[Crash-utility] [PATCH] Fix memory driver module build with kernel 5.8+

[lijiang]

在 2020年09月10日 16:49, HAGIO KAZUHITO(萩尾　一仁) 写道:
> -----Original Message-----
>> Kernel commit fe557319aa06c23cffc9346000f119547e0f289a renamed
>> probe_kernel_{read,write} to copy_{from,to}_kernel_nofault.
>>
>> Additionally, commit 0493cb086353e786be56010780a0b7025b5db34c
>> unexported probe_kernel_write(), so writing kernel memory is
>> no longer possible from a module.
>>
>> I have renamed the functions in source, but I'm also adding wrappers to
>> allow building the module with older kernel versions.
>>
>> Without this patch, build with kernel 5.8 and later fails:
>>
>> kbuild/default/crash.c: In function 'crash_write':
>> kbuild/default/crash.c:189:12: error: implicit declaration of function 'probe_kernel_write'; did you mean
>> 'kernel_write'? [-Werror=implicit-function-declaration]
>>   189 |        if (probe_kernel_write(vaddr, buffer, count)) {
>>       |            ^~~~~~~~~~~~~~~~~~
>>       |            kernel_write
>> kbuild/default/crash.c: In function 'crash_read':
>> kbuild/default/crash.c:225:13: error: implicit declaration of function 'probe_kernel_read'; did you mean
>> 'kernel_read'? [-Werror=implicit-function-declaration]
>>   225 |         if (probe_kernel_read(buffer, vaddr, count)) {
>>       |             ^~~~~~~~~~~~~~~~~
>>       |             kernel_read
>>
>> Signed-off-by: Petr Tesarik <ptesarik at suse.com>
> 
> Thank you for catching this, the patch looks good to me.
> 
> Acked-by: Kazuhito Hagio <k-hagio-ab at nec.com>
> 
> additionally, I think we should update the version number of this module.
> I'll add this change when applying, is it ok?  Lianbo, Bhupesh.
> 
That should be good.

For this patch: 
Acked-by: Lianbo Jiang <lijiang at redhat.com>


> -#define CRASH_VERSION   "1.4"
> +#define CRASH_VERSION   "1.5"
> 
> Anyway, please wait for another ack.
> 
> Thanks,
> Kazu
> 
>>
>> ---
>>  memory_driver/crash.c |   27 +++++++++++++++++++++++++--
>>  1 file changed, 25 insertions(+), 2 deletions(-)
>>
>> --- a/memory_driver/crash.c
>> +++ b/memory_driver/crash.c
>> @@ -25,6 +25,7 @@
>>   *****************************************************************************/
>>
>>  #include <linux/module.h>
>> +#include <linux/version.h>
>>  #include <linux/types.h>
>>  #include <linux/miscdevice.h>
>>  #include <linux/init.h>
>> @@ -37,6 +38,22 @@
>>
>>  extern int page_is_ram(unsigned long);
>>
>> +#if LINUX_VERSION_CODE < KERNEL_VERSION(5, 8, 0)
>> +
>> +#define CAN_WRITE_KERNEL	1
>> +
>> +static inline long copy_from_kernel_nofault(void *dst, const void *src, size_t size)
>> +{
>> +	return probe_kernel_read(dst, src, size);
>> +}
>> +
>> +static inline long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
>> +{
>> +	return probe_kernel_write(dst, src, size);
>> +}
>> +
>> +#endif
>> +
>>  #ifdef CONFIG_S390
>>  /*
>>   * For swapped prefix pages get bounce buffer using xlate_dev_mem_ptr()
>> @@ -160,6 +177,8 @@ crash_llseek(struct file * file, loff_t
>>  	}
>>  }
>>
>> +#ifdef CAN_WRITE_KERNEL
>> +
>>  static ssize_t
>>  crash_write(struct file *file, const char *buf, size_t count, loff_t *poff)
>>  {
>> @@ -186,7 +205,7 @@ crash_write(struct file *file, const cha
>>                 return -EFAULT;
>>         }
>>
>> -       if (probe_kernel_write(vaddr, buffer, count)) {
>> +       if (copy_to_kernel_nofault(vaddr, buffer, count)) {
>>                 unmap_virtual(page);
>>                 return -EFAULT;
>>         }
>> @@ -197,6 +216,8 @@ crash_write(struct file *file, const cha
>>         return written;
>>  }
>>
>> +#endif
>> +
>>  /*
>>   *  Determine the page address for an address offset value,
>>   *  get a virtual address for it, and copy it out.
>> @@ -222,7 +243,7 @@ crash_read(struct file *file, char *buf,
>>  	 * Use bounce buffer to bypass the CONFIG_HARDENED_USERCOPY
>>  	 * kernel text restriction.
>>  	 */
>> -        if (probe_kernel_read(buffer, vaddr, count)) {
>> +        if (copy_from_kernel_nofault(buffer, vaddr, count)) {
>>                  unmap_virtual(page);
>>                  return -EFAULT;
>>          }
>> @@ -294,7 +315,9 @@ static struct file_operations crash_fops
>>  	.owner = THIS_MODULE,
>>  	.llseek = crash_llseek,
>>  	.read = crash_read,
>> +#ifdef CAN_WRITE_KERNEL
>>  	.write = crash_write,
>> +#endif
>>  	.unlocked_ioctl = crash_ioctl,
>>  	.open = crash_open,
>>  	.release = crash_release,
>