Date: Mon, 20 May 2013 14:14:45 -0700 From: Julian Elischer <julian@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: Konstantin Belousov <kostikbel@gmail.com>, amd64@freebsd.org, current@freebsd.org, freebsd-amd64@freebsd.org Subject: Re: Fix amd64 ddb hardware watchpoints for SMP Message-ID: <519A9245.4080609@freebsd.org> In-Reply-To: <201305200948.46211.jhb@freebsd.org> References: <20130516064127.GC3047@kib.kiev.ua> <201305200948.46211.jhb@freebsd.org>
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On 5/20/13 6:48 AM, John Baldwin wrote: > On Thursday, May 16, 2013 2:41:27 am Konstantin Belousov wrote: >> The ddb use of hardware watchpoints on the x86 architectures is known to >> be lacking. There are at least two known problems. One is the improper >> interaction with the user-mode debuggers which use debug registers. >> Another is that ddb only loads the debug registers for the watchpoint >> into the CPU which is executing ddb code, not setting up non-current >> processors. >> >> Not touching the first problem for now, I want to fix the second issue, >> since as is, hardware watchpoints are useless on SMP. Patch below makes >> the stopped processors to load the debug registers after resuming from >> the stop handler, if directed by ddb. >> >> Also the patch contains two other commands for ddb which made my >> exprerience with debugger on amd64 better. The 'show pginfo[/p] addr' >> command dumps the vm_page_t information, either by vm_page address, or, >> if the /p modifier is specified, by the physical page address. The 'show >> phys2dmap addr' command translates physical address into the directly >> mapped address, which can be accessed from ddb then. > This looks fine to me. It would be nice to fix i386 as well to be consistent. > I would commit the new DDB commands as a separate patch from the watchpoint > fixes. > the big test is to add the support in the gdb stub to use these.. :-)
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