Re: [Crash-utility] enhance print command

Ming Zhang wrote: > Hi All > > I wonder if this is doable or already there? Now for example, if use > "print" to check a function pointer array, it only shows the content. > then for each value, we have run sym <value> to see which symbol it is. > is it possible for the "print" command do this automatically? Thanks. > > > It's all handled by the embedded gdb module, and it does attempt to translate structure members that are declared as function pointers. Take the file_operations structure for exmample: crash> file_operations struct file_operations { struct module *owner; loff_t (*llseek)(struct file *, loff_t, int); ssize_t (*read)(struct file *, char *, size_t, loff_t *); ssize_t (*aio_read)(struct kiocb *, char *, size_t, loff_t); ssize_t (*write)(struct file *, const char *, size_t, loff_t *); ssize_t (*aio_write)(struct kiocb *, const char *, size_t, loff_t); int (*readdir)(struct file *, void *, filldir_t); unsigned int (*poll)(struct file *, struct poll_table_struct *); int (*ioctl)(struct inode *, struct file *, unsigned int, long unsigned int); long int (*unlocked_ioctl)(struct file *, unsigned int, long unsigned int); long int (*compat_ioctl)(struct file *, unsigned int, long unsigned int); int (*mmap)(struct file *, struct vm_area_struct *); int (*open)(struct inode *, struct file *); int (*flush)(struct file *, fl_owner_t); int (*release)(struct inode *, struct file *); int (*fsync)(struct file *, struct dentry *, int); int (*aio_fsync)(struct kiocb *, int); int (*fasync)(int, struct file *, int); int (*lock)(struct file *, int, struct file_lock *); ssize_t (*readv)(struct file *, const struct iovec *, long unsigned int, loff_t *); ssize_t (*writev)(struct file *, const struct iovec *, long unsigned int, loff_t *); ssize_t (*sendfile)(struct file *, loff_t *, size_t, read_actor_t, void *); ssize_t (*sendpage)(struct file *, struct page *, int, size_t, loff_t *, int); long unsigned int (*get_unmapped_area)(struct file *, long unsigned int, long unsigned int, long unsigned int , long unsigned int); int (*check_flags)(int); int (*dir_notify)(struct file *, long unsigned int); int (*flock)(struct file *, int, struct file_lock *); ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int); ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int); } SIZE: 116 crash> And then here's an instance of one: crash> whatis sysfs_file_operations const struct file_operations sysfs_file_operations; crash> p sysfs_file_operations sysfs_file_operations = $5 = { owner = 0x0, llseek = 0xc04704d5 <generic_file_llseek>, read = 0xc04a4fb7 <sysfs_read_file>, aio_read = 0, write = 0xc04a49ab <sysfs_write_file>, aio_write = 0, readdir = 0, poll = 0xc04a4966 <sysfs_poll>, ioctl = 0, unlocked_ioctl = 0, compat_ioctl = 0, mmap = 0, open = 0xc04a4c92 <sysfs_open_file>, flush = 0, release = 0xc04a4e31 <sysfs_release>, fsync = 0, aio_fsync = 0, fasync = 0, lock = 0, readv = 0, writev = 0, sendfile = 0, sendpage = 0, get_unmapped_area = 0, check_flags = 0, dir_notify = 0, flock = 0, splice_write = 0, splice_read = 0 } crash> If it's from a module, it will require its debuginfo to be loaded: crash> p ext3_file_operations p: gdb request failed: p ext3_file_operations crash> mod -s ext3 MODULE NAME SIZE OBJECT FILE e08c4f80 ext3 123337 /lib/modules/2.6.18-53.el5/kernel/fs/ext3/ext3.ko crash> p ext3_file_operations ext3_file_operations = $8 = { owner = 0x0, llseek = 0xc04704d5 <generic_file_llseek>, read = 0xc046f9d6 <do_sync_read>, aio_read = 0xc0455989 <generic_file_aio_read>, write = 0xc046f8e5 <do_sync_write>, aio_write = 0xe08a9e70 <ext3_file_write>, readdir = 0, poll = 0, ioctl = 0xe08ae388 <ext3_ioctl>, unlocked_ioctl = 0, compat_ioctl = 0, mmap = 0xc0454476 <generic_file_mmap>, open = 0xc046e4a6 <generic_file_open>, flush = 0, release = 0xe08a9ef3 <ext3_release_file>, fsync = 0xe08a9f50 <ext3_sync_file>, aio_fsync = 0, fasync = 0, lock = 0, readv = 0xc0456b24 <generic_file_readv>, writev = 0xc045662a <generic_file_writev>, sendfile = 0xc0455109 <generic_file_sendfile>, sendpage = 0, get_unmapped_area = 0, check_flags = 0, dir_notify = 0, flock = 0, splice_write = 0xc0490781 <generic_file_splice_write>, splice_read = 0xc0490809 <generic_file_splice_read> } crash> If the debuginfo data is not available, or for whatever reason you're not getting symbolic translations, you can always "rd -s" the memory symbolically, which is probably more efficient than running "sym" on each address. For example, the file_operations structure is 116 bytes long, or 29 words on an 32-bit system. Even if I didn't have the ext3 module's debuginfo available, crash still knows about its exported symbols: crash> rd -s ext3_file_operations 29 e08b8d40: 00000000 generic_file_llseek do_sync_read generic_file_aio_read e08b8d50: do_sync_write ext3_file_write 00000000 00000000 e08b8d60: ext3_ioctl 00000000 00000000 generic_file_mmap e08b8d70: generic_file_open 00000000 ext3_release_file ext3_sync_file e08b8d80: 00000000 00000000 00000000 generic_file_readv e08b8d90: generic_file_writev generic_file_sendfile 00000000 00000000 e08b8da0: 00000000 00000000 00000000 generic_file_splice_write e08b8db0: generic_file_splice_read crash>

Hope this helps, Dave