[PATCH] SoC: sdm845: find and save KASLR to env variables

[Peter Robinson]

On Tue, Dec 27, 2022 at 7:47 PM Dzmitry Sankouski <dsankouski at gmail.com> wrote:
>
> KASLR address is needed to boot fully functional Android.
> KASLR is set by primary bootloader, and since u-boot is used
> as a secondary bootloader(replacing kernel) on sdm845 platform,
> KASLR may be found by comparing memory chunks at relocaddr over
> supposed KASLR range.

By KASLR I presume  you mean the random seed? KASLR is a technology
used in the kernel, but it's actually a random seed that's passed to
the kernel to generate the random layout.

> Signed-off-by: Dzmitry Sankouski <dsankouski at gmail.com>
> ---
>  arch/arm/mach-snapdragon/init_sdm845.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/arch/arm/mach-snapdragon/init_sdm845.c b/arch/arm/mach-snapdragon/init_sdm845.c
> index 5f53c21947..1f88502394 100644
> --- a/arch/arm/mach-snapdragon/init_sdm845.c
> +++ b/arch/arm/mach-snapdragon/init_sdm845.c
> @@ -78,5 +78,23 @@ __weak int misc_init_r(void)
>                 env_set("key_power", "0");
>         }
>
> +       /*
> +        * search for kaslr address, set by primary bootloader by searching first
> +        * 0x100 relocated bytes at u-boot's initial load address range
> +        */
> +       uintptr_t start = gd->ram_base;
> +       uintptr_t end = start + 0x800000;
> +       u8 *addr = (u8 *)start;
> +       phys_addr_t *relocaddr = (phys_addr_t *)gd->relocaddr;
> +       u32 block_size = 0x1000;
> +
> +       while (memcmp(addr, relocaddr, 0x100) && (uintptr_t)addr < end)
> +               addr += block_size;
> +
> +       if ((uintptr_t)addr >= end)
> +               printf("KASLR not found in range 0x%lx - 0x%lx", start, end);
> +       else
> +               env_set_addr("KASLR", addr);
> +
>         return 0;
>  }
> --
> 2.30.2
>