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| From: | Avi Kivity |
| Subject: | Re: [Qemu-devel] Re: software breakpoints disappearing/reappearing in KVM/qemu |
| Date: | Sun, 10 Apr 2011 17:41:24 +0300 |
| User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.15) Gecko/20110307 Fedora/3.1.9-0.39.b3pre.fc14 Lightning/1.0b3pre Thunderbird/3.1.9 |
On 04/10/2011 05:23 PM, Jan Kiszka wrote:
On 2011-04-10 16:01, Avi Kivity wrote: > On 04/08/2011 11:52 PM, Jan Kiszka wrote: >> QEMU's gdbstub in KVM mode is simply not designed to account for guests >> swapping out code pages that contain breakpoints. Due to the fact that >> the Linux kernel does not do these weird things to its own code, > > It actually happily patches its own code at certain circumstances. If > you debug early boot or suspend/resume or cpu hotplug you're likely to > encounter them. Yes, it patches (alternates, jump_labels, mcount etc.), but it doesn't swap or move code pages. At least so far.
Try using modules (though that's different - the virtual addresses will change too). Or debugging a mixed kernel/user workload.
If you need to break at such locations, there are still hardware breakpoints, though only 4.
Right. -- error compiling committee.c: too many arguments to function
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