* a idea about probe proc path like /proc/pid/root/xxx
@ 2022-07-13 5:18 Cong Wu
2022-08-18 17:35 ` Frank Ch. Eigler
0 siblings, 1 reply; 2+ messages in thread
From: Cong Wu @ 2022-07-13 5:18 UTC (permalink / raw)
To: systemtap
hi all. currently, I'm use stap to probe user process like `probe process("/proc/xx/root/xxx").function("a")`, what I really want is to probe a process running in docker, I make a small patch.
here is what i did. https://github.com/woodgear/systemtap-wg/commit/0872dc3f5594be520afd83fc5075fff8c6bec955.
basically if solib_pathname start with /proc/$(task->tgid)/root then i just compare the rest part of it.
```
--- a/runtime/linux/uprobes-inode.c
+++ b/runtime/linux/uprobes-inode.c
@@ -813,6 +813,8 @@ stapiu_mmap_found(struct stap_task_finder_target *tf_target,
struct stapiu_process* p;
int known_mapping_p;
unsigned long flags;
+ char proc_path_buff[100];
+ char *proc_path="/proc/";
dbug_uprobes("wg: in mmap_found pid %d inode %ld\n",task->tgid,dentry->d_inode->i_ino);
@@ -876,18 +878,33 @@ stapiu_mmap_found(struct stap_task_finder_target *tf_target,
if (! known_mapping_p) {
/* The file path or build-id must match. The build-id address
* is calculated using start address of this vma, the file
* offset of the vma start address and the file offset of
* the build-id. */
- if (c->solib_pathname && path && strcmp (path, c->solib_pathname))
- return 0;
+ if (c->solib_pathname && path) {
+ if (strncmp(proc_path, c->solib_pathname, strlen(proc_path)) == 0) {
+ sprintf(proc_path_buff,"/proc/%d/root%s",task->tgid,path);
+ if (strcmp (proc_path_buff, c->solib_pathname)) {
+ return 0;
+ }
+ }else {
+ // not proc path just compare
+ if (strcmp (path, c->solib_pathname)) {
+ return 0;
+ }
+ }
+ }
if (c->solib_build_id_len > 0 && !__verify_build_id(task,
addr - offset + c->solib_build_id_vaddr,
c->solib_build_id,
- c->solib_build_id_len))
+ c->solib_build_id_len)) {
+
return 0;
+ }
}
// If we made it this far, we have an interesting solib.
@@ -923,7 +940,7 @@ stapiu_mmap_found(struct stap_task_finder_target *tf_target,
spin_lock_irqsave (&c->process_list_lock, flags);
list_add(&p->process_list, &c->process_list_head);
spin_unlock_irqrestore (&c->process_list_lock, flags);
} else
_stp_warn("out of memory tracking solib %s in process %ld\n",
path, (long) task->tgid);
```
this is just a draft code to show what I want to change.
is this way work?
A further idea is that we can add an option like --use-proc-path to find the uprobe file path at a given pid.
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: a idea about probe proc path like /proc/pid/root/xxx
2022-07-13 5:18 a idea about probe proc path like /proc/pid/root/xxx Cong Wu
@ 2022-08-18 17:35 ` Frank Ch. Eigler
0 siblings, 0 replies; 2+ messages in thread
From: Frank Ch. Eigler @ 2022-08-18 17:35 UTC (permalink / raw)
To: Cong Wu; +Cc: systemtap
Cong Wu <congwu@alauda.io> writes:
> hi all. currently, I'm use stap to probe user process like `probe
> process("/proc/xx/root/xxx").function("a")`, what I really want is to
> probe a process running in docker, I make a small patch.
Interesting idea.
> [...]
> basically if solib_pathname start with /proc/$(task->tgid)/root then i
> just compare the rest part of it.
That's an interesting solution. Does it work fully? Have you tried the
buildid-based probing facility, which is independent of run-time paths
such as containers/namespace? We're also working on another extension
that is related: https://sourceware.org/bugzilla/show_bug.cgi?id=27410
- FChE
^ permalink raw reply [flat|nested] 2+ messages in thread
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