Hi Marco and Dmitry,

On Mon, Jul 05, 2021 at 07:14PM +0800, Kefeng Wang wrote:
[...]

+#ifdef CONFIG_KASAN_VMALLOC
+void __init __weak kasan_populate_early_vm_area_shadow(void *start,
+						       unsigned long size)

This should probably not be __weak, otherwise you now have 2 __weak
functions.

+{
+	unsigned long shadow_start, shadow_end;
+
+	if (!is_vmalloc_or_module_addr(start))
+		return;
+
+	shadow_start = (unsigned long)kasan_mem_to_shadow(start);
+	shadow_start = ALIGN_DOWN(shadow_start, PAGE_SIZE);
+	shadow_end = (unsigned long)kasan_mem_to_shadow(start + size);
+	shadow_end = ALIGN(shadow_end, PAGE_SIZE);
+	kasan_map_populate(shadow_start, shadow_end,
+			   early_pfn_to_nid(virt_to_pfn(start)));
+}
+#endif

This function looks quite generic -- would any of this also apply to
other architectures? I see that ppc and sparc at least also define
CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK.

I can't try ppc/sparc, but only ppc support KASAN_VMALLOC,

I check the x86, it supports CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK,

looks this issue is existing on x86 and ppc.

 void __init kasan_init(void)
 {
 	kasan_init_shadow();
diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 5310e217bd74..79d3895b0240 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -49,6 +49,8 @@ extern p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D];
 int kasan_populate_early_shadow(const void *shadow_start,
 				const void *shadow_end);
 
+void kasan_populate_early_vm_area_shadow(void *start, unsigned long size);
+
 static inline void *kasan_mem_to_shadow(const void *addr)
 {
 	return (void *)((unsigned long)addr >> KASAN_SHADOW_SCALE_SHIFT)
diff --git a/mm/kasan/init.c b/mm/kasan/init.c
index cc64ed6858c6..d39577d088a1 100644
--- a/mm/kasan/init.c
+++ b/mm/kasan/init.c
@@ -279,6 +279,11 @@ int __ref kasan_populate_early_shadow(const void *shadow_start,
 	return 0;
 }
 
+void __init __weak kasan_populate_early_vm_area_shadow(void *start,
+						       unsigned long size)
+{
+}

I'm just wondering if this could be a generic function, perhaps with an
appropriate IS_ENABLED() check of a generic Kconfig option
(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK ?) to short-circuit it, if it's
not only an arm64 problem.

kasan_map_populate() is arm64 special function, and the x86 has kasan_shallow_populate_pgds(),
ppc has kasan_init_shadow_page_tables(), so look those ARCHs should do the same way like ARM64,

Here we can't use kasan_populate_early_shadow(), this functions will make the early shadow maps
everything to a single page of zeroes（kasan_early_shadow_page), and set it pte_wrprotect, see
zero_pte_populate(), right? 

Also I try this, it crashs on ARM64 when change kasan_map_populate() to kasan_populate_early_shadow(),

Unable to handle kernel write to read-only memory at virtual address ffff700002938000
...
Call trace:
 __memset+0x16c/0x1c0
 kasan_unpoison+0x34/0x6c
 kasan_unpoison_vmalloc+0x2c/0x3c
 __get_vm_area_node.constprop.0+0x13c/0x240
 __vmalloc_node_range+0xf4/0x4f0
 __vmalloc_node+0x80/0x9c
 init_IRQ+0xe8/0x130
 start_kernel+0x188/0x360
 __primary_switched+0xc0/0xc8

But I haven't looked much further, so would appeal to you to either
confirm or reject this idea.

Thanks,
-- Marco
.