August 2014 - kernelnewbies@kernelnewbies.org

This is impossible to let the kernel module and the userspace program read/write the same memory area at the same time ?
by lx Aug. 30, 2014

Aug. 30, 2014

hi all: I have a kernel module, it provide some functions: 1. vmalloc a 4KB memory space (I built a ring buffer manage the 4KB memory space) 2. provide the special mmap(), which can remap the memory space. 3. write some data into the 4KB memory space And I have a userspace program, it provide some functions: 1.mmap the kernel memory space into userspace 2.read some data from that mmap space The question is: When I first insmod the kernel module until the data have written in the space, I run the userspace program which read some data. This way is OK. If I insmod the kernel module and run the userspace program at the same time, the kernel will stop and computer will reboot. I think the kernel module is writing the data and the userspace program is reading the data. How to fix it, thank you! the kernel module code is: ##################################################### #include <linux/module.h> #include <linux/kernel.h> #include <linux/fs.h> #include <linux/errno.h> #include <linux/types.h> #include <linux/fcntl.h> #include <linux/cdev.h> #include <linux/version.h> #include <linux/vmalloc.h> #include <linux/ctype.h> #include <linux/pagemap.h> #include <linux/mm.h> #include <linux/slab.h> #include <linux/proc_fs.h> #include <asm/io.h> #include <asm/system.h> #include <linux/uaccess.h> #include <linux/timer.h> #include <linux/pid.h> #include <linux/sched.h> //#define USE_KMALLOC #define PAGE_ORDER 0 #define PAGES_NUMBER 1 static int MAJOR_DEVICE = 30; void * mmap_buf = 0; unsigned long mmap_size = 4*1024; static int ws_open(struct inode *inode, struct file *file) { return 0; } #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,36) #define LIN_IOCTL_NAME .ioctl int ws_ioctl(struct inode *inode, struct file *file, u_int cmd, u_long data) #else #define LIN_IOCTL_NAME .unlocked_ioctl long ws_ioctl(struct file *file, u_int cmd, u_long data) #endif { //todo return 0; } int mmap_alloc(void) { //struct page *page; int i; mmap_size = PAGE_ALIGN(mmap_size); #ifdef USE_KMALLOC //for kmalloc mmap_buf = kzalloc(mmap_size, GFP_KERNEL); printk("kmalloc mmap_buf=%p\n", (void *)mmap_buf); if (!mmap_buf) { printk("kmalloc failed!\n"); return -1; } for (page = virt_to_page(mmap_buf); page < virt_to_page(mmap_buf + mmap_size); page++) { SetPageReserved(page); strcpy((void *)mmap_buf, "Hello world!\n"); } #else //for vmalloc mmap_buf = vmalloc(mmap_size); printk("vmalloc mmap_buf=%p mmap_size=%ld\n", (void *)mmap_buf, mmap_size); if (!mmap_buf ) { printk("vmalloc failed!\n"); return -1; } for (i = 0; i < mmap_size; i += PAGE_SIZE) { SetPageReserved(vmalloc_to_page(mmap_buf + i)); } #endif return 0; } int mmap_free(void) { #ifdef USE_KMALLOC struct page *page; for (page = virt_to_page(mmap_buf); page < virt_to_page(mmap_buf + mmap_size); page++) { ClearPageReserved(page); } kfree((void *)mmap_buf); #else int i; for (i = 0; i < mmap_size; i += PAGE_SIZE) { ClearPageReserved(vmalloc_to_page(mmap_buf + i)); } vfree((void *)mmap_buf); #endif mmap_buf = NULL; return 0; } static int ws_mmap(struct file *f, struct vm_area_struct *vma) { int ret; unsigned long pfn; unsigned long start = vma->vm_start; unsigned long size = PAGE_ALIGN(vma->vm_end - vma->vm_start); void * ptmp = mmap_buf; if (size > mmap_size || !mmap_buf) { return -EINVAL; } #ifdef USE_KMALLOC pfn = virt_to_phys(mmap_buf) >> PAGE_SHIFT; return remap_pfn_range(vma, start, pfn, size, PAGE_SHARED); #else /* loop over all pages, map it page individually */ while (size > 0) { pfn = vmalloc_to_pfn(ptmp); if ((ret = remap_pfn_range(vma, start, pfn, PAGE_SIZE, PAGE_SHARED)) < 0) { return ret; } start += PAGE_SIZE; ptmp += PAGE_SIZE; size -= PAGE_SIZE; } #endif return 0; } static int ws_release(struct inode *inode, struct file *file) { return 0; } static const struct file_operations ws_fops ={ .owner = THIS_MODULE, //.write = ws_write, //.read = ws_read, .mmap = ws_mmap, //.ioctl = ws_ioctl, //.open = ws_open, //.release = ws_release, }; static void wsmmap_exit(void) { if( 0 != mmap_free( )) printk("mmap free failed!\n"); unregister_chrdev(MAJOR_DEVICE,"wsmmap"); printk("rmmod wsmmap module!\n"); } /*manage data*/ typedef struct { char *buffer; int length; volatile int start; volatile int end; } RingBuffer; RingBuffer * ring_buffer; RingBuffer *RingBuffer_create(void *start_malloc, int length) { RingBuffer *buffer = (RingBuffer *)start_malloc; buffer->length = length + 1; buffer->start = 0; buffer->end = 0; buffer->buffer = (char *)start_malloc + sizeof(RingBuffer); return buffer; } #define RingBuffer_available_data(B) ((B)->end % (B)->length - (B)->start) #define RingBuffer_available_space(B) ((B)->length - (B)->end - 1) #define RingBuffer_commit_write(B, A) ((B)->end = ((B)->end + (A)) % (B)->length) #define RingBuffer_ends_at(B) ((B)->buffer + (B)->end) int RingBuffer_write(RingBuffer *buffer, char *data, int length) { if(RingBuffer_available_data(buffer) == 0) { buffer->start = buffer->end = 0; } if (length > RingBuffer_available_space(buffer)){ printk("Not enough space: %d request, %d available", RingBuffer_available_data(buffer), length); return -1; } void *result = memcpy(RingBuffer_ends_at(buffer), data, length); if (result != RingBuffer_ends_at(buffer)){ printk("Failed to write data into buffer."); return -1; } RingBuffer_commit_write(buffer, length); return length; } int kernel_thread_write(void *argc) { char *a = "aa"; int num = 2038; while (num){ RingBuffer_write(ring_buffer, a, 2); printk("write length is %d, start is %d, end is %d\n", ring_buffer->length, ring_buffer->start, ring_buffer->end); --num; msleep(10); } return 0; } int wsmmap_init(void) { //int i; if(register_chrdev(MAJOR_DEVICE, "wsmmap", &ws_fops)) printk("Cannot register mmap device as major device 0!\n"); else printk("wsmmap device driver registed sucessfully!\n"); printk("insmod wsmmap module successfully!\n"); if(0 != mmap_alloc( )) printk("mmap alloc failed!\n"); /* * Initialization RingBuffer */ ring_buffer = RingBuffer_create(mmap_buf, mmap_size - sizeof(RingBuffer) - 1); kernel_thread(kernel_thread_write, NULL, CLONE_KERNEL); /* int i; for (i = 0; i < mmap_size; i += PAGE_SIZE){ memset(mmap_buf + i, 'a', PAGE_SIZE); memset(mmap_buf + i + PAGE_SIZE - 1, '\0', 1); }*/ return 0; } module_init(wsmmap_init); module_exit(wsmmap_exit); MODULE_LICENSE("GPL"); MODULE_VERSION("1.0.0"); MODULE_DESCRIPTION("wskmmap"); MODULE_AUTHOR("wssys"); ##################################################### the userspace code is: ##################################################### #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/mman.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <string.h> #include <unistd.h> #include <pthread.h> #include <unistd.h> #include <stdio.h> #include <execinfo.h> #include <signal.h> #include <stdlib.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <time.h> #include <string.h> void handler(int sig) { #ifndef WIN32 void *array[10]; size_t size; size = backtrace(array, 10); int file_dump = open("/opt/dump.log", O_APPEND | O_RDWR); char message[7] = "BEGIN "; write(file_dump, message, 7); time_t now; struct tm *timenow; char strtemp[255]; time(&now); timenow = localtime(&now); sprintf(strtemp, "recent time is : %s\n", asctime(timenow)); int length=strlen(strtemp)+1; write(file_dump, strtemp, length); backtrace_symbols_fd(array, size, file_dump); close(file_dump); exit(1); #endif } unsigned long phymem_addr = 0; unsigned long phymem_size = 4*1024; /*manage data*/ typedef struct { char *buffer; int length; volatile int start; volatile int end; } RingBuffer; RingBuffer *ring; int read_dump; #define RingBuffer_available_data(B) ((B)->end % (B)->length - (B)->start) #define RingBuffer_starts_at(B) ((B)->buffer + (B)->start) #define RingBuffer_commit_read(B, A) ((B)->start = ((B)->start + (A)) % (B)->length) #define RingBuffer_available_space(B) ((B)->length - (B)->end - 1) #define RingBuffer_commit_write(B, A) ((B)->end = ((B)->end + (A)) % (B)->length) #define RingBuffer_ends_at(B) ((B)->buffer + (B)->end) int RingBuffer_read(RingBuffer *buffer, char *target, int amount) { if (amount > RingBuffer_available_data(buffer)){ printf("Not enough in the buffer: has %d, needs %d", RingBuffer_available_data(buffer), amount); return -1; } void *result = memcpy(target, RingBuffer_starts_at(buffer), amount); if (result != target){ printf("Failed to write buffer into data."); return -1; } RingBuffer_commit_read(buffer, amount); if(buffer->end == buffer->start) { buffer->start = buffer->end = 0; } return amount; } void *thread_read(void *arg) { char mem_data[64]; int num = 2038; while (num){ RingBuffer_read(ring, mem_data, 2); mem_data[2] = '\0'; printf("read length is %d, start is %d, end is %d, data is %s\n", ring->length, ring->start, ring->end, mem_data); --num; sleep(1); } } int main(void) { int fd; int i=0; void *mmap_addr = NULL; signal(SIGSEGV, handler); // install our handler fd = open("/dev/wsmmap", O_RDWR); if(fd < 0) { perror("open"); return 0; } mmap_addr = mmap(NULL, phymem_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); if(mmap_addr == MAP_FAILED) { perror("mmap"); return 0; } ring = (RingBuffer *)mmap_addr; ring->buffer = mmap_addr + sizeof(RingBuffer); int res; pthread_t t_read; res = pthread_create(&t_read, NULL, thread_read, NULL); if (res != 0){ perror("join failed"); return -1; } void *thread_r_read; res = pthread_join(t_read, &thread_r_read); if (res != 0){ perror("Thread join failed"); return -1; } free(mmap_addr); mmap_addr=NULL; close(fd); return 0; } #####################################################

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__devinit and __devexit removed in kernel ?
by Raj Ravi Aug. 30, 2014

Aug. 30, 2014

Hi, __devinit and __devexit removed from recent kernel (3.10 ? ) This was helpful to save some memory (to discard from memory once execution is done in case of __devexit). Any specific reason why this is removed ? any pointers? Thanks

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How to get the information from /proc/files from within a kernel module?
by ravali pullela Aug. 30, 2014

Aug. 30, 2014

Hi all, I want process related information like rss.(we can get this by doing cat /proc/<pid>status) Is there a way to get this from within a kernel module? I checked out the sources on /proc filesystem. They all show how to create, read, write a new proc file. But I want to read from an existing proc file specifically /proc/<pid>/status I could not find rss info of a process from its task struct in kernel version 3.10. I tried to look inside kernel to know how and where are these values (rss and all) are calculated by kernel. But I could not track it. Can anyone please point me to either resources or guide me to accomplish the task of reading information from /proc/files... I looked up call_usermodehelper but did not find it useful for my need. Thanks !

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Re:?
by Kristofer Hallin Aug. 29, 2014

Aug. 29, 2014

But _why_ would you port it? What is the reason behind that? That's just a lot of work for no reason. On 29 Aug 2014 17:53, "Ravi Raj" <nrnraviraj(a)gmail.com> wrote: > Hii Valdis, > Thank you for the response.We dont want to buy a board > with pre-configured linux, that is the first point why i asked you guys for > help, i googled too, i also got hundreds of boards with lot of board > support packages,every board support package varies from the development > board, so just as simple as it "i just want a recommendation from you guys > a good development board where i can port linux from scratch!!" > > > Cheers, > Ravi. > > > > On Fri, Aug 29, 2014 at 5:34 PM, <Valdis.Kletnieks(a)vt.edu> wrote: > >> On Fri, 29 Aug 2014 16:58:26 +0200, Ravi Raj said: >> > Thank you for the response ,So the project is a >> > communication between fpga and a imx6 Arm A9 processor using SPI >> protocol >> > and we are making a custom board for this, so first step is to find an >> imx6 >> > Arm a9 board and port linux to it and then establish SPI. >> >> Heck, these guys already have ANdroid Kitkat up and running: >> >> http://www.wandboard.org/ >> >> > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > >

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(no subject)
by Ravi Raj Aug. 29, 2014

Aug. 29, 2014

Hii Guys, I am an Embedded firmware Developer,I am looking for a Development board to port the linux kernal from scratch, could you guys please recommend me a good development board were i can port linux from scratch. Cheers, Ravi.

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Btrfs - What to Read and other Questions
by nick Aug. 29, 2014

Aug. 29, 2014

Hey Guys, I am reading through the btrfs code and am wondering what files/docs I need to read in order to start helping out with btrfs. In addition when you state size and offset in the page explaining On Disk Format, I am wondering what you mean by offset and size it the tables expanding definitions of certain key values to the disk layout of btrfs , I have an idea but just want to make sure I am understanding it correctly through :). Regards and Thanks, Nick

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What part of the kernel code maintains /proc/modules
by StephanT Aug. 28, 2014

Aug. 28, 2014

Hi, Just want to know why in /proc/modules some of the modules are marked (F). Like: usb_storage 56610 0 - Live 0xffffffffa005d000 (F) Thanks, Stephan.

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U64 Ordering in File System Code of Btrfs
by nick Aug. 28, 2014

Aug. 28, 2014

Hey Guys, Thanks for the help so far. I am wondering after reading the btrfs code for certain functions there seem to be a lot of u64 variable and function returns of this type. Is this common in file system due to the disk being in a certain format and depending on the CPU being big or small endian that this needed to not reorder the disk parts that are being read into main memory and preserve the data's ordering? Cheers Nick

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Re: Btrfs Issues
by Manish Katiyar Aug. 28, 2014

Aug. 28, 2014

On Wed, Aug 27, 2014 at 8:37 PM, nick <xerofoify(a)gmail.com> wrote: > > > On 14-08-27 11:07 PM, Manish Katiyar wrote: > > Is your btrfs on an external drive and did you remove the drive and then > > try to unmount the filesystem ? > > > > Thanks - > > Manish > > > > > > On Wed, Aug 27, 2014 at 1:22 PM, nick <xerofoify(a)gmail.com> wrote: > > > >> When booting on an Ubuntu kernel I am hitting this in my dmesg with an > >> external drive I have. > >> I am wondering if this is a bug or just a common issue. > >> 8518.918519] ------------[ cut here ]------------ > >> [ 8518.918528] WARNING: CPU: 1 PID: 13778 at > >> /build/buildd/linux-3.13.0/fs/btrfs/super.c:254 > >> __btrfs_abort_transaction+0x50/0x110 [btrfs]() > >> [ 8518.918529] btrfs: Transaction aborted (error -5) > >> [ 8518.918530] Modules linked in: btrfs raid6_pq libcrc32c xor ses > >> enclosure usb_storage bnep rfcomm bluetooth hid_generic usbhid hid > >> eeepc_wmi asus_wmi sparse_keymap intel_rapl x86_pkg_temp_thermal > >> intel_powerclamp coretemp kvm_intel kvm crct10dif_pclmul crc32_pclmul > >> ghash_clmulni_intel snd_hda_codec_hdmi aesni_intel aes_x86_64 lrw > gf128mul > >> glue_helper ablk_helper cryptd serio_raw snd_hda_codec_realtek lpc_ich > >> snd_hda_intel snd_hda_codec snd_hwdep snd_seq_midi snd_seq_midi_event > >> snd_pcm snd_rawmidi snd_page_alloc fglrx(POF) snd_seq parport_pc > >> snd_seq_device snd_timer ppdev wmi mei_me snd mei mac_hid lp parport > >> soundcore amd_iommu_v2 video ahci libahci r8169 mii > >> [ 8518.918560] CPU: 1 PID: 13778 Comm: umount Tainted: PF W O > >> 3.13.0-34-generic #60-Ubuntu > >> [ 8518.918561] Hardware name: System manufacturer System Product > >> Name/P8Z68-V LE, BIOS 3506 01/17/2012 > >> [ 8518.918562] 0000000000000009 ffff8801c9ad5c50 ffffffff8171bd94 > >> ffff8801c9ad5c98 > >> [ 8518.918564] ffff8801c9ad5c88 ffffffff810676cd 00000000fffffffb > >> ffff880211d72800 > >> [ 8518.918566] ffff8801c49d8000 ffffffffa0bb2e90 000000000000060b > >> ffff8801c9ad5ce8 > >> [ 8518.918568] Call Trace: > >> [ 8518.918573] [<ffffffff8171bd94>] dump_stack+0x45/0x56 > >> [ 8518.918576] [<ffffffff810676cd>] warn_slowpath_common+0x7d/0xa0 > >> [ 8518.918578] [<ffffffff8106773c>] warn_slowpath_fmt+0x4c/0x50 > >> [ 8518.918583] [<ffffffffa0b16f00>] > __btrfs_abort_transaction+0x50/0x110 > >> [btrfs] > >> [ 8518.918591] [<ffffffffa0b40ebe>] cleanup_transaction+0x6e/0x290 > [btrfs] > >> [ 8518.918594] [<ffffffff810aaf00>] ? prepare_to_wait_event+0x100/0x100 > >> [ 8518.918601] [<ffffffffa0b41e3a>] > btrfs_commit_transaction+0x6ea/0x970 > >> [btrfs] > >> [ 8518.918608] [<ffffffffa0b3c00f>] btrfs_commit_super+0x8f/0xa0 > [btrfs] > >> [ 8518.918614] [<ffffffffa0b3dac0>] close_ctree+0x1e0/0x290 [btrfs] > >> [ 8518.918617] [<ffffffff811d8c2c>] ? evict_inodes+0x11c/0x130 > >> [ 8518.918622] [<ffffffffa0b139b9>] btrfs_put_super+0x19/0x20 [btrfs] > >> [ 8518.918625] [<ffffffff811beda2>] generic_shutdown_super+0x72/0xf0 > >> [ 8518.918627] [<ffffffff811befe2>] kill_anon_super+0x12/0x20 > >> [ 8518.918631] [<ffffffffa0b15eb6>] btrfs_kill_super+0x16/0x90 [btrfs] > >> [ 8518.918634] [<ffffffff811bf33d>] deactivate_locked_super+0x3d/0x60 > >> [ 8518.918636] [<ffffffff811bf8f6>] deactivate_super+0x46/0x60 > >> [ 8518.918638] [<ffffffff811dc5f6>] mntput_no_expire+0xd6/0x170 > >> [ 8518.918640] [<ffffffff811ddb6e>] SyS_umount+0x8e/0x100 > >> [ 8518.918642] [<ffffffff8172c97f>] tracesys+0xe1/0xe6 > >> [ 8518.918644] ---[ end trace 1a6b295c1d8ad4c3 ]--- > >> Nick > >> > >> _______________________________________________ > >> Kernelnewbies mailing list > >> Kernelnewbies(a)kernelnewbies.org > >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > >> > > > No I just pulled it out and then I get this error. Maybe this is normally > when not unmounted? > Nick > This is expected then. It was middle of a journal transaction when you pulled the device out.

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Kernel Programming
by Prudhvee Narasimha Sadha Aug. 28, 2014

Aug. 28, 2014

Hi, I have learnt the basic OS concepts and I'm pretty good at c. Now I need to really work on it. Can you please help me with some basic programs, how to approach and how to work on it. Thank you in advance. :)

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