Re: how to creat watchpoint in kernel for data access debug

[Will Deacon <will.deacon@arm.com>]

On Sat, May 24, 2014 at 04:48:20AM +0100, Wang, Yalin wrote:
> Hi  Will,

Hello,

Sorry for the delayed reply, it took me a while to work out what your issue
is.

> Thanks for your suggestion,
> The scenario that I encounter is a little special :
> I found our kernel memory will be corrupt in stability test ,
> Seems that someone write a memory that doesn't belong to it .
> But I can't find who does it , the bug is hard to reproduce ,
> So I want make a debug SW in kernel , which can monitor some data access,
> When someone access it , the callback function can check if it's right .
> If it's wrong, then crash the kernel do get a ram dump .
> 
> 
> So kgdb or perf seems not suitable in this condition ,
> We need users to use devices, not just test the device in Lab .

I think Google did something similar to this with ChromeOS on the
Exynos5-based chromebooks:

  https://chromium-review.googlesource.com/#/c/188479/3/arch/arm/kernel/hw_breakpoint.c

I don't think that has a place in the mainline kernel, but you could
certainly adapt it for your debugging purposes.

Will