Date: Wed, 27 May 2009 09:32:01 -0500 From: Stacey Son <sson@freebsd.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r192859 - in head: share/man/man4 sys/conf sys/dev/ksyms sys/kern sys/modules sys/modules/ksyms sys/sys Message-ID: <4A1D4EE1.5040902@freebsd.org> In-Reply-To: <20090527111741.GH1927@deviant.kiev.zoral.com.ua> References: <200905262139.n4QLd9pI074530@svn.freebsd.org> <20090527111741.GH1927@deviant.kiev.zoral.com.ua>
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Kostik Belousov wrote: > On Tue, May 26, 2009 at 09:39:09PM +0000, Stacey Son wrote: > >> Author: sson >> Date: Tue May 26 21:39:09 2009 >> New Revision: 192859 >> URL: http://svn.freebsd.org/changeset/base/192859 >> >> Log: >> Add the ksyms(4) pseudo driver. The ksyms driver allows a process to >> get a quick snapshot of the kernel's symbol table including the symbols >> from any loaded modules (the symbols are all merged into one symbol >> table). Unlike like other implementations, this ksyms driver maps >> memory in the process memory space to store the snapshot at the time >> /dev/ksyms is opened. It also checks to see if the process has already >> a snapshot open and won't allow it to open /dev/ksyms it again until it >> closes first. This prevents kernel and process memory from being >> exhausted. Note that /dev/ksyms is used by the lockstat(1) command. >> >> Reviewed by: gallatin kib (freebsd-arch) >> Approved by: gnn (mentor) >> > > What is the reason to have ksyms_unmap() ? ksyms_unmap() is used to free the mapping of the memory when /dev/ksyms is closed or if the driver fails to create the symbol table snapshot. > Why do you think that checking > for the present mapping of the freed region is neccessary ? ksyms_unmap() does check to make sure the memory region is mapped since it is possible that the process could have unmap it or changed its protection before calling close(). I haven't looked at vm_map_delete() closely but maybe it make makes this check as well. If so, this check might be redundant. -stacey.
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