linux-kernel - Re: [PATCH] [RFC V1]s390/perf: fix 'start' address of module's map

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Date:	Mon, 11 Jul 2016 14:01:55 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Songshan Gong <gongss@...ux.vnet.ibm.com>
Cc:	acme@...nel.org, jolsa@...nel.org, dsahern@...il.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [RFC V1]s390/perf: fix 'start' address of module's map

On Mon, Jul 11, 2016 at 07:06:14PM +0800, Songshan Gong wrote:

SNIP

> > 
> > we have following functions in tools/lib/api/fs to read
> > single number from file, which I assume you do above:
> > 
> > int sysfs__read_int(const char *entry, int *value);
> > int sysfs__read_ull(const char *entry, unsigned long long *value);
> > 
> > please check if you could use some of them,
> > we could add some more generic one if needed
> 
> It seems infeasible.
> Each value in /sys/module/[module name]/sections/.text is a string like
> "0x000003ff8130078\n".
> But the core function 'strtoull(line, NULL, 10)' in sysfs__read_ull is based
> on decimal.
> 
> Maybe you can introduce a new argument indicating the value is based on hex
> or decimal, or binary?

yea we could specify it directly and add something like:

  int filename__read_ull(const char *filename, unsigned long long *value, int base)

plus some other higher layer helpers..

but I wonder if we could use the base 0 (like in the attached patch),
the man page says it should be able to detect the base

we'd need to check all the current usage to make sure nothing gets broken

jirka


---
diff --git a/tools/lib/api/fs/fs.c b/tools/lib/api/fs/fs.c
index 08556cf2c70d..d18ae548468a 100644
--- a/tools/lib/api/fs/fs.c
+++ b/tools/lib/api/fs/fs.c
@@ -292,7 +292,7 @@ int filename__read_ull(const char *filename, unsigned long long *value)
 		return -1;
 
 	if (read(fd, line, sizeof(line)) > 0) {
-		*value = strtoull(line, NULL, 10);
+		*value = strtoull(line, NULL, 0);
 		if (*value != ULLONG_MAX)
 			err = 0;
 	}