Read the followup by pagexec [LWN.net]

Read the followup by pagexec

Posted Jun 11, 2011 20:23 UTC (Sat) by Julie (guest, #66693)
In reply to: Read the followup by pagexec by spender
Parent article: Quotes of the week

he didn't consider the other side of the coin, the same person who chooses not to read configuration help and enables/disables options based on their config name alone, doesn't disable this feature...

If he didn't consider this maybe it was because he thought anyone config'ing their own kernel without checking the ---help--- is being at least a little silly.

I always build my own kernels and when I config one I feel it's only common sense to be expected to take some responsibility for the outcome myself, which means being able to work out (if I don't know) what does what, which implies checking the config help for new or unfamiliar features and not just making assumptions based on the name of the feature about what it is or does.
So I always check new config options, and if I didn't do this and I ended up disabling something I was relying on using or having some other unpleasant experience resulting from it well, that would be my own fault, wouldn't it. Because I shouldn't be messing with it in the first place. A really useful lesson in humility, at least...

I'm pretty sure distro and kernel maintainers and other users who have more at stake than me, or more of a measure of responsibility, check new configs too - isn't it just sensible?

CONFIG_UNSAFE_VSYSCALLS as a config name does seem rather histrionic though.

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Read the followup by pagexec

Posted Jun 11, 2011 20:29 UTC (Sat) by mingo (subscriber, #31122) [Link] (2 responses)

LOL, histrionic indeed :-)

Note that the config option is gone in the patches i've applied days ago and which are queued up for mainline integration.

Read the followup by pagexec

Posted Jun 12, 2011 10:36 UTC (Sun) by patrick_g (subscriber, #44470) [Link] (1 responses)

>>> the config option is gone in the patches i've applied days ago and which are queued up for mainline integration

Mainline integration in 3.0 or for the next merge window (ie 3.1) ?

Read the followup by pagexec

Posted Jun 12, 2011 12:27 UTC (Sun) by mingo (subscriber, #31122) [Link]

Next merge window for now - the patches are too big and complex to be included in 3.0.

You can try them on 3.0 a well, via the -tip tree.

The patches are available standalone as well, see the tip/x86/vdso branch.

Read the followup by pagexec

Posted Jun 11, 2011 20:36 UTC (Sat) by spender (guest, #23067) [Link]

I was trying to illustrate that the same person who disables the option because they're "scared" by "UNSAFE" in the config name itself, apparently without reading the following config help:
+ Legacy user code expects to be able to issue three syscalls
+ by calling fixed addresses in kernel space. If you say N,
+ then the kernel traps and emulates these calls. If you say
+ Y, then there is actual executable code at a fixed address
+ to implement time() efficiently.
+
+ On a system with recent enough glibc (probably 2.14 or
+ newer) and no static binaries, you can say N without a
+ performance penalty to improve security
+
+ If unsure, say Y.

is the same kind of foolish user who would leave it on because it says "COMPAT" in the name and they don't want to break anything (even though disabling it doesn't break anything). So we're not in disagreement, I just didn't state it as clearly as I should have apparently.

-Brad