2011/3/14 Gilboa Davara <gilboad@xxxxxxxxx>:
> On Sun, 2011-03-13 at 21:51 +0800, xinyou yan wrote:
>> It is a homework . Use a kernel spcae as a char decieve
>> Which can offer open write and so on.
>>
>> I just use a char buffer[128] in kernel space.
>>
>
> As a general rule, using static parameters in kernel space is considered
> hazardous; nevertheless, a 128 bytes is relatively safe.
>
>> Then i have some ideas.
>> I can use kernel space as char device. I can also use kernel spcae as
>> a file system? Could it be ?
>
> I'm not sure what you mean.
May be it can't be implement.
I mean . I create a file with a big size .
Then i write a super block struct ( I define it like the linux)
Then Inode table.
Then Date Blocks.
I reimplement some syscall on it .
I just want to make it like a filesystem .
However I stop at . How to init all of this struct.
So sorry to make you confuse . English is not my native language , I
will try to do better than what early i was .
> But in general, yes, you could register a character device that has
> read/write/seek operations on a memory buffer. (Preferably, dynamically
> allocated memory buffer)
> A relatively simple (and easy to understand / implement) example is
> the /proc file system. (Search for create_proc_entry in the kernel code)
>
>> If memory can be a filesystem . Can i use a file to simulate 。
>> It just not be taken as a file . Like something
>> we store file in it.
>>
>>
>>
>>
>>
>> 2011/3/13 Gilboa Davara <gilboad@xxxxxxxxx>:
>> > On Thu, 2011-03-10 at 15:17 +0800, xinyou yan wrote:
>> >> I want to and a new syscall
>> >> 1 add
>> >> .long sys_mysyscall
>> >> in arch/x86/kernel/syscall_table_32.S
>> >>
>> >> 2 add
>> >> #define __NR_mysyscall 341
>> >> in arch/x86/include/asm/unistd_32.
>> >>
>> >> 3. add
>> >>
>> >> asmlinkage int sys_mysyscall(char* sourceFile,char* destFile)
>> >> {
>> >> int source=sys_open(sourceFile,O_RDONLY,0);
>> >> int dest=sys_open(destFile,O_WRONLY|O_CREAT|O_TRUNC,0600);
>> >> char buf[1024];
>> >> mm_segment_t fs;
>> >> fs = get_fs();
>> >> set_fs(get_ds());
>> >> int nread;
>> >>
>> >> if(source>0 && dest>0)
>> >> {
>> >> while((nread=sys_read(source,buf,1024)) > 0)
>> >> sys_write(dest,buf,read);
>> >> }
>> >> else
>> >> {
>> >> printk("Error!");
>> >> }
>> >> sys_close(source);
>> >> sys_close(dest);
>> >> set_fs(fs);
>> >> return 0;
>> >> }
>> >> in kerrnel/sys.c
>> >>
>> >> 4. make menuconfig
>> >> 5. make all
>> >> 6 make modules_install
>> >>
>> >> reboot
>> >>
>> >>
>> >> Now I want just do it one time
>> >> How can i make sure the new syscall here is mysyscall work fine ?
>> >
>> > Are you locked on using syscalls?
>> > Unless you really require syscalls, I'd imagine that it's far easier to
>> > use ioctl's instead (doesn't require a custom kernel), and use
>> > filp_open / filp_close / file->read / file->write to access files from
>> > within kernel space.
>> >
>> > Two more things:
>> > 1. I'd avoid using stack based allocations in kernel mode. (Down to 8KB
>> > in certain situations)
>> > 2. Always check error codes.
>> >
>> > - Gilboa
>> >
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>
>
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