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authorHeiko Carstens <heiko.carstens@de.ibm.com>2015-03-13 12:55:56 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2015-03-25 11:49:43 +0100
commit8a5d8473dd7e2b0bc2864e34bd6836b520589fa1 (patch)
tree36997ac10fc75d5a0ed5fe5632e58684f90edf24 /arch/s390/mm
parentb2527d2009903a06b0076bb89166c72a0f17823b (diff)
s390/maccess: remove potentially broken probe_kernel_write()
Remove the s390 architecture implementation of probe_kernel_write() and instead use a new function s390_kernel_write() to modify kernel text and data everywhere. The s390 implementation of probe_kernel_write() was potentially broken since it modified memory in a read-modify-write fashion, which read four bytes, modified the requested bytes within those four bytes and wrote the result back. If two cpus would modify the same four byte area at different locations within that area, this could lead to corruption. Right now the only places which called probe_kernel_write() did run within stop_machine_run. Therefore the scenario can't happen right now, however that might change at any time. To fix this rename probe_kernel_write() to s390_kernel_write() which can have special semantics, like only call it while running within stop_machine(). Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/mm')
-rw-r--r--arch/s390/mm/maccess.c29
1 files changed, 19 insertions, 10 deletions
diff --git a/arch/s390/mm/maccess.c b/arch/s390/mm/maccess.c
index 2eb34bdfc613..fb737e9e0683 100644
--- a/arch/s390/mm/maccess.c
+++ b/arch/s390/mm/maccess.c
@@ -16,13 +16,7 @@
#include <asm/ctl_reg.h>
#include <asm/io.h>
-/*
- * This function writes to kernel memory bypassing DAT and possible
- * write protection. It copies one to four bytes from src to dst
- * using the stura instruction.
- * Returns the number of bytes copied or -EFAULT.
- */
-static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
+static notrace long s390_kernel_write_odd(void *dst, const void *src, size_t size)
{
unsigned long count, aligned;
int offset, mask;
@@ -48,19 +42,34 @@ static long probe_kernel_write_odd(void *dst, const void *src, size_t size)
return rc ? rc : count;
}
-long probe_kernel_write(void *dst, const void *src, size_t size)
+/*
+ * s390_kernel_write - write to kernel memory bypassing DAT
+ * @dst: destination address
+ * @src: source address
+ * @size: number of bytes to copy
+ *
+ * This function writes to kernel memory bypassing DAT and possible page table
+ * write protection. It writes to the destination using the sturg instruction.
+ * Therefore we have a read-modify-write sequence: the function reads four
+ * bytes from destination at a four byte boundary, modifies the bytes
+ * requested and writes the result back in a loop.
+ *
+ * Note: this means that this function may not be called concurrently on
+ * several cpus with overlapping words, since this may potentially
+ * cause data corruption.
+ */
+void notrace s390_kernel_write(void *dst, const void *src, size_t size)
{
long copied = 0;
while (size) {
- copied = probe_kernel_write_odd(dst, src, size);
+ copied = s390_kernel_write_odd(dst, src, size);
if (copied < 0)
break;
dst += copied;
src += copied;
size -= copied;
}
- return copied < 0 ? -EFAULT : 0;
}
static int __memcpy_real(void *dest, void *src, size_t count)