Re: proc(5): /proc/[number]/cmdline explanation update

[Michael Kerrisk <mtk.manpages-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>]

Fernando,

Do you know when (which kernel version) this change in behavior occurred?

Cheers,

Michael

Fernando Luis Vázquez Cao wrote:
> It used to be true that the command line arguments were not accessible
> when the process had been swapped out. In ancient kernels (circa 2.0.*)
> the problem was that the kernel relied on get_phys_addr to access the
> user space buffer, which stopped working as soon as the process was
> swapped out. Recent kernels use get_user_pages for the same purpose and
> thus they should not have that limitation.
> 
> Signed-off-by: Fernando Luis Vazquez Cao <fernando-gVGce1chcLdL9jVzuh4AOg@public.gmane.org>
> ---
> 
> --- proc.5.orig	2008-02-06 14:11:58.000000000 +0900
> +++ proc.5	2008-02-06 14:56:22.000000000 +0900
> @@ -87,12 +87,11 @@ plus one \fIunsigned long\fP value for e
>  The last entry contains two zeros.
>  .TP
>  .I /proc/[number]/cmdline
> -This holds the complete command line for the process, unless the whole
> -process has been swapped out or the process is a zombie.
> -In either of these latter cases, there is nothing in this file:
> -that is, a read on this file will return 0 characters.
> -The command line arguments appear in this file as a set of
> -null-separated strings, with a further null byte after the last string.
> +This holds the complete command line for the process, unless the process is a
> +zombie. In the latter case, there is nothing in this file: that is, a read on
> +this file will return 0 characters. The command line arguments appear in this
> +file as a set of null-separated strings, with a further null byte after the
> +last string.
>  .TP
>  .I /proc/[number]/cwd
>  This is a symbolic link to the current working directory of the process.
> 
> 
> 

-- 
Michael Kerrisk
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