linux-kernel - Re: [PATCH v2] cpupower: Make help command available for custom install dir

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Date: Tue, 25 Jun 2024 13:29:00 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Roman Storozhenko <romeusmeister@...il.com>,
 Thomas Renninger <trenn@...e.com>, Shuah Khan <shuah@...nel.org>
Cc: Javier Carrasco <javier.carrasco.cruz@...il.com>,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
 Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v2] cpupower: Make help command available for custom
 install dir

On 6/22/24 07:01, Roman Storozhenko wrote:
> When the 'cpupower' utility installed in the custom dir, it fails to
> render appropriate help info for a particular subcommand:
> $ LD_LIBRARY_PATH=lib64/ bin/cpupower help monitor
> with error message like 'No manual entry for cpupower-monitor.1'
> The issue is that under the hood it calls 'exec' function with
> the following args: 'man cpupower-monitor.1'. In turn, 'man' search
> path is defined in '/etc/manpath.config'. Of course it contains only
> standard system man paths.
> Make subcommands help available for a user by setting up 'MANPATH'
> environment variable to the custom installation man pages dir. That
> variable value will be prepended to the man pages standard search paths
> as described in 'SEARCH PATH' section of MANPATH(5).
> 
> Signed-off-by: Roman Storozhenko <romeusmeister@...il.com>
> ---
> Changes in v2:
> - Fixed spelling errors
> - Simplified man pages search approach by the 'MANPATH' variable usage
> - Link to v1: https://lore.kernel.org/r/20240621-fix-help-issue-v1-1-7906998d46eb@gmail.com
> ---
>   tools/power/cpupower/utils/cpupower.c | 41 ++++++++++++++++++++++++++++++-----
>   1 file changed, 35 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/power/cpupower/utils/cpupower.c b/tools/power/cpupower/utils/cpupower.c
> index 9ec973165af1..1b1b79c572ad 100644
> --- a/tools/power/cpupower/utils/cpupower.c
> +++ b/tools/power/cpupower/utils/cpupower.c
> @@ -12,6 +12,8 @@
>   #include <unistd.h>
>   #include <errno.h>
>   #include <sched.h>
> +#include <libgen.h>
> +#include <limits.h>
>   #include <sys/types.h>
>   #include <sys/stat.h>
>   #include <sys/utsname.h>
> @@ -80,14 +82,17 @@ static void print_help(void)
>   
>   static int print_man_page(const char *subpage)
>   {
> -	int len;
> -	char *page;
> +	char *page, *man_path, *exec_dir;
> +	char exec_path[PATH_MAX];
> +	int subpage_len;
>   
> -	len = 10; /* enough for "cpupower-" */
> -	if (subpage != NULL)
> -		len += strlen(subpage);
> +	if (!subpage)
> +		return -EINVAL;
>   
> -	page = malloc(len);
> +	subpage_len = 10; /* enough for "cpupower-" */
> +	subpage_len += strlen(subpage);
> +
> +	page = malloc(subpage_len);
>   	if (!page)
>   		return -ENOMEM;
>   
> @@ -97,6 +102,30 @@ static int print_man_page(const char *subpage)
>   		strcat(page, subpage);
>   	}
>   
> +	/* Get current process image name full path */
> +	if (readlink("/proc/self/exe", exec_path, PATH_MAX) > 0) {

Using /proc/self/exe is Linux and platform specific and not a
good solution. Did you loom into using argv[0]?

thanks,
-- Shuah