Messages in this thread |  | | Subject | Re: Security question: "Text file busy" overwriting executables but not shared libraries? | From | (Eric W. Biederman) | Date | 04 Oct 2001 00:15:01 -0600 |
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Alexander Viro <viro@math.psu.edu> writes:
> On 3 Oct 2001, Eric W. Biederman quoted: > > > > >/* The right way to map in the shared library files is MAP_COPY, which > > > > makes a virtual copy of the data at the time of the mmap call; this > > > > guarantees the mapped pages will be consistent even if the file is > > > > overwritten. Some losing VM systems like Linux's lack MAP_COPY. All we > > > > > get is MAP_PRIVATE, which copies each page when it is modified; this > > > > means if the file is overwritten, we may at some point get some pages > > > > from the new version after starting with pages from the old version. */ > > > IMO it needs a slight correction. > > + /* Unfortunately, that is not an option, since losing bloatware like GNU's > + relies heavily on equally bloated shared libraries and use of MAP_COPY > + would eat memory with no mercy. OTOH, implementing it might be a good > + idea, since results would force people to switch to something less obese */
Hmm. Perhaps. But if we went there we would need to add something like.
/* But finding a less obese platform to run these less obese libraries is a challenge. Unix clones like UZI have been shown to run a complete system including user space binaries in just 64KB of RAM, on systems originally designed to run CPM. But today you can't find a general purpose kernel whose binary much less it footprint fits in 256KB. It seems bloatware is everywhere. */
I have days when I'm frustrated by the size of both glibc and the linux kernel. stripped both the linux kernel and glibc are comparable in size. Though I think the 400KB of compressed glibc-2.1.2 is actually smaller than the kernel for the most part. I have to strip off practically everthing to get a useable bzImage under 400KB.
So any good ideas on how to get the size of linux down?
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