On Wed, 28 May 2008, Rob Landley wrote: > On Tuesday 27 May 2008 17:31:42 T Ziomek wrote: > > If I understand correctly David is talking about logging some trace-like > > info (so it exists before a HW watchdog expires), and having it somewhere > > "safe" from being disturbed by a HW reset. > > The standard way of doing this is to use the mem= kernel command line > parameter to tell the system it has less memory than it does, and using > what's left as a ramdisk. Years ago I saw some userspace thing running as > root mmap() /dev/mem (or whatever they're calling it these days) and log to > it. In theory you could even set the dmesg buffer up at the end of physical > memory with a smallish kernel patch, make it big, and set the kernel to doing > verbose printks. > > The trick is A) knowing the absolute physical address at which your debug > buffer lives so you can find it after the reboot, B) convincing the system to > do something useful with it on reboot rather than just overwriting it with > fresh log data. Yep, we've been doing this on Amiga for more than a decade, when `debug=mem' is passed. Cfr. arch/m68k/tools/amiga/dmesg.c. With kind regards, Geert Uytterhoeven Software Architect Sony Network and Software Technology Center Europe The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium Phone: +32 (0)2 700 8453 Fax: +32 (0)2 700 8622 E-mail: Geert.Uytterhoeven@xxxxxxxxxxx Internet: http://www.sony-europe.com/ Sony Network and Software Technology Center Europe A division of Sony Service Centre (Europe) N.V. Registered office: Technologielaan 7 · B-1840 Londerzeel · Belgium VAT BE 0413.825.160 · RPR Brussels Fortis Bank Zaventem · BIC GEBABEBB08A · IBAN BE39001382358619
