UbiquitousOS
/
OpenCloudOS-Kernel
mirror of https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel.git
11
0
Fork 0
Code Issues Projects Releases Wiki Activity

s390/crash: use static swap buffer for copy_to_user_real() 

Currently a temporary page-size buffer is allocated for copying
oldmem to user space. That limits copy_to_user_real() operation
only to stages when virtual memory is available and still makes
it possible to fail while the system is being dumped.

Instead of reallocating single page on each copy_oldmem_page()
iteration use a statically allocated buffer.

This also paves the way for a further memcpy_real() rework where
no swap buffer is needed altogether.

Acked-by: Heiko Carstens <hca@linux.ibm.com>
Tested-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Link: https://lore.kernel.org/r/334ed359680c4d45dd32feb104909f610312ef0f.1658206891.git.agordeev@linux.ibm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Alexander Gordeev 2022-07-19 07:16:35 +02:00
parent d6da673781
commit 6d2e5a4a13
1 changed files with 12 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
arch/s390/kernel/crash_dump.c
View File

@ -53,6 +53,8 @@ struct save_area {
};
static LIST_HEAD(dump_save_areas);
static DEFINE_MUTEX(memcpy_real_mutex);
static char memcpy_real_buf[PAGE_SIZE];
/*
* Allocate a save area
@ -178,25 +180,21 @@ int copy_oldmem_kernel(void *dst, unsigned long src, size_t count)
*/
static int copy_to_user_real(void __user *dest, unsigned long src, unsigned long count)
{
int offs = 0, size, rc;
char *buf;
unsigned long offs = 0, size;
buf = (char *)__get_free_page(GFP_KERNEL);
if (!buf)
return -ENOMEM;
rc = -EFAULT;
mutex_lock(&memcpy_real_mutex);
while (offs < count) {
size = min(PAGE_SIZE, count - offs);
if (memcpy_real(buf, src + offs, size))
goto out;
if (copy_to_user(dest + offs, buf, size))
goto out;
if (memcpy_real(memcpy_real_buf, src + offs, size))
break;
if (copy_to_user(dest + offs, memcpy_real_buf, size))
break;
offs += size;
}
rc = 0;
out:
free_page((unsigned long)buf);
return rc;
mutex_unlock(&memcpy_real_mutex);
if (offs < count)
return -EFAULT;
return 0;
}
/*