[PATCH] perf tools: get version from uname(2), not /proc

[PATCH] perf tools: get version from uname(2), not /proc

[Matt Mullins]

Tools in kmod (e.g. modprobe) compose the module path from the release
from uname(2).  Because we use the UNAME26 personality, we need perf to
find modules located at the same path as the system tools.

Signed-off-by: Matt Mullins <mmullins@twopensource.com>
Cc: Vinson Lee <vlee@twopensource.com>
---
 tools/perf/util/machine.c | 28 ++++++----------------------
 1 file changed, 6 insertions(+), 22 deletions(-)

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 5ef90be2a249..51199bc271e9 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -11,6 +11,7 @@
 #include "vdso.h"
 #include <stdbool.h>
 #include <symbol/kallsyms.h>
+#include <sys/utsname.h>
 #include "unwind.h"
 #include "linux/hash.h"
 
@@ -903,31 +904,14 @@ static void map_groups__fixup_end(struct map_groups *mg)
 		__map_groups__fixup_end(mg, i);
 }
 
-static char *get_kernel_version(const char *root_dir)
+static char *get_kernel_version(void)
 {
-	char version[PATH_MAX];
-	FILE *file;
-	char *name, *tmp;
-	const char *prefix = "Linux version ";
+	struct utsname utsname;
 
-	sprintf(version, "%s/proc/version", root_dir);
-	file = fopen(version, "r");
-	if (!file)
+	if (uname(&utsname))
 		return NULL;
 
-	version[0] = '\0';
-	tmp = fgets(version, sizeof(version), file);
-	fclose(file);
-
-	name = strstr(version, prefix);
-	if (!name)
-		return NULL;
-	name += strlen(prefix);
-	tmp = strchr(name, ' ');
-	if (tmp)
-		*tmp = '\0';
-
-	return strdup(name);
+	return strdup(utsname.release);
 }
 
 static bool is_kmod_dso(struct dso *dso)
@@ -1027,7 +1011,7 @@ static int machine__set_modules_path(struct machine *machine)
 	char *version;
 	char modules_path[PATH_MAX];
 
-	version = get_kernel_version(machine->root_dir);
+	version = get_kernel_version();
 	if (!version)
 		return -1;
 
-- 
2.1.0

Re: [PATCH] perf tools: get version from uname(2), not /proc

[Jiri Olsa]

On Tue, Oct 06, 2015 at 03:53:14PM -0700, Matt Mullins wrote:
> Tools in kmod (e.g. modprobe) compose the module path from the release
> from uname(2).  Because we use the UNAME26 personality, we need perf to
> find modules located at the same path as the system tools.

I guess it's easy to google this up, but could you
please state in the changelog what's the difference
between the current version and the UNAME26 one?

Also state (and check) this change wouldn't affect other
parts of the code that use this version (if there's any).

thanks,
jirka

> 
> Signed-off-by: Matt Mullins <mmullins@twopensource.com>
> Cc: Vinson Lee <vlee@twopensource.com>
> ---
>  tools/perf/util/machine.c | 28 ++++++----------------------
>  1 file changed, 6 insertions(+), 22 deletions(-)
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 5ef90be2a249..51199bc271e9 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -11,6 +11,7 @@
>  #include "vdso.h"
>  #include <stdbool.h>
>  #include <symbol/kallsyms.h>
> +#include <sys/utsname.h>
>  #include "unwind.h"
>  #include "linux/hash.h"
>  
> @@ -903,31 +904,14 @@ static void map_groups__fixup_end(struct map_groups *mg)
>  		__map_groups__fixup_end(mg, i);
>  }
>  
> -static char *get_kernel_version(const char *root_dir)
> +static char *get_kernel_version(void)
>  {
> -	char version[PATH_MAX];
> -	FILE *file;
> -	char *name, *tmp;
> -	const char *prefix = "Linux version ";
> +	struct utsname utsname;
>  
> -	sprintf(version, "%s/proc/version", root_dir);
> -	file = fopen(version, "r");
> -	if (!file)
> +	if (uname(&utsname))
>  		return NULL;
>  
> -	version[0] = '\0';
> -	tmp = fgets(version, sizeof(version), file);
> -	fclose(file);
> -
> -	name = strstr(version, prefix);
> -	if (!name)
> -		return NULL;
> -	name += strlen(prefix);
> -	tmp = strchr(name, ' ');
> -	if (tmp)
> -		*tmp = '\0';
> -
> -	return strdup(name);
> +	return strdup(utsname.release);
>  }
>  
>  static bool is_kmod_dso(struct dso *dso)
> @@ -1027,7 +1011,7 @@ static int machine__set_modules_path(struct machine *machine)
>  	char *version;
>  	char modules_path[PATH_MAX];
>  
> -	version = get_kernel_version(machine->root_dir);
> +	version = get_kernel_version();
>  	if (!version)
>  		return -1;
>  
> -- 
> 2.1.0
> 

Re: [PATCH] perf tools: get version from uname(2), not /proc

[Adrian Hunter]

On 07/10/15 11:18, Jiri Olsa wrote:
> On Tue, Oct 06, 2015 at 03:53:14PM -0700, Matt Mullins wrote:
>> Tools in kmod (e.g. modprobe) compose the module path from the release
>> from uname(2).  Because we use the UNAME26 personality, we need perf to
>> find modules located at the same path as the system tools.
> 
> I guess it's easy to google this up, but could you
> please state in the changelog what's the difference
> between the current version and the UNAME26 one?
> 
> Also state (and check) this change wouldn't affect other
> parts of the code that use this version (if there's any).

Isn't the machine root dir for guests? uname() won't work for them.

Re: [PATCH] perf tools: get version from uname(2), not /proc

[Matt Mullins]

On Wed, Oct 07, 2015 at 11:19:17AM +0300, Adrian Hunter wrote:
> On 07/10/15 11:18, Jiri Olsa wrote:
> > On Tue, Oct 06, 2015 at 03:53:14PM -0700, Matt Mullins wrote:
> >> Tools in kmod (e.g. modprobe) compose the module path from the release
> >> from uname(2).  Because we use the UNAME26 personality, we need perf to
> >> find modules located at the same path as the system tools.
> > 
> > I guess it's easy to google this up, but could you
> > please state in the changelog what's the difference
> > between the current version and the UNAME26 one?
> > 
> > Also state (and check) this change wouldn't affect other
> > parts of the code that use this version (if there's any).

This is the only caller of get_kernel_version.

> Isn't the machine root dir for guests? uname() won't work for them.

Aye, this would break --guestmount.  Would it make sense to use uname()
iff root_dir is the empty string, or is that too much special-casing for
good taste?

Re: [PATCH] perf tools: get version from uname(2), not /proc

[Adrian Hunter]

On 07/10/15 20:11, Matt Mullins wrote:
> On Wed, Oct 07, 2015 at 11:19:17AM +0300, Adrian Hunter wrote:
>> On 07/10/15 11:18, Jiri Olsa wrote:
>>> On Tue, Oct 06, 2015 at 03:53:14PM -0700, Matt Mullins wrote:
>>>> Tools in kmod (e.g. modprobe) compose the module path from the release
>>>> from uname(2).  Because we use the UNAME26 personality, we need perf to
>>>> find modules located at the same path as the system tools.
>>>
>>> I guess it's easy to google this up, but could you
>>> please state in the changelog what's the difference
>>> between the current version and the UNAME26 one?
>>>
>>> Also state (and check) this change wouldn't affect other
>>> parts of the code that use this version (if there's any).
> 
> This is the only caller of get_kernel_version.
> 
>> Isn't the machine root dir for guests? uname() won't work for them.
> 
> Aye, this would break --guestmount.  Would it make sense to use uname()
> iff root_dir is the empty string, or is that too much special-casing for
> good taste?

There is machine__is_host(), but what about /proc/sys/kernel/osrelease or
does that have the same problem?

Re: [PATCH] perf tools: get version from uname(2), not /proc

[Andi Kleen]

On Tue, Oct 06, 2015 at 03:53:14PM -0700, Matt Mullins wrote:
> Tools in kmod (e.g. modprobe) compose the module path from the release
> from uname(2).  Because we use the UNAME26 personality, we need perf to
> find modules located at the same path as the system tools.

May be easier to just reset the personality.

-Andi