Subject: Re: [PATCH] arm64: kvm: Annotate assembly using modern annoations

From: Marc Zyngier <[email-masked]>
Date: Thu, 13 Feb 2020 21:36:56 +0000

Hi Mark,

On 2020-02-13 15:38, Mark Brown wrote:
> In an effort to clarify and simplify the annotation of assembly 
> functions
> in the kernel new macros have been introduced. These replace ENTRY and
> ENDPROC with separate annotations for standard C callable functions,
> data and code with different calling conventions.  Update the
> annotations in the kvm code to the new macros.
> 
> Signed-off-by: Mark Brown <[email-masked]>
> ---
>  arch/arm64/kvm/hyp-init.S      |  8 ++++----
>  arch/arm64/kvm/hyp.S           |  4 ++--
>  arch/arm64/kvm/hyp/fpsimd.S    |  8 ++++----
>  arch/arm64/kvm/hyp/hyp-entry.S | 27 ++++++++++++++++-----------
>  4 files changed, 26 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
> index 160be2b4696d..84f32cf5abc7 100644
> --- a/arch/arm64/kvm/hyp-init.S
> +++ b/arch/arm64/kvm/hyp-init.S
> @@ -18,7 +18,7 @@
> 
>  	.align	11
> 
> -ENTRY(__kvm_hyp_init)
> +SYM_CODE_START(__kvm_hyp_init)
>  	ventry	__invalid		// Synchronous EL2t
>  	ventry	__invalid		// IRQ EL2t
>  	ventry	__invalid		// FIQ EL2t
> @@ -117,9 +117,9 @@ CPU_BE(	orr	x4, x4, #SCTLR_ELx_EE)
> 
>  	/* Hello, World! */
>  	eret
> -ENDPROC(__kvm_hyp_init)
> +SYM_CODE_END(__kvm_hyp_init)
> 
> -ENTRY(__kvm_handle_stub_hvc)
> +SYM_CODE_START(__kvm_handle_stub_hvc)
>  	cmp	x0, #HVC_SOFT_RESTART
>  	b.ne	1f
> 
> @@ -158,7 +158,7 @@ reset:
>  	ldr	x0, =HVC_STUB_ERR
>  	eret
> 
> -ENDPROC(__kvm_handle_stub_hvc)
> +SYM_CODE_END(__kvm_handle_stub_hvc)
> 
>  	.ltorg
> 
> diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
> index c0094d520dff..3c79a1124af2 100644
> --- a/arch/arm64/kvm/hyp.S
> +++ b/arch/arm64/kvm/hyp.S
> @@ -28,7 +28,7 @@
>   * and is used to implement hyp stubs in the same way as in
>   * arch/arm64/kernel/hyp_stub.S.
>   */
> -ENTRY(__kvm_call_hyp)
> +SYM_FUNC_START(__kvm_call_hyp)

I'm not convinced by this particular change. _kvm_call_hyp is called 
directly from
C, and behaves almost like a normal function. What's the issue here?

>  	hvc	#0
>  	ret
> -ENDPROC(__kvm_call_hyp)
> +SYM_FUNC_END(__kvm_call_hyp)
> diff --git a/arch/arm64/kvm/hyp/fpsimd.S b/arch/arm64/kvm/hyp/fpsimd.S
> index 78ff53225691..5b8ff517ff10 100644
> --- a/arch/arm64/kvm/hyp/fpsimd.S
> +++ b/arch/arm64/kvm/hyp/fpsimd.S
> @@ -11,12 +11,12 @@
>  	.text
>  	.pushsection	.hyp.text, "ax"
> 
> -ENTRY(__fpsimd_save_state)
> +SYM_FUNC_START(__fpsimd_save_state)
>  	fpsimd_save	x0, 1
>  	ret
> -ENDPROC(__fpsimd_save_state)
> +SYM_FUNC_END(__fpsimd_save_state)
> 
> -ENTRY(__fpsimd_restore_state)
> +SYM_FUNC_START(__fpsimd_restore_state)
>  	fpsimd_restore	x0, 1
>  	ret
> -ENDPROC(__fpsimd_restore_state)
> +SYM_FUNC_END(__fpsimd_restore_state)

Same for these. The only reason they are not written inline assemply
in a normal C function is that we have these fpsimd_* macros.

> diff --git a/arch/arm64/kvm/hyp/hyp-entry.S 
> b/arch/arm64/kvm/hyp/hyp-entry.S
> index ffa68d5713f1..f7b0cb189b77 100644
> --- a/arch/arm64/kvm/hyp/hyp-entry.S
> +++ b/arch/arm64/kvm/hyp/hyp-entry.S
> @@ -180,7 +180,7 @@ el2_error:
>  	eret
>  	sb
> 
> -ENTRY(__hyp_do_panic)
> +SYM_FUNC_START(__hyp_do_panic)
>  	mov	lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
>  		      PSR_MODE_EL1h)
>  	msr	spsr_el2, lr
> @@ -188,18 +188,19 @@ ENTRY(__hyp_do_panic)
>  	msr	elr_el2, lr
>  	eret
>  	sb
> -ENDPROC(__hyp_do_panic)
> +SYM_FUNC_END(__hyp_do_panic)
> 
> -ENTRY(__hyp_panic)
> +SYM_CODE_START(__hyp_panic)
>  	get_host_ctxt x0, x1
>  	b	hyp_panic
> -ENDPROC(__hyp_panic)
> +SYM_CODE_END(__hyp_panic)
> 
>  .macro invalid_vector	label, target = __hyp_panic
>  	.align	2
> +SYM_CODE_START(\label)
>  \label:
>  	b \target
> -ENDPROC(\label)
> +SYM_CODE_END(\label)
>  .endm
> 
>  	/* None of these should ever happen */
> @@ -246,7 +247,7 @@ check_preamble_length 661b, 662b
>  check_preamble_length 661b, 662b
>  .endm
> 
> -ENTRY(__kvm_hyp_vector)
> +SYM_CODE_START(__kvm_hyp_vector)
>  	invalid_vect	el2t_sync_invalid	// Synchronous EL2t
>  	invalid_vect	el2t_irq_invalid	// IRQ EL2t
>  	invalid_vect	el2t_fiq_invalid	// FIQ EL2t
> @@ -266,7 +267,7 @@ ENTRY(__kvm_hyp_vector)
>  	valid_vect	el1_irq			// IRQ 32-bit EL1
>  	invalid_vect	el1_fiq_invalid		// FIQ 32-bit EL1
>  	valid_vect	el1_error		// Error 32-bit EL1
> -ENDPROC(__kvm_hyp_vector)
> +SYM_CODE_END(__kvm_hyp_vector)
> 
>  #ifdef CONFIG_KVM_INDIRECT_VECTORS
>  .macro hyp_ventry
> @@ -311,15 +312,18 @@ alternative_cb_end
>  .endm
> 
>  	.align	11
> -ENTRY(__bp_harden_hyp_vecs_start)
> +SYM_CODE_START_NOALIGN(__bp_harden_hyp_vecs)
> +SYM_INNER_LABEL(__bp_harden_hyp_vecs_start, SYM_L_GLOBAL)

Why isn't SYM_CODE_START_NOALIGN enough? And what is the rational for
the _NOALIGN, btw? I'd expect an alignment of 2kB to be more than 
enough.

>  	.rept BP_HARDEN_EL2_SLOTS
>  	generate_vectors
>  	.endr
> -ENTRY(__bp_harden_hyp_vecs_end)
> +SYM_INNER_LABEL(__bp_harden_hyp_vecs_end, SYM_L_GLOBAL)
> +SYM_CODE_END(__bp_harden_hyp_vecs)

Same here.

> 
>  	.popsection
> 
> -ENTRY(__smccc_workaround_1_smc_start)
> +SYM_CODE_START(__smccc_workaround_1_smc)
> +SYM_INNER_LABEL(__smccc_workaround_1_smc_start, SYM_L_GLOBAL)
>  	esb
>  	sub	sp, sp, #(8 * 4)
>  	stp	x2, x3, [sp, #(8 * 0)]
> @@ -329,5 +333,6 @@ ENTRY(__smccc_workaround_1_smc_start)
>  	ldp	x2, x3, [sp, #(8 * 0)]
>  	ldp	x0, x1, [sp, #(8 * 2)]
>  	add	sp, sp, #(8 * 4)
> -ENTRY(__smccc_workaround_1_smc_end)
> +SYM_INNER_LABEL(__smccc_workaround_1_smc_end, SYM_L_GLOBAL)
> +SYM_CODE_END(__smccc_workaround_1_smc)
>  #endif

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

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