The google memconsole driver is currently broken upstream, as it tries
to read memory that is described as reserved in /proc/iomem, by
dereferencing a pointer obtained through phys_to_virt(). This triggers
a kernel fault as such regions are unmapped after early boot.
The proper workaround is to use ioremap_cache() / iounmap() around such
accesses.
As some unrelated changes, I also converted some printks to use pr_info()
and added some missing __init annotations.
Tested: booted dbg build, verified I could read /sys/firmware/log
Signed-off-by: Michel Lespinasse <wal...@google.com>
---
drivers/firmware/google/memconsole.c | 47 ++++++++++++++++++++----------------
1 file changed, 26 insertions(+), 21 deletions(-)
diff --git a/drivers/firmware/google/memconsole.c
b/drivers/firmware/google/memconsole.c
index 2a90ba613613..2f569aaed4c7 100644
--- a/drivers/firmware/google/memconsole.c
+++ b/drivers/firmware/google/memconsole.c
@@ -15,6 +15,7 @@
#include <linux/kobject.h>
#include <linux/module.h>
#include <linux/dmi.h>
+#include <linux/io.h>
#include <asm/bios_ebda.h>
#define BIOS_MEMCONSOLE_V1_MAGIC 0xDEADBABE
@@ -41,15 +42,25 @@ struct biosmemcon_ebda {
};
} __packed;
-static char *memconsole_baseaddr;
+static u32 memconsole_baseaddr;
static size_t memconsole_length;
static ssize_t memconsole_read(struct file *filp, struct kobject *kobp,
struct bin_attribute *bin_attr, char *buf,
loff_t pos, size_t count)
{
- return memory_read_from_buffer(buf, count, &pos, memconsole_baseaddr,
- memconsole_length);
+ char *memconsole;
+ ssize_t ret;
+
+ memconsole = ioremap_cache(memconsole_baseaddr, memconsole_length);
+ if (!memconsole) {
+ pr_err("memconsole: ioremap_cache failed\n");
+ return -ENOMEM;
+ }
+ ret = memory_read_from_buffer(buf, count, &pos, memconsole,
+ memconsole_length);
+ iounmap(memconsole);
+ return ret;
}
static struct bin_attribute memconsole_bin_attr = {
@@ -58,43 +69,42 @@ static struct bin_attribute memconsole_bin_attr = {
};
-static void found_v1_header(struct biosmemcon_ebda *hdr)
+static void __init found_v1_header(struct biosmemcon_ebda *hdr)
{
- printk(KERN_INFO "BIOS console v1 EBDA structure found at %p\n", hdr);
- printk(KERN_INFO "BIOS console buffer at 0x%.8x, "
+ pr_info("BIOS console v1 EBDA structure found at %p\n", hdr);
+ pr_info("BIOS console buffer at 0x%.8x, "
"start = %d, end = %d, num = %d\n",
hdr->v1.buffer_addr, hdr->v1.start,
hdr->v1.end, hdr->v1.num_chars);
memconsole_length = hdr->v1.num_chars;
- memconsole_baseaddr = phys_to_virt(hdr->v1.buffer_addr);
+ memconsole_baseaddr = hdr->v1.buffer_addr;
}
-static void found_v2_header(struct biosmemcon_ebda *hdr)
+static void __init found_v2_header(struct biosmemcon_ebda *hdr)
{
- printk(KERN_INFO "BIOS console v2 EBDA structure found at %p\n", hdr);
- printk(KERN_INFO "BIOS console buffer at 0x%.8x, "
+ pr_info("BIOS console v2 EBDA structure found at %p\n", hdr);
+ pr_info("BIOS console buffer at 0x%.8x, "
"start = %d, end = %d, num_bytes = %d\n",
hdr->v2.buffer_addr, hdr->v2.start,
hdr->v2.end, hdr->v2.num_bytes);
memconsole_length = hdr->v2.end - hdr->v2.start;
- memconsole_baseaddr = phys_to_virt(hdr->v2.buffer_addr
- + hdr->v2.start);
+ memconsole_baseaddr = hdr->v2.buffer_addr + hdr->v2.start;
}
/*
* Search through the EBDA for the BIOS Memory Console, and
* set the global variables to point to it. Return true if found.
*/
-static bool found_memconsole(void)
+static bool __init found_memconsole(void)
{
unsigned int address;
size_t length, cur;
address = get_bios_ebda();
if (!address) {
- printk(KERN_INFO "BIOS EBDA non-existent.\n");
+ pr_info("BIOS EBDA non-existent.\n");
return false;
}
@@ -122,7 +132,7 @@ static bool found_memconsole(void)
}
}
- printk(KERN_INFO "BIOS console EBDA structure not found!\n");
+ pr_info("BIOS console EBDA structure not found!\n");
return false;
}
@@ -139,8 +149,6 @@ MODULE_DEVICE_TABLE(dmi, memconsole_dmi_table);
static int __init memconsole_init(void)
{
- int ret;
-
if (!dmi_check_system(memconsole_dmi_table))
return -ENODEV;
@@ -148,10 +156,7 @@ static int __init memconsole_init(void)
return -ENODEV;
memconsole_bin_attr.size = memconsole_length;
-
- ret = sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr);
-
- return ret;
+ return sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr);
}
static void __exit memconsole_exit(void)
--
1.8.5.3
--
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