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SubjectRe: [RFC 16/17] arm64: initialize and switch ptrauth kernel keys
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On 10/05/2018 02:17 PM, Kristina Martsenko wrote:
> Set up keys to use pointer auth in the kernel. Each task has its own
> APIAKey, which is initialized during fork. The key is changed during
> context switch and on kernel entry from EL0.
>
> A function that changes the key cannot return, so inline such functions.


For all the RFC patches in this series,
Reviewed-by: Amit Daniel Kachhap <amit.kachhap@arm.com>

>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
> ---
> arch/arm64/include/asm/pointer_auth.h | 9 ++++++++-
> arch/arm64/include/asm/ptrauth-asm.h | 13 +++++++++++++
> arch/arm64/include/asm/thread_info.h | 1 +
> arch/arm64/kernel/asm-offsets.c | 1 +
> arch/arm64/kernel/entry.S | 4 ++++
> arch/arm64/kernel/process.c | 3 +++
> arch/arm64/kernel/smp.c | 3 +++
> 7 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
> index 0634f06c3af2..e94ca7df8dab 100644
> --- a/arch/arm64/include/asm/pointer_auth.h
> +++ b/arch/arm64/include/asm/pointer_auth.h
> @@ -50,12 +50,13 @@ do { \
> write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1); \
> } while (0)
>
> -static inline void ptrauth_keys_switch(struct ptrauth_keys *keys)
> +static __always_inline void ptrauth_keys_switch(struct ptrauth_keys *keys)
> {
> if (!cpus_have_const_cap(ARM64_HAS_ADDRESS_AUTH))
> return;
>
> __ptrauth_key_install(APIA, keys->apia);
> + isb();
> }
>
> static __always_inline void ptrauth_cpu_enable(void)
> @@ -85,11 +86,17 @@ static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr)
>
> #define ptrauth_task_init_user(tsk) \
> ptrauth_keys_init(&(tsk)->thread_info.keys_user)
> +#define ptrauth_task_init_kernel(tsk) \
> + ptrauth_keys_init(&(tsk)->thread_info.keys_kernel)
> +#define ptrauth_task_switch(tsk) \
> + ptrauth_keys_switch(&(tsk)->thread_info.keys_kernel)
>
> #else /* CONFIG_ARM64_PTR_AUTH */
> #define __no_ptrauth
> #define ptrauth_strip_insn_pac(lr) (lr)
> #define ptrauth_task_init_user(tsk)
> +#define ptrauth_task_init_kernel(tsk)
> +#define ptrauth_task_switch(tsk)
> #define ptrauth_cpu_enable(tsk)
> #endif /* CONFIG_ARM64_PTR_AUTH */
>
> diff --git a/arch/arm64/include/asm/ptrauth-asm.h b/arch/arm64/include/asm/ptrauth-asm.h
> index f50bdfc4046c..3ef1cc8903d5 100644
> --- a/arch/arm64/include/asm/ptrauth-asm.h
> +++ b/arch/arm64/include/asm/ptrauth-asm.h
> @@ -16,11 +16,24 @@ alternative_if ARM64_HAS_ADDRESS_AUTH
> alternative_else_nop_endif
> .endm
>
> + .macro ptrauth_keys_install_kernel tsk, tmp
> +alternative_if ARM64_HAS_ADDRESS_AUTH
> + ldr \tmp, [\tsk, #(TSK_TI_KEYS_KERNEL + PTRAUTH_KEY_APIALO)]
> + msr_s SYS_APIAKEYLO_EL1, \tmp
> + ldr \tmp, [\tsk, #(TSK_TI_KEYS_KERNEL + PTRAUTH_KEY_APIAHI)]
> + msr_s SYS_APIAKEYHI_EL1, \tmp
> + isb
> +alternative_else_nop_endif
> + .endm
> +
> #else /* CONFIG_ARM64_PTR_AUTH */
>
> .macro ptrauth_keys_install_user tsk, tmp
> .endm
>
> + .macro ptrauth_keys_install_kernel tsk, tmp
> + .endm
> +
> #endif /* CONFIG_ARM64_PTR_AUTH */
>
> #endif /* __ASM_PTRAUTH_ASM_H */
> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
> index ea9272fb52d4..e3ec5345addc 100644
> --- a/arch/arm64/include/asm/thread_info.h
> +++ b/arch/arm64/include/asm/thread_info.h
> @@ -46,6 +46,7 @@ struct thread_info {
> int preempt_count; /* 0 => preemptable, <0 => bug */
> #ifdef CONFIG_ARM64_PTR_AUTH
> struct ptrauth_keys keys_user;
> + struct ptrauth_keys keys_kernel;
> #endif
> };
>
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index b6be0dd037fd..6c61c9722b47 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -47,6 +47,7 @@ int main(void)
> #endif
> #ifdef CONFIG_ARM64_PTR_AUTH
> DEFINE(TSK_TI_KEYS_USER, offsetof(struct task_struct, thread_info.keys_user));
> + DEFINE(TSK_TI_KEYS_KERNEL, offsetof(struct task_struct, thread_info.keys_kernel));
> #endif
> DEFINE(TSK_STACK, offsetof(struct task_struct, stack));
> BLANK();
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index 1e925f6d2978..a4503da445f7 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -250,6 +250,10 @@ alternative_else_nop_endif
> msr sp_el0, tsk
> .endif
>
> + .if \el == 0
> + ptrauth_keys_install_kernel tsk, x20

There is 1 function before "__uaccess_ttbr0_disable" for which
__always_inline attribute can be set instead of just inline.

> + .endif
> +
> /*
> * Registers that may be useful after this macro is invoked:
> *
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 857ae05cd04c..a866996610de 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -330,6 +330,8 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
> */
> fpsimd_flush_task_state(p);
>
> + ptrauth_task_init_kernel(p);
> +
> if (likely(!(p->flags & PF_KTHREAD))) {
> *childregs = *current_pt_regs();
> childregs->regs[0] = 0;
> @@ -426,6 +428,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
> contextidr_thread_switch(next);
> entry_task_switch(next);
> uao_thread_switch(next);
> + ptrauth_task_switch(next);
>
> /*
> * Complete any pending TLB or cache maintenance on this CPU in case
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 09690024dce8..d952dd62c780 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -212,6 +212,7 @@ asmlinkage notrace void secondary_start_kernel(void)
> */
> check_local_cpu_capabilities();
>
> + ptrauth_task_switch(current);
> ptrauth_cpu_enable();
>
> if (cpu_ops[cpu]->cpu_postboot)
> @@ -418,6 +419,8 @@ void __init __no_ptrauth smp_prepare_boot_cpu(void)
> jump_label_init();
> cpuinfo_store_boot_cpu();
>
> + ptrauth_task_init_kernel(current);
> + ptrauth_task_switch(current);
> ptrauth_cpu_enable();
> }
>
>

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