Re: [U-Boot] [PATCH v2] arm64: booti: allow to place kernel image anywhere in physical memory

Hi Mark,

2017-03-09 1:05 GMT+09:00 Mark Rutland mark.rutland@arm.com:

...

  /*

•  * If we are not at the correct run-time location, set the new
  

•  * correct location and then move the image there.
  

•  * If bit 3 of the flags field is set, the 2MB aligned base of the
  

•  * kernel image can be anywhere in physical memory, so respect
  

•  * images->ep.  Otherwise, relocate the image to the base of RAM
  

•  * since memory below it is not accessible via the linear mapping.
   */
  

• dst = gd->bd->bi_dram[0].start + le64_to_cpu(ih->text_offset);
  

• if (le64_to_cpu(ih->flags) & BIT(3))
  

•         dst = images->ep - le64_to_cpu(ih->text_offset);
  

I take it this is a pre-correction for the ALIGN() below?

Without this, the image would be always relocated even if images->ep is already bootable location.

Unnecessary relocation should be avoided.

There's one last wrinkle to take care of here, if we want to boot a kernel older than commit a2c1d73b94ed49f5 (i.e. v3.16). Until then, the text_offset was of unknown endianness.

As mentiond in the Linux documentation, you can detect this based on the image_size field, e.g.

    uint64_t text_offset;

    /*
     * Prior to Linux commit a2c1d73b94ed49f5, the text_offset field
     * is of unknown endianness. In these cases, the image_size
     * field is zero, and we can assume a fixed value of 0x80000.
     */
    if (le64_to_cpu(ih->image_size) == 0)
            text_offset = 0x80000;
    else
            text_offset = (le64_to_cpu(ih->text_offset));

... then you can reuse that text_offset value for both cases above.

Thanks. I will fix this too.