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i386 msr.c devfs support 1/2

PATCH In review Andrey Borzenkov 2 participants 3 messages Aug 10, 2003

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Andrey Borzenkov

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#0 lore raw

PATCH 1/1 i386 msr.c devfs support 1/2

Please let me know if default permissions (644) are not appropriate. Tested on 2-way SMP kernel single CPU system; it correctly rejects access to no-existing CPU.

/dev/cpu/N is not removed on module unload. It is impossible to cleanly unregister directories shared by independent drivers given current devfs implementation (no actual refcounting)

-andrey

arch/i386/kernel/msr.c renamed from arch/i386/kernel/msr.c.devfs +13 -0
@@ -37,6 +37,8 @@
 #include <linux/major.h>
 #include <linux/fs.h>
 
+#include <linux/devfs_fs_kernel.h>
+
 #include <asm/processor.h>
 #include <asm/msr.h>
 #include <asm/uaccess.h>

@@ -263,17 +265,28 @@ static struct file_operations msr_fops =
 
 int __init msr_init(void)
 {
+  int i;
+
   if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
     printk(KERN_ERR "msr: unable to get major %d for msr\n",
 	   MSR_MAJOR);
     return -EBUSY;
   }
+
+  for (i = 0; i < NR_CPUS; i++)
+    devfs_mk_cdev(MKDEV(MSR_MAJOR, i), S_IFCHR | S_IRUGO | S_IWUSR,
+		  "cpu/%d/msr", i);
   
   return 0;
 }
 
 void __exit msr_exit(void)
 {
+  int i;
+
+  for (i = 0; i < NR_CPUS; i++)
+    devfs_remove("cpu/%d/msr", i);
+  
   unregister_chrdev(MSR_MAJOR, "cpu/msr");
 }
#1 lore raw
Quoted 1 line · Andrey Borzenkov

Please let me know if default permissions (644) are not appropriate.

bogus. They should be set to 600. Non-root access to MSRs (even read only) can cause instant lockup/reboot on some CPUs if user tries to read non-existant MSR.

Dave

Signature · 1 line
 Dave Jones     http://www.codemonkey.org.uk
author
#2 lore raw
Quoted 7 lines · Dave Jones
Quoted 1 line · Andrey Borzenkov

Please let me know if default permissions (644) are not appropriate.

bogus. They should be set to 600. Non-root access to MSRs (even read only) can cause instant lockup/reboot on some CPUs if user tries to read non-existant MSR.

update patch attached.

-andrey

arch/i386/kernel/msr.c renamed from tmp/linux-2.6.0-test3/arch/i386/kernel/msr.c +13 -0
@@ -37,6 +37,8 @@
 #include <linux/major.h>
 #include <linux/fs.h>
 
+#include <linux/devfs_fs_kernel.h>
+
 #include <asm/processor.h>
 #include <asm/msr.h>
 #include <asm/uaccess.h>

@@ -263,17 +265,28 @@ static struct file_operations msr_fops =
 
 int __init msr_init(void)
 {
+  int i;
+
   if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
     printk(KERN_ERR "msr: unable to get major %d for msr\n",
 	   MSR_MAJOR);
     return -EBUSY;
   }
+
+  for (i = 0; i < NR_CPUS; i++)
+    devfs_mk_cdev(MKDEV(MSR_MAJOR, i), S_IFCHR | S_IRUSR | S_IWUSR,
+		  "cpu/%d/msr", i);
   
   return 0;
 }
 
 void __exit msr_exit(void)
 {
+  int i;
+
+  for (i = 0; i < NR_CPUS; i++)
+    devfs_remove("cpu/%d/msr", i);
+  
   unregister_chrdev(MSR_MAJOR, "cpu/msr");
 }