On Fri, 2008-02-01 at 09:11 -0500, Dave Anderson wrote:
> 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>
thanks a lot, both tips helps. also i update to latest crash and it show
symbol more reliably than the one coming with RHEL4.
>
> Hope this helps,
> Dave
>
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--
Ming Zhang
@#$%^ purging memory... (*!%
http://blackmagic02881.wordpress.com/
http://www.linkedin.com/in/blackmagic02881
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