Hi Will, Thanks for your proposal, The patch google made is just like The one I tried before , Then the problems come : After register the perf_event callback, In the callback function , In google's patch , it is function crbug_345917_handler( ), It just call panic( ) , But My callback function will do some check , Sometimes, I want to bypass this time's breakpoint, Problems is that I don't know how to bypass it, If I return directly in the callback function , The breakpoint will trap again and again endless .. Thank you very much . -----Original Message----- From: Will Deacon [mailto:will.deacon@xxxxxxx] Sent: Wednesday, June 04, 2014 12:45 AM To: Wang, Yalin Cc: 'linux-mmc@xxxxxxxxxxxxxxx'; 'linux-arch-owner@xxxxxxxxxxxxxxx' Subject: Re: how to creat watchpoint in kernel for data access debug 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 -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
