From: Ard Biesheuvel <ardb@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: Prasad Sodagudi <psodagud@codeaurora.org>,
Srinivas Ramana <sramana@codeaurora.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ajay Patil <pajay@qti.qualcomm.com>,
Android Kernel Team <kernel-team@android.com>,
Will Deacon <will@kernel.org>,
kvmarm <kvmarm@lists.cs.columbia.edu>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v5 18/21] arm64: Move "nokaslr" over to the early cpufeature infrastructure
Date: Mon, 25 Jan 2021 15:19:30 +0100 [thread overview]
Message-ID: <CAMj1kXGTu8AtMnm7NxB8M2xFuXHSKzAx2hjjeaAW2v-usvavVQ@mail.gmail.com> (raw)
In-Reply-To: <3a98ff1db79c90c96038b924eb534643@kernel.org>
On Mon, 25 Jan 2021 at 14:54, Marc Zyngier <maz@kernel.org> wrote:
>
> On 2021-01-25 12:54, Ard Biesheuvel wrote:
> > On Mon, 25 Jan 2021 at 11:53, Marc Zyngier <maz@kernel.org> wrote:
> >>
> >> Given that the early cpufeature infrastructure has borrowed quite
> >> a lot of code from the kaslr implementation, let's reimplement
> >> the matching of the "nokaslr" option with it.
> >>
> >> Signed-off-by: Marc Zyngier <maz@kernel.org>
> >> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> >> Acked-by: David Brazdil <dbrazdil@google.com>
> >> ---
> >> arch/arm64/kernel/idreg-override.c | 15 +++++++++++++
> >> arch/arm64/kernel/kaslr.c | 36
> >> ++----------------------------
> >> 2 files changed, 17 insertions(+), 34 deletions(-)
> >>
> >> diff --git a/arch/arm64/kernel/idreg-override.c
> >> b/arch/arm64/kernel/idreg-override.c
> >> index cbb8eaa48742..3ccf51b84ba4 100644
> >> --- a/arch/arm64/kernel/idreg-override.c
> >> +++ b/arch/arm64/kernel/idreg-override.c
> >> @@ -31,8 +31,22 @@ static const struct ftr_set_desc mmfr1 __initdata =
> >> {
> >> },
> >> };
> >>
> >> +extern struct arm64_ftr_override kaslr_feature_override;
> >> +
> >> +static const struct ftr_set_desc kaslr __initdata = {
> >
> > This should be __initconst not __initdata (below too)
> >
> >> + .name = "kaslr",
> >> +#ifdef CONFIG_RANDOMIZE_BASE
> >> + .override = &kaslr_feature_override,
> >> +#endif
> >> + .fields = {
> >> + { "disabled", 0 },
> >> + {}
> >> + },
> >> +};
> >> +
> >> static const struct ftr_set_desc * const regs[] __initdata = {
> >> &mmfr1,
> >> + &kaslr,
> >> };
> >>
> >> static const struct {
> >> @@ -41,6 +55,7 @@ static const struct {
> >> } aliases[] __initdata = {
> >> { "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
> >> { "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
> >> + { "nokaslr", "kaslr.disabled=1" },
> >> };
> >>
> >
> > This struct now takes up
> > - ~100 bytes for the characters themselves (which btw are not emitted
> > into __initdata or __initconst)
> > - 6x8 bytes for the char pointers
> > - 6x24 bytes for the RELA relocations that annotate these pointers as
> > quantities that need to be relocated at boot (on a kernel built with
> > KASLR)
> >
> > I know it's only a drop in the ocean, but in this case, where the
> > struct is statically declared and defined only once, and in the same
> > place, we could easily turn this into
> >
> > static const struct {
> > char alias[24];
> > char param[20];
> > };
> >
> > and get rid of all the overhead. The only slightly annoying thing is
> > that the array sizes need to be kept in sync with the largest instance
> > appearing in the array, but this is easy when the struct type is
> > declared in the same place where its only instance is defined.
>
> Fair enough. I personally find the result butt-ugly, but I agree
> that it certainly saves some memory. Does the following work for
> you? I can even give symbolic names to the various constants (how
> generous of me! ;-).
>
To be honest, I was anticipating more of a discussion, but this looks
reasonable to me. Does 'char feature[80];' really need 80 bytes
though?
> diff --git a/arch/arm64/kernel/idreg-override.c
> b/arch/arm64/kernel/idreg-override.c
> index d1310438d95c..9e7043bdc808 100644
> --- a/arch/arm64/kernel/idreg-override.c
> +++ b/arch/arm64/kernel/idreg-override.c
> @@ -14,15 +14,15 @@
> #include <asm/setup.h>
>
> struct ftr_set_desc {
> - const char *name;
> + char name[20];
> struct arm64_ftr_override *override;
> struct {
> - const char *name;
> + char name[20];
> u8 shift;
> } fields[];
> };
>
> -static const struct ftr_set_desc mmfr1 __initdata = {
> +static const struct ftr_set_desc mmfr1 __initconst = {
> .name = "id_aa64mmfr1",
> .override = &id_aa64mmfr1_override,
> .fields = {
> @@ -31,7 +31,7 @@ static const struct ftr_set_desc mmfr1 __initdata = {
> },
> };
>
> -static const struct ftr_set_desc pfr1 __initdata = {
> +static const struct ftr_set_desc pfr1 __initconst = {
> .name = "id_aa64pfr1",
> .override = &id_aa64pfr1_override,
> .fields = {
> @@ -40,7 +40,7 @@ static const struct ftr_set_desc pfr1 __initdata = {
> },
> };
>
> -static const struct ftr_set_desc isar1 __initdata = {
> +static const struct ftr_set_desc isar1 __initconst = {
> .name = "id_aa64isar1",
> .override = &id_aa64isar1_override,
> .fields = {
> @@ -54,7 +54,7 @@ static const struct ftr_set_desc isar1 __initdata = {
>
> extern struct arm64_ftr_override kaslr_feature_override;
>
> -static const struct ftr_set_desc kaslr __initdata = {
> +static const struct ftr_set_desc kaslr __initconst = {
> .name = "kaslr",
> #ifdef CONFIG_RANDOMIZE_BASE
> .override = &kaslr_feature_override,
> @@ -65,7 +65,7 @@ static const struct ftr_set_desc kaslr __initdata = {
> },
> };
>
> -static const struct ftr_set_desc * const regs[] __initdata = {
> +static const struct ftr_set_desc * const regs[] __initconst = {
> &mmfr1,
> &pfr1,
> &isar1,
> @@ -73,9 +73,9 @@ static const struct ftr_set_desc * const regs[]
> __initdata = {
> };
>
> static const struct {
> - const char *alias;
> - const char *feature;
> -} aliases[] __initdata = {
> + char alias[30];
> + char feature[80];
> +} aliases[] __initconst = {
> { "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
> { "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
> { "arm64.nobti", "id_aa64pfr1.bt=0" },
>
> --
> Jazz is not dead. It just smells funny...
_______________________________________________
kvmarm mailing list
kvmarm@lists.cs.columbia.edu
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
next prev parent reply other threads:[~2021-01-25 14:19 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-25 10:49 [PATCH v5 00/21] arm64: Early CPU feature override, and applications to VHE, BTI and PAuth Marc Zyngier
2021-01-25 10:49 ` [PATCH v5 01/21] arm64: Fix labels in el2_setup macros Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 02/21] arm64: Fix outdated TCR setup comment Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 03/21] arm64: Turn the MMU-on sequence into a macro Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 04/21] arm64: Provide an 'upgrade to VHE' stub hypercall Marc Zyngier
2021-01-25 12:13 ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 05/21] arm64: Initialise as nVHE before switching to VHE Marc Zyngier
2021-01-25 12:13 ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 06/21] arm64: Move VHE-specific SPE setup to mutate_to_vhe() Marc Zyngier
2021-01-25 12:14 ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 07/21] arm64: Simplify init_el2_state to be non-VHE only Marc Zyngier
2021-01-25 12:14 ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 08/21] arm64: Move SCTLR_EL1 initialisation to EL-agnostic code Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 09/21] arm64: cpufeature: Add global feature override facility Marc Zyngier
2021-01-25 12:15 ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 10/21] arm64: cpufeature: Use IDreg override in __read_sysreg_by_encoding() Marc Zyngier
2021-01-25 12:19 ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 11/21] arm64: Extract early FDT mapping from kaslr_early_init() Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 12/21] arm64: cpufeature: Add an early command-line cpufeature override facility Marc Zyngier
2021-01-25 18:37 ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 13/21] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line Marc Zyngier
2021-01-25 13:15 ` Suzuki K Poulose
2021-01-25 13:55 ` Marc Zyngier
2021-01-25 18:37 ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 14/21] arm64: Honor VHE being disabled from the command-line Marc Zyngier
2021-01-25 18:38 ` Catalin Marinas
2021-01-25 10:50 ` [PATCH v5 15/21] arm64: Add an aliasing facility for the idreg override Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 16/21] arm64: Make kvm-arm.mode={nvhe, protected} an alias of id_aa64mmfr1.vh=0 Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 17/21] KVM: arm64: Document HVC_VHE_RESTART stub hypercall Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 18/21] arm64: Move "nokaslr" over to the early cpufeature infrastructure Marc Zyngier
2021-01-25 12:54 ` Ard Biesheuvel
2021-01-25 13:54 ` Marc Zyngier
2021-01-25 14:19 ` Ard Biesheuvel [this message]
2021-01-25 14:28 ` Marc Zyngier
2021-01-25 15:00 ` Ard Biesheuvel
2021-01-25 10:50 ` [PATCH v5 19/21] arm64: cpufeatures: Allow disabling of BTI from the command-line Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 20/21] arm64: Defer enabling pointer authentication on boot core Marc Zyngier
2021-01-25 10:50 ` [PATCH v5 21/21] arm64: cpufeatures: Allow disabling of Pointer Auth from the command-line Marc Zyngier
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAMj1kXGTu8AtMnm7NxB8M2xFuXHSKzAx2hjjeaAW2v-usvavVQ@mail.gmail.com \
--to=ardb@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=kernel-team@android.com \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=maz@kernel.org \
--cc=pajay@qti.qualcomm.com \
--cc=psodagud@codeaurora.org \
--cc=sramana@codeaurora.org \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).