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[Qemu-devel] [Bug 1035572] Re: Bug in Qemu User Mode
From: |
Dietmar Stölting |
Subject: |
[Qemu-devel] [Bug 1035572] Re: Bug in Qemu User Mode |
Date: |
Sat, 11 Aug 2012 22:15:34 -0000 |
I just compiled the testclone new on debian Wheezy,
for to understand what is going on and name it clonemi.
Before I have always an endless loop on Raspberry Pi
because waitpid was never fullfilled.
So I commened the two waitpid lines out.
Also I enlarged the STACK_SIZE to 262144.
Enlarging of the stack does not help. But now the Raspberry Pi with
qemu-1386 -strace clonemi
showed the following output:
address@hidden:/home/pi/raspidev# qemu-i386 clonemi
thread2: 0 hello2
thread1: 0 hello1
status1=0x80487ab
status2=0x42fd4788
End of clone test.
address@hidden:/home/pi/raspidev# qemu-i386 -strace clonemi
1583 brk(NULL) = 0x0804a000
1583 uname(0x42fcb4ca) = 0
1583 access("/etc/ld.so.nohwcap",F_OK) = -1 errno=2 (No such file or directory)
1583 mmap2(NULL,8192,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS,-1,0) =
0x43088000
1583 access("/etc/ld.so.preload",R_OK) = -1 errno=2 (No such file or directory)
1583 open("/etc/ld.so.cache",O_RDONLY) = 3
1583 fstat64(3,0x42fcb184) = 0
1583 mmap2(NULL,7566,PROT_READ,MAP_PRIVATE,3,0) = 0x4308a000
1583 close(3) = 0
1583 open("/lib/libc.so.6",O_RDONLY) = 3
1583 read(3,0x42fcb2b8,512) = 512
1583 fstat64(3,0x42fcb1d8) = 0
1583 mmap2(NULL,1345848,PROT_EXEC|PROT_READ,MAP_PRIVATE|MAP_DENYWRITE,3,0) =
0x4308c000
1583 mprotect(0x431ce000,4096,PROT_NONE) = 0
1583
mmap2(0x431cf000,12288,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_DENYWRITE|MAP_FIXED,3,0x142)
= 0x431cf000
1583
mmap2(0x431d2000,10552,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED,-1,0)
= 0x431d2000
1583 close(3) = 0
1583 mmap2(NULL,4096,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS,-1,0) =
0x431d5000
1583 set_thread_area(1123858048,1124618228,1125996224,1,0,1123858076) = 0
1583 mprotect(0x431cf000,8192,PROT_READ) = 0
1583 mprotect(0x43084000,4096,PROT_READ) = 0
1583 munmap(0x4308a000,7566) = 0
1583 mmap2(NULL,266240,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS,-1,0) =
0x431d6000
1583
clone(CLONE_VM|CLONE_FS|CLONE_FILES|0x11,child_stack=0x43215fe4,parent_tidptr=0x43076590,tls=0x08049a34,child_tidptr=0x42fcb788)
= 1584
1583 mmap2(NULL,266240,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS,-1,0) =
0x43303000
1583
clone(CLONE_VM|CLONE_FS|CLONE_FILES|0x11,child_stack=0x43342fe4,parent_tidptr=0x43076590,tls=0x08049a34,child_tidptr=0x42fcb788)
= 1585
1583 fstat64(1,0x42fcb09c) = 0
1583 mmap2(NULL,4096,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS,-1,0) =
0x43344000
1583 write(1,0x43342ddc,18)thread2: 0 hello2
= 18
1583 write(1,0x43215ddc,18)thread1: 0 hello1
= 18
1583 nanosleep(1126260128,0,134514044,0,1809,1126260136)1583
nanosleep(1127493024,0,134514175,0,1809,1127493032)1583
write(1,0x43344000,18)status1=0x80487ab
= 18
1583 write(1,0x43344000,19)status2=0x42fcb788
= 19
1583 write(1,0x43344000,19)End of clone test.
= 19
1583 exit_group(0)
address@hidden:/home/pi/raspidev#
You can see, that
child_stack=0x43215fe4,parent_tidptr=0x43076590
is unequal.
Is this the mistake?
Nice to hear from you,
Dietmar
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https://bugs.launchpad.net/bugs/1035572
Title:
Bug in Qemu User Mode
Status in QEMU:
New
Bug description:
Hi,
I make an interesting discovery.
My aim is to have a working qemu-i386 on Raspberry Pi.
After long searching in the dark what goes wrong with ANY Qemu version for
User Mode until today,
I find the following: The bug must be in at least one function, that the
program testclone
from the testpackage for i386 in linux-user-test-0.3 calls.
The wrong function is in the part, which enables more than one thread at the
same time, NPTL.
Funny, how I find this out: All the programs from the tests in
linux-user-test-0.3 I can now run succesfull with my new builded qemu-i386 for
Raspi.
But the program testclone does not stop after it gives out all the right
messages.
The program testclone stops on my Desktop computer with Debian Wheezy
installed.
So, the error is not in the program testclone.
So I make a look, what is going on there with strace. With strace you get
informations about all the values in the working program, here testclone.
I see, that the reason, why testclone not stops is in an infinite loop
because of
while (waitpid(pid1, &status1, 0) != pid1);
while (waitpid(pid2, &status2, 0) != pid2);
at its end is never fullfilled.
This is the reason for the famous error message from Qemu User Mode
qemu: uncaught target signal 11 (Segmentation fault) - core dumped
Segmentation fault
stack1 = malloc(STACK_SIZE);
pid1 = clone(thread1_func, stack1 + STACK_SIZE,
CLONE_VM | CLONE_FS | CLONE_FILES | SIGCHLD, "hello1");
stack2 = malloc(STACK_SIZE);
pid2 = clone(thread2_func, stack2 + STACK_SIZE,
CLONE_VM | CLONE_FS | CLONE_FILES | SIGCHLD, "hello2");
The error happens early in the program testclone. Strace says, it is because
no childprocess at all can be found. So, some basiccalculations in those four
lines must be done wrong from Qemu.
I think, that the adressspace for each thread is calculated wrong, or
overlapps.
Funny, it has nothing to do with the ARM processor. I get exact the same
errormessages, when I run the program testclone on my desktopcompi i386 with a
Wheezy in Qemu and then qemu-i386 testclone.
This is a good message, because it means it is an error, that belongs at
least to the i386 family but I think, every processor in Qemu User Mode is
involved, so until now NPTL does not work.
Today I make a hand by hand calculation with the source code from testclone
and compare it with the values, that Qemu User Mode give. The handcalculated
values should be the same which my
Desktop computer with Wheezy with tesclone produces, but who knows,
Dietmar
PS: I hope, that this is the right source code for testclone. Any help
is welcome:-)!
Code: Select all
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <inttypes.h>
#include <pthread.h>
#include <sys/wait.h>
#include <sched.h>
int thread1_func(void *arg)
{
int i;
char buf[512];
for(i=0;i<10;i++) {
snprintf(buf, sizeof(buf), "thread1: %d %s\n", i, (char *)arg);
write(1, buf, strlen(buf));
usleep(100 * 1000);
}
return 0;
}
int thread2_func(void *arg)
{
int i;
char buf[512];
for(i=0;i<20;i++) {
snprintf(buf, sizeof(buf), "thread2: %d %s\n", i, (char *)arg);
write(1, buf, strlen(buf));
usleep(120 * 1000);
}
return 0;
}
#define STACK_SIZE 16384
void test_clone(void)
{
uint8_t *stack1, *stack2;
int pid1, pid2, status1, status2;
stack1 = malloc(STACK_SIZE);
pid1 = clone(thread1_func, stack1 + STACK_SIZE,
CLONE_VM | CLONE_FS | CLONE_FILES | SIGCHLD, "hello1");
stack2 = malloc(STACK_SIZE);
pid2 = clone(thread2_func, stack2 + STACK_SIZE,
CLONE_VM | CLONE_FS | CLONE_FILES | SIGCHLD, "hello2");
while (waitpid(pid1, &status1, 0) != pid1);
while (waitpid(pid2, &status2, 0) != pid2);
printf("status1=0x%x\n", status1);
printf("status2=0x%x\n", status2);
printf("End of clone test.\n");
}
int main(int argc, char **argv)
{
test_clone();
return 0;
}
Posts: 210
Joined: 04 Sep 2011 17:43
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