linux-kernel - [PATCH 14/18] x86/cpu: Strip any /proc/cpuinfo model name field whitespace

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Date:	Tue, 26 May 2015 10:28:17 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	X86-ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 14/18] x86/cpu: Strip any /proc/cpuinfo model name field whitespace

From: Prarit Bhargava <prarit@...hat.com>

When comparing the 'model name' field of each core in /proc/cpuinfo it
was noticed that there is a whitespace difference between the cores'
model names.

After some quick investigation it was noticed that the model name fields
were actually different -- processor 0's model name field had trailing
whitespace 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 the discrepancy.

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 strips the whitespace at the end of the ->x86_model_id
field.

But, the ->x86_model_id field should be the same for the all identical
CPUs in the box. Thus, we need to remove both leading and trailing
whitespace.

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:

  _____64_model_name      :_AMD_Opteron(TM)_Processor_6272

Output is still correct on an Intel box:

  ____144_model_name      :_Intel(R)_Xeon(R)_CPU_E7-8890_v3_@...50GHz

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: Andy Lutomirski <luto@...capital.net>
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>
Cc: lkml <linux-kernel@...r.kernel.org>
Link: http://lkml.kernel.org/r/1432050210-32036-1-git-send-email-prarit@redhat.com
Signed-off-by: Borislav Petkov <bp@...e.de>
---
 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 a62cf04dac8a..41a8e9cb30bc 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);
 
-- 
1.9.0.258.g00eda23

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