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![Vlastimil Babka](/assets/img/avatar_default.png)
The debug_pagealloc functionality is useful to catch buggy page allocator users that cause e.g. use after free or double free. When page inconsistency is detected, debugging is often simpler by knowing the call stack of process that last allocated and freed the page. When page_owner is also enabled, we record the allocation stack trace, but not freeing. This patch therefore adds recording of freeing process stack trace to page owner info, if both page_owner and debug_pagealloc are configured and enabled. With only page_owner enabled, this info is not useful for the memory leak debugging use case. dump_page() is adjusted to print the info. An example result of calling __free_pages() twice may look like this (note the page last free stack trace): BUG: Bad page state in process bash pfn:13d8f8 page:ffffc31984f63e00 refcount:-1 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0x1affff800000000() raw: 01affff800000000 dead000000000100 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 ffffffffffffffff 0000000000000000 page dumped because: nonzero _refcount page_owner tracks the page as freed page last allocated via order 0, migratetype Unmovable, gfp_mask 0xcc0(GFP_KERNEL) prep_new_page+0x143/0x150 get_page_from_freelist+0x289/0x380 __alloc_pages_nodemask+0x13c/0x2d0 khugepaged+0x6e/0xc10 kthread+0xf9/0x130 ret_from_fork+0x3a/0x50 page last free stack trace: free_pcp_prepare+0x134/0x1e0 free_unref_page+0x18/0x90 khugepaged+0x7b/0xc10 kthread+0xf9/0x130 ret_from_fork+0x3a/0x50 Modules linked in: CPU: 3 PID: 271 Comm: bash Not tainted 5.3.0-rc4-2.g07a1a73-default+ #57 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-prebuilt.qemu.org 04/01/2014 Call Trace: dump_stack+0x85/0xc0 bad_page.cold+0xba/0xbf rmqueue_pcplist.isra.0+0x6c5/0x6d0 rmqueue+0x2d/0x810 get_page_from_freelist+0x191/0x380 __alloc_pages_nodemask+0x13c/0x2d0 __get_free_pages+0xd/0x30 __pud_alloc+0x2c/0x110 copy_page_range+0x4f9/0x630 dup_mmap+0x362/0x480 dup_mm+0x68/0x110 copy_process+0x19e1/0x1b40 _do_fork+0x73/0x310 __x64_sys_clone+0x75/0x80 do_syscall_64+0x6e/0x1e0 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f10af854a10 ... Link: http://lkml.kernel.org/r/20190820131828.22684-5-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Michal Hocko <mhocko@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
669 lines
16 KiB
C
669 lines
16 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/debugfs.h>
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/uaccess.h>
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#include <linux/memblock.h>
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#include <linux/stacktrace.h>
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#include <linux/page_owner.h>
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#include <linux/jump_label.h>
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#include <linux/migrate.h>
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#include <linux/stackdepot.h>
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#include <linux/seq_file.h>
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#include "internal.h"
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/*
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* TODO: teach PAGE_OWNER_STACK_DEPTH (__dump_page_owner and save_stack)
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* to use off stack temporal storage
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*/
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#define PAGE_OWNER_STACK_DEPTH (16)
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struct page_owner {
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unsigned short order;
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short last_migrate_reason;
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gfp_t gfp_mask;
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depot_stack_handle_t handle;
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#ifdef CONFIG_DEBUG_PAGEALLOC
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depot_stack_handle_t free_handle;
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#endif
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};
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static bool page_owner_disabled = true;
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DEFINE_STATIC_KEY_FALSE(page_owner_inited);
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static depot_stack_handle_t dummy_handle;
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static depot_stack_handle_t failure_handle;
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static depot_stack_handle_t early_handle;
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static void init_early_allocated_pages(void);
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static int __init early_page_owner_param(char *buf)
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{
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if (!buf)
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return -EINVAL;
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if (strcmp(buf, "on") == 0)
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page_owner_disabled = false;
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return 0;
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}
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early_param("page_owner", early_page_owner_param);
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static bool need_page_owner(void)
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{
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if (page_owner_disabled)
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return false;
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return true;
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}
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static __always_inline depot_stack_handle_t create_dummy_stack(void)
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{
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unsigned long entries[4];
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unsigned int nr_entries;
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nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
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return stack_depot_save(entries, nr_entries, GFP_KERNEL);
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}
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static noinline void register_dummy_stack(void)
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{
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dummy_handle = create_dummy_stack();
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}
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static noinline void register_failure_stack(void)
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{
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failure_handle = create_dummy_stack();
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}
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static noinline void register_early_stack(void)
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{
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early_handle = create_dummy_stack();
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}
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static void init_page_owner(void)
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{
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if (page_owner_disabled)
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return;
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register_dummy_stack();
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register_failure_stack();
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register_early_stack();
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static_branch_enable(&page_owner_inited);
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init_early_allocated_pages();
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}
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struct page_ext_operations page_owner_ops = {
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.size = sizeof(struct page_owner),
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.need = need_page_owner,
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.init = init_page_owner,
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};
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static inline struct page_owner *get_page_owner(struct page_ext *page_ext)
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{
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return (void *)page_ext + page_owner_ops.offset;
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}
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static inline bool check_recursive_alloc(unsigned long *entries,
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unsigned int nr_entries,
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unsigned long ip)
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{
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unsigned int i;
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for (i = 0; i < nr_entries; i++) {
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if (entries[i] == ip)
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return true;
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}
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return false;
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}
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static noinline depot_stack_handle_t save_stack(gfp_t flags)
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{
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unsigned long entries[PAGE_OWNER_STACK_DEPTH];
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depot_stack_handle_t handle;
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unsigned int nr_entries;
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nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
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/*
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* We need to check recursion here because our request to
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* stackdepot could trigger memory allocation to save new
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* entry. New memory allocation would reach here and call
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* stack_depot_save_entries() again if we don't catch it. There is
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* still not enough memory in stackdepot so it would try to
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* allocate memory again and loop forever.
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*/
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if (check_recursive_alloc(entries, nr_entries, _RET_IP_))
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return dummy_handle;
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handle = stack_depot_save(entries, nr_entries, flags);
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if (!handle)
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handle = failure_handle;
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return handle;
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}
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void __reset_page_owner(struct page *page, unsigned int order)
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{
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int i;
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struct page_ext *page_ext;
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#ifdef CONFIG_DEBUG_PAGEALLOC
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depot_stack_handle_t handle = 0;
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struct page_owner *page_owner;
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if (debug_pagealloc_enabled())
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handle = save_stack(GFP_NOWAIT | __GFP_NOWARN);
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#endif
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for (i = 0; i < (1 << order); i++) {
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page_ext = lookup_page_ext(page + i);
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if (unlikely(!page_ext))
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continue;
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__clear_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags);
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#ifdef CONFIG_DEBUG_PAGEALLOC
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if (debug_pagealloc_enabled()) {
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page_owner = get_page_owner(page_ext);
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page_owner->free_handle = handle;
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}
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#endif
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}
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}
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static inline void __set_page_owner_handle(struct page *page,
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struct page_ext *page_ext, depot_stack_handle_t handle,
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unsigned int order, gfp_t gfp_mask)
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{
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struct page_owner *page_owner;
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int i;
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for (i = 0; i < (1 << order); i++) {
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page_owner = get_page_owner(page_ext);
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page_owner->handle = handle;
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page_owner->order = order;
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page_owner->gfp_mask = gfp_mask;
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page_owner->last_migrate_reason = -1;
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__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
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__set_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags);
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page_ext = lookup_page_ext(page + i);
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}
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}
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noinline void __set_page_owner(struct page *page, unsigned int order,
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gfp_t gfp_mask)
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{
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struct page_ext *page_ext = lookup_page_ext(page);
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depot_stack_handle_t handle;
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if (unlikely(!page_ext))
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return;
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handle = save_stack(gfp_mask);
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__set_page_owner_handle(page, page_ext, handle, order, gfp_mask);
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}
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void __set_page_owner_migrate_reason(struct page *page, int reason)
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{
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struct page_ext *page_ext = lookup_page_ext(page);
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struct page_owner *page_owner;
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if (unlikely(!page_ext))
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return;
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page_owner = get_page_owner(page_ext);
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page_owner->last_migrate_reason = reason;
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}
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void __split_page_owner(struct page *page, unsigned int order)
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{
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int i;
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struct page_ext *page_ext = lookup_page_ext(page);
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struct page_owner *page_owner;
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if (unlikely(!page_ext))
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return;
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page_owner = get_page_owner(page_ext);
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page_owner->order = 0;
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for (i = 1; i < (1 << order); i++) {
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page_ext = lookup_page_ext(page + i);
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page_owner = get_page_owner(page_ext);
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page_owner->order = 0;
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}
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}
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void __copy_page_owner(struct page *oldpage, struct page *newpage)
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{
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struct page_ext *old_ext = lookup_page_ext(oldpage);
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struct page_ext *new_ext = lookup_page_ext(newpage);
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struct page_owner *old_page_owner, *new_page_owner;
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if (unlikely(!old_ext || !new_ext))
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return;
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old_page_owner = get_page_owner(old_ext);
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new_page_owner = get_page_owner(new_ext);
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new_page_owner->order = old_page_owner->order;
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new_page_owner->gfp_mask = old_page_owner->gfp_mask;
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new_page_owner->last_migrate_reason =
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old_page_owner->last_migrate_reason;
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new_page_owner->handle = old_page_owner->handle;
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/*
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* We don't clear the bit on the oldpage as it's going to be freed
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* after migration. Until then, the info can be useful in case of
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* a bug, and the overal stats will be off a bit only temporarily.
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* Also, migrate_misplaced_transhuge_page() can still fail the
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* migration and then we want the oldpage to retain the info. But
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* in that case we also don't need to explicitly clear the info from
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* the new page, which will be freed.
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*/
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__set_bit(PAGE_EXT_OWNER, &new_ext->flags);
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__set_bit(PAGE_EXT_OWNER_ACTIVE, &new_ext->flags);
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}
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void pagetypeinfo_showmixedcount_print(struct seq_file *m,
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pg_data_t *pgdat, struct zone *zone)
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{
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struct page *page;
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struct page_ext *page_ext;
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struct page_owner *page_owner;
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unsigned long pfn = zone->zone_start_pfn, block_end_pfn;
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unsigned long end_pfn = pfn + zone->spanned_pages;
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unsigned long count[MIGRATE_TYPES] = { 0, };
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int pageblock_mt, page_mt;
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int i;
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/* Scan block by block. First and last block may be incomplete */
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pfn = zone->zone_start_pfn;
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/*
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* Walk the zone in pageblock_nr_pages steps. If a page block spans
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* a zone boundary, it will be double counted between zones. This does
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* not matter as the mixed block count will still be correct
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*/
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for (; pfn < end_pfn; ) {
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if (!pfn_valid(pfn)) {
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pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
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continue;
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}
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block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
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block_end_pfn = min(block_end_pfn, end_pfn);
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page = pfn_to_page(pfn);
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pageblock_mt = get_pageblock_migratetype(page);
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for (; pfn < block_end_pfn; pfn++) {
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if (!pfn_valid_within(pfn))
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continue;
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page = pfn_to_page(pfn);
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if (page_zone(page) != zone)
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continue;
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if (PageBuddy(page)) {
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unsigned long freepage_order;
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freepage_order = page_order_unsafe(page);
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if (freepage_order < MAX_ORDER)
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pfn += (1UL << freepage_order) - 1;
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continue;
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}
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if (PageReserved(page))
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continue;
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page_ext = lookup_page_ext(page);
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if (unlikely(!page_ext))
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continue;
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if (!test_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags))
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continue;
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page_owner = get_page_owner(page_ext);
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page_mt = gfpflags_to_migratetype(
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page_owner->gfp_mask);
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if (pageblock_mt != page_mt) {
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if (is_migrate_cma(pageblock_mt))
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count[MIGRATE_MOVABLE]++;
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else
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count[pageblock_mt]++;
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pfn = block_end_pfn;
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break;
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}
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pfn += (1UL << page_owner->order) - 1;
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}
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}
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/* Print counts */
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seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
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for (i = 0; i < MIGRATE_TYPES; i++)
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seq_printf(m, "%12lu ", count[i]);
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seq_putc(m, '\n');
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}
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static ssize_t
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print_page_owner(char __user *buf, size_t count, unsigned long pfn,
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struct page *page, struct page_owner *page_owner,
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depot_stack_handle_t handle)
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{
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int ret, pageblock_mt, page_mt;
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unsigned long *entries;
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unsigned int nr_entries;
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char *kbuf;
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count = min_t(size_t, count, PAGE_SIZE);
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kbuf = kmalloc(count, GFP_KERNEL);
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if (!kbuf)
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return -ENOMEM;
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ret = snprintf(kbuf, count,
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"Page allocated via order %u, mask %#x(%pGg)\n",
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page_owner->order, page_owner->gfp_mask,
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&page_owner->gfp_mask);
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if (ret >= count)
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goto err;
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/* Print information relevant to grouping pages by mobility */
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pageblock_mt = get_pageblock_migratetype(page);
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page_mt = gfpflags_to_migratetype(page_owner->gfp_mask);
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ret += snprintf(kbuf + ret, count - ret,
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"PFN %lu type %s Block %lu type %s Flags %#lx(%pGp)\n",
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pfn,
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migratetype_names[page_mt],
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pfn >> pageblock_order,
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migratetype_names[pageblock_mt],
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page->flags, &page->flags);
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if (ret >= count)
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goto err;
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nr_entries = stack_depot_fetch(handle, &entries);
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ret += stack_trace_snprint(kbuf + ret, count - ret, entries, nr_entries, 0);
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if (ret >= count)
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goto err;
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if (page_owner->last_migrate_reason != -1) {
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ret += snprintf(kbuf + ret, count - ret,
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"Page has been migrated, last migrate reason: %s\n",
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migrate_reason_names[page_owner->last_migrate_reason]);
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if (ret >= count)
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goto err;
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}
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ret += snprintf(kbuf + ret, count - ret, "\n");
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if (ret >= count)
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goto err;
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if (copy_to_user(buf, kbuf, ret))
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ret = -EFAULT;
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kfree(kbuf);
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return ret;
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err:
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kfree(kbuf);
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return -ENOMEM;
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}
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void __dump_page_owner(struct page *page)
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{
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struct page_ext *page_ext = lookup_page_ext(page);
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struct page_owner *page_owner;
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depot_stack_handle_t handle;
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unsigned long *entries;
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unsigned int nr_entries;
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gfp_t gfp_mask;
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int mt;
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if (unlikely(!page_ext)) {
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pr_alert("There is not page extension available.\n");
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return;
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}
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page_owner = get_page_owner(page_ext);
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gfp_mask = page_owner->gfp_mask;
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mt = gfpflags_to_migratetype(gfp_mask);
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if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags)) {
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pr_alert("page_owner info is not present (never set?)\n");
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return;
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}
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if (test_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags))
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pr_alert("page_owner tracks the page as allocated\n");
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else
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pr_alert("page_owner tracks the page as freed\n");
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pr_alert("page last allocated via order %u, migratetype %s, gfp_mask %#x(%pGg)\n",
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page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask);
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|
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handle = READ_ONCE(page_owner->handle);
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if (!handle) {
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pr_alert("page_owner allocation stack trace missing\n");
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} else {
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nr_entries = stack_depot_fetch(handle, &entries);
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stack_trace_print(entries, nr_entries, 0);
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}
|
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|
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#ifdef CONFIG_DEBUG_PAGEALLOC
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handle = READ_ONCE(page_owner->free_handle);
|
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if (!handle) {
|
|
pr_alert("page_owner free stack trace missing\n");
|
|
} else {
|
|
nr_entries = stack_depot_fetch(handle, &entries);
|
|
pr_alert("page last free stack trace:\n");
|
|
stack_trace_print(entries, nr_entries, 0);
|
|
}
|
|
#endif
|
|
|
|
if (page_owner->last_migrate_reason != -1)
|
|
pr_alert("page has been migrated, last migrate reason: %s\n",
|
|
migrate_reason_names[page_owner->last_migrate_reason]);
|
|
}
|
|
|
|
static ssize_t
|
|
read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
|
|
{
|
|
unsigned long pfn;
|
|
struct page *page;
|
|
struct page_ext *page_ext;
|
|
struct page_owner *page_owner;
|
|
depot_stack_handle_t handle;
|
|
|
|
if (!static_branch_unlikely(&page_owner_inited))
|
|
return -EINVAL;
|
|
|
|
page = NULL;
|
|
pfn = min_low_pfn + *ppos;
|
|
|
|
/* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */
|
|
while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0)
|
|
pfn++;
|
|
|
|
drain_all_pages(NULL);
|
|
|
|
/* Find an allocated page */
|
|
for (; pfn < max_pfn; pfn++) {
|
|
/*
|
|
* If the new page is in a new MAX_ORDER_NR_PAGES area,
|
|
* validate the area as existing, skip it if not
|
|
*/
|
|
if ((pfn & (MAX_ORDER_NR_PAGES - 1)) == 0 && !pfn_valid(pfn)) {
|
|
pfn += MAX_ORDER_NR_PAGES - 1;
|
|
continue;
|
|
}
|
|
|
|
/* Check for holes within a MAX_ORDER area */
|
|
if (!pfn_valid_within(pfn))
|
|
continue;
|
|
|
|
page = pfn_to_page(pfn);
|
|
if (PageBuddy(page)) {
|
|
unsigned long freepage_order = page_order_unsafe(page);
|
|
|
|
if (freepage_order < MAX_ORDER)
|
|
pfn += (1UL << freepage_order) - 1;
|
|
continue;
|
|
}
|
|
|
|
page_ext = lookup_page_ext(page);
|
|
if (unlikely(!page_ext))
|
|
continue;
|
|
|
|
/*
|
|
* Some pages could be missed by concurrent allocation or free,
|
|
* because we don't hold the zone lock.
|
|
*/
|
|
if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
|
|
continue;
|
|
|
|
/*
|
|
* Although we do have the info about past allocation of free
|
|
* pages, it's not relevant for current memory usage.
|
|
*/
|
|
if (!test_bit(PAGE_EXT_OWNER_ACTIVE, &page_ext->flags))
|
|
continue;
|
|
|
|
page_owner = get_page_owner(page_ext);
|
|
|
|
/*
|
|
* Don't print "tail" pages of high-order allocations as that
|
|
* would inflate the stats.
|
|
*/
|
|
if (!IS_ALIGNED(pfn, 1 << page_owner->order))
|
|
continue;
|
|
|
|
/*
|
|
* Access to page_ext->handle isn't synchronous so we should
|
|
* be careful to access it.
|
|
*/
|
|
handle = READ_ONCE(page_owner->handle);
|
|
if (!handle)
|
|
continue;
|
|
|
|
/* Record the next PFN to read in the file offset */
|
|
*ppos = (pfn - min_low_pfn) + 1;
|
|
|
|
return print_page_owner(buf, count, pfn, page,
|
|
page_owner, handle);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
|
|
{
|
|
unsigned long pfn = zone->zone_start_pfn;
|
|
unsigned long end_pfn = zone_end_pfn(zone);
|
|
unsigned long count = 0;
|
|
|
|
/*
|
|
* Walk the zone in pageblock_nr_pages steps. If a page block spans
|
|
* a zone boundary, it will be double counted between zones. This does
|
|
* not matter as the mixed block count will still be correct
|
|
*/
|
|
for (; pfn < end_pfn; ) {
|
|
unsigned long block_end_pfn;
|
|
|
|
if (!pfn_valid(pfn)) {
|
|
pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
|
|
continue;
|
|
}
|
|
|
|
block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
|
|
block_end_pfn = min(block_end_pfn, end_pfn);
|
|
|
|
for (; pfn < block_end_pfn; pfn++) {
|
|
struct page *page;
|
|
struct page_ext *page_ext;
|
|
|
|
if (!pfn_valid_within(pfn))
|
|
continue;
|
|
|
|
page = pfn_to_page(pfn);
|
|
|
|
if (page_zone(page) != zone)
|
|
continue;
|
|
|
|
/*
|
|
* To avoid having to grab zone->lock, be a little
|
|
* careful when reading buddy page order. The only
|
|
* danger is that we skip too much and potentially miss
|
|
* some early allocated pages, which is better than
|
|
* heavy lock contention.
|
|
*/
|
|
if (PageBuddy(page)) {
|
|
unsigned long order = page_order_unsafe(page);
|
|
|
|
if (order > 0 && order < MAX_ORDER)
|
|
pfn += (1UL << order) - 1;
|
|
continue;
|
|
}
|
|
|
|
if (PageReserved(page))
|
|
continue;
|
|
|
|
page_ext = lookup_page_ext(page);
|
|
if (unlikely(!page_ext))
|
|
continue;
|
|
|
|
/* Maybe overlapping zone */
|
|
if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
|
|
continue;
|
|
|
|
/* Found early allocated page */
|
|
__set_page_owner_handle(page, page_ext, early_handle,
|
|
0, 0);
|
|
count++;
|
|
}
|
|
cond_resched();
|
|
}
|
|
|
|
pr_info("Node %d, zone %8s: page owner found early allocated %lu pages\n",
|
|
pgdat->node_id, zone->name, count);
|
|
}
|
|
|
|
static void init_zones_in_node(pg_data_t *pgdat)
|
|
{
|
|
struct zone *zone;
|
|
struct zone *node_zones = pgdat->node_zones;
|
|
|
|
for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
|
|
if (!populated_zone(zone))
|
|
continue;
|
|
|
|
init_pages_in_zone(pgdat, zone);
|
|
}
|
|
}
|
|
|
|
static void init_early_allocated_pages(void)
|
|
{
|
|
pg_data_t *pgdat;
|
|
|
|
for_each_online_pgdat(pgdat)
|
|
init_zones_in_node(pgdat);
|
|
}
|
|
|
|
static const struct file_operations proc_page_owner_operations = {
|
|
.read = read_page_owner,
|
|
};
|
|
|
|
static int __init pageowner_init(void)
|
|
{
|
|
if (!static_branch_unlikely(&page_owner_inited)) {
|
|
pr_info("page_owner is disabled\n");
|
|
return 0;
|
|
}
|
|
|
|
debugfs_create_file("page_owner", 0400, NULL, NULL,
|
|
&proc_page_owner_operations);
|
|
|
|
return 0;
|
|
}
|
|
late_initcall(pageowner_init)
|