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[Bug libc/7065] New: Support building glibc with -fstack-protector or -fstack-protector-all


Several distributions, including Gentoo, have patches which attempt to make 
glibc build when compiled with -fstack-protector. None of them that I have 
found actually work: at best, they make it crash instantly, because none of 
them suppress generation of stack guards around functions called before the 
guard is initialized (or even before ld-linux.so.2 has relocated itself).

For now I'd consider it more of a maintenance burden than it's worth to
isolate the parts of ld.so that are called before security_init(), so
I've just arranged to avoid using the stack-protector in ld.so, and
marked the few things not also in the dynamic loader which are used
during pre-guard-init static library initialization with
-fno-stack-protector. (An improvement might be to mark these with
-fno-stack-protector only when building the static library.)

I can't think of a way to isolate the functions in this set automatically, but 
if you get it wrong it's easy to tell because you get an instant coredump, so 
it's easy to prevent the set of -fno-stack-protectored functions from 
bitrotting, manually maintained though it must be.)

You can still use -fstack-protector-all in all the rest of glibc, which
is an order of magnitude more code than ld.so and includes really hairy
stuff like malloc() and lots of functions that themselves call
string-manipulation functions, so I'd say this is a pretty good
tradeoff.

Some of the module tests need adjustment: they don't link against
libc, so must specify -fno-stack-protector; the same is true of some of the 
configury, taking care not to specify that unless GCC is actually capable of 
accepting -fstack-protector. (We specify -lssp and leave the stack protector on 
where possible in configure tests.)

Results of tests and patch against glibc 2.9 following shortly.

-- 
           Summary: Support building glibc with -fstack-protector or -
                    fstack-protector-all
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: nix at esperi dot org dot uk
                CC: glibc-bugs at sources dot redhat dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://sourceware.org/bugzilla/show_bug.cgi?id=7065

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