[02/11] arm64: install user ptrauth keys at kernel exit time
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Message ID 1571300065-10236-3-git-send-email-amit.kachhap@arm.com
State New
Headers show
Series
  • arm64: return address signing
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Commit Message

Amit Kachhap Oct. 17, 2019, 8:14 a.m. UTC
From: Kristina Martsenko <kristina.martsenko@arm.com>

As we're going to enable pointer auth within the kernel and use a
different APIAKey for the kernel itself, then move the user APIAKey
switch to EL0 exception return.

The other 4 keys could remain switched during task switch, but are also
moved to keep things consistent.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
Changes since RFC v2:
 - Replaced 12 NOPs with a branch in ptrauth_keys_install_user [Catalin]

 arch/arm64/include/asm/asm_pointer_auth.h | 45 +++++++++++++++++++++++++++++++
 arch/arm64/include/asm/pointer_auth.h     | 30 +--------------------
 arch/arm64/kernel/asm-offsets.c           | 11 ++++++++
 arch/arm64/kernel/entry.S                 |  3 +++
 arch/arm64/kernel/pointer_auth.c          |  3 ---
 arch/arm64/kernel/process.c               |  1 -
 6 files changed, 60 insertions(+), 33 deletions(-)
 create mode 100644 arch/arm64/include/asm/asm_pointer_auth.h

Patch
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diff --git a/arch/arm64/include/asm/asm_pointer_auth.h b/arch/arm64/include/asm/asm_pointer_auth.h
new file mode 100644
index 0000000..cb21a06
--- /dev/null
+++ b/arch/arm64/include/asm/asm_pointer_auth.h
@@ -0,0 +1,45 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_ASM_POINTER_AUTH_H
+#define __ASM_ASM_POINTER_AUTH_H
+
+#include <asm/alternative.h>
+#include <asm/asm-offsets.h>
+#include <asm/cpufeature.h>
+#include <asm/sysreg.h>
+
+#ifdef CONFIG_ARM64_PTR_AUTH
+
+	.macro ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3
+	mov	\tmp1, #THREAD_KEYS_USER
+	add	\tmp1, \tsk, \tmp1
+alternative_if_not ARM64_HAS_ADDRESS_AUTH
+	b	.Laddr_auth_skip_\@
+alternative_else_nop_endif
+	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KEY_APIA]
+	msr_s	SYS_APIAKEYLO_EL1, \tmp2
+	msr_s	SYS_APIAKEYHI_EL1, \tmp3
+	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KEY_APIB]
+	msr_s	SYS_APIBKEYLO_EL1, \tmp2
+	msr_s	SYS_APIBKEYHI_EL1, \tmp3
+	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KEY_APDA]
+	msr_s	SYS_APDAKEYLO_EL1, \tmp2
+	msr_s	SYS_APDAKEYHI_EL1, \tmp3
+	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KEY_APDB]
+	msr_s	SYS_APDBKEYLO_EL1, \tmp2
+	msr_s	SYS_APDBKEYHI_EL1, \tmp3
+.Laddr_auth_skip_\@:
+alternative_if ARM64_HAS_GENERIC_AUTH
+	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KEY_APGA]
+	msr_s	SYS_APGAKEYLO_EL1, \tmp2
+	msr_s	SYS_APGAKEYHI_EL1, \tmp3
+alternative_else_nop_endif
+	.endm
+
+#else /* CONFIG_ARM64_PTR_AUTH */
+
+	.macro ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3
+	.endm
+
+#endif /* CONFIG_ARM64_PTR_AUTH */
+
+#endif /* __ASM_ASM_POINTER_AUTH_H */
diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index 7a24bad..21c2115 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -43,26 +43,6 @@  static inline void ptrauth_keys_init(struct ptrauth_keys *keys)
 		get_random_bytes(&keys->apga, sizeof(keys->apga));
 }
 
-#define __ptrauth_key_install(k, v)				\
-do {								\
-	struct ptrauth_key __pki_v = (v);			\
-	write_sysreg_s(__pki_v.lo, SYS_ ## k ## KEYLO_EL1);	\
-	write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1);	\
-} while (0)
-
-static inline void ptrauth_keys_switch(struct ptrauth_keys *keys)
-{
-	if (system_supports_address_auth()) {
-		__ptrauth_key_install(APIA, keys->apia);
-		__ptrauth_key_install(APIB, keys->apib);
-		__ptrauth_key_install(APDA, keys->apda);
-		__ptrauth_key_install(APDB, keys->apdb);
-	}
-
-	if (system_supports_generic_auth())
-		__ptrauth_key_install(APGA, keys->apga);
-}
-
 extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
 
 /*
@@ -78,20 +58,12 @@  static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 }
 
 #define ptrauth_thread_init_user(tsk)					\
-do {									\
-	struct task_struct *__ptiu_tsk = (tsk);				\
-	ptrauth_keys_init(&__ptiu_tsk->thread.keys_user);		\
-	ptrauth_keys_switch(&__ptiu_tsk->thread.keys_user);		\
-} while (0)
-
-#define ptrauth_thread_switch(tsk)	\
-	ptrauth_keys_switch(&(tsk)->thread.keys_user)
+	ptrauth_keys_init(&(tsk)->thread.keys_user)
 
 #else /* CONFIG_ARM64_PTR_AUTH */
 #define ptrauth_prctl_reset_keys(tsk, arg)	(-EINVAL)
 #define ptrauth_strip_insn_pac(lr)	(lr)
 #define ptrauth_thread_init_user(tsk)
-#define ptrauth_thread_switch(tsk)
 #endif /* CONFIG_ARM64_PTR_AUTH */
 
 #endif /* __ASM_POINTER_AUTH_H */
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 2146857..ef0c24b 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -40,6 +40,9 @@  int main(void)
 #endif
   BLANK();
   DEFINE(THREAD_CPU_CONTEXT,	offsetof(struct task_struct, thread.cpu_context));
+#ifdef CONFIG_ARM64_PTR_AUTH
+  DEFINE(THREAD_KEYS_USER,	offsetof(struct task_struct, thread.keys_user));
+#endif
   BLANK();
   DEFINE(S_X0,			offsetof(struct pt_regs, regs[0]));
   DEFINE(S_X2,			offsetof(struct pt_regs, regs[2]));
@@ -127,5 +130,13 @@  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_APIA,	offsetof(struct ptrauth_keys, apia));
+  DEFINE(PTRAUTH_KEY_APIB,	offsetof(struct ptrauth_keys, apib));
+  DEFINE(PTRAUTH_KEY_APDA,	offsetof(struct ptrauth_keys, apda));
+  DEFINE(PTRAUTH_KEY_APDB,	offsetof(struct ptrauth_keys, apdb));
+  DEFINE(PTRAUTH_KEY_APGA,	offsetof(struct ptrauth_keys, apga));
+  BLANK();
+#endif
   return 0;
 }
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 84a8227..b6272a3 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -14,6 +14,7 @@ 
 #include <asm/alternative.h>
 #include <asm/assembler.h>
 #include <asm/asm-offsets.h>
+#include <asm/asm_pointer_auth.h>
 #include <asm/cpufeature.h>
 #include <asm/errno.h>
 #include <asm/esr.h>
@@ -341,6 +342,8 @@  alternative_else_nop_endif
 	msr	cntkctl_el1, x1
 4:
 #endif
+	ptrauth_keys_install_user tsk, x0, x1, x2
+
 	apply_ssbd 0, x0, x1
 	.endif
 
diff --git a/arch/arm64/kernel/pointer_auth.c b/arch/arm64/kernel/pointer_auth.c
index c507b58..95985be 100644
--- a/arch/arm64/kernel/pointer_auth.c
+++ b/arch/arm64/kernel/pointer_auth.c
@@ -19,7 +19,6 @@  int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
 
 	if (!arg) {
 		ptrauth_keys_init(keys);
-		ptrauth_keys_switch(keys);
 		return 0;
 	}
 
@@ -41,7 +40,5 @@  int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
 	if (arg & PR_PAC_APGAKEY)
 		get_random_bytes(&keys->apga, sizeof(keys->apga));
 
-	ptrauth_keys_switch(keys);
-
 	return 0;
 }
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index a47462d..5b2b158 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -505,7 +505,6 @@  __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
 	contextidr_thread_switch(next);
 	entry_task_switch(next);
 	uao_thread_switch(next);
-	ptrauth_thread_switch(next);
 	ssbs_thread_switch(next);
 
 	/*