From: Albert ARIBAUD <albert.u.boot@aribaud.net>
To: u-boot@lists.denx.de
Subject: [U-Boot] printf and R9 in ARM architecture
Date: Tue, 20 Jan 2015 10:37:38 +0100 [thread overview]
Message-ID: <20150120103738.20a03f89@lilith> (raw)
In-Reply-To: <CAG3POBk3kjcqcE5-HF7xwFJfufrCnbvPuhLs9A=kiYC0SyEddA@mail.gmail.com>
Hello Dashi Cao,
On Tue, 20 Jan 2015 14:12:35 +0800, Da Shi Cao <dscao999@gmail.com>
wrote:
> In standalone applications, it seems that the execution of printf
> function in U-Boot is dependent on the value of register R9, which is
> setup in app_startup. But r9 can be used by your program at the
> decision of gcc compilation which is not aware of this dependence.
> This is especially the case if +O2 is used!
U-Boot follows the ARM EABI, in which ""The role of register r9 is
platform specific". In U-Boot r9 is specifically used for the global
data structure, and the standalone programs must follow this EABI.
If your standalone program is built with the same options as U-Boot
example standalone programs are (see hellow_world), then it should
have gcc option -ffixed-r9 which will prevent the compiler from ever
touching r9.
How exactly do you build your standalone application?
> My version is U-Boot 2014.10
>
> Regards,
> Dashi Cao
Amicalement,
--
Albert.
next prev parent reply other threads:[~2015-01-20 9:37 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-20 6:12 [U-Boot] printf and R9 in ARM architecture Da Shi Cao
2015-01-20 9:37 ` Albert ARIBAUD [this message]
2015-01-20 11:34 ` Da Shi Cao
2015-01-20 12:20 ` Albert ARIBAUD
2015-01-20 10:56 ` Marek Vasut
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