[PATCH 03/14] rtc: block registration of rtc-cmos when CMOS RTC Not Present

Lee, Chun-Yi
2013-12-19T07:44:02Z

We should not acess CMOS address when CMOS RTC Not Present bit set in
FADT. The ee5872be patch didn't avoid rtc-cmos driver loaded when system support
ACPI PNP PNP0B0* devices.
So this patch block the registion of rtc-cmos driver to avoid
user space access RTC through CMOS interface.

Signed-off-by: Lee, Chun-Yi <jlee-IBi9RG/b67k@public.gmane.org>
---
arch/x86/kernel/rtc.c | 20 ++++++++++++++++----
drivers/rtc/rtc-cmos.c | 9 +++++++++
2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index ca9622a..9b6c568 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -174,16 +174,27 @@ static __init int add_rtc_cmos(void)
{ "PNP0b00", "PNP0b01", "PNP0b02", };
struct pnp_dev *dev;
struct pnp_id *id;
- int i;
+ int i = 0;
+ bool found_pnp;

pnp_for_each_dev(dev) {
for (id = dev->id; id; id = id->next) {
for (i = 0; i < ARRAY_SIZE(ids); i++) {
- if (compare_pnp_id(id, ids[i]) != 0)
- return 0;
+ if (compare_pnp_id(id, ids[i]) != 0) {
+ found_pnp = true;
+ goto found_pnp;
+ }
}
}
}
+
+found_pnp:
+ if (found_pnp) {
+ if (acpi_gbl_FADT.header.revision >= 5 &&
+ acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC)
+ pr_err(FW_BUG "Found %s device but CMOS RTC Not Present flag set\n", ids[i]);
+ return 0;
+ }
#endif
if (of_have_populated_dt())
return 0;
@@ -193,7 +204,8 @@ static __init int add_rtc_cmos(void)
return -ENODEV;

#ifdef CONFIG_ACPI
- if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC) {
+ if (acpi_gbl_FADT.header.revision >= 5 &&
+ acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC) {
/* This warning can likely go away again in a year or two. */
pr_info("ACPI: not registering RTC platform device\n");
return -ENODEV;
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index f148762..3a84ca9 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -28,6 +28,9 @@
* interrupts disabled, holding the global rtc_lock, to exclude those
* other drivers and utilities on correctly configured systems.
*/
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
@@ -1144,6 +1147,12 @@ static int __init cmos_init(void)
{
int retval = 0;

+ if (acpi_gbl_FADT.header.revision >= 5 &&
+ acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_CMOS_RTC) {
+ pr_info("ACPI CMOS RTC Not Present detected - not loading\n");
+ return 0;
+ }
+
#ifdef CONFIG_PNP
retval = pnp_register_driver(&cmos_pnp_driver);
if (retval == 0)
--
1.6.4.2