Executable path from fd inode in Linux kernel module

Question

• Given the inode that exists in /proc/**/fd/*
• And the Linux kernel module, which should find the executable path from the /proc/**/exe symbolic link

How could I implement this so that from the inode number I get the path of the executable using fd?

Answer 1

proc_inode struct and PROC_I macro are internal. See [PATCH 27/28] proc: Make internal PROC_I () and PDE () macros internal for [RFC] .

Instead, what about iterating over the inode dentry list? You can use dentry_path_raw () to find the path name /*/fd/* :

 //struct inode *proc_inode; struct dentry *dentry; pid_t pid; int found_match = 0; printk(KERN_DEBUG "superblock type name: %s\n", proc_inode->i_sb->s_type->name); // An inode dentry list is protected by the i_lock. See: // - "dcache->d_inode->i_lock protects: i_dentry, d_u.d_alias, d_inode of aliases" // http://lxr.free-electrons.com/source/fs/dcache.c?v=4.0#L48 // - The implementation of d_prune_aliases() // http://lxr.free-electrons.com/source/fs/dcache.c?v=4.0#L882 spin_lock(&proc_inode->i_lock); hlist_for_each_entry(dentry, &proc_inode->i_dentry, d_u.d_alias) { char buf[64]; const char *path_raw; char c; path_raw = dentry_path_raw(dentry, buf, sizeof(buf)); // dentry_path_raw() places the path into `buf'. If `buf' is not large // enough, then continue on to the next dentry. if (!(buf <= path_raw && path_raw <= buf + sizeof(buf) - 1)) { printk(KERN_DEBUG "`buf' not large enough, dentry_path_raw() returned %ld\n", PTR_ERR(path_raw)); continue; } printk(KERN_DEBUG "path_raw = %s\n", path_raw); // We're looking to match: ^/(\d*)/fd/ if (*path_raw++ != '/') continue; pid = 0; for (c = *path_raw; c; c = *++path_raw) { if ('0' <= c && c <= '9') { pid = 10 * pid + (c - '0'); } else { break; } } if (*path_raw++ != '/') continue; if (*path_raw++ != 'f') continue; if (*path_raw++ != 'd') continue; if (*path_raw != '/' && *path_raw != '\0') continue; // Found a match. Break the dentry list loop. found_match = 1; printk(KERN_DEBUG "breaking dentry list loop\n"); break; } spin_unlock(&proc_inode->i_lock); if (found_match) { printk(KERN_DEBUG "pid = %d\n", (int)pid); } 

EDIT: I uploaded a demo project on GitHub:
https://github.com/dtrebbien/so16317923-proc-fs-kernel-module