2024-04-29 10:29:17

by Andrea della Porta

Subject: [PATCH v3] 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 V3:
- idreg-override.c has been moved to arch/arm64/kernel/pi/
directory, so this patch revision adjust for that change.

Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Andrea della Porta <[email protected]>
---
Documentation/admin-guide/kernel-parameters.txt | 3 +++
arch/arm64/kernel/pi/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 bb884c14b2f6..3e70963599df 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -431,6 +431,9 @@
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/pi/idreg-override.c b/arch/arm64/kernel/pi/idreg-override.c
index aad399796e81..48c1aa456af9 100644
--- a/arch/arm64/kernel/pi/idreg-override.c
+++ b/arch/arm64/kernel/pi/idreg-override.c
@@ -108,6 +108,7 @@ 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),
{}
},
};
@@ -223,6 +224,7 @@ static const struct {
{ "nokaslr", "arm64_sw.nokaslr=1" },
{ "rodata=off", "arm64_sw.rodataoff=1" },
{ "arm64.nolva", "id_aa64mmfr2.varange=0" },
+ { "arm64.no32bit_el0", "id_aa64pfr0.el0=1" },
};

static int __init parse_hexdigit(const char *p, u64 *v)
--
2.35.3

2024-05-03 17:33:12

by Will Deacon

Subject: Re: [PATCH v3] arm64: Add the arm64.no32bit_el0 command line option

On Mon, 29 Apr 2024 12:28:33 +0200, 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.
>
> [...]

Applied to arm64 (for-next/misc), thanks!

[1/1] arm64: Add the arm64.no32bit_el0 command line option
https://git.kernel.org/arm64/c/1279e8d0dcea

Cheers,
--
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev