linux-kernel - [RFC 2/3] arm64/ptdump: Enable console output in pt_dump_seq

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Message-Id: <20250818091436.938517-3-anshuman.khandual@arm.com>
Date: Mon, 18 Aug 2025 14:44:35 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: Anshuman Khandual <anshuman.khandual@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Mark Brown <broonie@...nel.org>,
	Ryan Roberts <ryan.roberts@....com>,
	Mark Rutland <mark.rutland@....com>,
	linux-kernel@...r.kernel.org
Subject: [RFC 2/3] arm64/ptdump: Enable console output in pt_dump_seq_[printf|puts]()

Enable console output in pt_dump_seq_[printf|puts]() in order to dump early
kernel page tables when required. CONFIG_DEBUG_WX enabled ptdump_check_wx()
already sets seq file as NULL to avoid any output. Hence just introduce a
special sentinel named CONSOLE as ((struct seq_file *)-1) which can be used
to identify kernel console output request for early kernel page table dump.

Suggested-by: Ryan Roberts <ryan.roberts@....com>
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 arch/arm64/mm/ptdump.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 7c42be62898b..c78e6b496dea 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -25,17 +25,26 @@
 #include <asm/pgtable-hwdef.h>
 #include <asm/ptdump.h>
 
-
-#define pt_dump_seq_printf(m, fmt, args...)	\
-({						\
-	if (m)					\
-		seq_printf(m, fmt, ##args);	\
+#define CONSOLE ((struct seq_file *)-1)
+
+#define pt_dump_seq_printf(m, fmt, args...)		\
+({							\
+	if (m) {					\
+		if (m == CONSOLE)			\
+			pr_cont(fmt, ##args);		\
+		else					\
+			seq_printf(m, fmt, ##args);	\
+	}						\
 })
 
-#define pt_dump_seq_puts(m, fmt)	\
-({					\
-	if (m)				\
-		seq_printf(m, fmt);	\
+#define pt_dump_seq_puts(m, fmt)		\
+({						\
+	if (m)	{				\
+		if (m == CONSOLE)		\
+			pr_cont(fmt);		\
+		else				\
+			seq_printf(m, fmt);	\
+	}					\
 })
 
 static const struct ptdump_prot_bits pte_bits[] = {
-- 
2.25.1