On 1/13/21 5:16 PM, Catalin Marinas wrote:

On Thu, Jan 07, 2021 at 05:29:05PM +0000, Vincenzo Frascino wrote:

quoted

Architectures supported by KASAN HW can provide a light mode of
execution. On an MTE enabled arm64 hw for example this can be identified
with the asynch mode of execution. If an async exception occurs, the
arm64 core updates a register which is asynchronously detected the next
time in which the kernel is accessed.

What do you mean by "the kernel is accessed"? Also, there is no
"exception" as such, only a bit in a register updated asynchronously. So
the last sentence could be something like:

  In this mode, if a tag check fault occurs, the TFSR_EL1 register is
  updated asynchronously. The kernel checks the corresponding bits
  periodically.

(or you can be more precise on when the kernel checks for such faults)

Yes, I agree, I will change it accordingly. What I wrote has a similar meaning
but your exposition is more clear.

quoted

KASAN requires a specific mode of execution to make use of this hw feature.

Add KASAN HW light execution mode.

Shall we call it "fast"? ;)

quoted

--- /dev/null
+++ b/include/linux/kasan_def.h

@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_KASAN_DEF_H
+#define _LINUX_KASAN_DEF_H
+
+enum kasan_arg_mode {
+	KASAN_ARG_MODE_DEFAULT,
+	KASAN_ARG_MODE_OFF,
+	KASAN_ARG_MODE_LIGHT,
+	KASAN_ARG_MODE_PROD,
+	KASAN_ARG_MODE_FULL,
+};
+
+enum kasan_arg_stacktrace {
+	KASAN_ARG_STACKTRACE_DEFAULT,
+	KASAN_ARG_STACKTRACE_OFF,
+	KASAN_ARG_STACKTRACE_ON,
+};
+
+enum kasan_arg_fault {
+	KASAN_ARG_FAULT_DEFAULT,
+	KASAN_ARG_FAULT_REPORT,
+	KASAN_ARG_FAULT_PANIC,
+};
+
+#endif /* _LINUX_KASAN_DEF_H */

I thought we agreed not to expose the KASAN internal but come up with
another abstraction. Maybe this was after you posted these patches.

Yes, indeed we agreed and I am going to change it in v3. The agreement
temporally came after I posted v2 hence it is not reflected here.

-- 
Regards,
Vincenzo

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