[PATCH v3 4/6] arm: Add icache invalidation on switch_mm for Cortex-A15

[Christoffer Dall]

On Thu, Jan 25, 2018 at 03:21:37PM +0000, Marc Zyngier wrote:
> In order to avoid aliasing attacks against the branch predictor,
> Cortex-A15 require to invalidate the BTB when switching
> from one user context to another. The only way to do so on this
> CPU is to perform an ICIALLU, having set ACTLR[0] to 1 from secure
> mode.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> ---
>  arch/arm/mm/proc-v7-2level.S | 10 ++++++++++
>  arch/arm/mm/proc-v7-3level.S | 16 ++++++++++++++++
>  arch/arm/mm/proc-v7.S        | 18 +++++++++++++++++-
>  3 files changed, 43 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/mm/proc-v7-2level.S b/arch/arm/mm/proc-v7-2level.S
> index 0422e58b74e8..7dc9e1c69039 100644
> --- a/arch/arm/mm/proc-v7-2level.S
> +++ b/arch/arm/mm/proc-v7-2level.S
> @@ -40,7 +40,17 @@
>   *	Note that we always need to flush BTAC/BTB if IBE is set
>   *	even on Cortex-A8 revisions not affected by 430973.
>   *	If IBE is not set, the flush BTAC/BTB won't do anything.
> + *
> + *	Cortex-A15 requires ACTLR[0] to be set from secure in order
> + *	for the icache invalidation to also invalidate the BTB.
>   */

Seems like we can read (but not write) this bit from non-secure.  Should
we test if it's set somewhere during boot and warn the user if not?

> +ENTRY(cpu_ca15_switch_mm)
> +#ifdef CONFIG_MMU
> +	mcr	p15, 0, r0, c7, c5, 0			@ ICIALLU
> +	isb
> +	b	cpu_v7_switch_mm
> +#endif
> +ENDPROC(cpu_ca15_switch_mm)
>  ENTRY(cpu_v7_btbinv_switch_mm)
>  #ifdef CONFIG_MMU
>  	mov	r2, #0
> diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S
> index 934272e1fa08..cae6bb4da956 100644
> --- a/arch/arm/mm/proc-v7-3level.S
> +++ b/arch/arm/mm/proc-v7-3level.S
> @@ -71,6 +71,22 @@ ENTRY(cpu_v7_switch_mm)
>  ENDPROC(cpu_v7_switch_mm)
>  ENDPROC(cpu_v7_btbinv_switch_mm)
>  
> +/*
> + *	Cortex-A15 requires ACTLR[0] to be set from secure in order
> + *	for the icache invalidation to also invalidate the BTB.
> + */
> +ENTRY(cpu_ca15_switch_mm)
> +#ifdef CONFIG_MMU
> +	mcr	p15, 0, r0, c7, c5, 0			@ ICIALLU
> +	mmid	r2, r2
> +	asid	r2, r2
> +	orr	rpgdh, rpgdh, r2, lsl #(48 - 32)	@ upper 32-bits of pgd
> +	mcrr	p15, 0, rpgdl, rpgdh, c2		@ set TTB 0
> +	isb
> +#endif
> +	ret	lr
> +ENDPROC(cpu_ca15_switch_mm)
> +

There's some potential for code shaing with cpu_v7_switch_mm here,
either via a macro or by simply calling cpu_v7_switch_mm from
cpu_ca15_switch_mm, but I'm not sure if we care?

>  #ifdef __ARMEB__
>  #define rl r3
>  #define rh r2
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
> index 0a14967fd400..9310fd9aa1cf 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -173,6 +173,21 @@ ENDPROC(cpu_v7_do_resume)
>  	globl_equ	cpu_v7_btbinv_do_resume,	cpu_v7_do_resume
>  #endif
>  
> +/*
> + * Cortex-A15 that require an icache invalidation on switch_mm

uber nit: The wording is weird here, how about "Cortex-A15 requires
an..." ?

> + */
> +	globl_equ	cpu_ca15_proc_init,		cpu_v7_proc_init
> +	globl_equ	cpu_ca15_proc_fin,		cpu_v7_proc_fin
> +	globl_equ	cpu_ca15_reset,			cpu_v7_reset
> +	globl_equ	cpu_ca15_do_idle,		cpu_v7_do_idle
> +	globl_equ	cpu_ca15_dcache_clean_area, 	cpu_v7_dcache_clean_area
> +	globl_equ	cpu_ca15_set_pte_ext,		cpu_v7_set_pte_ext
> +	globl_equ	cpu_ca15_suspend_size,		cpu_v7_suspend_size
> +#ifdef CONFIG_ARM_CPU_SUSPEND
> +	globl_equ	cpu_ca15_do_suspend,		cpu_v7_do_suspend
> +	globl_equ	cpu_ca15_do_resume,		cpu_v7_do_resume
> +#endif
> +
>  /*
>   * Cortex-A9 processor functions
>   */
> @@ -549,6 +564,7 @@ __v7_setup_stack:
>  	@ define struct processor (see <asm/proc-fns.h> and proc-macros.S)
>  	define_processor_functions v7, dabort=v7_early_abort, pabort=v7_pabort, suspend=1
>  	define_processor_functions v7_btbinv, dabort=v7_early_abort, pabort=v7_pabort, suspend=1
> +	define_processor_functions ca15, dabort=v7_early_abort, pabort=v7_pabort, suspend=1
>  #ifndef CONFIG_ARM_LPAE
>  	define_processor_functions ca9mp, dabort=v7_early_abort, pabort=v7_pabort, suspend=1
>  #endif
> @@ -668,7 +684,7 @@ __v7_ca12mp_proc_info:
>  __v7_ca15mp_proc_info:
>  	.long	0x410fc0f0
>  	.long	0xff0ffff0
> -	__v7_proc __v7_ca15mp_proc_info, __v7_ca15mp_setup
> +	__v7_proc __v7_ca15mp_proc_info, __v7_ca15mp_setup, proc_fns = ca15_processor_functions
>  	.size	__v7_ca15mp_proc_info, . - __v7_ca15mp_proc_info
>  
>  	/*
> -- 
> 2.14.2
> 

Thanks,
-Christoffer