x86/cpu: Trim model ID whitespace

We did try trimming whitespace surrounding the 'model name'
field in /proc/cpuinfo since reportedly some userspace uses it
in string comparisons and there were discrepancies:

  [thetango@prarit ~]# 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_________________

However, there were issues with overlapping buffers, string
sizes and non-byte-sized copies in the previous proposed
solutions; see Link tags below for the whole farce.

So, instead of diddling with this more, let's simply extend what
was there originally with trimming any present trailing
whitespace. Final result is really simple and obvious.

Testing with the most insane model IDs qemu can generate, looks
good:

  .model_id = "            My funny model ID CPU          ",
  ______4_model_name      :_My_funny_model_ID_CPU

  .model_id = "My funny model ID CPU          ",
  ______4_model_name      :_My_funny_model_ID_CPU

  .model_id = "            My funny model ID CPU",
  ______4_model_name      :_My_funny_model_ID_CPU

  .model_id = "            ",
  ______4_model_name      :__

  .model_id = "",
  ______4_model_name      :_15/02

Signed-off-by: Borislav Petkov <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Igor Mammedov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 17 insertions, 5 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 41a8e9cb30bc..351197cbbc8e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -5,6 +5,7 @@
 #include <linux/module.h>
 #include <linux/percpu.h>
 #include <linux/string.h>
+#include <linux/ctype.h>
 #include <linux/delay.h>
 #include <linux/sched.h>
 #include <linux/init.h>
@@ -419,6 +420,7 @@ 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, *s;
 
 	if (c->extended_cpuid_level < 0x80000004)
 		return;
@@ -429,11 +431,21 @@ static void get_model_name(struct cpuinfo_x86 *c)
 	cpuid(0x80000004, &v[8], &v[9], &v[10], &v[11]);
 	c->x86_model_id[48] = 0;
 
-	/*
-	 * Remove leading whitespace on Intel processors and trailing
-	 * whitespace on AMD processors.
-	 */
-	memmove(c->x86_model_id, strim(c->x86_model_id), 48);
+	/* Trim whitespace */
+	p = q = s = &c->x86_model_id[0];
+
+	while (*p == ' ')
+		p++;
+
+	while (*p) {
+		/* Note the last non-whitespace index */
+		if (!isspace(*p))
+			s = q;
+
+		*q++ = *p++;
+	}
+
+	*(s + 1) = '\0';
 }
 
 void cpu_detect_cache_sizes(struct cpuinfo_x86 *c)