On 1/17/20 10:14 AM, Catalin Marinas wrote:

On Mon, Dec 16, 2019 at 02:17:11PM +0530, Amit Daniel Kachhap wrote:

quoted

diff --git a/arch/arm64/include/asm/compiler.h b/arch/arm64/include/asm/compiler.h
new file mode 100644
index 0000000..3cb06f9
--- /dev/null
+++ b/arch/arm64/include/asm/compiler.h

@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_COMPILER_H
+#define __ASM_COMPILER_H
+
+#if defined(CONFIG_ARM64_PTR_AUTH)
+
+/*
+ * The EL0/EL1 pointer bits used by a pointer authentication code.
+ * This is dependent on TBI0/TBI1 being enabled, or bits 63:56 would also apply.
+ */
+#define ptrauth_user_pac_mask()		GENMASK_ULL(54, vabits_actual)

That's the current behaviour but I guess we could extend the mask to 63
here without breaking anything since we don't expect instruction
addresses to be tagged. I also think we should turn TCR_EL1.TBID0 on
when we have PAC present (in a separate patch for both the mask change
and the TCR_EL1 bit as this may be slightly more controversial, a
theoretical ABI change).

ok. For this there has to be 2 mask then as ptrace passes both the masks 
to user.

#define ptrauth_user_ins_pac_mask()	GENMASK_ULL(63, vabits_actual)

#define ptrauth_user_data_pac_mask()	GENMASK_ULL(54, vabits_actual)

quoted

+#define ptrauth_kernel_pac_mask()	(GENMASK_ULL(63, 56) | GENMASK_ULL(54, VA_BITS))

I think the kernel mask should be GENMASK_ULL(63, vabits_actual), no
need to skip bit 55 since it's 1 already.

With regards to VA_BITS (a constant), I'm not sure that's correct.
ARMv8.2-LVA (52-bit VA) is an optional feature and I don't think PAC in
8.3 mandates it.

yes. Thanks for the correction.

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