Re: vi and glibc 2.12: Assertion `_rtld_global_ro._dl_pagesize != 0

[Mike Frysinger <vapier at gentoo dot org>]

On Tue, Aug 17, 2010 at 10:36 PM, Mike Frysinger wrote:
> i'm certainly not familiar with glibc's ldso implementation due to
> it's crazy large & complicated code base, but i imagine this could be
> resolved best by having the ldso declare an initializer that calls the
> same functions as the ldso does when bootstrapping a normal
> application (_dl_sysdep_start/etc...). ?this is because the nss libs
> are dlopened like any other ELF, and it tails into libc.so which tails
> into the ldso. ?there is no special code that i can see that goes
> "this is the ldso, do xxx specially" which makes perfect sense. ?only
> outstanding issue there would be whether the ldso will process its own
> initializers when bootstrapping a standard application.
>
> we could back out the assert in __getpagesize(), but that would only
> "fix" things until the next time someone adds code which relies on
> initialized GLRO() state.

after some experimenting, i guess the init method isnt feasible.  as
the GLRO() name indicates, the struct is backed by read-only mappings,
and the ELF processing has already set up all the mappings with proper
permissions per the program headers by the time it calls any
initializers for that ELF.  temporarily remapping itself isnt feasible
as some kernels prevent re-enabling write access to a read/execute
only mapping.

the ldso doesnt have any problems with this since it initializes its
internal state before setting its own mappings to read-only.

which leaves us with the __getpagesize() function and simply reverting
commit 8f4a5048eea6536ee85c0f2670adbb97d71e427d.  unless anyone else
has an alternative, that's what i'm going to roll with in Gentoo.
there should be no need to recompile any static apps, just glibc
itself, since the issue is coming from libc.so/ldso itself being
dlopened.

--- a/sysdeps/unix/sysv/linux/getpagesize.c
+++ b/sysdeps/unix/sysv/linux/getpagesize.c
@@ -28,7 +28,7 @@
 int
 __getpagesize ()
 {
-#ifdef __ASSUME_AT_PAGESIZE
+#if 0
   assert (GLRO(dl_pagesize) != 0);
   return GLRO(dl_pagesize);
 #else
-mike