Re: [PATCH RFC 07/19] perf tools: Workaround missing maps for x86_64 KPTI entry trampolines

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Thu, May 10, 2018 at 05:19:22PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Thu, May 10, 2018 at 05:15:42PM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Thu, May 10, 2018 at 07:08:37PM +0000, Hunter, Adrian escreveu:
> > > Let me know if you want me to post the workaround patches separately,
> > > otherwise I will wait a bit before sending the patches again.

> > I'll see if I went thru all of the patches already...
 
> So I looked at the patches posted and one comment is about the terse
> commit logs for some of the kcore_copy patches, for instance:
 
> --------------------
>  In preparation to add more program headers, get rid of kernel_map and
> modules_map.
> --------------------
 
> Can't this be made a bit more verbose? Lemme re-read the patch...

So you had just one pointers to the kernel map and a module_maps, and
then this is replaced by kcore_copy__map() that instead of populating
those fields that are being removed:

-       struct phdr_data kernel_map;
-       struct phdr_data modules_map;

Will allocate and add "struct phdr_data" instances to the
kcore_copy_info->phdrs list, so I propose, to follow convention used
elsewhere in tools/perf/ that you rename kcore_copy__map() to

  kcore_copy_info__addnew(kci, fields)

I would do it as:

struct phdr_data *phdr_data__new(fields)
{
	return  zalloc() + init fields;
}

struct phdr_data *kcore_copy_info__addnew(kci, fields)
{
	struct phdr_data *pd = phdr_data__new(fields);

	if (pd)
		list_add(&pd->list, &kci->phdrs)
}

Also please rename pd->list to pd->node, to clarify that it is a node in
some list, not a list.

The commit log list then could reflect that somehow, with something
around:

----------------------

Move ->kernel_map and ->modules_map to newly allocated entries in the
->phdrs list.

----------------------

wdyt?

- Arnaldo