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On Wed, 02 Aug 2006 12:59:15 +0200 |
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pageexec@××××××××.hu wrote: |
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> On 2 Aug 2006 at 0:35, Kevin F. Quinn wrote: |
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> > I think solar's referring to -fno-stack-protector-all. Not too |
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> > worried about that myself, I think we can hide the change in |
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> > semantics in flag-o-matic.eclass - actual ebuild use of |
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> > -fno-stack-protector-all is rare. |
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> |
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> or we could patch that option in, i guess the 4.x version of ssp |
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> can also be convinced to apply to all functions. |
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I'd avoid doing that. In gcc-4.x the SSP support is a three-value |
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setting; no-stack-protector, stack-protector and stack-protector-all |
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with the semantics expected, where the last one specified wins. |
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"-fno-stack-protector-all" doesn't fit intuitively with this |
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approach. The old semantics of '-fno-stack-protector-all' was "if only |
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ssp-all was specified, reduce to no-ssp; if ssp was specified as well |
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as ssp-all reduce to ssp". |
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The reason for suggesting we hide it in flag-o-matic, is that ebuilds |
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generally do: |
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filter-flags -fstack-protector |
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or |
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filter-flags -fstack-protector-all |
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where the meaning is clear; it requires a bit of fiddling to get that |
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right with gcc-4.1 but it's not difficult. |
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In addition, Ebuilds generally don't use the '-fno-stack-*' options, so |
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there's no real need to support -fno-stack-protector-all for ebuilds. |
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The exceptions can be dealt with on a case-by-case basis. |
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> > It's that gcc-4.x doesn't pass the caller information (function name |
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> > and line number) to _stack_chk_fail. |
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> |
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> that too can be patched in, but even without this information it |
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> is still better than nothing (i guess the assumption was that one |
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> would get a coredump on abort() and could deduce all that and more |
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> from there). |
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> |
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> > I've been thinking that a PaX-style register, stack and perhaps map |
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> > dump might be a good idea for development environments at least. |
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> |
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> a coredump already has all that info, although it's not as easy to |
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> make use of as dr watson on windows yet, but that'll change when |
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> utrace (http://people.redhat.com/roland/utrace/) enters mainline. |
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Leveraging core makes a lot of sense, and would solve any worries about |
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information leaks since a "secure" system could be configured to never |
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dump core. |
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-- |
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Kevin F. Quinn |
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