2024-02-07 10:59:48

by Andrea della Porta

Subject: [PATCH v2] arm64: Add the arm64.no32bit_el0 command line option

Introducing the field 'el0' to the idreg-override for register
ID_AA64PFR0_EL1. This field is also aliased to the new kernel
command line option 'arm64.no32bit_el0' as a more recognizable
and mnemonic name to disable the execution of 32 bit userspace
applications (i.e. avoid Aarch32 execution state in EL0) from
kernel command line.

Changes in V2:
- fixed the order of appearance of arm64.no32bit_el0 entry in
kernel-parameters.txt documentation.

Link: https://lore.kernel.org/r/ZVTleETzfFUchs77@apocalypse
Signed-off-by: Andrea della Porta <[email protected]>
---
Documentation/admin-guide/kernel-parameters.txt | 3 +++
arch/arm64/kernel/idreg-override.c | 2 ++
2 files changed, 5 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 65731b060e3f..fa7cdf2f4f3a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -415,6 +415,9 @@
arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
Format: <io>,<irq>,<nodeID>

+ arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
+ 32 bit applications
+
arm64.nobti [ARM64] Unconditionally disable Branch Target
Identification support

diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index e30fd9e32ef3..642cda19e42d 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -86,6 +86,7 @@ static const struct ftr_set_desc pfr0 __prel64_initconst = {
.override = &id_aa64pfr0_override,
.fields = {
FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter),
+ FIELD("el0", ID_AA64PFR0_EL1_EL0_SHIFT, NULL),
{}
},
};
@@ -197,6 +198,7 @@ static const struct {
{ "arm64.nomops", "id_aa64isar2.mops=0" },
{ "arm64.nomte", "id_aa64pfr1.mte=0" },
{ "nokaslr", "arm64_sw.nokaslr=1" },
+ { "arm64.no32bit_el0", "id_aa64pfr0.el0=1" },
};

static int __init parse_hexdigit(const char *p, u64 *v)
--
2.41.0

2024-03-05 11:00:29

by Andrea della Porta

Subject: Re: [PATCH v2] arm64: Add the arm64.no32bit_el0 command line option

On 11:58 Wed 07 Feb , Andrea della Porta wrote:
> Introducing the field 'el0' to the idreg-override for register
> ID_AA64PFR0_EL1. This field is also aliased to the new kernel
> command line option 'arm64.no32bit_el0' as a more recognizable
> and mnemonic name to disable the execution of 32 bit userspace
> applications (i.e. avoid Aarch32 execution state in EL0) from
> kernel command line.
>
> Changes in V2:
> - fixed the order of appearance of arm64.no32bit_el0 entry in
> kernel-parameters.txt documentation.
>
> Link: https://lore.kernel.org/r/ZVTleETzfFUchs77@apocalypse
> Signed-off-by: Andrea della Porta <[email protected]>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 3 +++
> arch/arm64/kernel/idreg-override.c | 2 ++
> 2 files changed, 5 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 65731b060e3f..fa7cdf2f4f3a 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -415,6 +415,9 @@
> arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
> Format: <io>,<irq>,<nodeID>
>
> + arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
> + 32 bit applications
> +
> arm64.nobti [ARM64] Unconditionally disable Branch Target
> Identification support
>
> diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
> index e30fd9e32ef3..642cda19e42d 100644
> --- a/arch/arm64/kernel/idreg-override.c
> +++ b/arch/arm64/kernel/idreg-override.c
> @@ -86,6 +86,7 @@ static const struct ftr_set_desc pfr0 __prel64_initconst = {
> .override = &id_aa64pfr0_override,
> .fields = {
> FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter),
> + FIELD("el0", ID_AA64PFR0_EL1_EL0_SHIFT, NULL),
> {}
> },
> };
> @@ -197,6 +198,7 @@ static const struct {
> { "arm64.nomops", "id_aa64isar2.mops=0" },
> { "arm64.nomte", "id_aa64pfr1.mte=0" },
> { "nokaslr", "arm64_sw.nokaslr=1" },
> + { "arm64.no32bit_el0", "id_aa64pfr0.el0=1" },
> };
>
> static int __init parse_hexdigit(const char *p, u64 *v)
> --
> 2.41.0
>

A gentle ping about this patch... any thoughts about it?

Many thanks,
Andrea

2024-04-12 14:07:19

by Will Deacon

Subject: Re: [PATCH v2] arm64: Add the arm64.no32bit_el0 command line option

On Tue, Mar 05, 2024 at 11:56:05AM +0100, Andrea della Porta wrote:
> On 11:58 Wed 07 Feb , Andrea della Porta wrote:
> > Introducing the field 'el0' to the idreg-override for register
> > ID_AA64PFR0_EL1. This field is also aliased to the new kernel
> > command line option 'arm64.no32bit_el0' as a more recognizable
> > and mnemonic name to disable the execution of 32 bit userspace
> > applications (i.e. avoid Aarch32 execution state in EL0) from
> > kernel command line.
> >
> > Changes in V2:
> > - fixed the order of appearance of arm64.no32bit_el0 entry in
> > kernel-parameters.txt documentation.
> >
> > Link: https://lore.kernel.org/r/ZVTleETzfFUchs77@apocalypse
> > Signed-off-by: Andrea della Porta <[email protected]>
> > ---
> > Documentation/admin-guide/kernel-parameters.txt | 3 +++
> > arch/arm64/kernel/idreg-override.c | 2 ++
> > 2 files changed, 5 insertions(+)
> >
> > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> > index 65731b060e3f..fa7cdf2f4f3a 100644
> > --- a/Documentation/admin-guide/kernel-parameters.txt
> > +++ b/Documentation/admin-guide/kernel-parameters.txt
> > @@ -415,6 +415,9 @@
> > arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
> > Format: <io>,<irq>,<nodeID>
> >
> > + arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
> > + 32 bit applications
> > +
> > arm64.nobti [ARM64] Unconditionally disable Branch Target
> > Identification support
> >
> > diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
> > index e30fd9e32ef3..642cda19e42d 100644
> > --- a/arch/arm64/kernel/idreg-override.c
> > +++ b/arch/arm64/kernel/idreg-override.c
> > @@ -86,6 +86,7 @@ static const struct ftr_set_desc pfr0 __prel64_initconst = {
> > .override = &id_aa64pfr0_override,
> > .fields = {
> > FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter),
> > + FIELD("el0", ID_AA64PFR0_EL1_EL0_SHIFT, NULL),
> > {}
> > },
> > };
> > @@ -197,6 +198,7 @@ static const struct {
> > { "arm64.nomops", "id_aa64isar2.mops=0" },
> > { "arm64.nomte", "id_aa64pfr1.mte=0" },
> > { "nokaslr", "arm64_sw.nokaslr=1" },
> > + { "arm64.no32bit_el0", "id_aa64pfr0.el0=1" },
> > };
> >
> > static int __init parse_hexdigit(const char *p, u64 *v)
> > --
> > 2.41.0
> >
>
> A gentle ping about this patch... any thoughts about it?

It looks reasonable to me, but arch/arm64/kernel/idreg-override.c no
longer exists upstream, so you need to rebase.

Thanks,

Will