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Commit cb887591 authored by Michel Lespinasse's avatar Michel Lespinasse Committed by Greg Kroah-Hartman
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firmware: google memconsole driver fixes 



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: default avatarMichel Lespinasse <walken@google.com>
Acked-by: default avatarMike Waychison <mikew@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b12b73f1

drivers/firmware/google/memconsole.c

+26 −21
Original line number Diff line number Diff line
@@ -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,

	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)