On Tue, Oct 18, 2022 at 01:38:57PM +0200, Ard Biesheuvel wrote:
> On Tue, 18 Oct 2022 at 13:28, Catalin Marinas <catalin.marinas@xxxxxxx> wrote:
> > On Mon, Oct 17, 2022 at 07:16:40PM +0200, Ard Biesheuvel wrote:
> > > diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S
> > > index 61a87fa1c305..1c1be004a271 100644
> > > --- a/arch/arm64/kernel/efi-entry.S
> > > +++ b/arch/arm64/kernel/efi-entry.S
> > > @@ -23,15 +23,6 @@ SYM_CODE_START(efi_enter_kernel)
> > > add x19, x0, x2 // relocated Image entrypoint
> > > mov x20, x1 // DTB address
> > >
> > > - /*
> > > - * Clean the copied Image to the PoC, and ensure it is not shadowed by
> > > - * stale icache entries from before relocation.
> > > - */
> > > - ldr w1, =kernel_size
> > > - add x1, x0, x1
> > > - bl dcache_clean_poc
> > > - ic ialluis
> > > -
> > > /*
> > > * Clean the remainder of this routine to the PoC
> > > * so that we can safely disable the MMU and caches.
> > [...]
> > > diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
> > > index 598c76c4bbaa..e767a5ac8c3d 100644
> > > --- a/drivers/firmware/efi/libstub/arm64-stub.c
> > > +++ b/drivers/firmware/efi/libstub/arm64-stub.c
> > [...]
> > > @@ -174,5 +174,13 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
> > > *image_addr = *reserve_addr;
> > > memcpy((void *)*image_addr, _text, kernel_size);
> > >
> > > +clean_image_to_poc:
> > > + /*
> > > + * Clean the copied Image to the PoC, and ensure it is not shadowed by
> > > + * stale icache entries from before relocation.
> > > + */
> > > + dcache_clean_poc(*image_addr, *image_addr + kernel_size);
> > > + asm("ic ialluis");
> >
> > Does this need some barriers, at least a DSB? The original code had DSB
> > and ISB, though not immediately after the IC instruction.
>
> We are still relying on the implicit DSB done by the subsequent call
> to dcache_clean_to_poc() call in efi_enter_kernel(), which executes
> much later than this code.
Ah, ok.
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
