[PATCH 1/3] x86, ptdump: Add the functionality to dump an arbitrary pagetable

[Borislav Petkov <bp@alien8.de>]

From: Borislav Petkov <bp@suse.de>

With reusing the ->trampoline_pgd page table for mapping EFI regions in
order to use them after having switched to EFI virtual mode, it is very
useful to be able to dump aforementioned page table in dmesg. This adds
that functionality through the walk_pgd_level() interface which can be
called from somewhere else.

The original functionality of dumping to debugfs remains untouched.

Cc: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/include/asm/pgtable.h |  3 +-
 arch/x86/mm/dump_pagetables.c  | 77 ++++++++++++++++++++++++++++--------------
 2 files changed, 53 insertions(+), 27 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 3d1999458709..595305f59da0 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -15,9 +15,10 @@
 	 : (prot))
 
 #ifndef __ASSEMBLY__
-
 #include <asm/x86_init.h>
 
+void walk_pgd_level(struct seq_file *m, pgd_t *pgd);
+
 /*
  * ZERO_PAGE is a global shared page that is always zero: used
  * for zero-mapped memory areas etc..
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 0002a3a33081..f987ecff9226 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -19,6 +19,8 @@
 
 #include <asm/pgtable.h>
 
+static bool dump_to_dmesg;
+
 /*
  * The dumper groups pagetable entries of the same type into one, and for
  * that it needs to keep some state when walking, and flush this state
@@ -88,6 +90,24 @@ static struct addr_marker address_markers[] = {
 #define PUD_LEVEL_MULT (PTRS_PER_PMD * PMD_LEVEL_MULT)
 #define PGD_LEVEL_MULT (PTRS_PER_PUD * PUD_LEVEL_MULT)
 
+#define pt_dump_seq_printf(m, fmt, args...)			\
+({								\
+	if (dump_to_dmesg)					\
+		printk(KERN_INFO fmt, ##args);			\
+	else							\
+		if (m)						\
+			seq_printf(m, fmt, ##args);		\
+})
+
+#define pt_dump_cont_printf(m, fmt, args...)			\
+({								\
+	if (dump_to_dmesg)					\
+		printk(KERN_CONT fmt, ##args);			\
+	else							\
+		if (m)						\
+			seq_printf(m, fmt, ##args);		\
+})
+
 /*
  * Print a readable form of a pgprot_t to the seq_file
  */
@@ -99,47 +119,47 @@ static void printk_prot(struct seq_file *m, pgprot_t prot, int level)
 
 	if (!pgprot_val(prot)) {
 		/* Not present */
-		seq_printf(m, "                          ");
+		pt_dump_cont_printf(m, "                          ");
 	} else {
 		if (pr & _PAGE_USER)
-			seq_printf(m, "USR ");
+			pt_dump_cont_printf(m, "USR ");
 		else
-			seq_printf(m, "    ");
+			pt_dump_cont_printf(m, "    ");
 		if (pr & _PAGE_RW)
-			seq_printf(m, "RW ");
+			pt_dump_cont_printf(m, "RW ");
 		else
-			seq_printf(m, "ro ");
+			pt_dump_cont_printf(m, "ro ");
 		if (pr & _PAGE_PWT)
-			seq_printf(m, "PWT ");
+			pt_dump_cont_printf(m, "PWT ");
 		else
-			seq_printf(m, "    ");
+			pt_dump_cont_printf(m, "    ");
 		if (pr & _PAGE_PCD)
-			seq_printf(m, "PCD ");
+			pt_dump_cont_printf(m, "PCD ");
 		else
-			seq_printf(m, "    ");
+			pt_dump_cont_printf(m, "    ");
 
 		/* Bit 9 has a different meaning on level 3 vs 4 */
 		if (level <= 3) {
 			if (pr & _PAGE_PSE)
-				seq_printf(m, "PSE ");
+				pt_dump_cont_printf(m, "PSE ");
 			else
-				seq_printf(m, "    ");
+				pt_dump_cont_printf(m, "    ");
 		} else {
 			if (pr & _PAGE_PAT)
-				seq_printf(m, "pat ");
+				pt_dump_cont_printf(m, "pat ");
 			else
-				seq_printf(m, "    ");
+				pt_dump_cont_printf(m, "    ");
 		}
 		if (pr & _PAGE_GLOBAL)
-			seq_printf(m, "GLB ");
+			pt_dump_cont_printf(m, "GLB ");
 		else
-			seq_printf(m, "    ");
+			pt_dump_cont_printf(m, "    ");
 		if (pr & _PAGE_NX)
-			seq_printf(m, "NX ");
+			pt_dump_cont_printf(m, "NX ");
 		else
-			seq_printf(m, "x  ");
+			pt_dump_cont_printf(m, "x  ");
 	}
-	seq_printf(m, "%s\n", level_name[level]);
+	pt_dump_cont_printf(m, "%s\n", level_name[level]);
 }
 
 /*
@@ -178,7 +198,7 @@ static void note_page(struct seq_file *m, struct pg_state *st,
 		st->current_prot = new_prot;
 		st->level = level;
 		st->marker = address_markers;
-		seq_printf(m, "---[ %s ]---\n", st->marker->name);
+		pt_dump_seq_printf(m, "---[ %s ]---\n", st->marker->name);
 	} else if (prot != cur || level != st->level ||
 		   st->current_address >= st->marker[1].start_address) {
 		const char *unit = units;
@@ -188,16 +208,16 @@ static void note_page(struct seq_file *m, struct pg_state *st,
 		/*
 		 * Now print the actual finished series
 		 */
-		seq_printf(m, "0x%0*lx-0x%0*lx   ",
-			   width, st->start_address,
-			   width, st->current_address);
+		pt_dump_seq_printf(m, "0x%0*lx-0x%0*lx   ",
+				   width, st->start_address,
+				   width, st->current_address);
 
 		delta = (st->current_address - st->start_address) >> 10;
 		while (!(delta & 1023) && unit[1]) {
 			delta >>= 10;
 			unit++;
 		}
-		seq_printf(m, "%9lu%c ", delta, *unit);
+		pt_dump_cont_printf(m, "%9lu%c ", delta, *unit);
 		printk_prot(m, st->current_prot, st->level);
 
 		/*
@@ -207,7 +227,7 @@ static void note_page(struct seq_file *m, struct pg_state *st,
 		 */
 		if (st->current_address >= st->marker[1].start_address) {
 			st->marker++;
-			seq_printf(m, "---[ %s ]---\n", st->marker->name);
+			pt_dump_seq_printf(m, "---[ %s ]---\n", st->marker->name);
 		}
 
 		st->start_address = st->current_address;
@@ -296,7 +316,7 @@ static void walk_pud_level(struct seq_file *m, struct pg_state *st, pgd_t addr,
 #define pgd_none(a)  pud_none(__pud(pgd_val(a)))
 #endif
 
-static void walk_pgd_level(struct seq_file *m)
+void walk_pgd_level(struct seq_file *m, pgd_t *pgd)
 {
 #ifdef CONFIG_X86_64
 	pgd_t *start = (pgd_t *) &init_level4_pgt;
@@ -306,6 +326,11 @@ static void walk_pgd_level(struct seq_file *m)
 	int i;
 	struct pg_state st;
 
+	if (pgd) {
+		start = pgd;
+		dump_to_dmesg = true;
+	}
+
 	memset(&st, 0, sizeof(st));
 
 	for (i = 0; i < PTRS_PER_PGD; i++) {
@@ -331,7 +356,7 @@ static void walk_pgd_level(struct seq_file *m)
 
 static int ptdump_show(struct seq_file *m, void *v)
 {
-	walk_pgd_level(m);
+	walk_pgd_level(m, NULL);
 	return 0;
 }
 
-- 
1.8.4