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From: hev <r@hev.cc>
To: Lisa Robinson <lisa@bytefly.space>
Cc: ardb@kernel.org, chenhuacai@kernel.org,
	ilias.apalodimas@linaro.org,  kernel@xen0n.name,
	linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
	 loongarch@lists.linux.dev
Subject: Re: [RFC PATCH 2/3] efi/loongarch: Randomize kernel preferred address for KASLR
Date: Mon, 27 Apr 2026 15:49:21 +0800	[thread overview]
Message-ID: <CAHirt9jfnSFQfRHEANGeNGE2JowTcPV1Tz8L4cX=boJ6vSOa7Q@mail.gmail.com> (raw)
In-Reply-To: <20260427050735.3410-1-lisa@bytefly.space>

Hi Lisa,

On Mon, Apr 27, 2026 at 1:08 PM Lisa Robinson <lisa@bytefly.space> wrote:
>
> Hi Rui
>
> > diff --git a/drivers/firmware/efi/libstub/loongarch.c b/drivers/firmware/efi/libstub/loongarch.c
> > index 9825f5218137..80ba7d69e1b3 100644
> > --- a/drivers/firmware/efi/libstub/loongarch.c
> > +++ b/drivers/firmware/efi/libstub/loongarch.c
> > @@ -38,6 +38,21 @@ static efi_status_t exit_boot_func(struct efi_boot_memmap *map, void *priv)
> >       return EFI_SUCCESS;
> >  }
> >
> > +unsigned long efi_get_kimg_kaslr_address(void)
> > +{
> > +     unsigned int random_offset = 0;
> > +
> > +#ifdef CONFIG_RANDOMIZE_BASE
> > +     if (!efi_nokaslr) {
> > +             efi_get_random_bytes(sizeof(random_offset), (u8 *)&random_offset);
> > +             random_offset ^= (rdtime_l() << 16);
>
> random_offset &= ~(efi_get_kimg_min_align() - 1);

Thanks for pointing that out.

Aligning to 64K here seems preferable. Otherwise, it reduces the entropy.

Thanks,
Rui


>
> > +             random_offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);
> > +     }
> > +#endif
> > +
> > +     return PHYSADDR(VMLINUX_LOAD_ADDRESS) + random_offset;
> > +}
> > +
> >  unsigned long __weak kernel_entry_address(unsigned long kernel_addr,
> >               efi_loaded_image_t *image)
> >  {
>
> --
> Lisa

next prev parent reply	other threads:[~2026-04-27  7:49 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-04-26 12:02 [RFC PATCH 0/3] LoongArch: Move KASLR to EFI stub to avoid initrd overlap WANG Rui
2026-04-26 12:02 ` [RFC PATCH 1/3] LoongArch: Allow rdtime_h and rdtime_l in 64-bit builds WANG Rui
2026-04-26 12:02 ` [RFC PATCH 2/3] efi/loongarch: Randomize kernel preferred address for KASLR WANG Rui
2026-04-27  5:07   ` Lisa Robinson
2026-04-27  7:49     ` hev [this message]
2026-04-26 12:02 ` [RFC PATCH 3/3] LoongArch: Remove KASLR handling from relocate_kernel WANG Rui

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