On 01.12.19 02:53, akpm@xxxxxxxxxxxxxxxxxxxx wrote: > From: Steven Price <steven.price@xxxxxxx> > Subject: mm: add generic ptdump > > Add a generic version of page table dumping that architectures can opt-in > to > > [steven.price@xxxxxxx: v15] > Link: http://lkml.kernel.org/r/20191101140942.51554-20-steven.price@xxxxxxx > [cai@xxxxxx: fix a -Wold-style-declaration warning] > Link: http://lkml.kernel.org/r/1572895385-29194-1-git-send-email-cai@xxxxxx > Link: http://lkml.kernel.org/r/20191028135910.33253-20-steven.price@xxxxxxx > Signed-off-by: Steven Price <steven.price@xxxxxxx> > Signed-off-by: Qian Cai <cai@xxxxxx> > Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx> > Cc: Alexander Potapenko <glider@xxxxxxxxxx> > Cc: Alexandre Ghiti <alex@xxxxxxxx> > Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> > Cc: Andy Lutomirski <luto@xxxxxxxxxx> > Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > Cc: Arnd Bergmann <arnd@xxxxxxxx> > Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > Cc: Borislav Petkov <bp@xxxxxxxxx> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx> > Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > Cc: Dave Jiang <dave.jiang@xxxxxxxxx> > Cc: David S. Miller <davem@xxxxxxxxxxxxx> > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxx> > Cc: James Hogan <jhogan@xxxxxxxxxx> > Cc: James Morse <james.morse@xxxxxxx> > Cc: "Liang, Kan" <kan.liang@xxxxxxxxxxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Cc: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> > Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> > Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > Cc: Palmer Dabbelt <palmer@xxxxxxxxxx> > Cc: Paul Burton <paul.burton@xxxxxxxx> > Cc: Paul Mackerras <paulus@xxxxxxxxx> > Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> > Cc: Russell King <linux@xxxxxxxxxxxxxxx> > Cc: Shiraz Hashim <shashim@xxxxxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> > Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx> > Cc: Will Deacon <will@xxxxxxxxxx> > Cc: Zong Li <zong.li@xxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > include/linux/ptdump.h | 21 +++++ > mm/Kconfig.debug | 21 +++++ > mm/Makefile | 1 > mm/ptdump.c | 151 +++++++++++++++++++++++++++++++++++++++ > 4 files changed, 194 insertions(+) > > --- /dev/null > +++ a/include/linux/ptdump.h > @@ -0,0 +1,21 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > + > +#ifndef _LINUX_PTDUMP_H > +#define _LINUX_PTDUMP_H > + > +#include <linux/mm_types.h> > + > +struct ptdump_range { > + unsigned long start; > + unsigned long end; > +}; > + > +struct ptdump_state { > + void (*note_page)(struct ptdump_state *st, unsigned long addr, > + int level, unsigned long val); > + const struct ptdump_range *range; > +}; > + > +void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm); > + > +#endif /* _LINUX_PTDUMP_H */ > --- a/mm/Kconfig.debug~mm-add-generic-ptdump > +++ a/mm/Kconfig.debug > @@ -117,3 +117,24 @@ config DEBUG_RODATA_TEST > depends on STRICT_KERNEL_RWX > ---help--- > This option enables a testcase for the setting rodata read-only. > + > +config GENERIC_PTDUMP > + bool > + > +config PTDUMP_CORE > + bool > + > +config PTDUMP_DEBUGFS > + bool "Export kernel pagetable layout to userspace via debugfs" > + depends on DEBUG_KERNEL > + depends on DEBUG_FS > + depends on GENERIC_PTDUMP > + select 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. > --- a/mm/Makefile~mm-add-generic-ptdump > +++ a/mm/Makefile > @@ -98,6 +98,7 @@ obj-$(CONFIG_CMA) += cma.o > obj-$(CONFIG_MEMORY_BALLOON) += balloon_compaction.o > obj-$(CONFIG_PAGE_EXTENSION) += page_ext.o > obj-$(CONFIG_CMA_DEBUGFS) += cma_debug.o > +obj-$(CONFIG_PTDUMP_CORE) += ptdump.o > obj-$(CONFIG_USERFAULTFD) += userfaultfd.o > obj-$(CONFIG_IDLE_PAGE_TRACKING) += page_idle.o > obj-$(CONFIG_FRAME_VECTOR) += frame_vector.o > --- /dev/null > +++ a/mm/ptdump.c > @@ -0,0 +1,151 @@ > +// SPDX-License-Identifier: GPL-2.0 > + > +#include <linux/pagewalk.h> > +#include <linux/ptdump.h> > +#include <linux/kasan.h> > + > +static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr, > + unsigned long next, struct mm_walk *walk) > +{ > + struct ptdump_state *st = walk->private; > + pgd_t val = READ_ONCE(*pgd); > + > + if (pgd_leaf(val)) > + st->note_page(st, addr, 1, pgd_val(val)); > + > + return 0; > +} > + > +static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr, > + unsigned long next, struct mm_walk *walk) > +{ > + struct ptdump_state *st = walk->private; > + p4d_t val = READ_ONCE(*p4d); > + > + if (p4d_leaf(val)) > + st->note_page(st, addr, 2, p4d_val(val)); > + > + return 0; > +} > + > +static int ptdump_pud_entry(pud_t *pud, unsigned long addr, > + unsigned long next, struct mm_walk *walk) > +{ > + struct ptdump_state *st = walk->private; > + pud_t val = READ_ONCE(*pud); > + > + if (pud_leaf(val)) > + st->note_page(st, addr, 3, pud_val(val)); > + > + return 0; > +} > + > +static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr, > + unsigned long next, struct mm_walk *walk) > +{ > + struct ptdump_state *st = walk->private; > + pmd_t val = READ_ONCE(*pmd); > + > + if (pmd_leaf(val)) > + st->note_page(st, addr, 4, pmd_val(val)); > + > + return 0; > +} > + > +static int ptdump_pte_entry(pte_t *pte, unsigned long addr, > + unsigned long next, struct mm_walk *walk) > +{ > + struct ptdump_state *st = walk->private; > + > + st->note_page(st, addr, 5, pte_val(READ_ONCE(*pte))); > + > + 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 int note_kasan_page_table(struct mm_walk *walk, > + unsigned long addr) > +{ > + struct ptdump_state *st = walk->private; > + > + st->note_page(st, addr, 5, pte_val(kasan_early_shadow_pte[0])); > + return 1; > +} > + > +static int ptdump_test_p4d(unsigned long addr, unsigned long next, > + p4d_t *p4d, struct mm_walk *walk) > +{ > +#if CONFIG_PGTABLE_LEVELS > 4 > + if (p4d == lm_alias(kasan_early_shadow_p4d)) > + return note_kasan_page_table(walk, addr); > +#endif > + return 0; > +} > + > +static int ptdump_test_pud(unsigned long addr, unsigned long next, > + pud_t *pud, struct mm_walk *walk) > +{ > +#if CONFIG_PGTABLE_LEVELS > 3 > + if (pud == lm_alias(kasan_early_shadow_pud)) > + return note_kasan_page_table(walk, addr); > +#endif > + return 0; > +} > + > +static int ptdump_test_pmd(unsigned long addr, unsigned long next, > + pmd_t *pmd, struct mm_walk *walk) > +{ > +#if CONFIG_PGTABLE_LEVELS > 2 > + if (pmd == lm_alias(kasan_early_shadow_pmd)) > + return note_kasan_page_table(walk, addr); > +#endif > + return 0; > +} > +#endif /* CONFIG_KASAN */ > + > +static int ptdump_hole(unsigned long addr, unsigned long next, > + int depth, struct mm_walk *walk) > +{ > + struct ptdump_state *st = walk->private; > + > + st->note_page(st, addr, depth + 1, 0); > + > + return 0; > +} > + > +static const struct mm_walk_ops ptdump_ops = { > + .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, > +#ifdef CONFIG_KASAN > + .test_p4d = ptdump_test_p4d, > + .test_pud = ptdump_test_pud, > + .test_pmd = ptdump_test_pmd, > +#endif > + .pte_hole = ptdump_hole, > +}; > + > +void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm) > +{ > + const struct ptdump_range *range = st->range; > + > + down_read(&mm->mmap_sem); > + while (range->start != range->end) { > + walk_page_range_novma(mm, range->start, range->end, > + &ptdump_ops, st); > + range++; > + } > + up_read(&mm->mmap_sem); > + > + /* Flush out the last page */ > + st->note_page(st, 0, 0, 0); > +} > _ > On linux-next, booting a simple QEMU x86-64 guest (since I updated from pre-v5.4 base), I get: [ 1.231285] BUG: kernel NULL pointer dereference, address: 0000000000000018 [ 1.231897] #PF: supervisor read access in kernel mode [ 1.232354] #PF: error_code(0x0000) - not-present page [ 1.232803] PGD 0 P4D 0 [ 1.233033] Oops: 0000 [#1] SMP NOPTI [ 1.233359] CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.4.0-next-20191203+ #29 [ 1.233998] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu4 [ 1.235015] RIP: 0010:__lock_acquire+0x778/0x1940 [ 1.235428] Code: 00 45 31 ff 48 8b 44 24 48 65 48 33 04 25 28 00 00 00 0f 85 fd 0d 00 00 48 83 c4 50 44 89 f8 5b7 [ 1.237051] RSP: 0018:ffffbc6100637c48 EFLAGS: 00010002 [ 1.237512] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000 [ 1.238147] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000018 [ 1.238765] RBP: ffff92dd7db54d80 R08: 0000000000000001 R09: 0000000000000000 [ 1.239395] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 1.240012] R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000 [ 1.240626] FS: 0000000000000000(0000) GS:ffff92dd7dd00000(0000) knlGS:0000000000000000 [ 1.241316] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.241808] CR2: 0000000000000018 CR3: 00000000a8610000 CR4: 00000000000006e0 [ 1.242407] Call Trace: [ 1.242626] ? check_usage_backwards+0x99/0x140 [ 1.243023] ? stack_trace_save+0x4b/0x70 [ 1.243385] lock_acquire+0xa2/0x1b0 [ 1.243707] ? __walk_page_range+0x6e5/0xa00 [ 1.244104] _raw_spin_lock+0x2c/0x40 [ 1.244431] ? __walk_page_range+0x6e5/0xa00 [ 1.244817] __walk_page_range+0x6e5/0xa00 [ 1.245184] walk_page_range_novma+0x69/0xb0 [ 1.245562] ptdump_walk_pgd+0x46/0x80 [ 1.245904] ptdump_walk_pgd_level_core+0xb7/0xe0 [ 1.246318] ? ptdump_walk_pgd_level_core+0xe0/0xe0 [ 1.246748] ? rest_init+0x23a/0x23a [ 1.247076] ? rest_init+0x23a/0x23a [ 1.247392] kernel_init+0x2c/0x106 [ 1.247700] ret_from_fork+0x27/0x50 [ 1.248025] Modules linked in: [ 1.248298] CR2: 0000000000000018 [ 1.248594] ---[ end trace d9ad45dca0b4f3a3 ]--- [ 1.249020] RIP: 0010:__lock_acquire+0x778/0x1940 [ 1.249432] Code: 00 45 31 ff 48 8b 44 24 48 65 48 33 04 25 28 00 00 00 0f 85 fd 0d 00 00 48 83 c4 50 44 89 f8 5b7 [ 1.251059] RSP: 0018:ffffbc6100637c48 EFLAGS: 00010002 [ 1.251514] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000000 [ 1.252153] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000018 [ 1.252773] RBP: ffff92dd7db54d80 R08: 0000000000000001 R09: 0000000000000000 [ 1.253396] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 [ 1.254026] R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000 [ 1.254648] FS: 0000000000000000(0000) GS:ffff92dd7dd00000(0000) knlGS:0000000000000000 [ 1.255360] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.255867] CR2: 0000000000000018 CR3: 00000000a8610000 CR4: 00000000000006e0 [ 1.256491] BUG: sleeping function called from invalid context at include/linux/percpu-rwsem.h:38 [ 1.257268] in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 1, name: swapper/0 [ 1.257952] INFO: lockdep is turned off. [ 1.258299] irq event stamp: 1570043 [ 1.258617] hardirqs last enabled at (1570043): [<ffffffff9716dd2c>] console_unlock+0x45c/0x5c0 [ 1.259386] hardirqs last disabled at (1570042): [<ffffffff9716d964>] console_unlock+0x94/0x5c0 [ 1.260153] softirqs last enabled at (1570040): [<ffffffff97e0035d>] __do_softirq+0x35d/0x45d [ 1.260898] softirqs last disabled at (1570033): [<ffffffff970efe54>] irq_exit+0xf4/0x100 [ 1.261615] CPU: 3 PID: 1 Comm: swapper/0 Tainted: G D 5.4.0-next-20191203+ #29 [ 1.262370] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu4 [ 1.263372] Call Trace: [ 1.263595] dump_stack+0x8f/0xd0 [ 1.263895] ___might_sleep.cold+0xb3/0xc3 [ 1.264246] exit_signals+0x30/0x2d0 [ 1.264552] do_exit+0xb4/0xc40 [ 1.264832] rewind_stack_do_exit+0x17/0x20 [ 1.265198] note: swapper/0[1] exited with preempt_count 1 [ 1.265700] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 [ 1.266443] Kernel Offset: 0x16000000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbff) [ 1.267394] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 ]--- Related to this? -- Thanks, David / dhildenb
