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Subject[PATCH v3 1/5] arm64: kasan: don't populate vmalloc area for CONFIG_KASAN_VMALLOC
Date
Linux support KAsan for VMALLOC since commit 3c5c3cfb9ef4da9
("kasan: support backing vmalloc space with real shadow memory")

Like how the MODULES_VADDR does now, just not to early populate
the VMALLOC_START between VMALLOC_END.

Before:

MODULE_VADDR: no mapping, no zoreo shadow at init
VMALLOC_VADDR: backed with zero shadow at init

After:

MODULE_VADDR: no mapping, no zoreo shadow at init
VMALLOC_VADDR: no mapping, no zoreo shadow at init

Thus the mapping will get allocated on demand by the core function
of KASAN_VMALLOC.

----------- vmalloc_shadow_start
| |
| |
| | <= non-mapping
| |
| |
|-----------|
|///////////|<- kimage shadow with page table mapping.
|-----------|
| |
| | <= non-mapping
| |
------------- vmalloc_shadow_end
|00000000000|
|00000000000| <= Zero shadow
|00000000000|
------------- KASAN_SHADOW_END

Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
---
arch/arm64/mm/kasan_init.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
index d8e66c78440e..20d06008785f 100644
--- a/arch/arm64/mm/kasan_init.c
+++ b/arch/arm64/mm/kasan_init.c
@@ -214,6 +214,7 @@ static void __init kasan_init_shadow(void)
{
u64 kimg_shadow_start, kimg_shadow_end;
u64 mod_shadow_start, mod_shadow_end;
+ u64 vmalloc_shadow_end;
phys_addr_t pa_start, pa_end;
u64 i;

@@ -223,6 +224,8 @@ static void __init kasan_init_shadow(void)
mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);

+ vmalloc_shadow_end = (u64)kasan_mem_to_shadow((void *)VMALLOC_END);
+
/*
* We are going to perform proper setup of shadow memory.
* At first we should unmap early shadow (clear_pgds() call below).
@@ -241,12 +244,17 @@ static void __init kasan_init_shadow(void)

kasan_populate_early_shadow(kasan_mem_to_shadow((void *)PAGE_END),
(void *)mod_shadow_start);
- kasan_populate_early_shadow((void *)kimg_shadow_end,
- (void *)KASAN_SHADOW_END);

- if (kimg_shadow_start > mod_shadow_end)
- kasan_populate_early_shadow((void *)mod_shadow_end,
- (void *)kimg_shadow_start);
+ if (IS_ENABLED(CONFIG_KASAN_VMALLOC))
+ kasan_populate_early_shadow((void *)vmalloc_shadow_end,
+ (void *)KASAN_SHADOW_END);
+ else {
+ kasan_populate_early_shadow((void *)kimg_shadow_end,
+ (void *)KASAN_SHADOW_END);
+ if (kimg_shadow_start > mod_shadow_end)
+ kasan_populate_early_shadow((void *)mod_shadow_end,
+ (void *)kimg_shadow_start);
+ }

for_each_mem_range(i, &pa_start, &pa_end) {
void *start = (void *)__phys_to_virt(pa_start);
--
2.25.1
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