[RFC 13/17] arm64: install user ptrauth keys at kernel exit time

[Kristina Martsenko]

From: Mark Rutland <mark.rutland@xxxxxxx>

This will mean we do more work per EL0 exception return, but is a
stepping-stone to enable keys within the kernel.

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Kristina Martsenko <kristina.martsenko@xxxxxxx>
---
 arch/arm64/include/asm/pointer_auth.h |  7 +------
 arch/arm64/include/asm/ptrauth-asm.h  | 26 ++++++++++++++++++++++++++
 arch/arm64/kernel/asm-offsets.c       |  7 +++++++
 arch/arm64/kernel/entry.S             |  9 +++++++--
 arch/arm64/kernel/process.c           |  1 -
 5 files changed, 41 insertions(+), 9 deletions(-)
 create mode 100644 arch/arm64/include/asm/ptrauth-asm.h

diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index cedb03bd175b..5e40533f4ea2 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -64,16 +64,11 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 }
 
 #define ptrauth_task_init_user(tsk)	\
-	ptrauth_keys_init(&(tsk)->thread_info.keys_user); \
-	ptrauth_keys_switch(&(tsk)->thread_info.keys_user)
-
-#define ptrauth_task_switch(tsk)	\
-	ptrauth_keys_switch(&(tsk)->thread_info.keys_user)
+	ptrauth_keys_init(&(tsk)->thread_info.keys_user)
 
 #else /* CONFIG_ARM64_PTR_AUTH */
 #define ptrauth_strip_insn_pac(lr)	(lr)
 #define ptrauth_task_init_user(tsk)
-#define ptrauth_task_switch(tsk)
 #endif /* CONFIG_ARM64_PTR_AUTH */
 
 #endif /* __ASM_POINTER_AUTH_H */
diff --git a/arch/arm64/include/asm/ptrauth-asm.h b/arch/arm64/include/asm/ptrauth-asm.h
new file mode 100644
index 000000000000..f50bdfc4046c
--- /dev/null
+++ b/arch/arm64/include/asm/ptrauth-asm.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_PTRAUTH_ASM_H
+#define __ASM_PTRAUTH_ASM_H
+
+#include <asm/asm-offsets.h>
+#include <asm/sysreg.h>
+
+#ifdef CONFIG_ARM64_PTR_AUTH
+
+	.macro ptrauth_keys_install_user tsk, tmp
+alternative_if ARM64_HAS_ADDRESS_AUTH
+	ldr	\tmp, [\tsk, #(TSK_TI_KEYS_USER + PTRAUTH_KEY_APIALO)]
+	msr_s	SYS_APIAKEYLO_EL1, \tmp
+	ldr	\tmp, [\tsk, #(TSK_TI_KEYS_USER + PTRAUTH_KEY_APIAHI)]
+	msr_s	SYS_APIAKEYHI_EL1, \tmp
+alternative_else_nop_endif
+	.endm
+
+#else /* CONFIG_ARM64_PTR_AUTH */
+
+	.macro ptrauth_keys_install_user tsk, tmp
+	.endm
+
+#endif /* CONFIG_ARM64_PTR_AUTH */
+
+#endif /* __ASM_PTRAUTH_ASM_H */
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 323aeb5f2fe6..b6be0dd037fd 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -45,6 +45,9 @@ int main(void)
 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
   DEFINE(TSK_TI_TTBR0,		offsetof(struct task_struct, thread_info.ttbr0));
 #endif
+#ifdef CONFIG_ARM64_PTR_AUTH
+  DEFINE(TSK_TI_KEYS_USER, 	offsetof(struct task_struct, thread_info.keys_user));
+#endif
   DEFINE(TSK_STACK,		offsetof(struct task_struct, stack));
   BLANK();
   DEFINE(THREAD_CPU_CONTEXT,	offsetof(struct task_struct, thread.cpu_context));
@@ -169,5 +172,9 @@ int main(void)
   DEFINE(SDEI_EVENT_INTREGS,	offsetof(struct sdei_registered_event, interrupted_regs));
   DEFINE(SDEI_EVENT_PRIORITY,	offsetof(struct sdei_registered_event, priority));
 #endif
+#ifdef CONFIG_ARM64_PTR_AUTH
+  DEFINE(PTRAUTH_KEY_APIALO,	offsetof(struct ptrauth_keys, apia.lo));
+  DEFINE(PTRAUTH_KEY_APIAHI,	offsetof(struct ptrauth_keys, apia.hi));
+#endif
   return 0;
 }
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 09dbea221a27..1e925f6d2978 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -23,8 +23,9 @@
 #include <linux/linkage.h>
 
 #include <asm/alternative.h>
-#include <asm/assembler.h>
 #include <asm/asm-offsets.h>
+#include <asm/asm-uaccess.h>
+#include <asm/assembler.h>
 #include <asm/cpufeature.h>
 #include <asm/errno.h>
 #include <asm/esr.h>
@@ -33,8 +34,8 @@
 #include <asm/mmu.h>
 #include <asm/processor.h>
 #include <asm/ptrace.h>
+#include <asm/ptrauth-asm.h>
 #include <asm/thread_info.h>
-#include <asm/asm-uaccess.h>
 #include <asm/unistd.h>
 
 /*
@@ -325,6 +326,10 @@ alternative_else_nop_endif
 	apply_ssbd 0, x0, x1
 	.endif
 
+	.if	\el == 0
+	ptrauth_keys_install_user tsk, x0
+	.endif
+
 	msr	elr_el1, x21			// set up the return data
 	msr	spsr_el1, x22
 	ldp	x0, x1, [sp, #16 * 0]
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index fae52be66c92..857ae05cd04c 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -426,7 +426,6 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
 	contextidr_thread_switch(next);
 	entry_task_switch(next);
 	uao_thread_switch(next);
-	ptrauth_task_switch(next);
 
 	/*
 	 * Complete any pending TLB or cache maintenance on this CPU in case
-- 
2.11.0