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arm64: install user ptrauth keys at kernel exit time

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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>
Reviewed-by: James Morse <james.morse@arm.com>
Reviewed-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com>
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>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Kristina Martsenko 2020-03-13 14:34:51 +05:30 committed by Catalin Marinas
parent 91a1b6ccff
commit be12984256
6 changed files with 64 additions and 26 deletions
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49
arch/arm64/include/asm/asm_pointer_auth.h Normal file
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@ -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
* thread.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 */

23
arch/arm64/include/asm/pointer_auth.h
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@ -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 */

11
arch/arm64/kernel/asm-offsets.c
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@ -40,6 +40,9 @@ int main(void)
#endif
BLANK();
DEFINE(THREAD_CPU_CONTEXT, offsetof(struct task_struct, thread.cpu_context));
#ifdef CONFIG_ARM64_PTR_AUTH
DEFINE(THREAD_KEYS_USER, offsetof(struct task_struct, thread.keys_user));
#endif
BLANK();
DEFINE(S_X0, offsetof(struct pt_regs, regs[0]));
DEFINE(S_X2, offsetof(struct pt_regs, regs[2]));
@ -127,6 +130,14 @@ int main(void)
#ifdef CONFIG_ARM_SDE_INTERFACE
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;
}

3
arch/arm64/kernel/entry.S
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@ -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

3
arch/arm64/kernel/pointer_auth.c
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@ -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;
}

1
arch/arm64/kernel/process.c
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@ -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);
/*