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

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Message-ID: <tip-adafb98da6a7af5e45362933a7dae6ab0e5076bf@git.kernel.org>
Date:	Wed, 27 May 2015 07:16:42 -0700
From:	tip-bot for Prarit Bhargava <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	peterz@...radead.org, imammedo@...hat.com,
	torvalds@...ux-foundation.org, dvlasenk@...hat.com,
	mingo@...nel.org, brgerst@...il.com, luto@...capital.net,
	bp@...en8.de, tglx@...utronix.de, bp@...e.de, prarit@...hat.com,
	dave.hansen@...ux.intel.com, linux-kernel@...r.kernel.org,
	hpa@...or.com, fenghua.yu@...el.com
Subject: [tip:x86/cpu] x86/cpu: Strip any /proc/
 cpuinfo model name field whitespace

Commit-ID:  adafb98da6a7af5e45362933a7dae6ab0e5076bf
Gitweb:     http://git.kernel.org/tip/adafb98da6a7af5e45362933a7dae6ab0e5076bf
Author:     Prarit Bhargava <prarit@...hat.com>
AuthorDate: Tue, 26 May 2015 10:28:17 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 27 May 2015 14:38:24 +0200

x86/cpu: Strip any /proc/cpuinfo model name field whitespace

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>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Denys Vlasenko <dvlasenk@...hat.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Igor Mammedov <imammedo@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1432050210-32036-1-git-send-email-prarit@redhat.com
Link: http://lkml.kernel.org/r/1432628901-18044-15-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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);
 
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