[PATCH] efi_loader: Fix loaded image alignment

[Heinrich Schuchardt]

On 10/11/21 14:10, Ilias Apalodimas wrote:
> We are ignoring the alignment communicated via the PE/COFF header.
> Starting 5.10 the Linux kernel will loudly complain about it. For more
> details look at [1] (in linux kernel).
> 
> So add a function that can allocate aligned EFI memory and use it for our
> relocated loaded image.
> 
> [1] c32ac11da3f83 ("efi/libstub: arm64: Double check image alignment at entry")
> 
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---
>   include/efi_loader.h              |  2 ++
>   lib/efi_loader/efi_image_loader.c | 12 ++++----
>   lib/efi_loader/efi_memory.c       | 50 +++++++++++++++++++++++++++++++
>   3 files changed, 58 insertions(+), 6 deletions(-)
> 
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index c440962fe522..5cdc72345e52 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -675,6 +675,8 @@ struct efi_device_path *efi_get_dp_from_boot(const efi_guid_t guid);
>   #define efi_size_in_pages(size) (((size) + EFI_PAGE_MASK) >> EFI_PAGE_SHIFT)
>   /* Generic EFI memory allocator, call this to get memory */
>   void *efi_alloc(uint64_t len, int memory_type);
> +/* Allocate pages on the specified alignment */
> +void *efi_alloc_aligned_pages(u64 len, int memory_type, size_t align);
>   /* More specific EFI memory allocator, called by EFI payloads */
>   efi_status_t efi_allocate_pages(enum efi_allocate_type type,
>   				enum efi_memory_type memory_type,
> diff --git a/lib/efi_loader/efi_image_loader.c b/lib/efi_loader/efi_image_loader.c
> index e9572d4d5dbb..eb95580538cc 100644
> --- a/lib/efi_loader/efi_image_loader.c
> +++ b/lib/efi_loader/efi_image_loader.c
> @@ -898,9 +898,9 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle,
>   		image_base = opt->ImageBase;
>   		efi_set_code_and_data_type(loaded_image_info, opt->Subsystem);
>   		handle->image_type = opt->Subsystem;
> -		virt_size = ALIGN(virt_size, opt->SectionAlignment);
> -		efi_reloc = efi_alloc(virt_size,
> -				      loaded_image_info->image_code_type);
> +		efi_reloc = efi_alloc_aligned_pages(virt_size,
> +						    loaded_image_info->image_code_type,
> +						    opt->SectionAlignment);
>   		if (!efi_reloc) {
>   			log_err("Out of memory\n");
>   			ret = EFI_OUT_OF_RESOURCES;
> @@ -914,9 +914,9 @@ efi_status_t efi_load_pe(struct efi_loaded_image_obj *handle,
>   		image_base = opt->ImageBase;
>   		efi_set_code_and_data_type(loaded_image_info, opt->Subsystem);
>   		handle->image_type = opt->Subsystem;
> -		virt_size = ALIGN(virt_size, opt->SectionAlignment);
> -		efi_reloc = efi_alloc(virt_size,
> -				      loaded_image_info->image_code_type);
> +		efi_reloc = efi_alloc_aligned_pages(virt_size,
> +						    loaded_image_info->image_code_type,
> +						    opt->SectionAlignment);
>   		if (!efi_reloc) {
>   			log_err("Out of memory\n");
>   			ret = EFI_OUT_OF_RESOURCES;
> diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
> index f4acbee4f9b6..49d36d369aaa 100644
> --- a/lib/efi_loader/efi_memory.c
> +++ b/lib/efi_loader/efi_memory.c
> @@ -549,6 +549,56 @@ efi_status_t efi_free_pages(uint64_t memory, efi_uintn_t pages)
>   	return ret;
>   }
>   
> +/**
> + * efi_alloc_aligned_pages - allocate
> + *
> + * @len		len in bytes
> + * @memory_type	usage type of the allocated memory
> + * @align	alignment in bytes
> + * Return:	aligned memory or NULL
> + */
> +void *efi_alloc_aligned_pages(u64 len, int memory_type, size_t align)
> +{
> +	u64 req_pages = efi_size_in_pages(len);
> +	u64 true_pages = req_pages + efi_size_in_pages(align) - 1;
> +	u64 free_pages = 0;

The assigned value is never used. Please, remove the assignment.

> +	u64 aligned_mem;
> +	efi_status_t r;
> +	u64 mem;
> +

Please add a comment:

	/* Align must be a power of two */

I can apply these changes when merging.

Otherwise

Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>

> +	if (align & (align - 1))
> +		return NULL;
> +
> +	if (true_pages < req_pages)
> +		return NULL;
> +
> +	if (align < EFI_PAGE_SIZE) {
> +		r = efi_allocate_pages(EFI_ALLOCATE_ANY_PAGES, memory_type,
> +				       req_pages, &mem);
> +		return (r == EFI_SUCCESS) ? (void *)mem : NULL;
> +	}
> +
> +	r = efi_allocate_pages(EFI_ALLOCATE_ANY_PAGES, memory_type,
> +			       true_pages, &mem);
> +	if (r != EFI_SUCCESS)
> +		return NULL;
> +
> +	aligned_mem = ALIGN(mem, align);
> +	/* Free pages before alignment */
> +	free_pages = efi_size_in_pages(aligned_mem - mem);
> +	if (free_pages)
> +		efi_free_pages(mem, free_pages);
> +
> +	/* Free trailing pages */
> +	free_pages = true_pages - (req_pages + free_pages);
> +	if (free_pages) {
> +		mem = aligned_mem + req_pages * EFI_PAGE_SIZE;
> +		efi_free_pages(mem, free_pages);
> +	}
> +
> +	return (void *)aligned_mem;
> +}
> +
>   /**
>    * efi_allocate_pool - allocate memory from pool
>    *
>