On Friday 22 June 2007 19:13:19 Alexander Graf wrote: > Rob Landley wrote: > > Ok, it's a more fundamental problem: > > > > [EMAIL PROTECTED]:/sys$ qemu-i386 > > Segmentation fault (core dumped) > > > > Nothing to do with the program it's trying to run, it segfaults with no > > arguments. > > > > Is anybody else seeing this? > > > > Rob > > [EMAIL PROTECTED]:/vm/qemu-devel/patches/qemu> qemu-i386 ~/hello > Hello world! > > Well it works for me. I usually see this segfault when trying to compile > qemu with a gcc4. Try gcc3 and everything should be fine.
It's using gcc-3.4. The one that comes with Ubuntu 7.04. (Or at least ./configure said it had found gcc-3.4 during configuration, anyway.) I ran the sucker under strace and it seems to be segfaulting right before it calls main(). I stuck an exit(1) at the start of main and it doesn't get to it, but it's after all the shared libraries are loaded: > mprotect(0xb7f3f000, 4096, PROT_READ) = 0 > mprotect(0x80000000, 548864, PROT_READ|PROT_WRITE) = 0 > mprotect(0x80000000, 548864, PROT_READ|PROT_EXEC) = 0 > munmap(0xb7f76000, 57255) = 0 > set_tid_address(0xb7deca88) = 4338 > sendto(-1210135920, umovestr: Input/output error > 0xc, 3084914676, > MSG_DONTWAIT|MSG_CONFIRM|MSG_FIN|MSG_NOSIGNAL|MSG_MORE|0xb7de0000, > {sa_family=AF_DECnet, sa_data="\0\0\320=\0\0\r\0\0\0p\362\0\0"}, > 3217384328) = 0 rt_sigaction(SIGRTMIN, {0xb7df13f0, [], SA_SIGINFO}, NULL, > 8) = 0 > rt_sigaction(SIGRT_1, {0xb7df1300, [], SA_RESTART|SA_SIGINFO}, NULL, 8) = 0 > rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0 > getrlimit(RLIMIT_STACK, {rlim_cur=8192*1024, rlim_max=RLIM_INFINITY}) = 0 > uname({sys="Linux", node="triolith", ...}) = 0 > --- SIGSEGV (Segmentation fault) @ 0 (0) --- > +++ killed by SIGSEGV (core dumped) +++ > Process 4338 detached If I link "int main() {}" against -lm and -lrt I get the same set of calls up through the first mprotect. (The next two mprotects are probably setting up other segments like bss that an empty program doesn't have.) Then everything up through the uname() is the same... And then it would call "main". Right now I'm commenting out various global variable initializations because that's what comes to mind as "stuff that runs right before main()". By the way, by commenting out this bit: //const char interp[] __attribute__((section(".interp"))) = "/lib/ld-linux.so.2"; I made it go from "segmentation fault" to "illegal instruction" as the reason it dies. Which is weird because there's no non-x86 toolchain the path, this is all stock Ubuntu stuff. But oh well... > Alex Rob -- "One of my most productive days was throwing away 1000 lines of code." - Ken Thompson.