[PATCH v2 6/8] arm64: stacktrace: remove stack type from fp translator

[Will Deacon]

On Fri, Aug 05, 2022 at 01:45:20PM +0100, Mark Rutland wrote:
> In subsequent patches we'll remove the stack_type enum, and move the FP
> translation logic out of the raw FP unwind code.
> 
> In preparation for doing so, this patch removes the type parameter from
> the FP translation callback, and modifies kvm_nvhe_stack_kern_va() to
> determine the relevant stack directly.
> 
> So that kvm_nvhe_stack_kern_va() can use the stackinfo_*() helpers,
> these are moved earlier in the file, but are not modified in any way.
> 
> Signed-off-by: Mark Rutland <mark.rutland at arm.com>
> Reviewed-by: Kalesh Singh <kaleshsingh at google.com>
> Cc: Fuad Tabba <tabba at google.com>
> Cc: Madhavan T. Venkataraman <madvenka at linux.microsoft.com>
> Cc: Marc Zyngier <maz at kernel.org>
> Cc: Mark Brown <broonie at kernel.org>
> ---
>  arch/arm64/include/asm/stacktrace/common.h |  6 +-
>  arch/arm64/kvm/stacktrace.c                | 78 ++++++++++++----------
>  2 files changed, 43 insertions(+), 41 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/stacktrace/common.h b/arch/arm64/include/asm/stacktrace/common.h
> index 0071f2459c703..0bd9d7ad295e0 100644
> --- a/arch/arm64/include/asm/stacktrace/common.h
> +++ b/arch/arm64/include/asm/stacktrace/common.h
> @@ -114,13 +114,11 @@ static inline void unwind_init_common(struct unwind_state *state,
>   * a kernel address.
>   *
>   * @fp:   the frame pointer to be updated to its kernel address.
> - * @type: the stack type associated with frame pointer @fp
>   *
>   * Returns true and success and @fp is updated to the corresponding
>   * kernel virtual address; otherwise returns false.
>   */
> -typedef bool (*stack_trace_translate_fp_fn)(unsigned long *fp,
> -					    enum stack_type type);
> +typedef bool (*stack_trace_translate_fp_fn)(unsigned long *fp);
>  
>  /*
>   * on_accessible_stack_fn() - Check whether a stack range is on any
> @@ -165,7 +163,7 @@ unwind_next_frame_record(struct unwind_state *state,
>  	 * If fp is not from the current address space perform the necessary
>  	 * translation before dereferencing it to get the next fp.
>  	 */
> -	if (translate_fp && !translate_fp(&kern_fp, info.type))
> +	if (translate_fp && !translate_fp(&kern_fp))
>  		return -EINVAL;
>  
>  	/*
> diff --git a/arch/arm64/kvm/stacktrace.c b/arch/arm64/kvm/stacktrace.c
> index 26927344a2632..abdc231ae70fd 100644
> --- a/arch/arm64/kvm/stacktrace.c
> +++ b/arch/arm64/kvm/stacktrace.c
> @@ -21,6 +21,34 @@
>  
>  #include <asm/stacktrace/nvhe.h>
>  
> +static struct stack_info stackinfo_get_overflow(void)
> +{
> +	struct kvm_nvhe_stacktrace_info *stacktrace_info
> +				= this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
> +	unsigned long low = (unsigned long)stacktrace_info->overflow_stack_base;
> +	unsigned long high = low + OVERFLOW_STACK_SIZE;
> +
> +	return (struct stack_info) {
> +		.low = low,
> +		.high = high,
> +		.type = STACK_TYPE_OVERFLOW,
> +	};
> +}
> +
> +static struct stack_info stackinfo_get_hyp(void)
> +{
> +	struct kvm_nvhe_stacktrace_info *stacktrace_info
> +				= this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
> +	unsigned long low = (unsigned long)stacktrace_info->stack_base;
> +	unsigned long high = low + PAGE_SIZE;
> +
> +	return (struct stack_info) {
> +		.low = low,
> +		.high = high,
> +		.type = STACK_TYPE_HYP,
> +	};
> +}
> +
>  /*
>   * kvm_nvhe_stack_kern_va - Convert KVM nVHE HYP stack addresses to a kernel VAs
>   *
> @@ -34,27 +62,31 @@
>   * Returns true on success and updates @addr to its corresponding kernel VA;
>   * otherwise returns false.
>   */
> -static bool kvm_nvhe_stack_kern_va(unsigned long *addr,
> -				   enum stack_type type)
> +static bool kvm_nvhe_stack_kern_va(unsigned long *addr)
>  {
>  	struct kvm_nvhe_stacktrace_info *stacktrace_info;
>  	unsigned long hyp_base, kern_base, hyp_offset;
> +	struct stack_info stack;
>  
>  	stacktrace_info = this_cpu_ptr_nvhe_sym(kvm_stacktrace_info);
>  
> -	switch (type) {
> -	case STACK_TYPE_HYP:
> +	stack = stackinfo_get_hyp();
> +	if (stackinfo_on_stack(&stack, *addr, 1)) {
>  		kern_base = (unsigned long)*this_cpu_ptr(&kvm_arm_hyp_stack_page);
>  		hyp_base = (unsigned long)stacktrace_info->stack_base;
> -		break;
> -	case STACK_TYPE_OVERFLOW:
> +		goto found;
> +	}
> +
> +	stack = stackinfo_get_overflow();
> +	if (stackinfo_on_stack(&stack, *addr, 1)) {

Why is '1' the appropriate size for these two checks, given that addr points
at an unsigned long?

Will