[PATCH v2] cpupower: Make help command available for custom install dir

[PATCH v2] cpupower: Make help command available for custom install dir

[Roman Storozhenko]

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@gmail.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) {
+		exec_dir = strdup(exec_path);
+		if (!exec_dir) {
+			free(page);
+			free(man_path);
+			return -ENOMEM;
+		}
+
+		/* Prepend standard search path for man pages with relative path
+		 * to custom install man directory
+		 */
+		if (asprintf(&man_path, "%s/../man:", dirname(exec_dir)) > 0) {
+			setenv("MANPATH", man_path, 1);
+			free(exec_dir);
+			free(man_path);
+		} else {
+			free(page);
+			free(exec_dir);
+			free(man_path);
+			return -ENOMEM;
+		}
+	}
+
 	execlp("man", "man", page, NULL);
 
 	/* should not be reached */

---
base-commit: 2102cb0d050d34d50b9642a3a50861787527e922
change-id: 20240619-fix-help-issue-573c40bb6427

Best regards,
-- 
Roman Storozhenko <romeusmeister@gmail.com>

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

[Shuah Khan]

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@gmail.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

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

[Roman Storozhenko]

On Tue, Jun 25, 2024 at 9:29 PM Shuah Khan <skhan@linuxfoundation.org> wrote:
>
> 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@gmail.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]?

Yes, it is not the best solution. I would rather prefer to have a portable,
POSIX-based one. But after exploring possible options I came to the
conclusion that unfortunately such a solution doesn't exist.
According to C11 language standard:
"If the value of argc is greater than zero, the string pointed to by argv[0]
represents the program name;....".
Notice - program name, not the absolute path to the program. The actual
value of argv is under control of the calling environment.
You could look at the nice discussion of the topic for example here:
https://www.reddit.com/r/C_Programming/comments/dgcmhd/exactly_how_reliable_is_argv0_at_being_the/
Besides - this utility is a part of the Linux Kernel source tree and therefore
has no requirement of the portability to another OSes.

>
> thanks,
> -- Shuah



-- 
Kind regards,
Roman Storozhenko

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

[Shuah Khan]

On 6/26/24 01:29, Roman Storozhenko wrote:
> On Tue, Jun 25, 2024 at 9:29 PM Shuah Khan <skhan@linuxfoundation.org> wrote:
>>
>> 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@gmail.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]?
> 
> Yes, it is not the best solution. I would rather prefer to have a portable,
> POSIX-based one. But after exploring possible options I came to the
> conclusion that unfortunately such a solution doesn't exist.
> According to C11 language standard:
> "If the value of argc is greater than zero, the string pointed to by argv[0]
> represents the program name;....".
> Notice - program name, not the absolute path to the program. The actual
> value of argv is under control of the calling environment.
> You could look at the nice discussion of the topic for example here:
> https://www.reddit.com/r/C_Programming/comments/dgcmhd/exactly_how_reliable_is_argv0_at_being_the/
> Besides - this utility is a part of the Linux Kernel source tree and therefore
> has no requirement of the portability to another OSes.
> 

Even so, you don't want to move it towards non-portable. I think I asked
this before on your previous version of the patch:

What happens when you set the MANPATH before running the command?

thanks,
-- Shuah

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

[Roman Storozhenko]

On Wed, Jun 26, 2024 at 5:36 PM Shuah Khan <skhan@linuxfoundation.org> wrote:
>
> On 6/26/24 01:29, Roman Storozhenko wrote:
> > On Tue, Jun 25, 2024 at 9:29 PM Shuah Khan <skhan@linuxfoundation.org> wrote:
> >>
> >> 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@gmail.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]?
> >
> > Yes, it is not the best solution. I would rather prefer to have a portable,
> > POSIX-based one. But after exploring possible options I came to the
> > conclusion that unfortunately such a solution doesn't exist.
> > According to C11 language standard:
> > "If the value of argc is greater than zero, the string pointed to by argv[0]
> > represents the program name;....".
> > Notice - program name, not the absolute path to the program. The actual
> > value of argv is under control of the calling environment.
> > You could look at the nice discussion of the topic for example here:
> > https://www.reddit.com/r/C_Programming/comments/dgcmhd/exactly_how_reliable_is_argv0_at_being_the/
> > Besides - this utility is a part of the Linux Kernel source tree and therefore
> > has no requirement of the portability to another OSes.
> >
>
> Even so, you don't want to move it towards non-portable.

I tried to find a portable solution one more time but couldn't.
If you know how to do this please let me know.

> I think I asked
> this before on your previous version of the patch:
>
> What happens when you set the MANPATH before running the command?

Nice catch. Thanks. Will fix this and send v3.

>
> thanks,
> -- Shuah
>

-- 
Kind regards,
Roman Storozhenko