On 07/08/2019 00:58, Andrew Morton wrote:

On Wed, 31 Jul 2019 16:46:01 +0100 Steven Price [off-list ref] wrote:

quoted

Make use of the new functionality in walk_page_range to remove the
arch page walking code and use the generic code to walk the page tables.

The effective permissions are passed down the chain using new fields
in struct pg_state.

The KASAN optimisation is implemented by including test_p?d callbacks
which can decide to skip an entire tree of entries

...

+static const struct ptdump_range ptdump_ranges[] = {
+#ifdef CONFIG_X86_64
 
-#define pgd_large(a) (pgtable_l5_enabled() ? pgd_large(a) : p4d_large(__p4d(pgd_val(a))))
-#define pgd_none(a)  (pgtable_l5_enabled() ? pgd_none(a) : p4d_none(__p4d(pgd_val(a))))
+#define normalize_addr_shift (64 - (__VIRTUAL_MASK_SHIFT + 1))
+#define normalize_addr(u) ((signed long)(u << normalize_addr_shift) \
+				>> normalize_addr_shift)
 
-static inline bool is_hypervisor_range(int idx)
-{
-#ifdef CONFIG_X86_64
-	/*
-	 * A hole in the beginning of kernel address space reserved
-	 * for a hypervisor.
-	 */
-	return	(idx >= pgd_index(GUARD_HOLE_BASE_ADDR)) &&
-		(idx <  pgd_index(GUARD_HOLE_END_ADDR));
+	{0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
+	{normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},

This blows up because PGD_LEVEL_MULT is sometimes not a constant.

x86_64 allmodconfig:

In file included from ./arch/x86/include/asm/pgtable_types.h:249:0,
                 from ./arch/x86/include/asm/paravirt_types.h:45,
                 from ./arch/x86/include/asm/ptrace.h:94,
                 from ./arch/x86/include/asm/math_emu.h:5,
                 from ./arch/x86/include/asm/processor.h:12,
                 from ./arch/x86/include/asm/cpufeature.h:5,
                 from ./arch/x86/include/asm/thread_info.h:53,
                 from ./include/linux/thread_info.h:38,
                 from ./arch/x86/include/asm/preempt.h:7,
                 from ./include/linux/preempt.h:78,
                 from ./include/linux/spinlock.h:51,
                 from ./include/linux/wait.h:9,
                 from ./include/linux/wait_bit.h:8,
                 from ./include/linux/fs.h:6,
                 from ./include/linux/debugfs.h:15,
                 from arch/x86/mm/dump_pagetables.c:11:
./arch/x86/include/asm/pgtable_64_types.h:56:22: error: initializer element is not constant
 #define PTRS_PER_PGD 512
                      ^

This is very unhelpful of GCC - it's actually PTRS_PER_P4D which isn't
constant!

arch/x86/mm/dump_pagetables.c:363:6: note: in expansion of macro ‘PTRS_PER_PGD’
  {0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
      ^~~~~~~~~~~~
./arch/x86/include/asm/pgtable_64_types.h:56:22: note: (near initialization for ‘ptdump_ranges[0].end’)
 #define PTRS_PER_PGD 512
                      ^
arch/x86/mm/dump_pagetables.c:363:6: note: in expansion of macro ‘PTRS_PER_PGD’
  {0, PTRS_PER_PGD * PGD_LEVEL_MULT / 2},
      ^~~~~~~~~~~~
arch/x86/mm/dump_pagetables.c:360:27: error: initializer element is not constant
 #define normalize_addr(u) ((signed long)(u << normalize_addr_shift) \
                           ^
arch/x86/mm/dump_pagetables.c:364:3: note: in expansion of macro ‘normalize_addr’
  {normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},
   ^~~~~~~~~~~~~~
arch/x86/mm/dump_pagetables.c:360:27: note: (near initialization for ‘ptdump_ranges[1].start’)
 #define normalize_addr(u) ((signed long)(u << normalize_addr_shift) \
                           ^
arch/x86/mm/dump_pagetables.c:364:3: note: in expansion of macro ‘normalize_addr’
  {normalize_addr(PTRS_PER_PGD * PGD_LEVEL_MULT / 2), ~0UL},

I don't know what to do about this so I'll drop the series.

My best solution to this is to simply make ptdump_ranges dynamic (see
below). But there are other problems with this series (thanks for
spotting them), so I'll send out another version later.

Thanks,

Steve

----8<-----

diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 998c7f46763c..8fc129ff985e 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c

@@ -353,7 +353,10 @@ static void note_page(struct ptdump_state *pt_st,

unsigned long addr, int level,
        }
 }

-static const struct ptdump_range ptdump_ranges[] = {
+static void ptdump_walk_pgd_level_core(struct seq_file *m, struct
mm_struct *mm,
+                                      bool checkwx, bool dmesg)
+{
+       const struct ptdump_range ptdump_ranges[] = {
 #ifdef CONFIG_X86_64

 #define normalize_addr_shift (64 - (__VIRTUAL_MASK_SHIFT + 1))

@@ -368,9 +371,6 @@ static const struct ptdump_range ptdump_ranges[] = {
        {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 = {
                .ptdump = {
                        .note_page      = note_page,

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