2024-02-06 18:55:16

by Andrea della Porta

Subject: [PATCH] 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.

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..9f962deeef5a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -433,6 +433,9 @@
arm64.nosve [ARM64] Unconditionally disable Scalable Vector
Extension support

+ arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
+ 32 bit applications
+
ataflop= [HW,M68k]

atarimouse= [HW,MOUSE] Atari Mouse
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

2024-02-06 20:23:39

by Randy Dunlap

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

Hi--

On 2/6/24 10:54, 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.
>
> 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..9f962deeef5a 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -433,6 +433,9 @@
> arm64.nosve [ARM64] Unconditionally disable Scalable Vector
> Extension support
>
> + arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
> + 32 bit applications
> +

That new entry is not in alphabetical order like it should be.

> ataflop= [HW,M68k]
>
> atarimouse= [HW,MOUSE] Atari Mouse


--
#Randy