Re: [PATCH v1 2/4] x86/xen: add basic KASAN support for PV kernel

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On 08.01.20 16:20, Sergey Dyasli wrote:
This enables to use Outline instrumentation for Xen PV kernels.

KASAN_INLINE and KASAN_VMALLOC options currently lead to boot crashes
and hence disabled.

Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
---
RFC --> v1:
- New functions with declarations in xen/xen-ops.h
- Fixed the issue with free_kernel_image_pages() with the help of
   xen_pv_kasan_unpin_pgd()
---
  arch/x86/mm/kasan_init_64.c | 12 ++++++++++++
  arch/x86/xen/Makefile       |  7 +++++++
  arch/x86/xen/enlighten_pv.c |  3 +++
  arch/x86/xen/mmu_pv.c       | 39 +++++++++++++++++++++++++++++++++++++
  drivers/xen/Makefile        |  2 ++
  include/xen/xen-ops.h       |  4 ++++
  kernel/Makefile             |  2 ++
  lib/Kconfig.kasan           |  3 ++-
  8 files changed, 71 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index cf5bc37c90ac..902a6a152d33 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -13,6 +13,9 @@
  #include <linux/sched/task.h>
  #include <linux/vmalloc.h>
+#include <xen/xen.h>
+#include <xen/xen-ops.h>
+
  #include <asm/e820/types.h>
  #include <asm/pgalloc.h>
  #include <asm/tlbflush.h>
@@ -332,6 +335,11 @@ void __init kasan_early_init(void)
  	for (i = 0; pgtable_l5_enabled() && i < PTRS_PER_P4D; i++)
  		kasan_early_shadow_p4d[i] = __p4d(p4d_val);
+ if (xen_pv_domain()) {
+		pgd_t *pv_top_pgt = xen_pv_kasan_early_init();

You are breaking the build with CONFIG_XEN_PV undefined here.

+		kasan_map_early_shadow(pv_top_pgt);
+	}
+
  	kasan_map_early_shadow(early_top_pgt);
  	kasan_map_early_shadow(init_top_pgt);
  }
@@ -369,6 +377,8 @@ void __init kasan_init(void)
  				__pgd(__pa(tmp_p4d_table) | _KERNPG_TABLE));
  	}
+ xen_pv_kasan_pin_pgd(early_top_pgt);

Same here (and below). For the pin/unpin variants I'd rather have
an inline wrapper containing the "if (xen_pv_domain())" in xen-ops.h
which can easily contain the needed #ifdef CONFIG_XEN_PV.


Juergen




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