 at 07:23:11AM +0000, He Kuang wrote:

quoted

Since HAVE_KPROBES can be enabled in arm64, this patch introduces
regs_query_register_offset() to convert register name to offset for
arm64, so the BPF prologue feature is ready to use.

This patch also changes the 'dwarfnum' to 'offset' in register table,
so the related functions are consistent with x86.

Wouldn't it be an awful lot simpler just to leave the code as-is, and
implement regs_query_register_offset in the same way that we implement
get_arch_regstr but return the dwarfnum?

No, since the offset is not same as dwarfnum.

With this style, the index of array becomes the dwarfnum (the index of
each register defined by DWARF) and the "offset" member means the
byte-offset of the register in (user_)pt_regs. Those should be different.

Ok, then do it as two patches then, rather than introduce functionality
along with the renaming.

quoted

I don't really see the point of all the refactoring.

Also, from the maintenance point of view, this rewrite work makes
the code simply similar to x86 implementation, that will be easier to
maintain :)

Right, apart from the two howling bugs in the version that was nearly merged
initially :p. I tend to err on the "if it ain't broke, don't fix it" side
of the argument but if you really want the refactoring lets keep it as a
separate change.

Will