[SOLVED] In Linux, how can I get the filename from the "struct file" structure, while stepping thru the kernel with kgdb?

Issue

I'm trying to view the filename via kgdb, so I cannot call functions and macros to get it programatically. I need to find it by manually inspecting data structures.

Like if I had a breakpoint here in gdb, how could I look around with gdb and find the filename?

I've tried looking around in filp.f_path, filp.f_inode, etc. I cannot see the filename anywhere.

ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
{
     struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = len };
     struct kiocb kiocb;
     ssize_t ret;

     init_sync_kiocb(&kiocb, filp);
     kiocb.ki_pos = *ppos;
     kiocb.ki_left = len;
     kiocb.ki_nbytes = len;

     ret = filp->f_op->aio_write(&kiocb, &iov, 1, kiocb.ki_pos);
     if (-EIOCBQUEUED == ret)
             ret = wait_on_sync_kiocb(&kiocb);
     *ppos = kiocb.ki_pos;
     return ret;
}

Solution

In the Linux kernel, the file structure is essentially how the kernel "sees" the file. The kernel is not interested in the file name, just the inode of the open file. This means that all of the other information which is important to the user is lost.

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EDIT: This answer is wrong. You can get the dentry using filp->f_path.dentry. From there you can get the name of the dentry or the full path using the relevant FS flags.

Answered By - cyphar

Answer Checked By - Cary Denson (WPSolving Admin)