Re: [Qemu-devel] [PATCH] hw/arm/boot: take Linux/arm64 TEXT_OFFSET header field into account

[Peter Maydell]

On 9 March 2017 at 18:09, Ard Biesheuvel <address@hidden> wrote:
> The arm64 boot protocol stipulates that the kernel must be loaded
> TEXT_OFFSET bytes beyond a 2 MB aligned base address, where TEXT_OFFSET
> could be any 4 KB multiple between 0 and 2 MB, and whose value can be
> found in the header of the Image file.
>
> So after attempts to load the kernel image as an ELF file or as a
> U-Boot image (both of which have their own way of specifying the load
> offset) have failed, try to determine the TEXT_OFFSET from the image
> before proceeding with loading it as a gzipped or raw image.
>
> Signed-off-by: Ard Biesheuvel <address@hidden>
> ---
>  hw/arm/boot.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 56 insertions(+)
>
> diff --git a/hw/arm/boot.c b/hw/arm/boot.c
> index ff621e4b6a4b..0824f74c697f 100644
> --- a/hw/arm/boot.c
> +++ b/hw/arm/boot.c
> @@ -31,6 +31,11 @@
>  #define KERNEL_LOAD_ADDR 0x00010000
>  #define KERNEL64_LOAD_ADDR 0x00080000
>
> +#define ARM64_IMAGE_HEADER_SIZE     64
> +#define ARM64_TEXT_OFFSET_OFFSET    8
> +#define ARM64_IMAGE_SIZE_OFFSET     16
> +#define ARM64_MAGIC_OFFSET          56
> +
>  typedef enum {
>      FIXUP_NONE = 0,     /* do nothing */
>      FIXUP_TERMINATOR,   /* end of insns */
> @@ -768,6 +773,51 @@ static uint64_t arm_load_elf(struct arm_boot_info *info, 
> uint64_t *pentry,
>      return ret;
>  }
>
> +static void aarch64_get_text_offset(struct arm_boot_info *info,
> +                                    hwaddr *text_offset)
> +{

Hmm, this isn't quite what I had in mind when we talked about this.
I think what we want is a function like
static uint64_t load_aarch64_image(const char *filename, hwaddr *entry,
                                   other stuff you need)
which loads the image if it's the right format and writes
the entry point into *entry, and returns a negative value
if the image isn't the right format.

ie whose API is basically parallel to the load_uimage(),
load_image_gzipped(), etc functions. You can make it handle
both gzipped and non-gzipped images (and then drop the code
we currently have to call load_image_gzipped()).

PS: you'll want to use g_file_get_contents() for the load
in the non-compressed image case, and as the patchew
robot points out our coding style preferences mandate braces.

thanks
-- PMM