linux-kernel - [PATCH] x86/cpu: Strip leading and trailing spaces from the /proc/cpuinfo CPU model field

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Date:	Wed, 20 May 2015 07:36:54 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Prarit Bhargava <prarit@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Igor Mammedov <imammedo@...hat.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Brian Gerst <brgerst@...il.com>
Subject: [PATCH] x86/cpu: Strip leading and trailing spaces from the /proc/cpuinfo CPU model field

When comparing 'model name' fields in /proc/cpuinfo it was noticed that
a simple test comparing the model name fields was failing.  After some
quick investigation it was noticed that the model name fields were actually
different -- processor 0's model name field had trailing white space removed,
while the other processors did not.

Another way of seeing this behaviour is to convert spaces into underscores
in the output of /proc/cpuinfo,

[thetango@...rit ~]# grep "^model name" /proc/cpuinfo | uniq -c | sed 's/\ /_/g'
______1_model_name      :_AMD_Opteron(TM)_Processor_6272
_____63_model_name      :_AMD_Opteron(TM)_Processor_6272_________________

which shows two different model name fields even though they should be the
same.

This occurs because the kernel calls strim() on cpu 0's x86_model_id field
to output a pretty message to the console in print_cpu_info(), and as a
result truncates the whitespace at the end of the x86_model_id field.

The x86_model_id field should be the same for the same processors.  This
patch uses string functions to remove both leading and trailing whitespace
in the x86_model_id field.  As a result the print_cpu_info() output looks
like

smpboot: CPU0: AMD Opteron(TM) Processor 6272 (fam: 15, model: 01, stepping: 02)

and the x86_model_id field is correct on all processors on AMD platforms

[thetango@...rit ~]# grep "^model name" /proc/cpuinfo | uniq -c | sed 's/\ /_/g'
_____64_model_name      :_AMD_Opteron(TM)_Processor_6272

and the functionality is correct on an Intel box:

[thetango@...rit2]# grep "^model name" /proc/cpuinfo | uniq -c | sed 's/\ /_/g'
____144_model_name      :_Intel(R)_Xeon(R)_CPU_E7-8890_v3_@...50GHz

[v2]: use memmove and update patch subject

Signed-off-by: Prarit Bhargava <prarit@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Igor Mammedov <imammedo@...hat.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: Brian Gerst <brgerst@...il.com>
---
 arch/x86/kernel/cpu/common.c | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a62cf04..41a8e9c 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -419,7 +419,6 @@ static const struct cpu_dev *cpu_devs[X86_VENDOR_NUM] = {};
 static void get_model_name(struct cpuinfo_x86 *c)
 {
 	unsigned int *v;
-	char *p, *q;
 
 	if (c->extended_cpuid_level < 0x80000004)
 		return;
@@ -431,18 +430,10 @@ static void get_model_name(struct cpuinfo_x86 *c)
 	c->x86_model_id[48] = 0;
 
 	/*
-	 * Intel chips right-justify this string for some dumb reason;
-	 * undo that brain damage:
+	 * Remove leading whitespace on Intel processors and trailing
+	 * whitespace on AMD processors.
 	 */
-	p = q = &c->x86_model_id[0];
-	while (*p == ' ')
-		p++;
-	if (p != q) {
-		while (*p)
-			*q++ = *p++;
-		while (q <= &c->x86_model_id[48])
-			*q++ = '\0';	/* Zero-pad the rest */
-	}
+	memmove(c->x86_model_id, strim(c->x86_model_id), 48);
 }
 
 void cpu_detect_cache_sizes(struct cpuinfo_x86 *c)
@@ -1122,7 +1113,7 @@ void print_cpu_info(struct cpuinfo_x86 *c)
 		printk(KERN_CONT "%s ", vendor);
 
 	if (c->x86_model_id[0])
-		printk(KERN_CONT "%s", strim(c->x86_model_id));
+		printk(KERN_CONT "%s", c->x86_model_id);
 	else
 		printk(KERN_CONT "%d86", c->x86);
 
-- 
1.8.3.1

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