Allow systems with mismatched 32-bit support at EL0 to run 32-bit
applications based on a new kernel parameter.
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
---
Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++
arch/arm64/kernel/cpufeature.c | 7 +++++++
2 files changed, 15 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 44fde25bb221..9d191e6e020b 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -289,6 +289,14 @@
do not want to use tracing_snapshot_alloc() as it needs
to be done where GFP_KERNEL allocations are allowed.
+ allow_mismatched_32bit_el0 [ARM64]
+ Allow execve() of 32-bit applications and setting of the
+ PER_LINUX32 personality on systems where only a strict
+ subset of the CPUs support 32-bit EL0. When this
+ parameter is present, the set of CPUs supporting 32-bit
+ EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
+ and hot-unplug operations may be restricted.
+
amd_iommu= [HW,X86-64]
Pass parameters to the AMD IOMMU driver in the system.
Possible values are:
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 08b558a221b7..fea0f213d55c 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1291,6 +1291,13 @@ const struct cpumask *system_32bit_el0_cpumask(void)
return cpu_possible_mask;
}
+static int __init parse_32bit_el0_param(char *str)
+{
+ allow_mismatched_32bit_el0 = true;
+ return 0;
+}
+early_param("allow_mismatched_32bit_el0", parse_32bit_el0_param);
+
static ssize_t aarch32_el0_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
--
2.29.2.576.ga3fc446d84-goog
