leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

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

Browse Source 
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
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 LIST_HEAD(dump_save_areas);
static DEFINE_MUTEX(memcpy_real_mutex);
static char memcpy_real_buf[PAGE_SIZE];
/* /*
* Allocate a save area * 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) static int copy_to_user_real(void __user *dest, unsigned long src, unsigned long count)
{ {
int offs = 0, size, rc; unsigned long offs = 0, size;
char *buf;
buf = (char *)__get_free_page(GFP_KERNEL); mutex_lock(&memcpy_real_mutex);
if (!buf)
return -ENOMEM;
rc = -EFAULT;
while (offs < count) { while (offs < count) {
size = min(PAGE_SIZE, count - offs); size = min(PAGE_SIZE, count - offs);
if (memcpy_real(buf, src + offs, size)) if (memcpy_real(memcpy_real_buf, src + offs, size))
goto out; break;
if (copy_to_user(dest + offs, buf, size)) if (copy_to_user(dest + offs, memcpy_real_buf, size))
goto out; break;
offs += size; offs += size;
} }
rc = 0; mutex_unlock(&memcpy_real_mutex);
out: if (offs < count)
free_page((unsigned long)buf); return -EFAULT;
return rc; return 0;
} }
/* /*