linux-kernel - [PATCH v3 4/4] arm64: uaccess: Implement user_access_region

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Date:   Tue, 15 Jan 2019 13:58:29 +0000
From:   Julien Thierry <julien.thierry@....com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     mingo@...hat.com, peterz@...radead.org, catalin.marinas@....com,
        will.deacon@....com, james.morse@....com, hpa@...or.com,
        valentin.schneider@....com, Julien Thierry <julien.thierry@....com>
Subject: [PATCH v3 4/4] arm64: uaccess: Implement user_access_region_active

Provide arm64 implementation of user_access_region_active.

Check the status of PAN or SW PAN if needed.

Signed-off-by: Julien Thierry <julien.thierry@....com>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
---
 arch/arm64/include/asm/sysreg.h  |  2 ++
 arch/arm64/include/asm/uaccess.h | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 72dc4c0..f0b2f32 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -114,6 +114,8 @@
 #define SYS_DC_CSW			sys_insn(1, 0, 7, 10, 2)
 #define SYS_DC_CISW			sys_insn(1, 0, 7, 14, 2)

+#define SYS_PSTATE_PAN			sys_reg(3, 0, 4, 2, 3)
+
 #define SYS_OSDTRRX_EL1			sys_reg(2, 0, 0, 0, 2)
 #define SYS_MDCCINT_EL1			sys_reg(2, 0, 0, 2, 0)
 #define SYS_MDSCR_EL1			sys_reg(2, 0, 0, 2, 2)
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 6a70c75..1a8acc9 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -225,6 +225,18 @@ static inline void uaccess_enable_not_uao(void)
 	__uaccess_enable(ARM64_ALT_PAN_NOT_UAO);
 }

+#define unsafe_user_region_active	uaccess_region_active
+static inline bool uaccess_region_active(void)
+{
+	if (system_uses_ttbr0_pan()) {
+		return read_sysreg(ttbr1_el1) & TTBR_ASID_MASK;
+	} else if (cpus_have_const_cap(ARM64_ALT_PAN_NOT_UAO) &&
+		   alternatives_applied) {
+		return !read_sysreg_s(SYS_PSTATE_PAN);
+	}
+	return false;
+}
+
 /*
  * Sanitise a uaccess pointer such that it becomes NULL if above the
  * current addr_limit.
--
1.9.1