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From:   Phong Tran <tranmanphong@gmail.com>
To:     catalin.marinas@arm.com, will@kernel.org, alexios.zavras@intel.com,
        tglx@linutronix.de, akpm@linux-foundation.org,
        steven.price@arm.com, steve.capper@arm.com, mark.rutland@arm.com,
        broonie@kernel.org, keescook@chromium.org
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        kernel-hardening@lists.openwall.com,
        Phong Tran <tranmanphong@gmail.com>
Subject: [PATCH] arm64: add check_wx_pages debugfs for CHECK_WX
Date:   Sat,  7 Mar 2020 16:39:26 +0700
Message-Id: <20200307093926.27145-1-tranmanphong@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org
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follow the suggestion from
https://github.com/KSPP/linux/issues/35

Signed-off-by: Phong Tran <tranmanphong@gmail.com>
---
 arch/arm64/Kconfig.debug        |  3 ++-
 arch/arm64/include/asm/ptdump.h |  2 ++
 arch/arm64/mm/dump.c            |  1 +
 arch/arm64/mm/ptdump_debugfs.c  | 18 ++++++++++++++++++
 4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index 1c906d932d6b..be552fa351e2 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -48,7 +48,8 @@ config DEBUG_WX
 	  of other unfixed kernel bugs easier.
 
 	  There is no runtime or memory usage effect of this option
-	  once the kernel has booted up - it's a one time check.
+	  once the kernel has booted up - it's a one time check and
+	  can be checked by echo "1" to "check_wx_pages" debugfs in runtime.
 
 	  If in doubt, say "Y".
 
diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
index 38187f74e089..b80d6b4fc508 100644
--- a/arch/arm64/include/asm/ptdump.h
+++ b/arch/arm64/include/asm/ptdump.h
@@ -24,9 +24,11 @@ struct ptdump_info {
 void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
 #ifdef CONFIG_PTDUMP_DEBUGFS
 void ptdump_debugfs_register(struct ptdump_info *info, const char *name);
+int ptdump_check_wx_init(void);
 #else
 static inline void ptdump_debugfs_register(struct ptdump_info *info,
 					   const char *name) { }
+static inline int ptdump_check_wx_init(void) { return 0; }
 #endif
 void ptdump_check_wx(void);
 #endif /* CONFIG_PTDUMP_CORE */
diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
index 860c00ec8bd3..60c99a047763 100644
--- a/arch/arm64/mm/dump.c
+++ b/arch/arm64/mm/dump.c
@@ -378,6 +378,7 @@ static int ptdump_init(void)
 #endif
 	ptdump_initialize();
 	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
+	ptdump_check_wx_init();
 	return 0;
 }
 device_initcall(ptdump_init);
diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
index 1f2eae3e988b..73cddc12c3c2 100644
--- a/arch/arm64/mm/ptdump_debugfs.c
+++ b/arch/arm64/mm/ptdump_debugfs.c
@@ -16,3 +16,21 @@ void ptdump_debugfs_register(struct ptdump_info *info, const char *name)
 {
 	debugfs_create_file(name, 0400, NULL, info, &ptdump_fops);
 }
+
+static int check_wx_debugfs_set(void *data, u64 val)
+{
+	if (val != 1ULL)
+		return -EINVAL;
+
+	ptdump_check_wx();
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
+
+int ptdump_check_wx_init(void)
+{
+	return debugfs_create_file("check_wx_pages", 0200, NULL,
+				   NULL, &check_wx_fops) ? 0 : -ENOMEM;
+}
-- 
2.20.1