linux-kernel - [PATCH] arm64: Inform user if software PAN is in use

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Date:   Wed, 29 Nov 2017 15:39:49 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] arm64: Inform user if software PAN is in use

It isn't entirely obvious if we're using software PAN because we
don't say anything about it in the boot log. But if we're using
hardware PAN we'll print a nice CPU feature message indicating
it. Add a print for software PAN too so we know if it's being
used or not.

Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
---
 arch/arm64/kernel/cpufeature.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 21e2c95d24e7..c6f8da17146b 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1189,6 +1189,9 @@ void __init setup_cpu_features(void)
 	if (system_supports_32bit_el0())
 		setup_elf_hwcaps(compat_elf_hwcaps);
 
+	if (system_uses_ttbr0_pan())
+		pr_info("Emulating Privileged Access Never (PAN) using TTBR0_EL1 switching\n");
+
 	/* Advertise that we have computed the system capabilities */
 	set_sys_caps_initialised();
 
-- 
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