Re: [PATCH v1 2/2] Strip build path directories in tools, xen and xen/arch/x86

[Jan Beulich <jbeulich@xxxxxxxx>]

On 20.03.2025 15:36, Anthony PERARD wrote:
> On Thu, Mar 20, 2025 at 02:59:04PM +0100, Marek Marczykowski-Górecki wrote:
>> On Thu, Mar 20, 2025 at 02:49:27PM +0100, Jan Beulich wrote:
>>> On 20.03.2025 13:51, Marek Marczykowski-Górecki wrote:
>>>> On Thu, Mar 20, 2025 at 10:18:28AM +0000, Anthony PERARD wrote:
>>>>> On Wed, Mar 19, 2025 at 02:40:33PM +0100, Marek Marczykowski-Górecki 
>>>>> wrote:
>>>>>> There are clearly some build path embedding left. And
>>>>>> -ffile-prefix-map=/-fdebug-prefix-map= doesn't work correctly with
>>>>>> XEN_ROOT having xen/.. at the end.
>>>>>> BTW, would it be acceptable to have this?
>>>>>>
>>>>>>     $(call cc-option-add,CFLAGS,CC,-fdebug-prefix-map=$(realpath 
>>>>>> $(XEN_ROOT))=.)
>>>>>
>>>>> Hi,
>>>>>
>>>>> Could you avoid using $(XEN_ROOT) in hypervisor build system? (It's fine
>>>>> in "tools/"). In "xen/", there's a few variables you can use if they are
>>>>> needed: $(abs_objtree) $(abs_srctree) for absolutes path, and $(srctree)
>>>>> $(objtree) for relative path. That also should avoid the need to use
>>>>> $(realpath ).
>>>>
>>>> XEN_ROOT is literally "$(abs_srctree)/..". And I need to resolve it to
>>>> not have /.. for prefix-map to work correctly. Would it be better to use
>>>> literal $(realpath $(abs_srctree)/..)? Or use just $(abs_srctree) and
>>>> have paths in debug symbols relative to hypervisor source dir, instead
>>>> of xen repo root? I'm not sure if that wouldn't confuse some tools...
>>>
>>> abs_srctree being computed using realpath, can't we replace
>>>
>>> export XEN_ROOT := $(abs_srctree)/..
>>>
>>> by something as simpl{e,istic} as
>>>
>>> export XEN_ROOT := $(patsubst %/xen,%,$(abs_srctree))
>>>
>>> ?
>>
>> That works too. It's slightly less robust, but I don't expect "xen"
>> directory to be renamed, so shouldn't be an issue. I'll leave also a
>> comment there why not /.. .
> 
> I don't think $(XEN_ROOT) is present in the binaries produce by the
> hypervisor's build system.

It is, in the symbol table that tools/symbols produces. In a random
out-of-tree build I can see various static symbols being prefixed by
the full paths to the source files. I can't quite spot a pattern
between when this is the case and when it's not. In in-tree builds I
can't spot any such occurrences.

I also think Marek said debug info may contain full paths.

Jan

> There's only a few use if that variable: to
> load some makefile, to execute makefile that build xsm policy and to
> generate cpuid-autogen.h. Otherwise I don't think the compile have this
> path in the command line. What is going to be in the binary is
> $(abs_srctree), which you can replace by "./xen" if you want; which mean
> it doesn't matter if the directory is renamed or not. You might want to
> also take care of $(abs_objtree) which seems to also be in `xen-syms`
> when doing out-of-tree build.
> 
> Cheers,
>