linux-kernel - Re: [PATCH -mm v2 1/3] elfcore: replace old hard-code 16 with TASK_COMM_LEN

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Message-ID: <b0539137-c91d-0787-721e-c6ed4ced69ec@redhat.com>
Date:   Mon, 13 Dec 2021 15:41:43 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Yafang Shao <laoar.shao@...il.com>, akpm@...ux-foundation.org,
        rostedt@...dmis.org, keescook@...omium.org, pmladek@...e.com,
        arnaldo.melo@...il.com, andrii.nakryiko@...il.com,
        alexei.starovoitov@...il.com
Cc:     linux-mm@...ck.org, bpf@...r.kernel.org,
        linux-perf-users@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Michal Miroslaw <mirq-linux@...e.qmqm.pl>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH -mm v2 1/3] elfcore: replace old hard-code 16 with
 TASK_COMM_LEN_16

On 11.12.21 07:39, Yafang Shao wrote:
> A new macro TASK_COMM_LEN_16 is introduced for the old hard-coded 16 to
> make it more grepable. As explained above this marco, the difference
> between TASK_COMM_LEN and TASK_COMM_LEN_16 is that TASK_COMM_LEN_16 must
> be a fixed size 16 and can't be changed.
> 
> Suggested-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
> Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>
> Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>
> Cc: Michal Miroslaw <mirq-linux@...e.qmqm.pl>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Petr Mladek <pmladek@...e.com>
> ---
>  include/linux/elfcore-compat.h | 8 ++------
>  include/linux/elfcore.h        | 9 ++-------
>  include/linux/sched.h          | 5 +++++
>  3 files changed, 9 insertions(+), 13 deletions(-)
> 
> diff --git a/include/linux/elfcore-compat.h b/include/linux/elfcore-compat.h
> index 54feb64e9b5d..69fa1a728964 100644
> --- a/include/linux/elfcore-compat.h
> +++ b/include/linux/elfcore-compat.h
> @@ -5,6 +5,7 @@
>  #include <linux/elf.h>
>  #include <linux/elfcore.h>
>  #include <linux/compat.h>
> +#include <linux/sched.h>
>  
>  /*
>   * Make sure these layouts match the linux/elfcore.h native definitions.
> @@ -43,12 +44,7 @@ struct compat_elf_prpsinfo
>  	__compat_uid_t			pr_uid;
>  	__compat_gid_t			pr_gid;
>  	compat_pid_t			pr_pid, pr_ppid, pr_pgrp, pr_sid;
> -	/*
> -	 * The hard-coded 16 is derived from TASK_COMM_LEN, but it can't be
> -	 * changed as it is exposed to userspace. We'd better make it hard-coded
> -	 * here.
> -	 */
> -	char				pr_fname[16];
> +	char				pr_fname[TASK_COMM_LEN_16];
>  	char				pr_psargs[ELF_PRARGSZ];
>  };
>  
> diff --git a/include/linux/elfcore.h b/include/linux/elfcore.h
> index 746e081879a5..d3bb4bd3c985 100644
> --- a/include/linux/elfcore.h
> +++ b/include/linux/elfcore.h
> @@ -65,13 +65,8 @@ struct elf_prpsinfo
>  	__kernel_gid_t	pr_gid;
>  	pid_t	pr_pid, pr_ppid, pr_pgrp, pr_sid;
>  	/* Lots missing */
> -	/*
> -	 * The hard-coded 16 is derived from TASK_COMM_LEN, but it can't be
> -	 * changed as it is exposed to userspace. We'd better make it hard-coded
> -	 * here.
> -	 */
> -	char	pr_fname[16];	/* filename of executable */
> -	char	pr_psargs[ELF_PRARGSZ];	/* initial part of arg list */
> +	char	pr_fname[TASK_COMM_LEN_16];	/* filename of executable */
> +	char	pr_psargs[ELF_PRARGSZ];		/* initial part of arg list */
>  };
>  
>  static inline void elf_core_copy_regs(elf_gregset_t *elfregs, struct pt_regs *regs)
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index c79bd7ee6029..8d963a50a2a8 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -279,6 +279,11 @@ struct task_group;
>   * BPF programs.
>   */
>  enum {
> +	/*
> +	 * For the old hard-coded 16, which is exposed to userspace and can't
> +	 * be changed.
> +	 */
> +	TASK_COMM_LEN_16 = 16,
>  	TASK_COMM_LEN = 16,
>  };
>  
> 

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb