> hi, zhangfx,
> I followed your advice by adding printf to the do_ri function and
> found that when the kernel init the system, this function was called
> hundreds of times and then the kernel panic, so it means that there
> are illegal instruction exist, but why do_ri will be called so many
> times?
for some instructions, they are not supported by the hardware, but the
kernel will simulate it in software correctly, so it won't cause a fatal
error. But if the kernel has no code to simulate it, the related user land
process will be killed with SIGILL(if it happens in kernel mode, kernel
will panic). So check which instruction cause the exception and check if
do_ri has code to handle it.
> another question is that by add printf to the init source code, I
> found that the kernel panics in the open_devnull_stdio,
the kernel panic because init exit. e.g. if your init process is just one
line code
int main() ｛ return 0; ｝
you will see the kernel panic.
I am not sure about your detail situation, but if the second dup2 cause a
segmentation fault or some other fatal fault for init process, the kernel
will panic shortly after. Also it is possible if the init has several
threads and some other threads cause the exit of the process.
The init code should have some existing switchable debug code, try to turn
them on to find more clues.
>
> void open_devnull_stdio(void)
> {
> int fd;
> static const char *name = "/dev/__null__";
> if (mknod(name, S_IFCHR | 0600, (1 << 8) | 3) == 0) {
> fd = open(name, O_RDWR);
> unlink(name);
> if (fd >= 0) {
> dup2(fd, 0); //*************************this call don't
> panic the kernel*******************
> dup2(fd, 1); //*************************panic
> here**************************
> dup2(fd, 2);
> if (fd > 2) {
> close(fd);
> }
> return;
> }
> }
>
> exit(1);
> }
>
> as you can see from the source code, the dup2 is a system call, and
> the kernel was compiled by using cross-compile from loongson
> community, there should no illegal instructions exist?
> If it possible the kernel panic at other position and the printf
> information don't flush out?
>
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