Re: [PATCH] arm: fix u-boot port syscall interface va_arg handling (was Re: [PATCH] [ARM] Enable boot module for arm)

[Vladimir 'φ-coder/phcoder' Serbinenko]

On 16.11.2013 14:53, Leif Lindholm wrote:
> On Sat, Nov 16, 2013 at 02:17:51PM +0100, Vladimir 'φ-coder/phcoder' 
> Serbinenko wrote:
>>> From an ABI perspective, grub_uboot_syscall is a veneer:
>>> the only visible side effect it is permitted to have is to corrupt r12.
>>>
>> According to wikipedia:
>> "Subroutines must preserve the contents of r4 to r11 and the stack pointer."
>> So changing r9 sounds to me like this is actually U-Boot bug and
>> preserving it sounds like right way to handle it.
> 
> No. grub_uboot_syscall is not a subroutine - it is a veneer.
> We have a specific reason to need to preserve r8, over and above what
> the ABI says, because u-boot has hijacked it.
> 
> But now I went to look at the u-boot code, and suddenly I want to cry.
> Commit fe1378a961e508b31b1f29a2bb08ba1dac063155 changes the register
> reserved for global data from r8 to r9. Which means we need to preserve
> both since they didn't step the API version number.
> 
> *sigh*
> 
> Updated patch attached.

Go ahead.
> 
> /
>     Leif
> 
> 
> 
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