[PATCH 3.16 039/306] pstore/ram: Use memcpy_fromio() to save old buffer

From: Ben Hutchings
Date: Wed Feb 15 2017 - 19:01:24 EST

3.16.40-rc1 review patch. If anyone has any objections, please let me know.


From: Andrew Bresticker <abrestic@xxxxxxxxxxxx>

commit d771fdf94180de2bd811ac90cba75f0f346abf8d upstream.

The ramoops buffer may be mapped as either I/O memory or uncached
memory. On ARM64, this results in a device-type (strongly-ordered)
mapping. Since unnaligned accesses to device-type memory will
generate an alignment fault (regardless of whether or not strict
alignment checking is enabled), it is not safe to use memcpy().
memcpy_fromio() is guaranteed to only use aligned accesses, so use
that instead.

Signed-off-by: Andrew Bresticker <abrestic@xxxxxxxxxxxx>
Signed-off-by: Enric Balletbo Serra <enric.balletbo@xxxxxxxxxxxxx>
Reviewed-by: Puneet Kumar <puneetster@xxxxxxxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
fs/pstore/ram_core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -286,8 +286,8 @@ void persistent_ram_save_old(struct pers

prz->old_log_size = size;
- memcpy(prz->old_log, &buffer->data[start], size - start);
- memcpy(prz->old_log + size - start, &buffer->data[0], start);
+ memcpy_fromio(prz->old_log, &buffer->data[start], size - start);
+ memcpy_fromio(prz->old_log + size - start, &buffer->data[0], start);

int notrace persistent_ram_write(struct persistent_ram_zone *prz,