path - linux内核模块中fd inode的可执行路径

Question

• 给定一个inode存在于/proc/**/fd/*
• 以及需要从符号链接中找到可执行路径的 Linux 内核模块/proc/**/exe

我怎样才能实现这一点，以便从一个 inode 号我使用 fd 获得可执行文件的路径？

Answer 1

proc_inode结构和PROC_I宏都是内部的。请参阅[PATCH 27/28] proc：将 PROC_I() 和 PDE() 宏设置为内部 toprocfs [RFC]。

相反，如何迭代 inode 的 dentry 列表呢？您可以使用dentry_path_raw()来查找/*/fd/*路径名：

//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's 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);
}

编辑：我已将演示项目上传到 GitHub：
https ://github.com/dtrebbien/so16317923-proc-fs-kernel-module