Hey Alex,
On Wed, Jan 25, 2023 at 09:23:30AM +0100, Alexandre Ghiti wrote:
> The early virtual address should lie in the kernel address space for
> inline kasan instrumentation to succeed, otherwise kasan tries to
> dereference an address that does not exist in the address space (since
> kasan only maps *kernel* address space, not the userspace).
>
> Simply use the very first address of the kernel address space for the
> early fdt mapping.
>
> It allowed an Ubuntu kernel to boot successfully with inline
> instrumentation.
>
> Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Been poking around in this area the last few days trying to hunt down
some bugs... Things look functionally the same w/ this patch and we do
get rid of the odd looking pointer which is nice.
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
Probably would've made the cause of 50e63dd8ed92 ("riscv: fix reserved
memory setup") more difficult to find so glad I got that out of the way
well before this patch!
Thanks,
Conor.
> ---
> arch/riscv/mm/init.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 478d6763a01a..87f6a5d475a6 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -57,7 +57,7 @@ unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
> EXPORT_SYMBOL(empty_zero_page);
>
> extern char _start[];
> -#define DTB_EARLY_BASE_VA PGDIR_SIZE
> +#define DTB_EARLY_BASE_VA (ADDRESS_SPACE_END - (PTRS_PER_PGD / 2 * PGDIR_SIZE) + 1)
> void *_dtb_early_va __initdata;
> uintptr_t _dtb_early_pa __initdata;
>
> --
> 2.37.2
>
>
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