3.2.52-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
commit d1211af3049f4c9c1d8d4eb8f8098cc4f4f0d0c7 upstream.
arch/powerpc/kernel/sysfs.c exports PURR with write permission.
This may be valid for kernel in phyp mode. But writing to
the file in guest mode causes crash due to a priviledge violation
Signed-off-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2:
- Adjust context
- CPUs are sysdev and we must use the sysdev API]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/sysfs.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -18,6 +18,7 @@
#include <asm/machdep.h>
#include <asm/smp.h>
#include <asm/pmc.h>
+#include <asm/firmware.h>
#include "cacheinfo.h"
@@ -178,14 +179,24 @@ SYSFS_PMCSETUP(purr, SPRN_PURR);
SYSFS_PMCSETUP(spurr, SPRN_SPURR);
SYSFS_PMCSETUP(dscr, SPRN_DSCR);
+/*
+ Lets only enable read for phyp resources and
+ enable write when needed with a separate function.
+ Lets be conservative and default to pseries.
+*/
static SYSDEV_ATTR(mmcra, 0600, show_mmcra, store_mmcra);
static SYSDEV_ATTR(spurr, 0600, show_spurr, NULL);
static SYSDEV_ATTR(dscr, 0600, show_dscr, store_dscr);
-static SYSDEV_ATTR(purr, 0600, show_purr, store_purr);
+static SYSDEV_ATTR(purr, 0400, show_purr, store_purr);
unsigned long dscr_default = 0;
EXPORT_SYMBOL(dscr_default);
+static void add_write_permission_dev_attr(struct sysdev_attribute *attr)
+{
+ attr->attr.mode |= 0200;
+}
+
static ssize_t show_dscr_default(struct sysdev_class *class,
struct sysdev_class_attribute *attr, char *buf)
{
@@ -394,8 +405,11 @@ static void __cpuinit register_cpu_onlin
if (cpu_has_feature(CPU_FTR_MMCRA))
sysdev_create_file(s, &attr_mmcra);
- if (cpu_has_feature(CPU_FTR_PURR))
+ if (cpu_has_feature(CPU_FTR_PURR)) {
+ if (!firmware_has_feature(FW_FEATURE_LPAR))
+ add_write_permission_dev_attr(&attr_purr);
sysdev_create_file(s, &attr_purr);
+ }
if (cpu_has_feature(CPU_FTR_SPURR))
sysdev_create_file(s, &attr_spurr);
--
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