[PATCH v5 00/17] arm64: return address signing

[PATCH v5 00/17] arm64: return address signing

[Amit Daniel Kachhap]

Hi,

This series improves function return address protection for the arm64 kernel, by
compiling the kernel with ARMv8.3 Pointer Authentication instructions (referred
ptrauth hereafter). This should help protect the kernel against attacks using
return-oriented programming.

This series is based on Linux version v5.6-rc2.

Changes since v4 [1]:
 - Rebased the patch series to v5.6-rc2.
 - Patch "arm64: cpufeature: Fix meta-capability" updated as per Suzuki's
   review comments.

This series do not implement few things:
 - kdump tools may need some rework to work with ptrauth. The kdump
   tools may need the ptrauth information to strip PAC bits. This will
   be sent in a separate patch.
 - Few more ptrauth generic lkdtm tests as requested by Kees Cook.
 - Generate compile time warnings if requested Kconfig feature not 
   supported by compilers.

Feedback welcome!

Thanks,
Amit Daniel

[1]: http://lists.infradead.org/pipermail/linux-arm-kernel/2020-January/707567.html

Amit Daniel Kachhap (8):
  arm64: cpufeature: Fix meta-capability cpufeature check
  arm64: create macro to park cpu in an infinite loop
  arm64: ptrauth: Add bootup/runtime flags for __cpu_setup
  arm64: initialize ptrauth keys for kernel booting task
  arm64: mask PAC bits of __builtin_return_address
  arm64: __show_regs: strip PAC from lr in printk
  arm64: suspend: restore the kernel ptrauth keys
  lkdtm: arm64: test kernel pointer authentication

Kristina Martsenko (7):
  arm64: cpufeature: add pointer auth meta-capabilities
  arm64: rename ptrauth key structures to be user-specific
  arm64: install user ptrauth keys at kernel exit time
  arm64: cpufeature: handle conflicts based on capability
  arm64: enable ptrauth earlier
  arm64: initialize and switch ptrauth kernel keys
  arm64: compile the kernel with ptrauth return address signing

Mark Rutland (1):
  arm64: unwind: strip PAC from kernel addresses

Vincenzo Frascino (1):
  kconfig: Add support for 'as-option'

 arch/arm64/Kconfig                        | 27 +++++++++++-
 arch/arm64/Makefile                       | 11 +++++
 arch/arm64/include/asm/asm_pointer_auth.h | 63 ++++++++++++++++++++++++++++
 arch/arm64/include/asm/compiler.h         | 20 +++++++++
 arch/arm64/include/asm/cpucaps.h          |  4 +-
 arch/arm64/include/asm/cpufeature.h       | 33 ++++++++++++---
 arch/arm64/include/asm/pointer_auth.h     | 54 ++++++++++++------------
 arch/arm64/include/asm/processor.h        |  3 +-
 arch/arm64/include/asm/smp.h              | 10 +++++
 arch/arm64/include/asm/stackprotector.h   |  5 +++
 arch/arm64/kernel/asm-offsets.c           | 16 +++++++
 arch/arm64/kernel/cpufeature.c            | 68 ++++++++++++++++++++----------
 arch/arm64/kernel/entry.S                 |  6 +++
 arch/arm64/kernel/head.S                  | 27 ++++++------
 arch/arm64/kernel/pointer_auth.c          |  7 +---
 arch/arm64/kernel/process.c               |  5 ++-
 arch/arm64/kernel/ptrace.c                | 16 +++----
 arch/arm64/kernel/sleep.S                 |  8 ++++
 arch/arm64/kernel/smp.c                   | 10 +++++
 arch/arm64/kernel/stacktrace.c            |  3 ++
 arch/arm64/mm/proc.S                      | 69 ++++++++++++++++++++++++++-----
 drivers/misc/lkdtm/bugs.c                 | 36 ++++++++++++++++
 drivers/misc/lkdtm/core.c                 |  1 +
 drivers/misc/lkdtm/lkdtm.h                |  1 +
 include/linux/stackprotector.h            |  2 +-
 scripts/Kconfig.include                   |  4 ++
 26 files changed, 411 insertions(+), 98 deletions(-)
 create mode 100644 arch/arm64/include/asm/asm_pointer_auth.h
 create mode 100644 arch/arm64/include/asm/compiler.h

-- 
2.7.4


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[PATCH v5 01/17] arm64: cpufeature: Fix meta-capability cpufeature check

[Amit Daniel Kachhap]

Some existing/future meta cpucaps match need the presence of individual
cpucaps. Currently the individual cpucaps checks it via an array based
flag and this introduces dependency on the array entry order.
This limitation exists only for system scope cpufeature.

This patch introduces an internal helper function (__system_matches_cap)
to invoke the matching handler for system scope. This helper has to be
used during a narrow window when,
- The system wide safe registers are set with all the SMP CPUs and,
- The SYSTEM_FEATURE cpu_hwcaps may not have been set.

Normal users should use the existing cpus_have_{const_}cap() global
function.

Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
Changes since v4:
 * Made the helper function static and updated the commit message
   as suggested by Suzuki [1].

[1]: http://lists.infradead.org/pipermail/linux-arm-kernel/2020-January/707722.html

 arch/arm64/kernel/cpufeature.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 0b67156..3818685 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -116,6 +116,8 @@ cpufeature_pan_not_uao(const struct arm64_cpu_capabilities *entry, int __unused)
 
 static void cpu_enable_cnp(struct arm64_cpu_capabilities const *cap);
 
+static bool __system_matches_cap(unsigned int n);
+
 /*
  * NOTE: Any changes to the visibility of features should be kept in
  * sync with the documentation of the CPU feature register ABI.
@@ -2146,6 +2148,17 @@ bool this_cpu_has_cap(unsigned int n)
 	return false;
 }
 
+static bool __system_matches_cap(unsigned int n)
+{
+	if (n < ARM64_NCAPS) {
+		const struct arm64_cpu_capabilities *cap = cpu_hwcaps_ptrs[n];
+
+		if (cap)
+			return cap->matches(cap, SCOPE_SYSTEM);
+	}
+	return false;
+}
+
 void cpu_set_feature(unsigned int num)
 {
 	WARN_ON(num >= MAX_CPU_FEATURES);
@@ -2218,7 +2231,7 @@ void __init setup_cpu_features(void)
 static bool __maybe_unused
 cpufeature_pan_not_uao(const struct arm64_cpu_capabilities *entry, int __unused)
 {
-	return (cpus_have_const_cap(ARM64_HAS_PAN) && !cpus_have_const_cap(ARM64_HAS_UAO));
+	return (__system_matches_cap(ARM64_HAS_PAN) && !__system_matches_cap(ARM64_HAS_UAO));
 }
 
 static void __maybe_unused cpu_enable_cnp(struct arm64_cpu_capabilities const *cap)
-- 
2.7.4


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[PATCH v5 02/17] arm64: cpufeature: add pointer auth meta-capabilities

[Amit Daniel Kachhap]

From: Kristina Martsenko <kristina.martsenko@arm.com>

To enable pointer auth for the kernel, we're going to need to check for
the presence of address auth and generic auth using alternative_if. We
currently have two cpucaps for each, but alternative_if needs to check a
single cpucap. So define meta-capabilities that are present when either
of the current two capabilities is present.

Leave the existing four cpucaps in place, as they are still needed to
check for mismatched systems where one CPU has the architected algorithm
but another has the IMP DEF algorithm.

Note, the meta-capabilities were present before but were removed in
commit a56005d32105 ("arm64: cpufeature: Reduce number of pointer auth
CPU caps from 6 to 4") and commit 1e013d06120c ("arm64: cpufeature: Rework
ptr auth hwcaps using multi_entry_cap_matches"), as they were not needed
then. Note, unlike before, the current patch checks the cpucap values
directly, instead of reading the CPU ID register value.

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[Amit: commit message and macro rebase, use __system_matches_cap]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/include/asm/cpucaps.h    |  4 +++-
 arch/arm64/include/asm/cpufeature.h |  6 ++----
 arch/arm64/kernel/cpufeature.c      | 25 ++++++++++++++++++++++++-
 3 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 865e025..72e4e05 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -58,7 +58,9 @@
 #define ARM64_WORKAROUND_SPECULATIVE_AT_NVHE	48
 #define ARM64_HAS_E0PD				49
 #define ARM64_HAS_RNG				50
+#define ARM64_HAS_ADDRESS_AUTH			51
+#define ARM64_HAS_GENERIC_AUTH			52
 
-#define ARM64_NCAPS				51
+#define ARM64_NCAPS				53
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 92ef953..8c80483 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -590,15 +590,13 @@ static inline bool system_supports_cnp(void)
 static inline bool system_supports_address_auth(void)
 {
 	return IS_ENABLED(CONFIG_ARM64_PTR_AUTH) &&
-		(cpus_have_const_cap(ARM64_HAS_ADDRESS_AUTH_ARCH) ||
-		 cpus_have_const_cap(ARM64_HAS_ADDRESS_AUTH_IMP_DEF));
+		cpus_have_const_cap(ARM64_HAS_ADDRESS_AUTH);
 }
 
 static inline bool system_supports_generic_auth(void)
 {
 	return IS_ENABLED(CONFIG_ARM64_PTR_AUTH) &&
-		(cpus_have_const_cap(ARM64_HAS_GENERIC_AUTH_ARCH) ||
-		 cpus_have_const_cap(ARM64_HAS_GENERIC_AUTH_IMP_DEF));
+		cpus_have_const_cap(ARM64_HAS_GENERIC_AUTH);
 }
 
 static inline bool system_uses_irq_prio_masking(void)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 3818685..b12e386 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1323,6 +1323,20 @@ static void cpu_enable_address_auth(struct arm64_cpu_capabilities const *cap)
 	sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_ENIA | SCTLR_ELx_ENIB |
 				       SCTLR_ELx_ENDA | SCTLR_ELx_ENDB);
 }
+
+static bool has_address_auth(const struct arm64_cpu_capabilities *entry,
+			     int __unused)
+{
+	return __system_matches_cap(ARM64_HAS_ADDRESS_AUTH_ARCH) ||
+	       __system_matches_cap(ARM64_HAS_ADDRESS_AUTH_IMP_DEF);
+}
+
+static bool has_generic_auth(const struct arm64_cpu_capabilities *entry,
+			     int __unused)
+{
+	return __system_matches_cap(ARM64_HAS_GENERIC_AUTH_ARCH) ||
+	       __system_matches_cap(ARM64_HAS_GENERIC_AUTH_IMP_DEF);
+}
 #endif /* CONFIG_ARM64_PTR_AUTH */
 
 #ifdef CONFIG_ARM64_E0PD
@@ -1600,7 +1614,6 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.field_pos = ID_AA64ISAR1_APA_SHIFT,
 		.min_field_value = ID_AA64ISAR1_APA_ARCHITECTED,
 		.matches = has_cpuid_feature,
-		.cpu_enable = cpu_enable_address_auth,
 	},
 	{
 		.desc = "Address authentication (IMP DEF algorithm)",
@@ -1611,6 +1624,11 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.field_pos = ID_AA64ISAR1_API_SHIFT,
 		.min_field_value = ID_AA64ISAR1_API_IMP_DEF,
 		.matches = has_cpuid_feature,
+	},
+	{
+		.capability = ARM64_HAS_ADDRESS_AUTH,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_address_auth,
 		.cpu_enable = cpu_enable_address_auth,
 	},
 	{
@@ -1633,6 +1651,11 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.min_field_value = ID_AA64ISAR1_GPI_IMP_DEF,
 		.matches = has_cpuid_feature,
 	},
+	{
+		.capability = ARM64_HAS_GENERIC_AUTH,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_generic_auth,
+	},
 #endif /* CONFIG_ARM64_PTR_AUTH */
 #ifdef CONFIG_ARM64_PSEUDO_NMI
 	{
-- 
2.7.4


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[PATCH v5 03/17] arm64: rename ptrauth key structures to be user-specific

[Amit Daniel Kachhap]

From: Kristina Martsenko <kristina.martsenko@arm.com>

We currently enable ptrauth for userspace, but do not use it within the
kernel. We're going to enable it for the kernel, and will need to manage
a separate set of ptrauth keys for the kernel.

We currently keep all 5 keys in struct ptrauth_keys. However, as the
kernel will only need to use 1 key, it is a bit wasteful to allocate a
whole ptrauth_keys struct for every thread.

Therefore, a subsequent patch will define a separate struct, with only 1
key, for the kernel. In preparation for that, rename the existing struct
(and associated macros and functions) to reflect that they are specific
to userspace.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[Amit: Re-positioned the patch to reduce the diff]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/include/asm/pointer_auth.h | 12 ++++++------
 arch/arm64/include/asm/processor.h    |  2 +-
 arch/arm64/kernel/pointer_auth.c      |  8 ++++----
 arch/arm64/kernel/ptrace.c            | 16 ++++++++--------
 4 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index 7a24bad..799b079 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -22,7 +22,7 @@ struct ptrauth_key {
  * We give each process its own keys, which are shared by all threads. The keys
  * are inherited upon fork(), and reinitialised upon exec*().
  */
-struct ptrauth_keys {
+struct ptrauth_keys_user {
 	struct ptrauth_key apia;
 	struct ptrauth_key apib;
 	struct ptrauth_key apda;
@@ -30,7 +30,7 @@ struct ptrauth_keys {
 	struct ptrauth_key apga;
 };
 
-static inline void ptrauth_keys_init(struct ptrauth_keys *keys)
+static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
 {
 	if (system_supports_address_auth()) {
 		get_random_bytes(&keys->apia, sizeof(keys->apia));
@@ -50,7 +50,7 @@ do {								\
 	write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1);	\
 } while (0)
 
-static inline void ptrauth_keys_switch(struct ptrauth_keys *keys)
+static inline void ptrauth_keys_switch_user(struct ptrauth_keys_user *keys)
 {
 	if (system_supports_address_auth()) {
 		__ptrauth_key_install(APIA, keys->apia);
@@ -80,12 +80,12 @@ 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);		\
+	ptrauth_keys_init_user(&__ptiu_tsk->thread.keys_user);		\
+	ptrauth_keys_switch_user(&__ptiu_tsk->thread.keys_user);		\
 } while (0)
 
 #define ptrauth_thread_switch(tsk)	\
-	ptrauth_keys_switch(&(tsk)->thread.keys_user)
+	ptrauth_keys_switch_user(&(tsk)->thread.keys_user)
 
 #else /* CONFIG_ARM64_PTR_AUTH */
 #define ptrauth_prctl_reset_keys(tsk, arg)	(-EINVAL)
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 5ba6320..496a928 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -146,7 +146,7 @@ struct thread_struct {
 	unsigned long		fault_code;	/* ESR_EL1 value */
 	struct debug_info	debug;		/* debugging */
 #ifdef CONFIG_ARM64_PTR_AUTH
-	struct ptrauth_keys	keys_user;
+	struct ptrauth_keys_user	keys_user;
 #endif
 };
 
diff --git a/arch/arm64/kernel/pointer_auth.c b/arch/arm64/kernel/pointer_auth.c
index c507b58..af5a638 100644
--- a/arch/arm64/kernel/pointer_auth.c
+++ b/arch/arm64/kernel/pointer_auth.c
@@ -9,7 +9,7 @@
 
 int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
 {
-	struct ptrauth_keys *keys = &tsk->thread.keys_user;
+	struct ptrauth_keys_user *keys = &tsk->thread.keys_user;
 	unsigned long addr_key_mask = PR_PAC_APIAKEY | PR_PAC_APIBKEY |
 				      PR_PAC_APDAKEY | PR_PAC_APDBKEY;
 	unsigned long key_mask = addr_key_mask | PR_PAC_APGAKEY;
@@ -18,8 +18,8 @@ int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg)
 		return -EINVAL;
 
 	if (!arg) {
-		ptrauth_keys_init(keys);
-		ptrauth_keys_switch(keys);
+		ptrauth_keys_init_user(keys);
+		ptrauth_keys_switch_user(keys);
 		return 0;
 	}
 
@@ -41,7 +41,7 @@ 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);
+	ptrauth_keys_switch_user(keys);
 
 	return 0;
 }
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index cd6e5fa..b3d3005 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -999,7 +999,7 @@ static struct ptrauth_key pac_key_from_user(__uint128_t ukey)
 }
 
 static void pac_address_keys_to_user(struct user_pac_address_keys *ukeys,
-				     const struct ptrauth_keys *keys)
+				     const struct ptrauth_keys_user *keys)
 {
 	ukeys->apiakey = pac_key_to_user(&keys->apia);
 	ukeys->apibkey = pac_key_to_user(&keys->apib);
@@ -1007,7 +1007,7 @@ static void pac_address_keys_to_user(struct user_pac_address_keys *ukeys,
 	ukeys->apdbkey = pac_key_to_user(&keys->apdb);
 }
 
-static void pac_address_keys_from_user(struct ptrauth_keys *keys,
+static void pac_address_keys_from_user(struct ptrauth_keys_user *keys,
 				       const struct user_pac_address_keys *ukeys)
 {
 	keys->apia = pac_key_from_user(ukeys->apiakey);
@@ -1021,7 +1021,7 @@ static int pac_address_keys_get(struct task_struct *target,
 				unsigned int pos, unsigned int count,
 				void *kbuf, void __user *ubuf)
 {
-	struct ptrauth_keys *keys = &target->thread.keys_user;
+	struct ptrauth_keys_user *keys = &target->thread.keys_user;
 	struct user_pac_address_keys user_keys;
 
 	if (!system_supports_address_auth())
@@ -1038,7 +1038,7 @@ static int pac_address_keys_set(struct task_struct *target,
 				unsigned int pos, unsigned int count,
 				const void *kbuf, const void __user *ubuf)
 {
-	struct ptrauth_keys *keys = &target->thread.keys_user;
+	struct ptrauth_keys_user *keys = &target->thread.keys_user;
 	struct user_pac_address_keys user_keys;
 	int ret;
 
@@ -1056,12 +1056,12 @@ static int pac_address_keys_set(struct task_struct *target,
 }
 
 static void pac_generic_keys_to_user(struct user_pac_generic_keys *ukeys,
-				     const struct ptrauth_keys *keys)
+				     const struct ptrauth_keys_user *keys)
 {
 	ukeys->apgakey = pac_key_to_user(&keys->apga);
 }
 
-static void pac_generic_keys_from_user(struct ptrauth_keys *keys,
+static void pac_generic_keys_from_user(struct ptrauth_keys_user *keys,
 				       const struct user_pac_generic_keys *ukeys)
 {
 	keys->apga = pac_key_from_user(ukeys->apgakey);
@@ -1072,7 +1072,7 @@ static int pac_generic_keys_get(struct task_struct *target,
 				unsigned int pos, unsigned int count,
 				void *kbuf, void __user *ubuf)
 {
-	struct ptrauth_keys *keys = &target->thread.keys_user;
+	struct ptrauth_keys_user *keys = &target->thread.keys_user;
 	struct user_pac_generic_keys user_keys;
 
 	if (!system_supports_generic_auth())
@@ -1089,7 +1089,7 @@ static int pac_generic_keys_set(struct task_struct *target,
 				unsigned int pos, unsigned int count,
 				const void *kbuf, const void __user *ubuf)
 {
-	struct ptrauth_keys *keys = &target->thread.keys_user;
+	struct ptrauth_keys_user *keys = &target->thread.keys_user;
 	struct user_pac_generic_keys user_keys;
 	int ret;
 
-- 
2.7.4


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[PATCH v5 04/17] arm64: install user ptrauth keys at kernel exit time

[Amit Daniel Kachhap]

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, so 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>
[Amit: commit msg, re-positioned the patch, comments]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/include/asm/asm_pointer_auth.h | 49 +++++++++++++++++++++++++++++++
 arch/arm64/include/asm/pointer_auth.h     | 23 +--------------
 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, 64 insertions(+), 26 deletions(-)
 create mode 100644 arch/arm64/include/asm/asm_pointer_auth.h

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..f820a13
--- /dev/null
+++ b/arch/arm64/include/asm/asm_pointer_auth.h
@@ -0,0 +1,49 @@
+/* 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
+/*
+ * thread.keys_user.ap* as offset exceeds the #imm offset range
+ * so use the base value of ldp as thread.keys_user and offset as
+ * keys_user.ap*.
+ */
+	.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_USER_KEY_APIA]
+	msr_s	SYS_APIAKEYLO_EL1, \tmp2
+	msr_s	SYS_APIAKEYHI_EL1, \tmp3
+	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APIB]
+	msr_s	SYS_APIBKEYLO_EL1, \tmp2
+	msr_s	SYS_APIBKEYHI_EL1, \tmp3
+	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APDA]
+	msr_s	SYS_APDAKEYLO_EL1, \tmp2
+	msr_s	SYS_APDAKEYHI_EL1, \tmp3
+	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_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_USER_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 799b079..dabe026 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -50,19 +50,6 @@ do {								\
 	write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1);	\
 } while (0)
 
-static inline void ptrauth_keys_switch_user(struct ptrauth_keys_user *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 +65,12 @@ 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_user(&__ptiu_tsk->thread.keys_user);		\
-	ptrauth_keys_switch_user(&__ptiu_tsk->thread.keys_user);		\
-} while (0)
-
-#define ptrauth_thread_switch(tsk)	\
-	ptrauth_keys_switch_user(&(tsk)->thread.keys_user)
+	ptrauth_keys_init_user(&(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 a5bdce8..7b1ea2a 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]));
@@ -128,5 +131,13 @@ 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_USER_KEY_APIA,		offsetof(struct ptrauth_keys_user, apia));
+  DEFINE(PTRAUTH_USER_KEY_APIB,		offsetof(struct ptrauth_keys_user, apib));
+  DEFINE(PTRAUTH_USER_KEY_APDA,		offsetof(struct ptrauth_keys_user, apda));
+  DEFINE(PTRAUTH_USER_KEY_APDB,		offsetof(struct ptrauth_keys_user, apdb));
+  DEFINE(PTRAUTH_USER_KEY_APGA,		offsetof(struct ptrauth_keys_user, apga));
+  BLANK();
+#endif
   return 0;
 }
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 9461d81..684e475 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 af5a638..1e77736 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_user(keys);
-		ptrauth_keys_switch_user(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_user(keys);
-
 	return 0;
 }
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 0062605..6140e79 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -512,7 +512,6 @@ __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);
 
 	/*
-- 
2.7.4


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[PATCH v5 05/17] arm64: create macro to park cpu in an infinite loop

[Amit Daniel Kachhap]

A macro early_park_cpu is added to park the faulted cpu in an infinite
loop. Currently, this macro is substituted in two instances and may be
reused in future.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/kernel/head.S | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 989b194..3d18163 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -761,6 +761,17 @@ ENDPROC(__secondary_too_slow)
 	.endm
 
 /*
+ * Macro to park the cpu in an infinite loop.
+ */
+	.macro	early_park_cpu status
+	update_early_cpu_boot_status \status | CPU_STUCK_IN_KERNEL, x1, x2
+.Lepc_\@:
+	wfe
+	wfi
+	b	.Lepc_\@
+	.endm
+
+/*
  * Enable the MMU.
  *
  *  x0  = SCTLR_EL1 value for turning on the MMU.
@@ -808,24 +819,14 @@ ENTRY(__cpu_secondary_check52bitva)
 	and	x0, x0, #(0xf << ID_AA64MMFR2_LVA_SHIFT)
 	cbnz	x0, 2f
 
-	update_early_cpu_boot_status \
-		CPU_STUCK_IN_KERNEL | CPU_STUCK_REASON_52_BIT_VA, x0, x1
-1:	wfe
-	wfi
-	b	1b
-
+	early_park_cpu CPU_STUCK_REASON_52_BIT_VA
 #endif
 2:	ret
 ENDPROC(__cpu_secondary_check52bitva)
 
 __no_granule_support:
 	/* Indicate that this CPU can't boot and is stuck in the kernel */
-	update_early_cpu_boot_status \
-		CPU_STUCK_IN_KERNEL | CPU_STUCK_REASON_NO_GRAN, x1, x2
-1:
-	wfe
-	wfi
-	b	1b
+	early_park_cpu CPU_STUCK_REASON_NO_GRAN
 ENDPROC(__no_granule_support)
 
 #ifdef CONFIG_RELOCATABLE
-- 
2.7.4


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[PATCH v5 06/17] arm64: add bootup/runtime flags for __cpu_setup

[Amit Daniel Kachhap]

This patch allows __cpu_setup to be invoked with one of these flags,
ARM64_CPU_BOOT_PRIMARY, ARM64_CPU_BOOT_SECONDARY or ARM64_CPU_RUNTIME.
This is required as some cpufeatures need different handling during
different scenarios.

The input parameter in x0 is preserved till the end to be used inside
this function.

There should be no functional change with this patch and is useful
for the subsequent ptrauth patch which utilizes it. Some upcoming
arm cpufeatures can also utilize these flags.

Suggested-by: James Morse <james.morse@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/include/asm/smp.h |  5 +++++
 arch/arm64/kernel/head.S     |  2 ++
 arch/arm64/kernel/sleep.S    |  2 ++
 arch/arm64/mm/proc.S         | 26 +++++++++++++++-----------
 4 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index a0c8a0b..8159000 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h
@@ -23,6 +23,11 @@
 #define CPU_STUCK_REASON_52_BIT_VA	(UL(1) << CPU_STUCK_REASON_SHIFT)
 #define CPU_STUCK_REASON_NO_GRAN	(UL(2) << CPU_STUCK_REASON_SHIFT)
 
+/* Options for __cpu_setup */
+#define ARM64_CPU_BOOT_PRIMARY		(1)
+#define ARM64_CPU_BOOT_SECONDARY	(2)
+#define ARM64_CPU_RUNTIME		(3)
+
 #ifndef __ASSEMBLY__
 
 #include <asm/percpu.h>
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 3d18163..5a7ce15 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -118,6 +118,7 @@ ENTRY(stext)
 	 * On return, the CPU will be ready for the MMU to be turned on and
 	 * the TCR will have been set.
 	 */
+	mov	x0, #ARM64_CPU_BOOT_PRIMARY
 	bl	__cpu_setup			// initialise processor
 	b	__primary_switch
 ENDPROC(stext)
@@ -712,6 +713,7 @@ secondary_startup:
 	 * Common entry point for secondary CPUs.
 	 */
 	bl	__cpu_secondary_check52bitva
+	mov	x0, #ARM64_CPU_BOOT_SECONDARY
 	bl	__cpu_setup			// initialise processor
 	adrp	x1, swapper_pg_dir
 	bl	__enable_mmu
diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index f5b04dd..7b2f2e6 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -3,6 +3,7 @@
 #include <linux/linkage.h>
 #include <asm/asm-offsets.h>
 #include <asm/assembler.h>
+#include <asm/smp.h>
 
 	.text
 /*
@@ -99,6 +100,7 @@ ENDPROC(__cpu_suspend_enter)
 	.pushsection ".idmap.text", "awx"
 ENTRY(cpu_resume)
 	bl	el2_setup		// if in EL2 drop to EL1 cleanly
+	mov	x0, #ARM64_CPU_RUNTIME
 	bl	__cpu_setup
 	/* enable the MMU early - so we can access sleep_save_stash by va */
 	adrp	x1, swapper_pg_dir
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index aafed69..ea0db17 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -408,31 +408,31 @@ SYM_FUNC_END(idmap_kpti_install_ng_mappings)
 /*
  *	__cpu_setup
  *
- *	Initialise the processor for turning the MMU on.  Return in x0 the
- *	value of the SCTLR_EL1 register.
+ *	Initialise the processor for turning the MMU on.
+ *
+ * Input:
+ *	x0 with a flag ARM64_CPU_BOOT_PRIMARY/ARM64_CPU_BOOT_SECONDARY/ARM64_CPU_RUNTIME.
+ * Output:
+ *	Return in x0 the value of the SCTLR_EL1 register.
  */
 	.pushsection ".idmap.text", "awx"
 SYM_FUNC_START(__cpu_setup)
 	tlbi	vmalle1				// Invalidate local TLB
 	dsb	nsh
 
-	mov	x0, #3 << 20
-	msr	cpacr_el1, x0			// Enable FP/ASIMD
-	mov	x0, #1 << 12			// Reset mdscr_el1 and disable
-	msr	mdscr_el1, x0			// access to the DCC from EL0
+	mov	x1, #3 << 20
+	msr	cpacr_el1, x1			// Enable FP/ASIMD
+	mov	x1, #1 << 12			// Reset mdscr_el1 and disable
+	msr	mdscr_el1, x1			// access to the DCC from EL0
 	isb					// Unmask debug exceptions now,
 	enable_dbg				// since this is per-cpu
-	reset_pmuserenr_el0 x0			// Disable PMU access from EL0
+	reset_pmuserenr_el0 x1			// Disable PMU access from EL0
 	/*
 	 * Memory region attributes
 	 */
 	mov_q	x5, MAIR_EL1_SET
 	msr	mair_el1, x5
 	/*
-	 * Prepare SCTLR
-	 */
-	mov_q	x0, SCTLR_EL1_SET
-	/*
 	 * Set/prepare TCR and TTBR. We use 512GB (39-bit) address range for
 	 * both user and kernel.
 	 */
@@ -468,5 +468,9 @@ SYM_FUNC_START(__cpu_setup)
 1:
 #endif	/* CONFIG_ARM64_HW_AFDBM */
 	msr	tcr_el1, x10
+	/*
+	 * Prepare SCTLR
+	 */
+	mov_q	x0, SCTLR_EL1_SET
 	ret					// return to head.S
 SYM_FUNC_END(__cpu_setup)
-- 
2.7.4


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[PATCH v5 07/17] arm64: cpufeature: handle conflicts based on capability

[Amit Daniel Kachhap]

From: Kristina Martsenko <kristina.martsenko@arm.com>

Each system capability can be of either boot, local, or system scope,
depending on when the state of the capability is finalized. When we
detect a conflict on a late CPU, we either offline the CPU or panic the
system. We currently always panic if the conflict is caused by a boot
scope capability, and offline the CPU if the conflict is caused by a
local or system scope capability.

We're going to want to add a new capability (for pointer authentication)
which needs to be boot scope but doesn't need to panic the system when a
conflict is detected. So add a new flag to specify whether the
capability requires the system to panic or not. Current boot scope
capabilities are updated to set the flag, so there should be no
functional change as a result of this patch.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/include/asm/cpufeature.h | 18 ++++++++++++++++--
 arch/arm64/kernel/cpufeature.c      | 23 +++++++++--------------
 2 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 8c80483..1e88aee 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -208,6 +208,10 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
  *     In some non-typical cases either both (a) and (b), or neither,
  *     should be permitted. This can be described by including neither
  *     or both flags in the capability's type field.
+ *
+ *     In case of a conflict, the CPU is prevented from booting. If the
+ *     ARM64_CPUCAP_PANIC_ON_CONFLICT flag is specified for the capability,
+ *     then a kernel panic is triggered.
  */
 
 
@@ -240,6 +244,8 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
 #define ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU	((u16)BIT(4))
 /* Is it safe for a late CPU to miss this capability when system has it */
 #define ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU	((u16)BIT(5))
+/* Panic when a conflict is detected */
+#define ARM64_CPUCAP_PANIC_ON_CONFLICT		((u16)BIT(6))
 
 /*
  * CPU errata workarounds that need to be enabled at boot time if one or
@@ -279,9 +285,11 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
 
 /*
  * CPU feature used early in the boot based on the boot CPU. All secondary
- * CPUs must match the state of the capability as detected by the boot CPU.
+ * CPUs must match the state of the capability as detected by the boot CPU. In
+ * case of a conflict, a kernel panic is triggered.
  */
-#define ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE ARM64_CPUCAP_SCOPE_BOOT_CPU
+#define ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE		\
+	(ARM64_CPUCAP_SCOPE_BOOT_CPU | ARM64_CPUCAP_PANIC_ON_CONFLICT)
 
 struct arm64_cpu_capabilities {
 	const char *desc;
@@ -352,6 +360,12 @@ cpucap_late_cpu_permitted(const struct arm64_cpu_capabilities *cap)
 	return !!(cap->type & ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU);
 }
 
+static inline bool
+cpucap_panic_on_conflict(const struct arm64_cpu_capabilities *cap)
+{
+	return !!(cap->type & ARM64_CPUCAP_PANIC_ON_CONFLICT);
+}
+
 /*
  * Generic helper for handling capabilties with multiple (match,enable) pairs
  * of call backs, sharing the same capability bit.
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index b12e386..ee1e8f3 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2005,10 +2005,8 @@ static void __init enable_cpu_capabilities(u16 scope_mask)
  * Run through the list of capabilities to check for conflicts.
  * If the system has already detected a capability, take necessary
  * action on this CPU.
- *
- * Returns "false" on conflicts.
  */
-static bool verify_local_cpu_caps(u16 scope_mask)
+static void verify_local_cpu_caps(u16 scope_mask)
 {
 	int i;
 	bool cpu_has_cap, system_has_cap;
@@ -2053,10 +2051,12 @@ static bool verify_local_cpu_caps(u16 scope_mask)
 		pr_crit("CPU%d: Detected conflict for capability %d (%s), System: %d, CPU: %d\n",
 			smp_processor_id(), caps->capability,
 			caps->desc, system_has_cap, cpu_has_cap);
-		return false;
-	}
 
-	return true;
+		if (cpucap_panic_on_conflict(caps))
+			cpu_panic_kernel();
+		else
+			cpu_die_early();
+	}
 }
 
 /*
@@ -2066,12 +2066,8 @@ static bool verify_local_cpu_caps(u16 scope_mask)
 static void check_early_cpu_features(void)
 {
 	verify_cpu_asid_bits();
-	/*
-	 * Early features are used by the kernel already. If there
-	 * is a conflict, we cannot proceed further.
-	 */
-	if (!verify_local_cpu_caps(SCOPE_BOOT_CPU))
-		cpu_panic_kernel();
+
+	verify_local_cpu_caps(SCOPE_BOOT_CPU);
 }
 
 static void
@@ -2119,8 +2115,7 @@ static void verify_local_cpu_capabilities(void)
 	 * check_early_cpu_features(), as they need to be verified
 	 * on all secondary CPUs.
 	 */
-	if (!verify_local_cpu_caps(SCOPE_ALL & ~SCOPE_BOOT_CPU))
-		cpu_die_early();
+	verify_local_cpu_caps(SCOPE_ALL & ~SCOPE_BOOT_CPU);
 
 	verify_local_elf_hwcaps(arm64_elf_hwcaps);
 
-- 
2.7.4


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Re: [PATCH v5 07/17] arm64: cpufeature: handle conflicts based on capability

[Catalin Marinas]

On Mon, Feb 17, 2020 at 02:57:38PM +0530, Amit Daniel Kachhap wrote:
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index 8c80483..1e88aee 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -352,6 +360,12 @@ cpucap_late_cpu_permitted(const struct arm64_cpu_capabilities *cap)
>  	return !!(cap->type & ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU);
>  }
>  
> +static inline bool
> +cpucap_panic_on_conflict(const struct arm64_cpu_capabilities *cap)
> +{
> +	return !!(cap->type & ARM64_CPUCAP_PANIC_ON_CONFLICT);
> +}

Does this need to be in the header file? If not, please move it to
cpufeature.c (and drop 'inline' if moved).

-- 
Catalin

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Re: [PATCH v5 07/17] arm64: cpufeature: handle conflicts based on capability

[Amit Kachhap]

On 2/28/20 11:48 PM, Catalin Marinas wrote:
> On Mon, Feb 17, 2020 at 02:57:38PM +0530, Amit Daniel Kachhap wrote:
>> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
>> index 8c80483..1e88aee 100644
>> --- a/arch/arm64/include/asm/cpufeature.h
>> +++ b/arch/arm64/include/asm/cpufeature.h
>> @@ -352,6 +360,12 @@ cpucap_late_cpu_permitted(const struct arm64_cpu_capabilities *cap)
>>   	return !!(cap->type & ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU);
>>   }
>>   
>> +static inline bool
>> +cpucap_panic_on_conflict(const struct arm64_cpu_capabilities *cap)
>> +{
>> +	return !!(cap->type & ARM64_CPUCAP_PANIC_ON_CONFLICT);
>> +}
> 
> Does this need to be in the header file? If not, please move it to
> cpufeature.c (and drop 'inline' if moved).

Actually there are similar functions in cpufeature.h such as
cpucap_late_cpu_permitted, cpucap_late_cpu_optional etc in the
file cpufeature.h so done this way.

But yes all these functions are consumed only in cpufeature.c so can be 
moved there. I can send as a cleanup patch.

> 

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[PATCH v5 08/17] arm64: enable ptrauth earlier

[Amit Daniel Kachhap]

From: Kristina Martsenko <kristina.martsenko@arm.com>

When the kernel is compiled with pointer auth instructions, the boot CPU
needs to start using address auth very early, so change the cpucap to
account for this.

Pointer auth must be enabled before we call C functions, because it is
not possible to enter a function with pointer auth disabled and exit it
with pointer auth enabled. Note, mismatches between architected and
IMPDEF algorithms will still be caught by the cpufeature framework (the
separate *_ARCH and *_IMP_DEF cpucaps).

Note the change in behavior: if the boot CPU has address auth and a
late CPU does not, then the late CPU is parked by the cpufeature
framework. Also, if the boot CPU does not have address auth and the late
CPU has then the late cpu will still boot but with ptrauth feature
disabled.

Leave generic authentication as a "system scope" cpucap for now, since
initially the kernel will only use address authentication.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[Amit: Re-worked ptrauth setup logic, comments]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/Kconfig                  |  6 ++++++
 arch/arm64/include/asm/cpufeature.h |  9 +++++++++
 arch/arm64/include/asm/smp.h        |  1 +
 arch/arm64/kernel/cpufeature.c      | 13 +++----------
 arch/arm64/kernel/smp.c             |  2 ++
 arch/arm64/mm/proc.S                | 31 +++++++++++++++++++++++++++++++
 6 files changed, 52 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0b30e88..87e2cbb 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1515,6 +1515,12 @@ config ARM64_PTR_AUTH
 	  be enabled. However, KVM guest also require VHE mode and hence
 	  CONFIG_ARM64_VHE=y option to use this feature.
 
+	  If the feature is present on the boot CPU but not on a late CPU, then
+	  the late CPU will be parked. Also, if the boot CPU does not have
+	  address auth and the late CPU has then the late CPU will still boot
+	  but with the feature disabled. On such a system, this option should
+	  not be selected.
+
 endmenu
 
 menu "ARMv8.5 architectural features"
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 1e88aee..e59477c 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -291,6 +291,15 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0;
 #define ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE		\
 	(ARM64_CPUCAP_SCOPE_BOOT_CPU | ARM64_CPUCAP_PANIC_ON_CONFLICT)
 
+/*
+ * CPU feature used early in the boot based on the boot CPU. It is safe for a
+ * late CPU to have this feature even though the boot CPU hasn't enabled it,
+ * although the feature will not be used by Linux in this case. If the boot CPU
+ * has enabled this feature already, then every late CPU must have it.
+ */
+#define ARM64_CPUCAP_BOOT_CPU_FEATURE                  \
+	(ARM64_CPUCAP_SCOPE_BOOT_CPU | ARM64_CPUCAP_PERMITTED_FOR_LATE_CPU)
+
 struct arm64_cpu_capabilities {
 	const char *desc;
 	u16 capability;
diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index 8159000..5334d69 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h
@@ -22,6 +22,7 @@
 
 #define CPU_STUCK_REASON_52_BIT_VA	(UL(1) << CPU_STUCK_REASON_SHIFT)
 #define CPU_STUCK_REASON_NO_GRAN	(UL(2) << CPU_STUCK_REASON_SHIFT)
+#define CPU_STUCK_REASON_NO_PTRAUTH	(UL(4) << CPU_STUCK_REASON_SHIFT)
 
 /* Options for __cpu_setup */
 #define ARM64_CPU_BOOT_PRIMARY		(1)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index ee1e8f3..8d1c979 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1318,12 +1318,6 @@ static void cpu_clear_disr(const struct arm64_cpu_capabilities *__unused)
 #endif /* CONFIG_ARM64_RAS_EXTN */
 
 #ifdef CONFIG_ARM64_PTR_AUTH
-static void cpu_enable_address_auth(struct arm64_cpu_capabilities const *cap)
-{
-	sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_ENIA | SCTLR_ELx_ENIB |
-				       SCTLR_ELx_ENDA | SCTLR_ELx_ENDB);
-}
-
 static bool has_address_auth(const struct arm64_cpu_capabilities *entry,
 			     int __unused)
 {
@@ -1608,7 +1602,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 	{
 		.desc = "Address authentication (architected algorithm)",
 		.capability = ARM64_HAS_ADDRESS_AUTH_ARCH,
-		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
 		.sys_reg = SYS_ID_AA64ISAR1_EL1,
 		.sign = FTR_UNSIGNED,
 		.field_pos = ID_AA64ISAR1_APA_SHIFT,
@@ -1618,7 +1612,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 	{
 		.desc = "Address authentication (IMP DEF algorithm)",
 		.capability = ARM64_HAS_ADDRESS_AUTH_IMP_DEF,
-		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
 		.sys_reg = SYS_ID_AA64ISAR1_EL1,
 		.sign = FTR_UNSIGNED,
 		.field_pos = ID_AA64ISAR1_API_SHIFT,
@@ -1627,9 +1621,8 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 	},
 	{
 		.capability = ARM64_HAS_ADDRESS_AUTH,
-		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.type = ARM64_CPUCAP_BOOT_CPU_FEATURE,
 		.matches = has_address_auth,
-		.cpu_enable = cpu_enable_address_auth,
 	},
 	{
 		.desc = "Generic authentication (architected algorithm)",
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index d4ed9a1..f2761a9 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -164,6 +164,8 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 				pr_crit("CPU%u: does not support 52-bit VAs\n", cpu);
 			if (status & CPU_STUCK_REASON_NO_GRAN)
 				pr_crit("CPU%u: does not support %luK granule \n", cpu, PAGE_SIZE / SZ_1K);
+			if (status & CPU_STUCK_REASON_NO_PTRAUTH)
+				pr_crit("CPU%u: does not support pointer authentication\n", cpu);
 			cpus_stuck_in_kernel++;
 			break;
 		case CPU_PANIC_KERNEL:
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index ea0db17..4cf19a2 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -16,6 +16,7 @@
 #include <asm/pgtable-hwdef.h>
 #include <asm/cpufeature.h>
 #include <asm/alternative.h>
+#include <asm/smp.h>
 
 #ifdef CONFIG_ARM64_64K_PAGES
 #define TCR_TG_FLAGS	TCR_TG0_64K | TCR_TG1_64K
@@ -468,9 +469,39 @@ SYM_FUNC_START(__cpu_setup)
 1:
 #endif	/* CONFIG_ARM64_HW_AFDBM */
 	msr	tcr_el1, x10
+	mov	x1, x0
 	/*
 	 * Prepare SCTLR
 	 */
 	mov_q	x0, SCTLR_EL1_SET
+
+#ifdef CONFIG_ARM64_PTR_AUTH
+	/* No ptrauth setup for run time cpus */
+	cmp	x1, #ARM64_CPU_RUNTIME
+	b.eq	3f
+
+	/* Check if the CPU supports ptrauth */
+	mrs	x2, id_aa64isar1_el1
+	ubfx	x2, x2, #ID_AA64ISAR1_APA_SHIFT, #8
+	cbz	x2, 3f
+
+	msr_s	SYS_APIAKEYLO_EL1, xzr
+	msr_s	SYS_APIAKEYHI_EL1, xzr
+
+	/* Just enable ptrauth for primary cpu */
+	cmp	x1, #ARM64_CPU_BOOT_PRIMARY
+	b.eq	2f
+
+	/* if !system_supports_address_auth() then skip enable */
+alternative_if_not ARM64_HAS_ADDRESS_AUTH
+	b	3f
+alternative_else_nop_endif
+
+2:	/* Enable ptrauth instructions */
+	ldr	x2, =SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \
+		     SCTLR_ELx_ENDA | SCTLR_ELx_ENDB
+	orr	x0, x0, x2
+3:
+#endif
 	ret					// return to head.S
 SYM_FUNC_END(__cpu_setup)
-- 
2.7.4


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[PATCH v5 09/17] arm64: initialize and switch ptrauth kernel keys

[Amit Daniel Kachhap]

From: Kristina Martsenko <kristina.martsenko@arm.com>

Set up keys to use pointer authentication within the kernel. The kernel
will be compiled with APIAKey instructions, the other keys are currently
unused. Each task is given its own APIAKey, which is initialized during
fork. The key is changed during context switch and on kernel entry from
EL0.

The keys for idle threads need to be set before calling any C functions,
because it is not possible to enter and exit a function with different
keys.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[Amit: Modified secondary cores key structure, comments]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/include/asm/asm_pointer_auth.h | 14 ++++++++++++++
 arch/arm64/include/asm/pointer_auth.h     | 13 +++++++++++++
 arch/arm64/include/asm/processor.h        |  1 +
 arch/arm64/include/asm/smp.h              |  4 ++++
 arch/arm64/kernel/asm-offsets.c           |  5 +++++
 arch/arm64/kernel/entry.S                 |  3 +++
 arch/arm64/kernel/process.c               |  2 ++
 arch/arm64/kernel/smp.c                   |  8 ++++++++
 arch/arm64/mm/proc.S                      | 12 ++++++++++++
 9 files changed, 62 insertions(+)

diff --git a/arch/arm64/include/asm/asm_pointer_auth.h b/arch/arm64/include/asm/asm_pointer_auth.h
index f820a13..4152afe 100644
--- a/arch/arm64/include/asm/asm_pointer_auth.h
+++ b/arch/arm64/include/asm/asm_pointer_auth.h
@@ -39,11 +39,25 @@ alternative_if ARM64_HAS_GENERIC_AUTH
 alternative_else_nop_endif
 	.endm
 
+	.macro ptrauth_keys_install_kernel tsk, tmp1, tmp2, tmp3
+alternative_if ARM64_HAS_ADDRESS_AUTH
+	mov	\tmp1, #THREAD_KEYS_KERNEL
+	add	\tmp1, \tsk, \tmp1
+	ldp	\tmp2, \tmp3, [\tmp1, #PTRAUTH_KERNEL_KEY_APIA]
+	msr_s	SYS_APIAKEYLO_EL1, \tmp2
+	msr_s	SYS_APIAKEYHI_EL1, \tmp3
+	isb
+alternative_else_nop_endif
+	.endm
+
 #else /* CONFIG_ARM64_PTR_AUTH */
 
 	.macro ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3
 	.endm
 
+	.macro ptrauth_keys_install_kernel 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 dabe026..aa956ca 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -30,6 +30,10 @@ struct ptrauth_keys_user {
 	struct ptrauth_key apga;
 };
 
+struct ptrauth_keys_kernel {
+	struct ptrauth_key apia;
+};
+
 static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys)
 {
 	if (system_supports_address_auth()) {
@@ -50,6 +54,12 @@ do {								\
 	write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1);	\
 } while (0)
 
+static inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
+{
+	if (system_supports_address_auth())
+		get_random_bytes(&keys->apia, sizeof(keys->apia));
+}
+
 extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
 
 /*
@@ -66,11 +76,14 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 
 #define ptrauth_thread_init_user(tsk)					\
 	ptrauth_keys_init_user(&(tsk)->thread.keys_user)
+#define ptrauth_thread_init_kernel(tsk)					\
+	ptrauth_keys_init_kernel(&(tsk)->thread.keys_kernel)
 
 #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_init_kernel(tsk)
 #endif /* CONFIG_ARM64_PTR_AUTH */
 
 #endif /* __ASM_POINTER_AUTH_H */
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 496a928..4c77da5 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -147,6 +147,7 @@ struct thread_struct {
 	struct debug_info	debug;		/* debugging */
 #ifdef CONFIG_ARM64_PTR_AUTH
 	struct ptrauth_keys_user	keys_user;
+	struct ptrauth_keys_kernel	keys_kernel;
 #endif
 };
 
diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index 5334d69..4e92150 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h
@@ -36,6 +36,7 @@
 #include <linux/threads.h>
 #include <linux/cpumask.h>
 #include <linux/thread_info.h>
+#include <asm/pointer_auth.h>
 
 DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number);
 
@@ -93,6 +94,9 @@ asmlinkage void secondary_start_kernel(void);
 struct secondary_data {
 	void *stack;
 	struct task_struct *task;
+#ifdef CONFIG_ARM64_PTR_AUTH
+	struct ptrauth_keys_kernel ptrauth_key;
+#endif
 	long status;
 };
 
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 7b1ea2a..9981a0a 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -42,6 +42,7 @@ int main(void)
   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));
+  DEFINE(THREAD_KEYS_KERNEL,	offsetof(struct task_struct, thread.keys_kernel));
 #endif
   BLANK();
   DEFINE(S_X0,			offsetof(struct pt_regs, regs[0]));
@@ -91,6 +92,9 @@ int main(void)
   BLANK();
   DEFINE(CPU_BOOT_STACK,	offsetof(struct secondary_data, stack));
   DEFINE(CPU_BOOT_TASK,		offsetof(struct secondary_data, task));
+#ifdef CONFIG_ARM64_PTR_AUTH
+  DEFINE(CPU_BOOT_PTRAUTH_KEY,	offsetof(struct secondary_data, ptrauth_key));
+#endif
   BLANK();
 #ifdef CONFIG_KVM_ARM_HOST
   DEFINE(VCPU_CONTEXT,		offsetof(struct kvm_vcpu, arch.ctxt));
@@ -137,6 +141,7 @@ int main(void)
   DEFINE(PTRAUTH_USER_KEY_APDA,		offsetof(struct ptrauth_keys_user, apda));
   DEFINE(PTRAUTH_USER_KEY_APDB,		offsetof(struct ptrauth_keys_user, apdb));
   DEFINE(PTRAUTH_USER_KEY_APGA,		offsetof(struct ptrauth_keys_user, apga));
+  DEFINE(PTRAUTH_KERNEL_KEY_APIA,	offsetof(struct ptrauth_keys_kernel, apia));
   BLANK();
 #endif
   return 0;
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 684e475..3dad2d0 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -178,6 +178,7 @@ alternative_cb_end
 
 	apply_ssbd 1, x22, x23
 
+	ptrauth_keys_install_kernel tsk, x20, x22, x23
 	.else
 	add	x21, sp, #S_FRAME_SIZE
 	get_current_task tsk
@@ -342,6 +343,7 @@ alternative_else_nop_endif
 	msr	cntkctl_el1, x1
 4:
 #endif
+	/* No kernel C function calls after this as user keys are set. */
 	ptrauth_keys_install_user tsk, x0, x1, x2
 
 	apply_ssbd 0, x0, x1
@@ -898,6 +900,7 @@ ENTRY(cpu_switch_to)
 	ldr	lr, [x8]
 	mov	sp, x9
 	msr	sp_el0, x1
+	ptrauth_keys_install_kernel x1, x8, x9, x10
 	ret
 ENDPROC(cpu_switch_to)
 NOKPROBE(cpu_switch_to)
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 6140e79..7db0302 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -376,6 +376,8 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long stack_start,
 	 */
 	fpsimd_flush_task_state(p);
 
+	ptrauth_thread_init_kernel(p);
+
 	if (likely(!(p->flags & PF_KTHREAD))) {
 		*childregs = *current_pt_regs();
 		childregs->regs[0] = 0;
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index f2761a9..3fa0fbf 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -112,6 +112,10 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	 */
 	secondary_data.task = idle;
 	secondary_data.stack = task_stack_page(idle) + THREAD_SIZE;
+#if defined(CONFIG_ARM64_PTR_AUTH)
+	secondary_data.ptrauth_key.apia.lo = idle->thread.keys_kernel.apia.lo;
+	secondary_data.ptrauth_key.apia.hi = idle->thread.keys_kernel.apia.hi;
+#endif
 	update_cpu_boot_status(CPU_MMU_OFF);
 	__flush_dcache_area(&secondary_data, sizeof(secondary_data));
 
@@ -138,6 +142,10 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 
 	secondary_data.task = NULL;
 	secondary_data.stack = NULL;
+#if defined(CONFIG_ARM64_PTR_AUTH)
+	secondary_data.ptrauth_key.apia.lo = 0;
+	secondary_data.ptrauth_key.apia.hi = 0;
+#endif
 	__flush_dcache_area(&secondary_data, sizeof(secondary_data));
 	status = READ_ONCE(secondary_data.status);
 	if (ret && status) {
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index 4cf19a2..5a11a89 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -485,6 +485,10 @@ SYM_FUNC_START(__cpu_setup)
 	ubfx	x2, x2, #ID_AA64ISAR1_APA_SHIFT, #8
 	cbz	x2, 3f
 
+	/*
+	 * The primary cpu keys are reset here and can be
+	 * re-initialised with some proper values later.
+	 */
 	msr_s	SYS_APIAKEYLO_EL1, xzr
 	msr_s	SYS_APIAKEYHI_EL1, xzr
 
@@ -497,6 +501,14 @@ alternative_if_not ARM64_HAS_ADDRESS_AUTH
 	b	3f
 alternative_else_nop_endif
 
+	/* Install ptrauth key for secondary cpus */
+	adr_l	x2, secondary_data
+	ldr	x3, [x2, #CPU_BOOT_TASK]	// get secondary_data.task
+	cbz	x3, 2f				// check for slow booting cpus
+	ldp	x3, x4, [x2, #CPU_BOOT_PTRAUTH_KEY]
+	msr_s	SYS_APIAKEYLO_EL1, x3
+	msr_s	SYS_APIAKEYHI_EL1, x4
+
 2:	/* Enable ptrauth instructions */
 	ldr	x2, =SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \
 		     SCTLR_ELx_ENDA | SCTLR_ELx_ENDB
-- 
2.7.4


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[PATCH v5 10/17] arm64: initialize ptrauth keys for kernel booting task

[Amit Daniel Kachhap]

This patch uses the existing boot_init_stack_canary arch function
to initialize the ptrauth keys for the booting task in the primary
core. The requirement here is that it should be always inline and
the caller must never return.

As pointer authentication too detects a subset of stack corruption
so it makes sense to place this code here.

Both pointer authentication and stack canary codes are protected
by their respective config option.

Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/include/asm/pointer_auth.h   | 11 ++++++++++-
 arch/arm64/include/asm/stackprotector.h |  5 +++++
 include/linux/stackprotector.h          |  2 +-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index aa956ca..833d3f9 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -54,12 +54,18 @@ do {								\
 	write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1);	\
 } while (0)
 
-static inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
+static __always_inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys)
 {
 	if (system_supports_address_auth())
 		get_random_bytes(&keys->apia, sizeof(keys->apia));
 }
 
+static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kernel *keys)
+{
+	if (system_supports_address_auth())
+		__ptrauth_key_install(APIA, keys->apia);
+}
+
 extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
 
 /*
@@ -78,12 +84,15 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 	ptrauth_keys_init_user(&(tsk)->thread.keys_user)
 #define ptrauth_thread_init_kernel(tsk)					\
 	ptrauth_keys_init_kernel(&(tsk)->thread.keys_kernel)
+#define ptrauth_thread_switch_kernel(tsk)				\
+	ptrauth_keys_switch_kernel(&(tsk)->thread.keys_kernel)
 
 #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_init_kernel(tsk)
+#define ptrauth_thread_switch_kernel(tsk)
 #endif /* CONFIG_ARM64_PTR_AUTH */
 
 #endif /* __ASM_POINTER_AUTH_H */
diff --git a/arch/arm64/include/asm/stackprotector.h b/arch/arm64/include/asm/stackprotector.h
index 5884a2b..7263e0b 100644
--- a/arch/arm64/include/asm/stackprotector.h
+++ b/arch/arm64/include/asm/stackprotector.h
@@ -15,6 +15,7 @@
 
 #include <linux/random.h>
 #include <linux/version.h>
+#include <asm/pointer_auth.h>
 
 extern unsigned long __stack_chk_guard;
 
@@ -26,6 +27,7 @@ extern unsigned long __stack_chk_guard;
  */
 static __always_inline void boot_init_stack_canary(void)
 {
+#if defined(CONFIG_STACKPROTECTOR)
 	unsigned long canary;
 
 	/* Try to get a semi random initial value. */
@@ -36,6 +38,9 @@ static __always_inline void boot_init_stack_canary(void)
 	current->stack_canary = canary;
 	if (!IS_ENABLED(CONFIG_STACKPROTECTOR_PER_TASK))
 		__stack_chk_guard = current->stack_canary;
+#endif
+	ptrauth_thread_init_kernel(current);
+	ptrauth_thread_switch_kernel(current);
 }
 
 #endif	/* _ASM_STACKPROTECTOR_H */
diff --git a/include/linux/stackprotector.h b/include/linux/stackprotector.h
index 6b792d0..4c678c4 100644
--- a/include/linux/stackprotector.h
+++ b/include/linux/stackprotector.h
@@ -6,7 +6,7 @@
 #include <linux/sched.h>
 #include <linux/random.h>
 
-#ifdef CONFIG_STACKPROTECTOR
+#if defined(CONFIG_STACKPROTECTOR) || defined(CONFIG_ARM64_PTR_AUTH)
 # include <asm/stackprotector.h>
 #else
 static inline void boot_init_stack_canary(void)
-- 
2.7.4


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[PATCH v5 11/17] arm64: mask PAC bits of __builtin_return_address

[Amit Daniel Kachhap]

This redefines __builtin_return_address to mask pac bits
when Pointer Authentication is enabled. As __builtin_return_address
is used mostly used to refer to the caller function symbol address
so masking runtime generated pac bits will help to find the match.

This patch adds a new file (asm/compiler.h) and is transitively
included (via include/compiler_types.h) on the compiler command line
so it is guaranteed to be loaded and the users of this macro will
not find a wrong version.

A helper macro ptrauth_kernel_pac_mask is created for this purpose
and added in this file. A similar macro ptrauth_user_pac_mask exists
in pointer_auth.h and is now moved here for the sake of consistency.

This change fixes the utilities like cat /proc/vmallocinfo to show
correct symbol names.

Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/Kconfig                    |  1 +
 arch/arm64/include/asm/compiler.h     | 20 ++++++++++++++++++++
 arch/arm64/include/asm/pointer_auth.h | 13 +++++--------
 3 files changed, 26 insertions(+), 8 deletions(-)
 create mode 100644 arch/arm64/include/asm/compiler.h

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 87e2cbb..115ceea 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -118,6 +118,7 @@ config ARM64
 	select HAVE_ALIGNED_STRUCT_PAGE if SLUB
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_BITREVERSE
+	select HAVE_ARCH_COMPILER_H
 	select HAVE_ARCH_HUGE_VMAP
 	select HAVE_ARCH_JUMP_LABEL
 	select HAVE_ARCH_JUMP_LABEL_RELATIVE
diff --git a/arch/arm64/include/asm/compiler.h b/arch/arm64/include/asm/compiler.h
new file mode 100644
index 0000000..085e7cd0
--- /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)
+#define ptrauth_kernel_pac_mask()	GENMASK_ULL(63, vabits_actual)
+
+#define __builtin_return_address(val)				\
+	(void *)((unsigned long)__builtin_return_address(val) |	\
+	ptrauth_kernel_pac_mask())
+
+#endif /* CONFIG_ARM64_PTR_AUTH */
+
+#endif /* __ASM_COMPILER_H */
diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
index 833d3f9..5340dbb 100644
--- a/arch/arm64/include/asm/pointer_auth.h
+++ b/arch/arm64/include/asm/pointer_auth.h
@@ -68,16 +68,13 @@ static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kerne
 
 extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg);
 
-/*
- * The EL0 pointer bits used by a pointer authentication code.
- * This is dependent on TBI0 being enabled, or bits 63:56 would also apply.
- */
-#define ptrauth_user_pac_mask()	GENMASK(54, vabits_actual)
-
-/* Only valid for EL0 TTBR0 instruction pointers */
+/* Valid for EL0 TTBR0 and EL1 TTBR1 instruction pointers */
 static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
 {
-	return ptr & ~ptrauth_user_pac_mask();
+	if (ptr & BIT_ULL(55))
+		return ptr | ptrauth_kernel_pac_mask();
+	else
+		return ptr & ~ptrauth_user_pac_mask();
 }
 
 #define ptrauth_thread_init_user(tsk)					\
-- 
2.7.4


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[PATCH v5 12/17] arm64: unwind: strip PAC from kernel addresses

[Amit Daniel Kachhap]

From: Mark Rutland <mark.rutland@arm.com>

When we enable pointer authentication in the kernel, LR values saved to
the stack will have a PAC which we must strip in order to retrieve the
real return address.

Strip PACs when unwinding the stack in order to account for this.

Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[Amit: Re-position ptrauth_strip_insn_pac, comment]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/kernel/stacktrace.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index a336cb1..b479df7 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -14,6 +14,7 @@
 #include <linux/stacktrace.h>
 
 #include <asm/irq.h>
+#include <asm/pointer_auth.h>
 #include <asm/stack_pointer.h>
 #include <asm/stacktrace.h>
 
@@ -101,6 +102,8 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 	}
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
+	frame->pc = ptrauth_strip_insn_pac(frame->pc);
+
 	/*
 	 * Frames created upon entry from EL0 have NULL FP and PC values, so
 	 * don't bother reporting these. Frames created by __noreturn functions
-- 
2.7.4


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[PATCH v5 13/17] arm64: __show_regs: strip PAC from lr in printk

[Amit Daniel Kachhap]

lr is printed with %pS which will try to find an entry in kallsyms.
After enabling pointer authentication, this match will fail due to
PAC present in the lr.

Strip PAC from the lr to display the correct symbol name.

Suggested-by: James Morse <james.morse@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/kernel/process.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 7db0302..cacae29 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -262,7 +262,7 @@ void __show_regs(struct pt_regs *regs)
 
 	if (!user_mode(regs)) {
 		printk("pc : %pS\n", (void *)regs->pc);
-		printk("lr : %pS\n", (void *)lr);
+		printk("lr : %pS\n", (void *)ptrauth_strip_insn_pac(lr));
 	} else {
 		printk("pc : %016llx\n", regs->pc);
 		printk("lr : %016llx\n", lr);
-- 
2.7.4


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[PATCH v5 14/17] arm64: suspend: restore the kernel ptrauth keys

[Amit Daniel Kachhap]

This patch restores the kernel keys from current task during
cpu resume after the mmu is turned on and ptrauth is enabled.

Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/kernel/sleep.S | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index 7b2f2e6..f9db925 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -2,6 +2,7 @@
 #include <linux/errno.h>
 #include <linux/linkage.h>
 #include <asm/asm-offsets.h>
+#include <asm/asm_pointer_auth.h>
 #include <asm/assembler.h>
 #include <asm/smp.h>
 
@@ -134,6 +135,11 @@ ENTRY(_cpu_resume)
 	 */
 	bl	cpu_do_resume
 
+#ifdef CONFIG_ARM64_PTR_AUTH
+	get_current_task x1
+	ptrauth_keys_install_kernel x1, x2, x3, x4
+#endif
+
 #ifdef CONFIG_KASAN
 	mov	x0, sp
 	bl	kasan_unpoison_task_stack_below
-- 
2.7.4


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Re: [PATCH v5 14/17] arm64: suspend: restore the kernel ptrauth keys

[Catalin Marinas]

On Mon, Feb 17, 2020 at 02:57:45PM +0530, Amit Daniel Kachhap wrote:
> This patch restores the kernel keys from current task during
> cpu resume after the mmu is turned on and ptrauth is enabled.
> 
> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
> ---
>  arch/arm64/kernel/sleep.S | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
> index 7b2f2e6..f9db925 100644
> --- a/arch/arm64/kernel/sleep.S
> +++ b/arch/arm64/kernel/sleep.S
> @@ -2,6 +2,7 @@
>  #include <linux/errno.h>
>  #include <linux/linkage.h>
>  #include <asm/asm-offsets.h>
> +#include <asm/asm_pointer_auth.h>
>  #include <asm/assembler.h>
>  #include <asm/smp.h>
>  
> @@ -134,6 +135,11 @@ ENTRY(_cpu_resume)
>  	 */
>  	bl	cpu_do_resume
>  
> +#ifdef CONFIG_ARM64_PTR_AUTH
> +	get_current_task x1
> +	ptrauth_keys_install_kernel x1, x2, x3, x4
> +#endif

Could we move this to cpu_do_resume? Most of the sysreg initialisation
during resume is done there.

-- 
Catalin

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Re: [PATCH v5 14/17] arm64: suspend: restore the kernel ptrauth keys

[Amit Kachhap]

On 2/28/20 11:48 PM, Catalin Marinas wrote:
> On Mon, Feb 17, 2020 at 02:57:45PM +0530, Amit Daniel Kachhap wrote:
>> This patch restores the kernel keys from current task during
>> cpu resume after the mmu is turned on and ptrauth is enabled.
>>
>> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
>> ---
>>   arch/arm64/kernel/sleep.S | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
>> index 7b2f2e6..f9db925 100644
>> --- a/arch/arm64/kernel/sleep.S
>> +++ b/arch/arm64/kernel/sleep.S
>> @@ -2,6 +2,7 @@
>>   #include <linux/errno.h>
>>   #include <linux/linkage.h>
>>   #include <asm/asm-offsets.h>
>> +#include <asm/asm_pointer_auth.h>
>>   #include <asm/assembler.h>
>>   #include <asm/smp.h>
>>   
>> @@ -134,6 +135,11 @@ ENTRY(_cpu_resume)
>>   	 */
>>   	bl	cpu_do_resume
>>   
>> +#ifdef CONFIG_ARM64_PTR_AUTH
>> +	get_current_task x1
>> +	ptrauth_keys_install_kernel x1, x2, x3, x4
>> +#endif
> 
> Could we move this to cpu_do_resume? Most of the sysreg initialisation
> during resume is done there.

Yes it makes sense. I will implement in my v6 series.

> 

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[PATCH v5 15/17] kconfig: Add support for 'as-option'

[Amit Daniel Kachhap]

From: Vincenzo Frascino <vincenzo.frascino@arm.com>

Currently kconfig does not have a feature that allows to detect if the
used assembler supports a specific compilation option.

Introduce 'as-option' to serve this purpose in the context of Kconfig:

        config X
                def_bool $(as-option,...)

Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-kbuild@vger.kernel.org
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 scripts/Kconfig.include | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 85334dc..374e251 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -35,6 +35,10 @@ ld-option = $(success,$(LD) -v $(1))
 # Return y if the assembler supports <instr>, n otherwise
 as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
 
+# $(as-option,<flag>)
+# Return y if the assembler supports <flag>, n otherwise
+as-option = $(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero)
+
 # check if $(CC) and $(LD) exist
 $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
 $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
-- 
2.7.4

[PATCH v5 15/17] kconfig: Add support for 'as-option'

[Amit Daniel Kachhap]

From: Vincenzo Frascino <vincenzo.frascino@arm.com>

Currently kconfig does not have a feature that allows to detect if the
used assembler supports a specific compilation option.

Introduce 'as-option' to serve this purpose in the context of Kconfig:

        config X
                def_bool $(as-option,...)

Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: linux-kbuild@vger.kernel.org
Acked-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 scripts/Kconfig.include | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 85334dc..374e251 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -35,6 +35,10 @@ ld-option = $(success,$(LD) -v $(1))
 # Return y if the assembler supports <instr>, n otherwise
 as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
 
+# $(as-option,<flag>)
+# Return y if the assembler supports <flag>, n otherwise
+as-option = $(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero)
+
 # check if $(CC) and $(LD) exist
 $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
 $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
-- 
2.7.4


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Re: [PATCH v5 15/17] kconfig: Add support for 'as-option'

[Masahiro Yamada]

Hi.

On Mon, Feb 17, 2020 at 6:29 PM Amit Daniel Kachhap
<amit.kachhap@arm.com> wrote:
>
> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
>
> Currently kconfig does not have a feature that allows to detect if the
> used assembler supports a specific compilation option.
>
> Introduce 'as-option' to serve this purpose in the context of Kconfig:
>
>         config X
>                 def_bool $(as-option,...)
>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: linux-kbuild@vger.kernel.org
> Acked-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
> ---
>  scripts/Kconfig.include | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
> index 85334dc..374e251 100644
> --- a/scripts/Kconfig.include
> +++ b/scripts/Kconfig.include
> @@ -35,6 +35,10 @@ ld-option = $(success,$(LD) -v $(1))
>  # Return y if the assembler supports <instr>, n otherwise
>  as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
>
> +# $(as-option,<flag>)
> +# Return y if the assembler supports <flag>, n otherwise
> +as-option =$(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero)
> +


I am still not convinced with using /dev/zero here.


Does this work?

as-option = $(success, cat /dev/null | $(CC) $(CLANG_FLAGS) $(1) -c -x
assembler -o /dev/null -)


[1] Could you insert as-option between ld-option and as-instr ?

[2] Could you add some comments to explain why
     /dev/null -o /dev/null does not work?





>  # check if $(CC) and $(LD) exist
>  $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
>  $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
> --
> 2.7.4
>


-- 
Best Regards
Masahiro Yamada

Re: [PATCH v5 15/17] kconfig: Add support for 'as-option'

[Masahiro Yamada]

Hi.

On Mon, Feb 17, 2020 at 6:29 PM Amit Daniel Kachhap
<amit.kachhap@arm.com> wrote:
>
> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
>
> Currently kconfig does not have a feature that allows to detect if the
> used assembler supports a specific compilation option.
>
> Introduce 'as-option' to serve this purpose in the context of Kconfig:
>
>         config X
>                 def_bool $(as-option,...)
>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: linux-kbuild@vger.kernel.org
> Acked-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
> ---
>  scripts/Kconfig.include | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
> index 85334dc..374e251 100644
> --- a/scripts/Kconfig.include
> +++ b/scripts/Kconfig.include
> @@ -35,6 +35,10 @@ ld-option = $(success,$(LD) -v $(1))
>  # Return y if the assembler supports <instr>, n otherwise
>  as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
>
> +# $(as-option,<flag>)
> +# Return y if the assembler supports <flag>, n otherwise
> +as-option =$(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero)
> +


I am still not convinced with using /dev/zero here.


Does this work?

as-option = $(success, cat /dev/null | $(CC) $(CLANG_FLAGS) $(1) -c -x
assembler -o /dev/null -)


[1] Could you insert as-option between ld-option and as-instr ?

[2] Could you add some comments to explain why
     /dev/null -o /dev/null does not work?





>  # check if $(CC) and $(LD) exist
>  $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
>  $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
> --
> 2.7.4
>


-- 
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Masahiro Yamada

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Re: [PATCH v5 15/17] kconfig: Add support for 'as-option'

[Vincenzo Frascino]

[-- Attachment #1: Type: text/plain, Size: 2275 bytes --]

Hi,

On 17/02/2020 09:39, Masahiro Yamada wrote:
> Hi.
> 
> On Mon, Feb 17, 2020 at 6:29 PM Amit Daniel Kachhap
> <amit.kachhap@arm.com> wrote:
>>
>> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
>>
>> Currently kconfig does not have a feature that allows to detect if the
>> used assembler supports a specific compilation option.
>>
>> Introduce 'as-option' to serve this purpose in the context of Kconfig:
>>
>>         config X
>>                 def_bool $(as-option,...)
>>
>> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
>> Cc: linux-kbuild@vger.kernel.org
>> Acked-by: Masahiro Yamada <masahiroy@kernel.org>
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
>> ---
>>  scripts/Kconfig.include | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
>> index 85334dc..374e251 100644
>> --- a/scripts/Kconfig.include
>> +++ b/scripts/Kconfig.include
>> @@ -35,6 +35,10 @@ ld-option = $(success,$(LD) -v $(1))
>>  # Return y if the assembler supports <instr>, n otherwise
>>  as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
>>
>> +# $(as-option,<flag>)
>> +# Return y if the assembler supports <flag>, n otherwise
>> +as-option =$(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero)
>> +
> 
> 
> I am still not convinced with using /dev/zero here.
> 

Could you please elaborate a bit more?

> 
> Does this work?
> 
> as-option = $(success, cat /dev/null | $(CC) $(CLANG_FLAGS) $(1) -c -x
> assembler -o /dev/null -)
> 

I will try and get back to you.

> 
> [1] Could you insert as-option between ld-option and as-instr ?
> 

Sure, I will do it in the next version.

> [2] Could you add some comments to explain why
>      /dev/null -o /dev/null does not work?
> 
> 

Comments are always a good think :) I will do in the next version.

> 
> 
> 
>>  # check if $(CC) and $(LD) exist
>>  $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
>>  $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
>> --
>> 2.7.4
>>
> 
> 

-- 
Regards,
Vincenzo

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Re: [PATCH v5 15/17] kconfig: Add support for 'as-option'

[Vincenzo Frascino]

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Hi,

On 17/02/2020 09:39, Masahiro Yamada wrote:
> Hi.
> 
> On Mon, Feb 17, 2020 at 6:29 PM Amit Daniel Kachhap
> <amit.kachhap@arm.com> wrote:
>>
>> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
>>
>> Currently kconfig does not have a feature that allows to detect if the
>> used assembler supports a specific compilation option.
>>
>> Introduce 'as-option' to serve this purpose in the context of Kconfig:
>>
>>         config X
>>                 def_bool $(as-option,...)
>>
>> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
>> Cc: linux-kbuild@vger.kernel.org
>> Acked-by: Masahiro Yamada <masahiroy@kernel.org>
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
>> ---
>>  scripts/Kconfig.include | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
>> index 85334dc..374e251 100644
>> --- a/scripts/Kconfig.include
>> +++ b/scripts/Kconfig.include
>> @@ -35,6 +35,10 @@ ld-option = $(success,$(LD) -v $(1))
>>  # Return y if the assembler supports <instr>, n otherwise
>>  as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
>>
>> +# $(as-option,<flag>)
>> +# Return y if the assembler supports <flag>, n otherwise
>> +as-option =$(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero)
>> +
> 
> 
> I am still not convinced with using /dev/zero here.
> 

Could you please elaborate a bit more?

> 
> Does this work?
> 
> as-option = $(success, cat /dev/null | $(CC) $(CLANG_FLAGS) $(1) -c -x
> assembler -o /dev/null -)
> 

I will try and get back to you.

> 
> [1] Could you insert as-option between ld-option and as-instr ?
> 

Sure, I will do it in the next version.

> [2] Could you add some comments to explain why
>      /dev/null -o /dev/null does not work?
> 
> 

Comments are always a good think :) I will do in the next version.

> 
> 
> 
>>  # check if $(CC) and $(LD) exist
>>  $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
>>  $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
>> --
>> 2.7.4
>>
> 
> 

-- 
Regards,
Vincenzo

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Re: [PATCH v5 15/17] kconfig: Add support for 'as-option'

[Masahiro Yamada]

Hi,

On Mon, Feb 17, 2020 at 7:16 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> Hi,
>
> On 17/02/2020 09:39, Masahiro Yamada wrote:
> > Hi.
> >
> > On Mon, Feb 17, 2020 at 6:29 PM Amit Daniel Kachhap
> > <amit.kachhap@arm.com> wrote:
> >>
> >> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
> >>
> >> Currently kconfig does not have a feature that allows to detect if the
> >> used assembler supports a specific compilation option.
> >>
> >> Introduce 'as-option' to serve this purpose in the context of Kconfig:
> >>
> >>         config X
> >>                 def_bool $(as-option,...)
> >>
> >> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> >> Cc: linux-kbuild@vger.kernel.org
> >> Acked-by: Masahiro Yamada <masahiroy@kernel.org>
> >> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> >> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
> >> ---
> >>  scripts/Kconfig.include | 4 ++++
> >>  1 file changed, 4 insertions(+)
> >>
> >> diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
> >> index 85334dc..374e251 100644
> >> --- a/scripts/Kconfig.include
> >> +++ b/scripts/Kconfig.include
> >> @@ -35,6 +35,10 @@ ld-option = $(success,$(LD) -v $(1))
> >>  # Return y if the assembler supports <instr>, n otherwise
> >>  as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
> >>
> >> +# $(as-option,<flag>)
> >> +# Return y if the assembler supports <flag>, n otherwise
> >> +as-option =$(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero)
> >> +
> >
> >
> > I am still not convinced with using /dev/zero here.
> >
>
> Could you please elaborate a bit more?


I am just not familiar with this usage of /dev/zero.


The behavior of /dev/null is clear.
The read/write to /dev/null is described in the standard:
https://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap10.html

I just do not know whether the write to /dev/zero is
the defined-behavior or not.


Masahiro Yamada


>
> >
> > Does this work?
> >
> > as-option = $(success, cat /dev/null | $(CC) $(CLANG_FLAGS) $(1) -c -x
> > assembler -o /dev/null -)
> >
>
> I will try and get back to you.



Masahiro Yamada


>
> >
> > [1] Could you insert as-option between ld-option and as-instr ?
> >
>
> Sure, I will do it in the next version.
>
> > [2] Could you add some comments to explain why
> >      /dev/null -o /dev/null does not work?
> >
> >
>
> Comments are always a good think :) I will do in the next version.
>
> >
> >
> >
> >>  # check if $(CC) and $(LD) exist
> >>  $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
> >>  $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
> >> --
> >> 2.7.4
> >>
> >
> >
>
> --
> Regards,
> Vincenzo
--
Best Regards
Masahiro Yamada

Re: [PATCH v5 15/17] kconfig: Add support for 'as-option'

[Masahiro Yamada]

Hi,

On Mon, Feb 17, 2020 at 7:16 PM Vincenzo Frascino
<vincenzo.frascino@arm.com> wrote:
>
> Hi,
>
> On 17/02/2020 09:39, Masahiro Yamada wrote:
> > Hi.
> >
> > On Mon, Feb 17, 2020 at 6:29 PM Amit Daniel Kachhap
> > <amit.kachhap@arm.com> wrote:
> >>
> >> From: Vincenzo Frascino <vincenzo.frascino@arm.com>
> >>
> >> Currently kconfig does not have a feature that allows to detect if the
> >> used assembler supports a specific compilation option.
> >>
> >> Introduce 'as-option' to serve this purpose in the context of Kconfig:
> >>
> >>         config X
> >>                 def_bool $(as-option,...)
> >>
> >> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> >> Cc: linux-kbuild@vger.kernel.org
> >> Acked-by: Masahiro Yamada <masahiroy@kernel.org>
> >> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> >> Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
> >> ---
> >>  scripts/Kconfig.include | 4 ++++
> >>  1 file changed, 4 insertions(+)
> >>
> >> diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
> >> index 85334dc..374e251 100644
> >> --- a/scripts/Kconfig.include
> >> +++ b/scripts/Kconfig.include
> >> @@ -35,6 +35,10 @@ ld-option = $(success,$(LD) -v $(1))
> >>  # Return y if the assembler supports <instr>, n otherwise
> >>  as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
> >>
> >> +# $(as-option,<flag>)
> >> +# Return y if the assembler supports <flag>, n otherwise
> >> +as-option =$(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero)
> >> +
> >
> >
> > I am still not convinced with using /dev/zero here.
> >
>
> Could you please elaborate a bit more?


I am just not familiar with this usage of /dev/zero.


The behavior of /dev/null is clear.
The read/write to /dev/null is described in the standard:
https://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap10.html

I just do not know whether the write to /dev/zero is
the defined-behavior or not.


Masahiro Yamada


>
> >
> > Does this work?
> >
> > as-option = $(success, cat /dev/null | $(CC) $(CLANG_FLAGS) $(1) -c -x
> > assembler -o /dev/null -)
> >
>
> I will try and get back to you.



Masahiro Yamada


>
> >
> > [1] Could you insert as-option between ld-option and as-instr ?
> >
>
> Sure, I will do it in the next version.
>
> > [2] Could you add some comments to explain why
> >      /dev/null -o /dev/null does not work?
> >
> >
>
> Comments are always a good think :) I will do in the next version.
>
> >
> >
> >
> >>  # check if $(CC) and $(LD) exist
> >>  $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
> >>  $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
> >> --
> >> 2.7.4
> >>
> >
> >
>
> --
> Regards,
> Vincenzo
--
Best Regards
Masahiro Yamada

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Re: [PATCH v5 15/17] kconfig: Add support for 'as-option'

[Vincenzo Frascino]

[-- Attachment #1: Type: text/plain, Size: 1376 bytes --]

Hi Masahiro,

On 18/02/2020 00:37, Masahiro Yamada wrote:
> Hi,
> 

[...]
>>>
>>
>> Could you please elaborate a bit more?
> 
> 
> I am just not familiar with this usage of /dev/zero.
> 
> > The behavior of /dev/null is clear.
> The read/write to /dev/null is described in the standard:
> https://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap10.html
> 
> I just do not know whether the write to /dev/zero is
> the defined-behavior or not.
>

Even if /dev/null is more common for this use, in linux /dev/zero has the same
behavior for what concerns the write operation. In particular all write
operations to /dev/zero succeed with no other effects.

You do not find it at the link you provided because existence of /dev/zero is
not required by POSIX as far as I know, but the behavior is standardized by
Linux ABI hence I do not think it is going to change.

Please have a look at drivers/char/mem.c +818 where the operation is defined.

Based on this I propose to put a comment on why we are not using /dev/null in
this case accordingly with what you stated in your previous email, but to leave
the rule as is.

> 
> Masahiro Yamada
> 
> 
>>
>>>
>>> Does this work?
>>>
>>> as-option = $(success, cat /dev/null | $(CC) $(CLANG_FLAGS) $(1) -c -x
>>> assembler -o /dev/null -)
>>>
>>
[...]

-- 
Regards,
Vincenzo

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Re: [PATCH v5 15/17] kconfig: Add support for 'as-option'

[Vincenzo Frascino]

[-- Attachment #1: Type: text/plain, Size: 1376 bytes --]

Hi Masahiro,

On 18/02/2020 00:37, Masahiro Yamada wrote:
> Hi,
> 

[...]
>>>
>>
>> Could you please elaborate a bit more?
> 
> 
> I am just not familiar with this usage of /dev/zero.
> 
> > The behavior of /dev/null is clear.
> The read/write to /dev/null is described in the standard:
> https://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap10.html
> 
> I just do not know whether the write to /dev/zero is
> the defined-behavior or not.
>

Even if /dev/null is more common for this use, in linux /dev/zero has the same
behavior for what concerns the write operation. In particular all write
operations to /dev/zero succeed with no other effects.

You do not find it at the link you provided because existence of /dev/zero is
not required by POSIX as far as I know, but the behavior is standardized by
Linux ABI hence I do not think it is going to change.

Please have a look at drivers/char/mem.c +818 where the operation is defined.

Based on this I propose to put a comment on why we are not using /dev/null in
this case accordingly with what you stated in your previous email, but to leave
the rule as is.

> 
> Masahiro Yamada
> 
> 
>>
>>>
>>> Does this work?
>>>
>>> as-option = $(success, cat /dev/null | $(CC) $(CLANG_FLAGS) $(1) -c -x
>>> assembler -o /dev/null -)
>>>
>>
[...]

-- 
Regards,
Vincenzo

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[PATCH v5 16/17] arm64: compile the kernel with ptrauth return address signing

[Amit Daniel Kachhap]

From: Kristina Martsenko <kristina.martsenko@arm.com>

Compile all functions with two ptrauth instructions: PACIASP in the
prologue to sign the return address, and AUTIASP in the epilogue to
authenticate the return address (from the stack). If authentication
fails, the return will cause an instruction abort to be taken, followed
by an oops and killing the task.

This should help protect the kernel against attacks using
return-oriented programming. As ptrauth protects the return address, it
can also serve as a replacement for CONFIG_STACKPROTECTOR, although note
that it does not protect other parts of the stack.

The new instructions are in the HINT encoding space, so on a system
without ptrauth they execute as NOPs.

CONFIG_ARM64_PTR_AUTH now not only enables ptrauth for userspace and KVM
guests, but also automatically builds the kernel with ptrauth
instructions if the compiler supports it. If there is no compiler
support, we do not warn that the kernel was built without ptrauth
instructions.

GCC 7 and 8 support the -msign-return-address option, while GCC 9
deprecates that option and replaces it with -mbranch-protection. Support
both options.

Clang uses an external assembler hence this patch makes sure that the
correct parameters (-march=armv8.3-a) are passed down to help it recognize
the ptrauth instructions. This option is not used for GNU toolchain.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Co-developed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
[Amit: Cover leaf function, comments]
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 arch/arm64/Kconfig  | 20 +++++++++++++++++++-
 arch/arm64/Makefile | 11 +++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 115ceea..0f3ea01 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1499,6 +1499,7 @@ config ARM64_PTR_AUTH
 	bool "Enable support for pointer authentication"
 	default y
 	depends on !KVM || ARM64_VHE
+	depends on (CC_HAS_SIGN_RETURN_ADDRESS || CC_HAS_BRANCH_PROT_PAC_RET) && AS_HAS_PAC
 	help
 	  Pointer authentication (part of the ARMv8.3 Extensions) provides
 	  instructions for signing and authenticating pointers against secret
@@ -1506,11 +1507,17 @@ config ARM64_PTR_AUTH
 	  and other attacks.
 
 	  This option enables these instructions at EL0 (i.e. for userspace).
-
 	  Choosing this option will cause the kernel to initialise secret keys
 	  for each process at exec() time, with these keys being
 	  context-switched along with the process.
 
+	  If the compiler supports the -mbranch-protection or
+	  -msign-return-address flag (e.g. GCC 7 or later), then this option
+	  will also cause the kernel itself to be compiled with return address
+	  protection. In this case, and if the target hardware is known to
+	  support pointer authentication, then CONFIG_STACKPROTECTOR can be
+	  disabled with minimal loss of protection.
+
 	  The feature is detected at runtime. If the feature is not present in
 	  hardware it will not be advertised to userspace/KVM guest nor will it
 	  be enabled. However, KVM guest also require VHE mode and hence
@@ -1522,6 +1529,17 @@ config ARM64_PTR_AUTH
 	  but with the feature disabled. On such a system, this option should
 	  not be selected.
 
+config CC_HAS_BRANCH_PROT_PAC_RET
+	# GCC 9 or later, clang 8 or later
+	def_bool $(cc-option,-mbranch-protection=pac-ret+leaf)
+
+config CC_HAS_SIGN_RETURN_ADDRESS
+	# GCC 7, 8
+	def_bool $(cc-option,-msign-return-address=all)
+
+config AS_HAS_PAC
+	def_bool $(as-option,-Wa$(comma)-march=armv8.3-a)
+
 endmenu
 
 menu "ARMv8.5 architectural features"
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index dca1a97..ce5bdeb 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -65,6 +65,17 @@ stack_protector_prepare: prepare0
 					include/generated/asm-offsets.h))
 endif
 
+ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
+branch-prot-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all
+branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf
+# -march=armv8.3-a enables the non-nops instructions for PAC, to avoid the compiler
+# to generate them and consequently to break the single image contract we pass it
+# only to the assembler when clang is selected as a compiler. For the GNU toolchain
+# this option is not used.
+branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a
+KBUILD_CFLAGS += $(branch-prot-flags-y)
+endif
+
 ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
 KBUILD_CPPFLAGS	+= -mbig-endian
 CHECKFLAGS	+= -D__AARCH64EB__
-- 
2.7.4


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Re: [PATCH v5 16/17] arm64: compile the kernel with ptrauth return address signing

[Catalin Marinas]

On Mon, Feb 17, 2020 at 02:57:47PM +0530, Amit Daniel Kachhap wrote:
> +ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
> +branch-prot-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all
> +branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf
> +# -march=armv8.3-a enables the non-nops instructions for PAC, to avoid the compiler
> +# to generate them and consequently to break the single image contract we pass it
> +# only to the assembler when clang is selected as a compiler. For the GNU toolchain
> +# this option is not used.
> +branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a
> +KBUILD_CFLAGS += $(branch-prot-flags-y)
> +endif

Does this work with the clang integrated assembler? AFAIK it ignores the
-Wa, though it may be fine with the instructions generated by the
compiler. (while we don't officially support it, we merged patches to
facilitate it).

Also, the above comment says that the -Wa option is used only when
building with clang. I don't see this being the case in the patch above.

-- 
Catalin

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Re: [PATCH v5 16/17] arm64: compile the kernel with ptrauth return address signing

[Amit Kachhap]

On 2/28/20 11:53 PM, Catalin Marinas wrote:
> On Mon, Feb 17, 2020 at 02:57:47PM +0530, Amit Daniel Kachhap wrote:
>> +ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
>> +branch-prot-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all
>> +branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf
>> +# -march=armv8.3-a enables the non-nops instructions for PAC, to avoid the compiler
>> +# to generate them and consequently to break the single image contract we pass it
>> +# only to the assembler when clang is selected as a compiler. For the GNU toolchain
>> +# this option is not used.
>> +branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a
>> +KBUILD_CFLAGS += $(branch-prot-flags-y)
>> +endif
> 
> Does this work with the clang integrated assembler? AFAIK it ignores the
> -Wa, though it may be fine with the instructions generated by the
> compiler. (while we don't officially support it, we merged patches to
> facilitate it).
> 
> Also, the above comment says that the -Wa option is used only when
> building with clang. I don't see this being the case in the patch above.

I will check on this and get back.

> 

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Re: [PATCH v5 16/17] arm64: compile the kernel with ptrauth return address signing

[Mark Brown]

[-- Attachment #1.1: Type: text/plain, Size: 794 bytes --]

On Fri, Feb 28, 2020 at 06:23:37PM +0000, Catalin Marinas wrote:
> On Mon, Feb 17, 2020 at 02:57:47PM +0530, Amit Daniel Kachhap wrote:

> > +# only to the assembler when clang is selected as a compiler. For the GNU toolchain
> > +# this option is not used.
> > +branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a
> > +KBUILD_CFLAGS += $(branch-prot-flags-y)
> > +endif

> Does this work with the clang integrated assembler? AFAIK it ignores the
> -Wa, though it may be fine with the instructions generated by the
> compiler. (while we don't officially support it, we merged patches to
> facilitate it).

If the assembler integrated into the compiler doesn't cope with
instructions emitted by the compiler that seems like something we should
push to get fixed on the compiler side.

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Re: [PATCH v5 16/17] arm64: compile the kernel with ptrauth return address signing

[Vincenzo Frascino]

Hi Mark,

On 3/2/20 1:16 PM, Mark Brown wrote:
> On Fri, Feb 28, 2020 at 06:23:37PM +0000, Catalin Marinas wrote:
>> On Mon, Feb 17, 2020 at 02:57:47PM +0530, Amit Daniel Kachhap wrote:
> 
>>> +# only to the assembler when clang is selected as a compiler. For the GNU toolchain
>>> +# this option is not used.
>>> +branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a
>>> +KBUILD_CFLAGS += $(branch-prot-flags-y)
>>> +endif
> 
>> Does this work with the clang integrated assembler? AFAIK it ignores the
>> -Wa, though it may be fine with the instructions generated by the
>> compiler. (while we don't officially support it, we merged patches to
>> facilitate it).
> 
> If the assembler integrated into the compiler doesn't cope with
> instructions emitted by the compiler that seems like something we should
> push to get fixed on the compiler side.
> 

This option should be required only in the "hybrid" scenario of building the
kernel with clang+binutils.

The llvm assembler relies on "--target" and "-mbranch-protection=pac-ret+leaf"
so I do not think we should report or fix anything in this case.

This series is already passing the correct parameters to clang hence seems safe
to assume that it will continue doing so once the assembler will be switched to
the native version.

-- 
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Vincenzo

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Re: [PATCH v5 16/17] arm64: compile the kernel with ptrauth return address signing

[Amit Kachhap]

On 2/28/20 11:53 PM, Catalin Marinas wrote:
> On Mon, Feb 17, 2020 at 02:57:47PM +0530, Amit Daniel Kachhap wrote:
>> +ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
>> +branch-prot-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all
>> +branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf
>> +# -march=armv8.3-a enables the non-nops instructions for PAC, to avoid the compiler
>> +# to generate them and consequently to break the single image contract we pass it
>> +# only to the assembler when clang is selected as a compiler. For the GNU toolchain
>> +# this option is not used.
>> +branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a
>> +KBUILD_CFLAGS += $(branch-prot-flags-y)
>> +endif
> 
> Does this work with the clang integrated assembler? AFAIK it ignores the
> -Wa, though it may be fine with the instructions generated by the
> compiler. (while we don't officially support it, we merged patches to
> facilitate it).

Clang integrated assembler compiles some initial c files into object
files and those contains the ptrauth instructions.

As you said it ignores the -Wa flag.

> 
> Also, the above comment says that the -Wa option is used only when
> building with clang. I don't see this being the case in the patch above.

I will update the comments.

> 

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Re: [PATCH v5 16/17] arm64: compile the kernel with ptrauth return address signing

[Vincenzo Frascino]

Hi Catalin,

On 2/28/20 6:23 PM, Catalin Marinas wrote:
> On Mon, Feb 17, 2020 at 02:57:47PM +0530, Amit Daniel Kachhap wrote:
>> +ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
>> +branch-prot-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all
>> +branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf
>> +# -march=armv8.3-a enables the non-nops instructions for PAC, to avoid the compiler
>> +# to generate them and consequently to break the single image contract we pass it
>> +# only to the assembler when clang is selected as a compiler. For the GNU toolchain
>> +# this option is not used.
>> +branch-prot-flags-$(CONFIG_AS_HAS_PAC) += -Wa,-march=armv8.3-a
>> +KBUILD_CFLAGS += $(branch-prot-flags-y)
>> +endif
> 
> Does this work with the clang integrated assembler? AFAIK it ignores the
> -Wa, though it may be fine with the instructions generated by the
> compiler. (while we don't officially support it, we merged patches to
> facilitate it).
> 

The kernel is currently built with "-no-integrated-as" (Makefile +538) when
clang is selected. This means that the only assembler supported is the one
provide by binutils in this scenario.

The only patch series that I am aware of that is trying to do something with the
integrated as is [1] that uses it for inline assembly when LTO is enabled
(mainly for Android kernels at the moment). And this series is still being
reviewed.

Curiosity, which one is the series you are referring to? And how do I enable the
clang assembler for building the kernel?

[1] https://github.com/samitolvanen/linux/commits/clang-cfi

-- 
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Vincenzo

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[PATCH v5 17/17] lkdtm: arm64: test kernel pointer authentication

[Amit Daniel Kachhap]

This test is specific for arm64. When in-kernel Pointer Authentication
config is enabled, the return address stored in the stack is signed.
This feature helps in ROP kind of attack. If any parameters used to
generate the pac (<key, sp, lr>) is modified then this will fail in
the authentication stage and will lead to abort.

This test changes the input parameter APIA kernel keys to cause abort.
The pac computed from the new key can be same as last due to hash
collision so this is retried for few times as there is no reliable way
to compare the pacs. Even though this test may fail even after retries
but this may cause authentication failure at a later stage in earlier
function returns.

This test can be invoked as,
echo CORRUPT_PAC > /sys/kernel/debug/provoke-crash/DIRECT

or as below if inserted as a module,
insmod lkdtm.ko cpoint_name=DIRECT cpoint_type=CORRUPT_PAC cpoint_count=1

[   13.118166] lkdtm: Performing direct entry CORRUPT_PAC
[   13.118298] lkdtm: Clearing PAC from the return address
[   13.118466] Unable to handle kernel paging request at virtual address bfff8000108648ec
[   13.118626] Mem abort info:
[   13.118666]   ESR = 0x86000004
[   13.118866]   EC = 0x21: IABT (current EL), IL = 32 bits
[   13.118966]   SET = 0, FnV = 0
[   13.119117]   EA = 0, S1PTW = 0

Cc: Kees Cook <keescook@chromium.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
 drivers/misc/lkdtm/bugs.c  | 36 ++++++++++++++++++++++++++++++++++++
 drivers/misc/lkdtm/core.c  |  1 +
 drivers/misc/lkdtm/lkdtm.h |  1 +
 3 files changed, 38 insertions(+)

diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index de87693..cc92bc3 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -378,3 +378,39 @@ void lkdtm_DOUBLE_FAULT(void)
 	pr_err("XFAIL: this test is ia32-only\n");
 #endif
 }
+
+#ifdef CONFIG_ARM64_PTR_AUTH
+static noinline void change_pac_parameters(void)
+{
+	/* Reset the keys of current task */
+	ptrauth_thread_init_kernel(current);
+	ptrauth_thread_switch_kernel(current);
+}
+
+#define CORRUPT_PAC_ITERATE	10
+noinline void lkdtm_CORRUPT_PAC(void)
+{
+	int i;
+
+	if (!system_supports_address_auth()) {
+		pr_err("FAIL: arm64 pointer authentication feature not present\n");
+		return;
+	}
+
+	pr_info("Change the PAC parameters to force function return failure\n");
+	/*
+	 * Pac is a hash value computed from input keys, return address and
+	 * stack pointer. As pac has fewer bits so there is a chance of
+	 * collision, so iterate few times to reduce the collision probability.
+	 */
+	for (i = 0; i < CORRUPT_PAC_ITERATE; i++)
+		change_pac_parameters();
+
+	pr_err("FAIL: %s test failed. Kernel may be unstable from here\n", __func__);
+}
+#else /* !CONFIG_ARM64_PTR_AUTH */
+noinline void lkdtm_CORRUPT_PAC(void)
+{
+	pr_err("FAIL: arm64 pointer authentication config disabled\n");
+}
+#endif
diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index ee0d6e7..5ce4ac8 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -116,6 +116,7 @@ static const struct crashtype crashtypes[] = {
 	CRASHTYPE(STACK_GUARD_PAGE_LEADING),
 	CRASHTYPE(STACK_GUARD_PAGE_TRAILING),
 	CRASHTYPE(UNSET_SMEP),
+	CRASHTYPE(CORRUPT_PAC),
 	CRASHTYPE(UNALIGNED_LOAD_STORE_WRITE),
 	CRASHTYPE(OVERWRITE_ALLOCATION),
 	CRASHTYPE(WRITE_AFTER_FREE),
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index c56d23e..8d13d01 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -31,6 +31,7 @@ void lkdtm_UNSET_SMEP(void);
 #ifdef CONFIG_X86_32
 void lkdtm_DOUBLE_FAULT(void);
 #endif
+void lkdtm_CORRUPT_PAC(void);
 
 /* lkdtm_heap.c */
 void __init lkdtm_heap_init(void);
-- 
2.7.4


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