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Subject[PATCH] arm64: cpufeature: Trim feature reporting and include PAN emulation
The PAN emulation notification was only happening for non-boot CPUs
if CPU capabilities had already been configured. This seems to be the
wrong place, as it's system-wide and isn't attached to capabilities,
so its reporting didn't normally happen. Instead, report it once from
the boot CPU. Additionally removes the redundant "feature" word from the
"CPU features:" line.

Before (redundant "feature", and missing PAN emulation report):

SMP: Total of 4 processors activated.
CPU features: detected feature: 32-bit EL0 Support
CPU features: detected feature: Kernel page table isolation (KPTI)
CPU: All CPU(s) started at EL2

After:

SMP: Total of 4 processors activated.
CPU features: detected: 32-bit EL0 Support
CPU features: detected: Kernel page table isolation (KPTI)
CPU features: emulated: Privileged Access Never (PAN) using TTBR0_EL1 switching
CPU: All CPU(s) started at EL2

Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/arm64/kernel/cpufeature.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 29b1f873e337..6c799ca58b53 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1333,9 +1333,6 @@ static void verify_local_cpu_capabilities(void)

if (system_supports_sve())
verify_sve_features();
-
- if (system_uses_ttbr0_pan())
- pr_info("Emulating Privileged Access Never (PAN) using TTBR0_EL1 switching\n");
}

void check_local_cpu_capabilities(void)
@@ -1360,7 +1357,7 @@ void check_local_cpu_capabilities(void)

static void __init setup_feature_capabilities(void)
{
- update_cpu_capabilities(arm64_features, "detected feature:");
+ update_cpu_capabilities(arm64_features, "detected:");
enable_cpu_capabilities(arm64_features);
}

@@ -1394,6 +1391,9 @@ void __init setup_cpu_features(void)
if (system_supports_32bit_el0())
setup_elf_hwcaps(compat_elf_hwcaps);

+ if (system_uses_ttbr0_pan())
+ pr_info("emulated: Privileged Access Never (PAN) using TTBR0_EL1 switching\n");
+
sve_setup();

/* Advertise that we have computed the system capabilities */
--
2.7.4

--
Kees Cook
Pixel Security

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