Re: [PATCH v5 5/6] of: kexec: Refactor IMA buffer related functions to make them reusable

[Jonathan McDowell]

On Wed, Jul 06, 2022 at 11:23:28AM -0400, Stefan Berger wrote:
> Refactor IMA buffer related functions to make them reusable for carrying
> TPM logs across kexec.
> 
> Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> Cc: Frank Rowand <frowand.list@xxxxxxxxx>
> Cc: Mimi Zohar <zohar@xxxxxxxxxxxxx>
> 
> ---
> v5:
>  - Rebased on Jonathan McDowell's commit "b69a2afd5afc x86/kexec: Carry
>    forward IMA measurement log on kexec"
> v4:
>  - Move debug output into setup_buffer()
> ---
>  drivers/of/kexec.c | 125 ++++++++++++++++++++++++++-------------------
>  1 file changed, 73 insertions(+), 52 deletions(-)
> 
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> index 548dd5b1b5c1..404a86bb3978 100644
> --- a/drivers/of/kexec.c
> +++ b/drivers/of/kexec.c
> @@ -117,45 +117,56 @@ static int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr,
>  }
>  
>  #ifdef CONFIG_HAVE_IMA_KEXEC
> -/**
> - * ima_get_kexec_buffer - get IMA buffer from the previous kernel
> - * @addr:	On successful return, set to point to the buffer contents.
> - * @size:	On successful return, set to the buffer size.
> - *
> - * Return: 0 on success, negative errno on error.
> - */
> -int __init ima_get_kexec_buffer(void **addr, size_t *size)
> +static int get_kexec_buffer(const char *name, unsigned long *addr, size_t *size)

I think this new function can + should be marked __init as well; it's
only called from the existing IMA functions and your new
tpm_get_kexec_buffer which is already __init.

>  {
>  	int ret, len;
> -	unsigned long tmp_addr;
>  	unsigned long start_pfn, end_pfn;
> -	size_t tmp_size;
>  	const void *prop;
>  
> -	prop = of_get_property(of_chosen, "linux,ima-kexec-buffer", &len);
> +	prop = of_get_property(of_chosen, name, &len);
>  	if (!prop)
>  		return -ENOENT;
>  
> -	ret = do_get_kexec_buffer(prop, len, &tmp_addr, &tmp_size);
> +	ret = do_get_kexec_buffer(prop, len, addr, size);
>  	if (ret)
>  		return ret;
>  
> -	/* Do some sanity on the returned size for the ima-kexec buffer */
> -	if (!tmp_size)
> +	/* Do some sanity on the returned size for the kexec buffer */
> +	if (!*size)
>  		return -ENOENT;
>  
>  	/*
>  	 * Calculate the PFNs for the buffer and ensure
>  	 * they are with in addressable memory.
>  	 */
> -	start_pfn = PHYS_PFN(tmp_addr);
> -	end_pfn = PHYS_PFN(tmp_addr + tmp_size - 1);
> +	start_pfn = PHYS_PFN(*addr);
> +	end_pfn = PHYS_PFN(*addr + *size - 1);
>  	if (!page_is_ram(start_pfn) || !page_is_ram(end_pfn)) {
> -		pr_warn("IMA buffer at 0x%lx, size = 0x%zx beyond memory\n",
> -			tmp_addr, tmp_size);
> +		pr_warn("%s buffer at 0x%lx, size = 0x%zx beyond memory\n",
> +			name, *addr, *size);
>  		return -EINVAL;
>  	}
>  
> +	return 0;
> +}
> +
> +/**
> + * ima_get_kexec_buffer - get IMA buffer from the previous kernel
> + * @addr:	On successful return, set to point to the buffer contents.
> + * @size:	On successful return, set to the buffer size.
> + *
> + * Return: 0 on success, negative errno on error.
> + */
> +int __init ima_get_kexec_buffer(void **addr, size_t *size)
> +{
> +	int ret;
> +	unsigned long tmp_addr;
> +	size_t tmp_size;
> +
> +	ret = get_kexec_buffer("linux,ima-kexec-buffer", &tmp_addr, &tmp_size);
> +	if (ret)
> +		return ret;
> +
>  	*addr = __va(tmp_addr);
>  	*size = tmp_size;
>  
> @@ -188,72 +199,82 @@ int __init ima_free_kexec_buffer(void)
>  }
>  #endif
>  
> -/**
> - * remove_ima_buffer - remove the IMA buffer property and reservation from @fdt
> - *
> - * @fdt: Flattened Device Tree to update
> - * @chosen_node: Offset to the chosen node in the device tree
> - *
> - * The IMA measurement buffer is of no use to a subsequent kernel, so we always
> - * remove it from the device tree.
> - */
> -static void remove_ima_buffer(void *fdt, int chosen_node)
> +static int remove_buffer(void *fdt, int chosen_node, const char *name)
>  {
>  	int ret, len;
>  	unsigned long addr;
>  	size_t size;
>  	const void *prop;
>  
> -	if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
> -		return;
> -
> -	prop = fdt_getprop(fdt, chosen_node, "linux,ima-kexec-buffer", &len);
> +	prop = fdt_getprop(fdt, chosen_node, name, &len);
>  	if (!prop)
> -		return;
> +		return -ENOENT;
>  
>  	ret = do_get_kexec_buffer(prop, len, &addr, &size);
> -	fdt_delprop(fdt, chosen_node, "linux,ima-kexec-buffer");
> +	fdt_delprop(fdt, chosen_node, name);
>  	if (ret)
> -		return;
> +		return ret;
>  
>  	ret = fdt_find_and_del_mem_rsv(fdt, addr, size);
>  	if (!ret)
> -		pr_debug("Removed old IMA buffer reservation.\n");
> +		pr_debug("Remove old %s buffer reserveration", name);
> +	return ret;
>  }
>  
> -#ifdef CONFIG_IMA_KEXEC
>  /**
> - * setup_ima_buffer - add IMA buffer information to the fdt
> - * @image:		kexec image being loaded.
> - * @fdt:		Flattened device tree for the next kernel.
> - * @chosen_node:	Offset to the chosen node.
> + * remove_ima_buffer - remove the IMA buffer property and reservation from @fdt
>   *
> - * Return: 0 on success, or negative errno on error.
> + * @fdt: Flattened Device Tree to update
> + * @chosen_node: Offset to the chosen node in the device tree
> + *
> + * The IMA measurement buffer is of no use to a subsequent kernel, so we always
> + * remove it from the device tree.
>   */
> -static int setup_ima_buffer(const struct kimage *image, void *fdt,
> -			    int chosen_node)
> +static void remove_ima_buffer(void *fdt, int chosen_node)
> +{
> +	if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
> +		return;
> +
> +	remove_buffer(fdt, chosen_node, "linux,ima-kexec-buffer");
> +}
> +
> +#ifdef CONFIG_IMA_KEXEC
> +static int setup_buffer(void *fdt, int chosen_node, const char *name,
> +			phys_addr_t addr, size_t size)
>  {
>  	int ret;
>  
> -	if (!image->ima_buffer_size)
> +	if (!size)
>  		return 0;
>  
>  	ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
> -				       "linux,ima-kexec-buffer",
> -				       image->ima_buffer_addr,
> -				       image->ima_buffer_size);
> +				       name, addr, size);
>  	if (ret < 0)
>  		return -EINVAL;
>  
> -	ret = fdt_add_mem_rsv(fdt, image->ima_buffer_addr,
> -			      image->ima_buffer_size);
> +	ret = fdt_add_mem_rsv(fdt, addr, size);
>  	if (ret)
>  		return -EINVAL;
>  
> -	pr_debug("IMA buffer at 0x%pa, size = 0x%zx\n",
> -		 &image->ima_buffer_addr, image->ima_buffer_size);
> +	pr_debug("%s at 0x%pa, size = 0x%zx\n", name, &addr, size);
>  
>  	return 0;
> +
> +}
> +
> +/**
> + * setup_ima_buffer - add IMA buffer information to the fdt
> + * @image:		kexec image being loaded.
> + * @fdt:		Flattened device tree for the next kernel.
> + * @chosen_node:	Offset to the chosen node.
> + *
> + * Return: 0 on success, or negative errno on error.
> + */
> +static int setup_ima_buffer(const struct kimage *image, void *fdt,
> +			    int chosen_node)
> +{
> +	return setup_buffer(fdt, chosen_node, "linux,ima-kexec-buffer",
> +			    image->ima_buffer_addr, image->ima_buffer_size);
>  }
>  #else /* CONFIG_IMA_KEXEC */
>  static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
> -- 
> 2.35.1
>