URL:
<http://savannah.gnu.org/bugs/?49730>
Summary: /proc/PID/environ returns I/O errors on read
attempts
Project: The GNU Hurd
Submitted by: baccala
Submitted on: Tue 29 Nov 2016 07:42:00 AM GMT
Category: Hurd Servers
Severity: 3 - Normal
Priority: 5 - Normal
Item Group: None
Status: None
Privacy: Public
Assigned to: None
Originator Name:
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Reproducibility: None
Size (loc): None
Planned Release: None
Effort: 0.00
Wiki-like text discussion box:
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Details:
I'm having problems retrieving process environment from /proc. Something like
"cat /proc/936/environ" often (but not always) returns an I/O error, while
"msgport --getenv -p 936" works fine. I'm not sure exactly which processes
suffer from this, but translators seem particularly vulnerable.
Studying the problem with rpctrace, it seems that there are two different ways
to obtain a process's environment. The proc server hold a pointer to the
environment array (in the process's address space, not its own), and then
vm_read's it to answer proc_procgetenv RPCs. This is how procfs does it, and
this is what isn't working.
I've written a short program (attached) to fetch the argument locations and
print them. Comparing this output to /proc/PID/maps shows that on the
affected processes, the addresses appear sane, but do not correspond to mapped
memory locations, thus the I/O errors.
The other way to get a process's environment is to fetch the process's msg
port and query it using a msg_get_environment RPC. The msgport program does
this, and is able to successfully retrieve environment information.
Related: Do we need two different ways to retrieve a process's environment?
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File Attachments:
-------------------------------------------------------
Date: Tue 29 Nov 2016 07:42:00 AM GMT Name: get_arg_locations.c Size: 380B
By: baccala
<http://savannah.gnu.org/bugs/download.php?file_id=39096>
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