[PATCH v6 06/18] khwasan, arm64: untag virt address in __kimg_to_phys and _virt_addr_is_linear

On Wed, Sep 12, 2018 at 6:33 PM, Dmitry Vyukov [off-list ref] wrote:

On Wed, Aug 29, 2018 at 1:35 PM, Andrey Konovalov [off-list ref] wrote:

quoted

+#ifdef CONFIG_KASAN_HW
+#define KASAN_TAG_SHIFTED(tag)         ((unsigned long)(tag) << 56)
+#define KASAN_SET_TAG(addr, tag)       (((addr) & ~KASAN_TAG_SHIFTED(0xff)) | \
+                                               KASAN_TAG_SHIFTED(tag))
+#define KASAN_RESET_TAG(addr)          KASAN_SET_TAG(addr, 0xff)
+#endif
+

Wouldn't it be better to
#define KASAN_RESET_TAG(addr) addr
when CONFIG_KASAN_HW is not enabled, and then not duplicate the macros
below? That's what we do in kasan.h for all hooks.
I see that a subsequent patch duplicates yet another macro in this
file. While we could use:

#define __kimg_to_phys(addr)   (KASAN_RESET_TAG(addr) - kimage_voffset)

with and without kasan. Duplicating them increases risk that somebody
will change only the non-kasan version but forget kasan version.

Will do in v7.