Dixi quod… >This is fun – I built a sid and a precise chroot today, i386, >and built mksh against dietlibc-dev_0.33~cvs20110918-4_i386.deb >from Debian sid (dpkg -i’d on precise). It segfaults only on >Ubuntu, not on Debian. It is _not_ -fstack-protector-all. > >Investigating. May be some gcc default flags difference… >Matthias, if you have an idea already, shoot.
OK, I got it: Dump of assembler code for function main: 0x0804820c <+0>: push ebp 0x0804820d <+1>: push edi 0x0804820e <+2>: push esi 0x0804820f <+3>: push ebx 0x08048210 <+4>: sub esp,0x90 0x08048216 <+10>: mov ebp,DWORD PTR [esp+0xa8] => 0x0804821d <+17>: mov eax,gs:0x14 0x08048223 <+23>: mov DWORD PTR [esp+0x8c],eax 0x0804822a <+30>: xor eax,eax 0x0804822c <+32>: call 0x805dfd4 <chvt_reinit> […] The marked line SIGSEGVs. (gdb) info r eax 0xf7ffd420 -134228960 ecx 0x3 3 edx 0x0 0 ebx 0x0 0 esp 0xffffd2e0 0xffffd2e0 ebp 0xffffd394 0xffffd394 esi 0xffffd4a8 -11096 edi 0x0 0 eip 0x804821d 0x804821d <main+17> eflags 0x10282 [ SF IF RF ] cs 0x23 35 ss 0x2b 43 ds 0x2b 43 es 0x2b 43 fs 0x0 0 gs 0x0 0 What’s in GS and why does the gcc-generated function prologue try to access it, anyway? This doesn’t happen on MirBSD… nor, incidentally, on Debian sid, where main() starts like this: Dump of assembler code for function main: => 0x0804820c <+0>: push ebp 0x0804820d <+1>: push edi 0x0804820e <+2>: push esi 0x0804820f <+3>: push ebx 0x08048210 <+4>: add esp,0xffffff80 0x08048213 <+7>: mov edi,DWORD PTR [esp+0x98] 0x0804821a <+14>: call 0x805debc <chvt_reinit> Since this issue arises in gcc-generated code, similar breakage may occur on other platforms (I can check amd64 but not ARM or, at the moment, powerpc; I’m just most familiar with i8086/i386, myself). bye, //mirabilos -- In traditional syntax ' is ignored, but in c99 everything between two ' is handled as character constant. Therefore you cannot use ' in a preproces- sing file in c99 mode. -- Ragge No faith left in ISO C99, undefined behaviour, etc. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/584980 Title: Please merge dietlibc 0.32-5 (universe) from Debian unstable (main) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/dietlibc/+bug/584980/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
