linux-hardening - [PATCH v2 4/6] kasan: Add __HAVE_ARCH_SHADOW

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Date:   Tue,  4 Apr 2023 16:43:06 +0800
From:   Qing Zhang <zhangqing@...ngson.cn>
To:     Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Huacai Chen <chenhuacai@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        WANG Xuerui <kernel@...0n.name>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        kasan-dev@...glegroups.com, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v2 4/6] kasan: Add __HAVE_ARCH_SHADOW_MAP to support arch specific mapping

Like the LoongArch, which has many holes between different segments
and valid address space(256T available) is insufficient to map all
these segments to kasan shadow memory with the common formula provided
by kasan core, We need architecture specific mapping formula,different
segments are mapped individually, and only limited length of space of
that specific segment is mapped to shadow.

Therefore, when the incoming address is converted to a shadow, we need
to add a condition to determine whether it is valid.

Signed-off-by: Qing Zhang <zhangqing@...ngson.cn>
---
 include/linux/kasan.h | 2 ++
 mm/kasan/kasan.h      | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index f7ef70661ce2..3b91b941873d 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -54,11 +54,13 @@ extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
 int kasan_populate_early_shadow(const void *shadow_start,
 				const void *shadow_end);
 
+#ifndef __HAVE_ARCH_SHADOW_MAP
 static inline void *kasan_mem_to_shadow(const void *addr)
 {
 	return (void *)((unsigned long)addr >> KASAN_SHADOW_SCALE_SHIFT)
 		+ KASAN_SHADOW_OFFSET;
 }
+#endif
 
 int kasan_add_zero_shadow(void *start, unsigned long size);
 void kasan_remove_zero_shadow(void *start, unsigned long size);
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index a61eeee3095a..033335c13b25 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -291,16 +291,22 @@ struct kasan_stack_ring {
 
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 
+#ifndef __HAVE_ARCH_SHADOW_MAP
 static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
 {
 	return (void *)(((unsigned long)shadow_addr - KASAN_SHADOW_OFFSET)
 		<< KASAN_SHADOW_SCALE_SHIFT);
 }
+#endif
 
 static __always_inline bool addr_has_metadata(const void *addr)
 {
+#ifdef __HAVE_ARCH_SHADOW_MAP
+	return (kasan_mem_to_shadow((void *)addr) != NULL);
+#else
 	return (kasan_reset_tag(addr) >=
 		kasan_shadow_to_mem((void *)KASAN_SHADOW_START));
+#endif
 }
 
 /**
-- 
2.20.1