linux-kernel - Re: [PATCH v2 02/10] x86: assembly, FUNC_START for fn, DATA

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Date:   Wed, 22 Mar 2017 16:52:45 +0100
From:   Pavel Machek <pavel@....cz>
To:     Jiri Slaby <jslaby@...e.cz>
Cc:     mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
        x86@...nel.org, jpoimboe@...hat.com, linux-kernel@...r.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        xen-devel@...ts.xenproject.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 02/10] x86: assembly, FUNC_START for fn, DATA_START
 for data

On Wed 2017-03-22 13:06:54, Jiri Slaby wrote:
> Hi,
> 
> On 03/21/2017, 03:08 PM, Pavel Machek wrote:
> >> -ENTRY(saved_rbp)	.quad	0
> >> -ENTRY(saved_rsi)	.quad	0
> >> -ENTRY(saved_rdi)	.quad	0
> >> -ENTRY(saved_rbx)	.quad	0
> >> +SYM_DATA_START(saved_rbp)		.quad	0
> >> +SYM_DATA_START(saved_rsi)		.quad	0
> >> +SYM_DATA_START(saved_rdi)		.quad	0
> >> +SYM_DATA_START(saved_rbx)		.quad	0
> > 
> > Does it make sense to call it SYM_DATA_*START* when there's no
> > corresponding end?
> > 
> > Plus... it looks like saved_rsi (and friends) are only used inside
> > wakeup_64.S. Could we just delete the "ENTRY" annotations?
> 
> 
> So, now I have:
> 
> === linkage.h ===
> 
> /* SYM_DATA_SIMPLE -- start+end wrapper around simple global data */
> #ifndef SYM_DATA_SIMPLE
> #define SYM_DATA_SIMPLE(name, data)                             \
>         SYM_DATA_START(name) ASM_NL                             \
>         data ASM_NL                                             \
>         SYM_DATA_END(name)
> #endif
> 
> /* SYM_DATA_SIMPLE_LOCAL -- start+end wrapper around simple local data */
> #ifndef SYM_DATA_SIMPLE_LOCAL
> #define SYM_DATA_SIMPLE_LOCAL(name, data)                       \
>         SYM_DATA_START_LOCAL(name) ASM_NL                       \
>         data ASM_NL                                             \
>         SYM_DATA_END(name)
> #endif
> 
> === wakeup_64.S ===
> 
> SYM_DATA_SIMPLE_LOCAL(saved_rbp, .quad 0)
> SYM_DATA_SIMPLE_LOCAL(saved_rsi, .quad 0)
> SYM_DATA_SIMPLE_LOCAL(saved_rdi, .quad 0)
> SYM_DATA_SIMPLE_LOCAL(saved_rbx, .quad 0)
> 
> SYM_DATA_SIMPLE_LOCAL(saved_rip, .quad 0)
> SYM_DATA_SIMPLE_LOCAL(saved_rsp, .quad 0)
> 
> SYM_DATA_SIMPLE_LOCAL(saved_magic, .quad 0)
> 
> === original ===
> 
>     10: 0000000000000060     0 NOTYPE  GLOBAL DEFAULT    3 saved_magic
>     11: 0000000000000050     0 NOTYPE  GLOBAL DEFAULT    3 saved_rsp
>     12: 0000000000000030     0 NOTYPE  GLOBAL DEFAULT    3 saved_rbx
>     13: 0000000000000020     0 NOTYPE  GLOBAL DEFAULT    3 saved_rdi
>     14: 0000000000000010     0 NOTYPE  GLOBAL DEFAULT    3 saved_rsi
>     15: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT    3 saved_rbp
>     16: 0000000000000040     0 NOTYPE  GLOBAL DEFAULT    3 saved_rip
> 
> === new ===
> 
>      4: 0000000000000030     8 OBJECT  LOCAL  DEFAULT    3 saved_magic
>      6: 0000000000000028     8 OBJECT  LOCAL  DEFAULT    3 saved_rsp
>      7: 0000000000000018     8 OBJECT  LOCAL  DEFAULT    3 saved_rbx
>      8: 0000000000000010     8 OBJECT  LOCAL  DEFAULT    3 saved_rdi
>      9: 0000000000000008     8 OBJECT  LOCAL  DEFAULT    3 saved_rsi
>     10: 0000000000000000     8 OBJECT  LOCAL  DEFAULT    3 saved_rbp
>     11: 0000000000000020     8 OBJECT  LOCAL  DEFAULT    3 saved_rip
> 
> === EOF ===
> 
> BTW, ENTRY() aligned the data to 2^4 = 16 as we can see in the original.
> But I see no point aligning data like this.

Yep, that's a bug, too. I guess it hurts even more on 32-bit....

Thanks for fixing this,
									Pavel

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