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tools/opensnoop: support mount full-path #5339

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Merged
yonghong-song merged 1 commit into from
Jun 24, 2025
Merged

tools/opensnoop: support mount full-path #5339

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62 changes: 55 additions & 7 deletions tools/opensnoop.py
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Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,17 @@
#ifdef FULLPATH
#include <linux/fs_struct.h>
#include <linux/dcache.h>
#include <linux/fs.h>
#include <linux/mount.h>

/* see https://github.com/torvalds/linux/blob/master/fs/mount.h */
struct mount {
struct hlist_node mnt_hash;
struct mount *mnt_parent;
struct dentry *mnt_mountpoint;
struct vfsmount mnt;
/* ... */
};
#endif

#define NAME_MAX 255
Expand Down Expand Up @@ -408,28 +419,60 @@
bpf_text = bpf_text.replace('SUBMIT_DATA', """
if (data->name[0] != '/') { // relative path
struct task_struct *task;
struct dentry *dentry;
struct dentry *dentry, *parent_dentry, *mnt_root;
struct vfsmount *vfsmnt;
struct fs_struct *fs;
struct path *path;
struct mount *mnt;
size_t filepart_length;
char *payload = data->name;
struct qstr d_name;
int i;

task = (struct task_struct *)bpf_get_current_task_btf();
dentry = task->fs->pwd.dentry;

fs = task->fs;
path = &fs->pwd;
dentry = path->dentry;
vfsmnt = path->mnt;

mnt = container_of(vfsmnt, struct mount, mnt);

for (i = 1, payload += NAME_MAX; i < MAX_ENTRIES; i++) {
bpf_probe_read_kernel(&d_name, sizeof(d_name), &dentry->d_name);
filepart_length =
bpf_probe_read_kernel(payload, NAME_MAX, (void *)dentry->d_name.name);
bpf_probe_read_kernel_str(payload, NAME_MAX, (void *)d_name.name);

if (filepart_length < 0 || filepart_length > NAME_MAX)
break;

if (dentry == dentry->d_parent) { // root directory
break;
bpf_probe_read_kernel(&mnt_root, sizeof(mnt_root), &vfsmnt->mnt_root);
bpf_probe_read_kernel(&parent_dentry, sizeof(parent_dentry), &dentry->d_parent);

if (dentry == parent_dentry || dentry == mnt_root) {
struct mount *mnt_parent;
bpf_probe_read_kernel(&mnt_parent, sizeof(mnt_parent), &mnt->mnt_parent);

if (mnt != mnt_parent) {
bpf_probe_read_kernel(&dentry, sizeof(dentry), &mnt->mnt_mountpoint);

mnt = mnt_parent;
vfsmnt = &mnt->mnt;

bpf_probe_read_kernel(&mnt_root, sizeof(mnt_root), &vfsmnt->mnt_root);

data->path_depth++;
payload += NAME_MAX;
continue;
} else {
/* Real root directory */
break;
}
}

payload += NAME_MAX;

dentry = dentry->d_parent;
dentry = parent_dentry;
data->path_depth++;
}
}
Expand Down Expand Up @@ -529,7 +572,12 @@ def print_event(cpu, data, size):
# see struct data_t::name field comment.
names = split_names(bytes(event.name))
picked = names[:event.path_depth + 1]
picked_str = [x.decode('utf-8', 'ignore') if isinstance(x, bytes) else str(x) for x in picked]
picked_str = []
for x in picked:
s = x.decode('utf-8', 'ignore') if isinstance(x, bytes) else str(x)
# remove mountpoint '/' and empty string
if s != "/" and s != "":
picked_str.append(s)
joined = '/'.join(picked_str[::-1])
result = joined if joined.startswith('/') else '/' + joined
printb(b"%s" % result.encode("utf-8"))
Expand Down
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