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Re: [patch 0/3] Live PIDs with deleted files by /dev/PID/mem
- From: Jan Kratochvil <jan dot kratochvil at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Thu, 06 Mar 2014 20:55:28 +0100
- Subject: Re: [patch 0/3] Live PIDs with deleted files by /dev/PID/mem
On Tue, 04 Mar 2014 11:40:21 +0100, Mark Wielaard wrote:
[...]
> --- a/libdwfl/libdwflP.h
> +++ b/libdwfl/libdwflP.h
[...]
> @@ -387,6 +388,39 @@ struct dwfl_arange
> };
>
>
> +/* Structure used for keeping track of ptrace attaching a thread.
> + Shared by linux-pid-attach and linux-proc-maps. If it has been setup
> + then get the instance through __libdwfl_get_pid_arg. */
> +struct pid_arg
IMO the namespace should be 'struct __libdwfl_pid_arg'.
[...]
> --- a/libdwfl/linux-proc-maps.c
> +++ b/libdwfl/linux-proc-maps.c
> @@ -339,34 +339,60 @@ dwfl_linux_proc_find_elf (Dwfl_Module *mod __attribute__ ((unused)),
[...]
> + bool detach = false;
> + bool tid_was_stopped = false;
> + struct pid_arg *pid_arg = __libdwfl_get_pid_arg (mod->dwfl);
> + if (pid_arg != NULL && ! pid_arg->assume_ptrace_stopped)
> + {
> + pid_t tid = pid_arg->tid_attached;
> + if (tid != 0)
> + {
> + /* If the pid already is attached we are fine, otherwise
> + just read through the thread that is attached. */
> + if (tid != pid)
> + pid = tid;
The 'if' conditional has no meaning but it is probably meant for possible
better code readability.
> + }
> + else
> + detach = __libdwfl_ptrace_attach (pid, &tid_was_stopped);
> + }
> +
> char *fname;
> if (asprintf (&fname, PROCMEMFMT, pid) < 0)
> return -1;
[...]
In general I believe reading /proc/PID/maps is safer than the guessing by
elf_from_remote_memory(), for example because the image may come from mmap()
and not from dlopen(). But I guess it may be the common disagreement.
I do not mind much using elf_from_remote_memory() instead.
Jan