From: "Jan Beulich" <JBeulich@suse.com>
To: "Baodong Chen" <chenbaodong@mxnavi.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>, WeiLiu <wl@xen.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
George Dunlap <George.Dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <Ian.Jackson@eu.citrix.com>, Tim Deegan <tim@xen.org>,
Julien Grall <julien.grall@arm.com>,
xen-devel <xen-devel@lists.xenproject.org>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH] xen/coverage: wrap coverage related things under 'CONFIG_COVERAGE'
Date: Wed, 12 Jun 2019 00:34:14 -0600 [thread overview]
Message-ID: <5D009CE602000078002374B3@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <492c0277-7413-d306-b350-58167a526486@mxnavi.com>
>>> On 12.06.19 at 02:23, <chenbaodong@mxnavi.com> wrote:
> On 6/11/19 22:03, Jan Beulich wrote:
>>>>> On 11.06.19 at 08:02, <chenbaodong@mxnavi.com> wrote:
>>> --- a/xen/arch/x86/xen.lds.S
>>> +++ b/xen/arch/x86/xen.lds.S
>>> @@ -240,12 +240,14 @@ SECTIONS
>>> *(.altinstructions)
>>> __alt_instructions_end = .;
>>>
>>> +#if defined(CONFIG_COVERAGE)
>>> . = ALIGN(8);
>>> __ctors_start = .;
>>> *(.ctors)
>>> *(.init_array)
>>> *(SORT(.init_array.*))
>>> __ctors_end = .;
>>> +#endif
>> How is this (only) coverage related? And how is making this conditional
>> going to help in any way?
>
> Hello Jan,
>
> When i read the code 'init_constructors()', i want to understand when
> it's used.
>
> I can not find any helper macros like '__init' in init.h, put things in
> this section.
>
> Also run under arm foundation platform, the section is empty.
>
> So i check commit history and found it's commit logs: it is coverage
> related.
>
> And compiled with CONFIG_COVERAGE enabled, this section is not empty
> anymore.
>
> So the patch mainly want to clarify the code is coverage related,
>
> which want to help newcomer easily understand this code.
>
> Am i misunderstanding here?
The code may have been _introduced_ for coverage, but are you
willing to guarantee it's coverage-only? Plus - what does removing
an empty section buy you?
>>> --- a/xen/common/lib.c
>>> +++ b/xen/common/lib.c
>>> @@ -491,15 +491,20 @@ unsigned long long parse_size_and_unit(const char *s, const char **ps)
>>> return ret;
>>> }
>>>
>>> +#if defined(CONFIG_COVERAGE)
>>> typedef void (*ctor_func_t)(void);
>>> extern const ctor_func_t __ctors_start[], __ctors_end[];
>>> +#endif
>> Again - how does this help?
> Want to clarify this is coverage related code.
If only it really was (provably).
>>> +/* see 'docs/hypervisor-guide/code-coverage.rst' */
>>> void __init init_constructors(void)
>> There's no mention of this function in the referenced docs file.
>
> Same as above.
No. The reference makes no sense here without that doc somehow
mentioning the function you attach the comment to.
>>> {
>>> +#if defined(CONFIG_COVERAGE)
>>> const ctor_func_t *f;
>>> for ( f = __ctors_start; f < __ctors_end; ++f )
>>> (*f)();
>>>
>>> +#endif
>>> /* Putting this here seems as good (or bad) as any other place. */
>> Again, besides lacking suitable reasoning you also should look
>> more closely, in this case where exactly it makes sense to place
>> the #endif.
>
> The blank line here? If yes, can be removed. i missed this.
Removed? No. If anything there's one missing. You've inserted
the #ifdef after the blank line rather than before it.
Jan
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next prev parent reply other threads:[~2019-06-12 6:34 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-11 6:02 [Xen-devel] [PATCH] xen/coverage: wrap coverage related things under 'CONFIG_COVERAGE' Baodong Chen
2019-06-11 14:03 ` Jan Beulich
2019-06-12 0:23 ` chenbaodong
2019-06-12 6:34 ` Jan Beulich [this message]
2019-06-12 7:36 ` chenbaodong
2019-06-12 7:58 ` Jan Beulich
2019-06-12 8:49 ` chenbaodong
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