On Jun 23, 2007, at 7:31 AM, Rob Landley wrote:
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.
I guess you're running on i586 then? I only tried this on ppc.
Last time I checked the code-copy stuff was broken, so maybe it helps
to disable that?
If that doesn't work either - would you mind to gdb it and run a "bt"
when it segfaulted so we can see if the segfault is in the generated
code?
Alex
