[RFC PATCH 3/3] x86: mm: Switch to using generic pt_dump

From: Steven Price <steven.price@arm.com>
To: Dave Hansen <dave.hansen@intel.com>,
	linux-mm@kvack.org,
	Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Mark Rutland" <Mark.Rutland@arm.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	x86@kernel.org, "Will Deacon" <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Borislav Petkov" <bp@alien8.de>,
	"Andy Lutomirski" <luto@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"James Morse" <james.morse@arm.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-arm-kernel@lists.infradead.org, "Liang,
	Kan" <kan.liang@linux.intel.com>,
	"Steven Price" <steven.price@arm.com>
Subject: [RFC PATCH 3/3] x86: mm: Switch to using generic pt_dump
Date: Wed, 17 Apr 2019 15:34:23 +0100	[thread overview]
Message-ID: <20190417143423.26665-3-steven.price@arm.com> (raw)
In-Reply-To: <20190417143423.26665-1-steven.price@arm.com>

Instead of providing our own callbacks for walking the page tables,
switch to using the generic version instead.

Signed-off-by: Steven Price <steven.price@arm.com>
---
 arch/x86/Kconfig              |   1 +
 arch/x86/Kconfig.debug        |  20 +--
 arch/x86/mm/Makefile          |   4 +-
 arch/x86/mm/dump_pagetables.c | 297 +++++++---------------------------
 4 files changed, 62 insertions(+), 260 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c1f9b3cf437c..122c24055f02 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -106,6 +106,7 @@ config X86
 	select GENERIC_IRQ_RESERVATION_MODE
 	select GENERIC_IRQ_SHOW
 	select GENERIC_PENDING_IRQ		if SMP
+	select GENERIC_PTDUMP
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_STRNCPY_FROM_USER
 	select GENERIC_STRNLEN_USER
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 15d0fbe27872..dc1dfe213657 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -62,26 +62,10 @@ config EARLY_PRINTK_USB_XDBC
 config MCSAFE_TEST
 	def_bool n
 
-config X86_PTDUMP_CORE
-	def_bool n
-
-config X86_PTDUMP
-	tristate "Export kernel pagetable layout to userspace via debugfs"
-	depends on DEBUG_KERNEL
-	select DEBUG_FS
-	select X86_PTDUMP_CORE
-	---help---
-	  Say Y here if you want to show the kernel pagetable layout in a
-	  debugfs file. This information is only useful for kernel developers
-	  who are working in architecture specific areas of the kernel.
-	  It is probably not a good idea to enable this feature in a production
-	  kernel.
-	  If in doubt, say "N"
-
 config EFI_PGT_DUMP
 	bool "Dump the EFI pagetable"
 	depends on EFI
-	select X86_PTDUMP_CORE
+	select PTDUMP_CORE
 	---help---
 	  Enable this if you want to dump the EFI page table before
 	  enabling virtual mode. This can be used to debug miscellaneous
@@ -90,7 +74,7 @@ config EFI_PGT_DUMP
 
 config DEBUG_WX
 	bool "Warn on W+X mappings at boot"
-	select X86_PTDUMP_CORE
+	select PTDUMP_CORE
 	---help---
 	  Generate a warning if any W+X mappings are found at boot.
 
diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
index 4b101dd6e52f..5233190fc6bf 100644
--- a/arch/x86/mm/Makefile
+++ b/arch/x86/mm/Makefile
@@ -28,8 +28,8 @@ obj-$(CONFIG_X86_PAT)		+= pat_rbtree.o
 obj-$(CONFIG_X86_32)		+= pgtable_32.o iomap_32.o
 
 obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
-obj-$(CONFIG_X86_PTDUMP_CORE)	+= dump_pagetables.o
-obj-$(CONFIG_X86_PTDUMP)	+= debug_pagetables.o
+obj-$(CONFIG_PTDUMP_CORE)	+= dump_pagetables.o
+obj-$(CONFIG_PTDUMP_DEBUGFS)	+= debug_pagetables.o
 
 obj-$(CONFIG_HIGHMEM)		+= highmem_32.o
 
diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index f6b814aaddf7..955824c7cddb 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -20,6 +20,7 @@
 #include <linux/seq_file.h>
 #include <linux/highmem.h>
 #include <linux/pci.h>
+#include <linux/ptdump.h>
 
 #include <asm/e820/types.h>
 #include <asm/pgtable.h>
@@ -30,15 +31,12 @@
  * when a "break" in the continuity is found.
  */
 struct pg_state {
+	struct ptdump_state ptdump;
 	int level;
-	pgprot_t current_prot;
+	pgprotval_t current_prot;
 	pgprotval_t effective_prot;
-	pgprotval_t effective_prot_pgd;
-	pgprotval_t effective_prot_p4d;
-	pgprotval_t effective_prot_pud;
-	pgprotval_t effective_prot_pmd;
+	pgprotval_t prot_levels[5];
 	unsigned long start_address;
-	unsigned long current_address;
 	const struct addr_marker *marker;
 	unsigned long lines;
 	bool to_dmesg;
@@ -179,9 +177,8 @@ static struct addr_marker address_markers[] = {
 /*
  * Print a readable form of a pgprot_t to the seq_file
  */
-static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
+static void printk_prot(struct seq_file *m, pgprotval_t pr, int level, bool dmsg)
 {
-	pgprotval_t pr = pgprot_val(prot);
 	static const char * const level_name[] =
 		{ "cr3", "pgd", "p4d", "pud", "pmd", "pte" };
 
@@ -228,24 +225,11 @@ static void printk_prot(struct seq_file *m, pgprot_t prot, int level, bool dmsg)
 	pt_dump_cont_printf(m, dmsg, "%s\n", level_name[level]);
 }
 
-/*
- * On 64 bits, sign-extend the 48 bit address to 64 bit
- */
-static unsigned long normalize_addr(unsigned long u)
-{
-	int shift;
-	if (!IS_ENABLED(CONFIG_X86_64))
-		return u;
-
-	shift = 64 - (__VIRTUAL_MASK_SHIFT + 1);
-	return (signed long)(u << shift) >> shift;
-}
-
-static void note_wx(struct pg_state *st)
+static void note_wx(struct pg_state *st, unsigned long addr)
 {
 	unsigned long npages;
 
-	npages = (st->current_address - st->start_address) / PAGE_SIZE;
+	npages = (addr - st->start_address) / PAGE_SIZE;
 
 #ifdef CONFIG_PCI_BIOS
 	/*
@@ -253,7 +237,7 @@ static void note_wx(struct pg_state *st)
 	 * Inform about it, but avoid the warning.
 	 */
 	if (pcibios_enabled && st->start_address >= PAGE_OFFSET + BIOS_BEGIN &&
-	    st->current_address <= PAGE_OFFSET + BIOS_END) {
+	    addr <= PAGE_OFFSET + BIOS_END) {
 		pr_warn_once("x86/mm: PCI BIOS W+X mapping %lu pages\n", npages);
 		return;
 	}
@@ -264,25 +248,44 @@ static void note_wx(struct pg_state *st)
 		  (void *)st->start_address);
 }
 
+static inline pgprotval_t effective_prot(pgprotval_t prot1, pgprotval_t prot2)
+{
+	return (prot1 & prot2 & (_PAGE_USER | _PAGE_RW)) |
+	       ((prot1 | prot2) & _PAGE_NX);
+}
+
 /*
  * This function gets called on a break in a continuous series
  * of PTE entries; the next one is different so we need to
  * print what we collected so far.
  */
-static void note_page(struct pg_state *st, pgprot_t new_prot,
-		      pgprotval_t new_eff, int level)
+static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
+		      unsigned long val)
 {
-	pgprotval_t prot, cur, eff;
+	struct pg_state *st = container_of(pt_st, struct pg_state, ptdump);
+	pgprotval_t new_prot, new_eff;
+	pgprotval_t cur, eff;
 	static const char units[] = "BKMGTPE";
 	struct seq_file *m = st->seq;
 
+	new_prot = val & PTE_FLAGS_MASK;
+
+	if (level > 1) {
+		new_eff = effective_prot(st->prot_levels[level - 2],
+					 new_prot);
+	} else {
+		new_eff = new_prot;
+	}
+
+	if (level > 0)
+		st->prot_levels[level-1] = new_eff;
+
 	/*
 	 * If we have a "break" in the series, we need to flush the state that
 	 * we have now. "break" is either changing perms, levels or
 	 * address space marker.
 	 */
-	prot = pgprot_val(new_prot);
-	cur = pgprot_val(st->current_prot);
+	cur = st->current_prot;
 	eff = st->effective_prot;
 
 	if (!st->level) {
@@ -294,14 +297,14 @@ static void note_page(struct pg_state *st, pgprot_t new_prot,
 		st->lines = 0;
 		pt_dump_seq_printf(m, st->to_dmesg, "---[ %s ]---\n",
 				   st->marker->name);
-	} else if (prot != cur || new_eff != eff || level != st->level ||
-		   st->current_address >= st->marker[1].start_address) {
+	} else if (new_prot != cur || new_eff != eff || level != st->level ||
+		   addr >= st->marker[1].start_address) {
 		const char *unit = units;
 		unsigned long delta;
 		int width = sizeof(unsigned long) * 2;
 
 		if (st->check_wx && (eff & _PAGE_RW) && !(eff & _PAGE_NX))
-			note_wx(st);
+			note_wx(st, addr);
 
 		/*
 		 * Now print the actual finished series
@@ -311,9 +314,9 @@ static void note_page(struct pg_state *st, pgprot_t new_prot,
 			pt_dump_seq_printf(m, st->to_dmesg,
 					   "0x%0*lx-0x%0*lx   ",
 					   width, st->start_address,
-					   width, st->current_address);
+					   width, addr);
 
-			delta = st->current_address - st->start_address;
+			delta = addr - st->start_address;
 			while (!(delta & 1023) && unit[1]) {
 				delta >>= 10;
 				unit++;
@@ -331,7 +334,7 @@ static void note_page(struct pg_state *st, pgprot_t new_prot,
 		 * such as the start of vmalloc space etc.
 		 * This helps in the interpretation.
 		 */
-		if (st->current_address >= st->marker[1].start_address) {
+		if (addr >= st->marker[1].start_address) {
 			if (st->marker->max_lines &&
 			    st->lines > st->marker->max_lines) {
 				unsigned long nskip =
@@ -347,228 +350,42 @@ static void note_page(struct pg_state *st, pgprot_t new_prot,
 					   st->marker->name);
 		}
 
-		st->start_address = st->current_address;
+		st->start_address = addr;
 		st->current_prot = new_prot;
 		st->effective_prot = new_eff;
 		st->level = level;
 	}
 }
 
-static inline pgprotval_t effective_prot(pgprotval_t prot1, pgprotval_t prot2)
-{
-	return (prot1 & prot2 & (_PAGE_USER | _PAGE_RW)) |
-	       ((prot1 | prot2) & _PAGE_NX);
-}
-
-static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
-			    unsigned long next, struct mm_walk *walk)
-{
-	struct pg_state *st = walk->private;
-	pgprotval_t eff, prot;
-
-	st->current_address = normalize_addr(addr);
-
-	prot = pte_flags(*pte);
-	eff = effective_prot(st->effective_prot_pmd, prot);
-	note_page(st, __pgprot(prot), eff, 5);
-
-	return 0;
-}
-
-#ifdef CONFIG_KASAN
-
-/*
- * This is an optimization for KASAN=y case. Since all kasan page tables
- * eventually point to the kasan_early_shadow_page we could call note_page()
- * right away without walking through lower level page tables. This saves
- * us dozens of seconds (minutes for 5-level config) while checking for
- * W+X mapping or reading kernel_page_tables debugfs file.
- */
-static inline bool kasan_page_table(struct pg_state *st, void *pt)
-{
-	if (__pa(pt) == __pa(kasan_early_shadow_pmd) ||
-	    (pgtable_l5_enabled() &&
-			__pa(pt) == __pa(kasan_early_shadow_p4d)) ||
-	    __pa(pt) == __pa(kasan_early_shadow_pud)) {
-		pgprotval_t prot = pte_flags(kasan_early_shadow_pte[0]);
-		note_page(st, __pgprot(prot), 0, 5);
-		return true;
-	}
-	return false;
-}
-#else
-static inline bool kasan_page_table(struct pg_state *st, void *pt)
-{
-	return false;
-}
-#endif
-
-static int ptdump_test_pmd(unsigned long addr, unsigned long next,
-			   pmd_t *pmd, struct mm_walk *walk)
-{
-	struct pg_state *st = walk->private;
-
-	st->current_address = normalize_addr(addr);
-
-	if (kasan_page_table(st, pmd))
-		return 1;
-	return 0;
-}
-
-static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
-			    unsigned long next, struct mm_walk *walk)
-{
-	struct pg_state *st = walk->private;
-	pgprotval_t eff, prot;
-
-	prot = pmd_flags(*pmd);
-	eff = effective_prot(st->effective_prot_pud, prot);
-
-	st->current_address = normalize_addr(addr);
-
-	if (pmd_large(*pmd))
-		note_page(st, __pgprot(prot), eff, 4);
-
-	st->effective_prot_pmd = eff;
-
-	return 0;
-}
-
-static int ptdump_test_pud(unsigned long addr, unsigned long next,
-			   pud_t *pud, struct mm_walk *walk)
-{
-	struct pg_state *st = walk->private;
-
-	st->current_address = normalize_addr(addr);
-
-	if (kasan_page_table(st, pud))
-		return 1;
-	return 0;
-}
-
-static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
-			    unsigned long next, struct mm_walk *walk)
-{
-	struct pg_state *st = walk->private;
-	pgprotval_t eff, prot;
-
-	prot = pud_flags(*pud);
-	eff = effective_prot(st->effective_prot_p4d, prot);
-
-	st->current_address = normalize_addr(addr);
-
-	if (pud_large(*pud))
-		note_page(st, __pgprot(prot), eff, 3);
-
-	st->effective_prot_pud = eff;
-
-	return 0;
-}
-
-static int ptdump_test_p4d(unsigned long addr, unsigned long next,
-			   p4d_t *p4d, struct mm_walk *walk)
-{
-	struct pg_state *st = walk->private;
-
-	st->current_address = normalize_addr(addr);
-
-	if (kasan_page_table(st, p4d))
-		return 1;
-	return 0;
-}
-
-static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
-			    unsigned long next, struct mm_walk *walk)
-{
-	struct pg_state *st = walk->private;
-	pgprotval_t eff, prot;
-
-	prot = p4d_flags(*p4d);
-	eff = effective_prot(st->effective_prot_pgd, prot);
-
-	st->current_address = normalize_addr(addr);
-
-	if (p4d_large(*p4d))
-		note_page(st, __pgprot(prot), eff, 2);
-
-	st->effective_prot_p4d = eff;
-
-	return 0;
-}
-
-static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
-			    unsigned long next, struct mm_walk *walk)
-{
-	struct pg_state *st = walk->private;
-	pgprotval_t eff, prot;
+static const struct ptdump_range ptdump_ranges[] = {
+#ifdef CONFIG_X86_64
 
-	prot = pgd_flags(*pgd);
+#define normalize_addr_shift (64 - (__VIRTUAL_MASK_SHIFT + 1))
+#define normalize_addr(u) ((signed long)(u << normalize_addr_shift) >> normalize_addr_shift)
 
-#ifdef CONFIG_X86_PAE
-	eff = _PAGE_USER | _PAGE_RW;
+	{0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
+	{normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},
 #else
-	eff = prot;
+	{0, ~0UL},
 #endif
-
-	st->current_address = normalize_addr(addr);
-
-	if (pgd_large(*pgd))
-		note_page(st, __pgprot(prot), eff, 1);
-
-	st->effective_prot_pgd = eff;
-
-	return 0;
-}
-
-static int ptdump_hole(unsigned long addr, unsigned long next,
-		       struct mm_walk *walk)
-{
-	struct pg_state *st = walk->private;
-
-	st->current_address = normalize_addr(addr);
-
-	note_page(st, __pgprot(0), 0, -1);
-
-	return 0;
-}
+	{0, 0}
+};
 
 static void ptdump_walk_pgd_level_core(struct seq_file *m, struct mm_struct *mm,
 				       bool checkwx, bool dmesg)
 {
-	struct pg_state st = {};
-	struct mm_walk walk = {
-		.mm		= mm,
-		.pgd_entry	= ptdump_pgd_entry,
-		.p4d_entry	= ptdump_p4d_entry,
-		.pud_entry	= ptdump_pud_entry,
-		.pmd_entry	= ptdump_pmd_entry,
-		.pte_entry	= ptdump_pte_entry,
-		.test_p4d	= ptdump_test_p4d,
-		.test_pud	= ptdump_test_pud,
-		.test_pmd	= ptdump_test_pmd,
-		.pte_hole	= ptdump_hole,
-		.private	= &st
+	struct pg_state st = {
+		.ptdump = {
+			.note_page	= note_page,
+			.range		= ptdump_ranges
+		},
+		.to_dmesg	= dmesg,
+		.check_wx	= checkwx,
+		.seq		= m
 	};
 
-	st.to_dmesg = dmesg;
-	st.check_wx = checkwx;
-	st.seq = m;
-	if (checkwx)
-		st.wx_pages = 0;
-
-	down_read(&mm->mmap_sem);
-#ifdef CONFIG_X86_64
-	walk_page_range(0, PTRS_PER_PGD*PGD_LEVEL_MULT/2, &walk);
-	walk_page_range(normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT/2), ~0,
-			&walk);
-#else
-	walk_page_range(0, ~0, &walk);
-#endif
-	up_read(&mm->mmap_sem);
+	ptdump_walk_pgd(&st.ptdump, mm);
 
-	/* Flush out the last page */
-	st.current_address = normalize_addr(PTRS_PER_PGD*PGD_LEVEL_MULT);
-	note_page(&st, __pgprot(0), 0, 0);
 	if (!checkwx)
 		return;
 	if (st.wx_pages)
-- 
2.20.1

