Red Hat Bugzilla – Bug 195755
gcc segfaults with malloc_perturb
Last modified: 2015-01-04 17:27:26 EST
whilst building the kernel on i686, I puzzled as to why as segfaulted when
compiling the i386 vsyscall code.
as was segfaulting whilst assembling arch/i386/kernel/vsyscall.S
in particular, on an incbin of two files..
Looking at the files that were incbin'd explained it..
$ ll arch/i386/kernel/vsyscall-*.so
-rwxr-xr-x 1 davej davej 623185380 Jun 17 00:50 arch/i386/kernel/vsyscall-int80.so*
-rwxr-xr-x 1 davej davej 623185404 Jun 17 00:50
Why were they so enormous ?
LOAD off 0x00000000 vaddr 0xdadadada paddr 0xdadadada align 2**30
filesz 0x25250b3a memsz 0x25250b3a flags r-x
DYNAMIC off 0x25250ab6 vaddr 0xffffe590 paddr 0xffffe590 align 2**2
filesz 0x00000078 memsz 0x00000078 flags r--
NOTE off 0x25250986 vaddr 0xffffe460 paddr 0xffffe460 align 2**2
filesz 0x00000018 memsz 0x00000018 flags r--
EH_FRAME off 0x2525099e vaddr 0xffffe478 paddr 0xffffe478 align 2**2
filesz 0x00000024 memsz 0x00000024 flags r--
Normally, without the perturb, it comes out as ..
-rwxr-xr-x 1 davej davej 2192 Jun 17 01:38 arch/i386/kernel/vsyscall-int80.so*
-rwxr-xr-x 1 davej davej 2216 Jun 17 01:38 arch/i386/kernel/vsyscall-sysenter.so*
I tried to put together a small testcase, but there's a bunch of dependant .o's
from arch/i386/kernel. Let me know if you can't reproduce, and I'll try again
to come up with something small.
I have found two places where ld used uninitialized memory:
but all that it caused to the i386 vsyscall-int80.so was that it couldn't be
linked at all, so I'd like to verify this is the same thing as you were seeing
and not something else.
So, please create a reproducer:
1) note the exact gcc commands to build vsyscall-*.o files as well as
2) add -save-temps to the command lines, attach here the preprocessed
vsyscall-*.s files as well as vmlinux.lds you used
3) what exact binutils you were using?
4) what exact MALLOC_PERTURB_=N value was used?
Assuming binutils-126.96.36.199.2-3 fixes this, if not, please reopen with details.