[PATCH] arm64/mm: skip hwasan callbacks for pgtable walker

[Qian Cai]

Page table walkers trigger soft lockups below with KASAN_SW_TAGS outline
mode on a large ThunderX2 system, because there is too much overhead to
call check_memory_region() for every memory access where it needs to
dereference every byte of the corresponding KASAN shadow address for the
correct tag.

[   76.531328] watchdog: BUG: soft lockup - CPU#65 stuck for 23s! [swapper/0:1]
[   76.538372] Modules linked in:
[   76.541433] CPU: 65 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc6+ #62
[   76.557697] pstate: 60400009 (nZCv daif +PAN -UAO)
[   76.562491] pc : check_memory_region+0x64/0x94
[   76.566934] lr : __hwasan_load8_noabort+0x20/0x2c
[   76.571633] sp : 7eff808ba0247ca0
[   76.574943] x29: 7eff808ba0247cc0 x28: ffff068cef720000
[   76.580256] x27: ffff080000000000 x26: 0060000000000793
[   76.585568] x25: ffff068d00000000 x24: ffff800003537b98
[   76.590880] x23: 7eff808ba0247e08 x22: 0000000000000000
[   76.596192] x21: 7eff808ba0247e08 x20: 0000000000000008
[   76.601503] x19: ffff1000100a8d64 x18: 0000000000000000
[   76.606814] x17: 0000000001000100 x16: 0000000000000000
[   76.612125] x15: ffff100013805578 x14: ffff100014085000
[   76.617437] x13: 0000000030373a2e x12: 00f0000000000793
[   76.622749] x11: ffff808ba0247e0f x10: ffff0808ba0247e0
[   76.628060] x9 : ffff0808ba0247e0 x8 : 000000000000007e
[   76.633371] x7 : 0000000000000000 x6 : 0000000000000002
[   76.638682] x5 : 0000000000000000 x4 : 00e0000000000793
[   76.643994] x3 : ffff1000100a8d64 x2 : 0000000000000000
[   76.649305] x1 : 0000000000000008 x0 : 7eff808ba0247e08
[   76.654617] Call trace:
[   76.657066]  check_memory_region+0x64/0x94
[   76.661162]  __hwasan_load8_noabort+0x20/0x2c
[   76.665519]  note_page+0x84/0x708
[   76.668833]  walk_pgd+0x174/0x258
[   76.672147]  ptdump_check_wx+0x90/0xfc
[   76.675894]  mark_rodata_ro+0x38/0x44
[   76.679557]  kernel_init+0x48/0x180
[   76.683045]  ret_from_fork+0x10/0x18

Signed-off-by: Qian Cai <cai@xxxxxx>
---
 arch/arm64/mm/Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile
index 849c1df3d214..4b9a7a50faaf 100644
--- a/arch/arm64/mm/Makefile
+++ b/arch/arm64/mm/Makefile
@@ -12,3 +12,9 @@ KASAN_SANITIZE_physaddr.o	+= n
 
 obj-$(CONFIG_KASAN)		+= kasan_init.o
 KASAN_SANITIZE_kasan_init.o	:= n
+
+ifdef CONFIG_KASAN_SW_TAGS
+ifdef CONFIG_KASAN_OUTLINE
+KASAN_SANITIZE_dump.o		:= n
+endif
+endif
-- 
2.17.2 (Apple Git-113)