[PATCH v2 6/8] scripts/gdb/page_owner: add page owner support

From: Kuan-Ying Lee
Date: Tue Aug 08 2023 - 12:18:14 EST

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This GDB scripts print page owner information for user to
analyze the memory usage or memory corruption issue.

Example output from an aarch64 system:

(gdb) lx-dump-page-owner --pfn 655360
page_owner tracks the page as allocated
Page last allocated via order 0, gfp_mask: 0x8, pid: 1, tgid: 1 ("swapper/0\000\000\000\000\000\000"), ts 1295948880 ns, free_ts 1011852016 ns
PFN: 655360, Flags: 0x3fffc0000000000
0xffff8000086ab964 <post_alloc_hook+452>: ldp x19, x20, [sp, #16]
0xffff80000862e4e0 <split_map_pages+344>: cbnz w22, 0xffff80000862e57c <split_map_pages+500>
0xffff8000086370c4 <isolate_freepages_range+556>: mov x0, x27
0xffff8000086bc1cc <alloc_contig_range+808>: mov x24, x0
0xffff80000877d6d8 <cma_alloc+772>: mov w1, w0
0xffff8000082c8d18 <dma_alloc_from_contiguous+104>: ldr x19, [sp, #16]
0xffff8000082ce0e8 <atomic_pool_expand+208>: mov x19, x0
0xffff80000c1e41b4 <__dma_atomic_pool_init+172>: Cannot access memory at address 0xffff80000c1e41b4
0xffff80000c1e4298 <dma_atomic_pool_init+92>: Cannot access memory at address 0xffff80000c1e4298
0xffff8000080161d4 <do_one_initcall+176>: mov w21, w0
0xffff80000c1c1b50 <kernel_init_freeable+952>: Cannot access memory at address 0xffff80000c1c1b50
0xffff80000acf87dc <kernel_init+36>: bl 0xffff8000081ab100 <async_synchronize_full>
0xffff800008018d00 <ret_from_fork+16>: mrs x28, sp_el0
page last free stack trace:
0xffff8000086a6e8c <free_unref_page_prepare+796>: mov w2, w23
0xffff8000086aee1c <free_unref_page+96>: tst w0, #0xff
0xffff8000086af3f8 <__free_pages+292>: ldp x19, x20, [sp, #16]
0xffff80000c1f3214 <init_cma_reserved_pageblock+220>: Cannot access memory at address 0xffff80000c1f3214
0xffff80000c20363c <cma_init_reserved_areas+1284>: Cannot access memory at address 0xffff80000c20363c
0xffff8000080161d4 <do_one_initcall+176>: mov w21, w0
0xffff80000c1c1b50 <kernel_init_freeable+952>: Cannot access memory at address 0xffff80000c1c1b50
0xffff80000acf87dc <kernel_init+36>: bl 0xffff8000081ab100 <async_synchronize_full>
0xffff800008018d00 <ret_from_fork+16>: mrs x28, sp_el0

Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@xxxxxxxxxxxx>
---
scripts/gdb/linux/constants.py.in | 7 ++
scripts/gdb/linux/page_owner.py | 190 ++++++++++++++++++++++++++++++
scripts/gdb/vmlinux-gdb.py | 1 +
3 files changed, 198 insertions(+)
create mode 100644 scripts/gdb/linux/page_owner.py

diff --git a/scripts/gdb/linux/constants.py.in b/scripts/gdb/linux/constants.py.in
index f33be26253d2..52f61d65f430 100644
--- a/scripts/gdb/linux/constants.py.in
+++ b/scripts/gdb/linux/constants.py.in
@@ -18,6 +18,7 @@
#include <linux/irq.h>
#include <linux/mount.h>
#include <linux/of_fdt.h>
+#include <linux/page_ext.h>
#include <linux/radix-tree.h>
#include <linux/threads.h>

@@ -89,6 +90,11 @@ LX_GDBPARSED(RADIX_TREE_MAP_SIZE)
LX_GDBPARSED(RADIX_TREE_MAP_SHIFT)
LX_GDBPARSED(RADIX_TREE_MAP_MASK)

+/* linux/page_ext.h */
+if IS_BUILTIN(CONFIG_PAGE_OWNER):
+ LX_GDBPARSED(PAGE_EXT_OWNER)
+ LX_GDBPARSED(PAGE_EXT_OWNER_ALLOCATED)
+
/* Kernel Configs */
LX_CONFIG(CONFIG_GENERIC_CLOCKEVENTS)
LX_CONFIG(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST)
@@ -129,3 +135,4 @@ if IS_BUILTIN(CONFIG_NUMA):
LX_VALUE(CONFIG_NODES_SHIFT)
LX_CONFIG(CONFIG_DEBUG_VIRTUAL)
LX_CONFIG(CONFIG_STACKDEPOT)
+LX_CONFIG(CONFIG_PAGE_OWNER)
diff --git a/scripts/gdb/linux/page_owner.py b/scripts/gdb/linux/page_owner.py
new file mode 100644
index 000000000000..844fd5d0c912
--- /dev/null
+++ b/scripts/gdb/linux/page_owner.py
@@ -0,0 +1,190 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (c) 2023 MediaTek Inc.
+#
+# Authors:
+# Kuan-Ying Lee <Kuan-Ying.Lee@xxxxxxxxxxxx>
+#
+
+import gdb
+from linux import utils, stackdepot, constants, mm
+
+if constants.LX_CONFIG_PAGE_OWNER:
+ page_ext_t = utils.CachedType('struct page_ext')
+ page_owner_t = utils.CachedType('struct page_owner')
+
+ PAGE_OWNER_STACK_DEPTH = 16
+ PAGE_EXT_OWNER = constants.LX_PAGE_EXT_OWNER
+ PAGE_EXT_INVALID = 0x1
+ PAGE_EXT_OWNER_ALLOCATED = constants.LX_PAGE_EXT_OWNER_ALLOCATED
+
+def help():
+ t = """Usage: lx-dump-page-owner [Option]
+ Option:
+ --pfn [Decimal pfn]
+ Example:
+ lx-dump-page-owner --pfn 655360\n"""
+ gdb.write("Unrecognized command\n")
+ raise gdb.GdbError(t)
+
+class DumpPageOwner(gdb.Command):
+ """Dump page owner"""
+
+ min_pfn = None
+ max_pfn = None
+ p_ops = None
+ migrate_reason_names = None
+
+ def __init__(self):
+ super(DumpPageOwner, self).__init__("lx-dump-page-owner", gdb.COMMAND_SUPPORT)
+
+ def invoke(self, args, from_tty):
+ if not constants.LX_CONFIG_PAGE_OWNER:
+ raise gdb.GdbError('CONFIG_PAGE_OWNER does not enable')
+
+ page_owner_inited = gdb.parse_and_eval('page_owner_inited')
+ if page_owner_inited['key']['enabled']['counter'] != 0x1:
+ raise gdb.GdbError('page_owner_inited is not enabled')
+
+ self.p_ops = mm.page_ops().ops
+ self.get_page_owner_info()
+ argv = gdb.string_to_argv(args)
+ if len(argv) == 0:
+ self.read_page_owner()
+ elif len(argv) == 2:
+ if argv[0] == "--pfn":
+ pfn = int(argv[1])
+ self.read_page_owner_by_addr(self.p_ops.pfn_to_page(pfn))
+ else:
+ help()
+ else:
+ help()
+
+ def get_page_owner_info(self):
+ self.min_pfn = int(gdb.parse_and_eval("min_low_pfn"))
+ self.max_pfn = int(gdb.parse_and_eval("max_pfn"))
+ self.page_ext_size = int(gdb.parse_and_eval("page_ext_size"))
+ self.migrate_reason_names = gdb.parse_and_eval('migrate_reason_names')
+
+ def page_ext_invalid(self, page_ext):
+ if page_ext == gdb.Value(0):
+ return True
+ if page_ext.cast(utils.get_ulong_type()) & PAGE_EXT_INVALID == PAGE_EXT_INVALID:
+ return True
+ return False
+
+ def get_entry(self, base, index):
+ return (base.cast(utils.get_ulong_type()) + self.page_ext_size * index).cast(page_ext_t.get_type().pointer())
+
+ def lookup_page_ext(self, page):
+ pfn = self.p_ops.page_to_pfn(page)
+ section = self.p_ops.pfn_to_section(pfn)
+ page_ext = section["page_ext"]
+ if self.page_ext_invalid(page_ext):
+ return gdb.Value(0)
+ return self.get_entry(page_ext, pfn)
+
+ def page_ext_get(self, page):
+ page_ext = self.lookup_page_ext(page)
+ if page_ext != gdb.Value(0):
+ return page_ext
+ else:
+ return gdb.Value(0)
+
+ def get_page_owner(self, page_ext):
+ addr = page_ext.cast(utils.get_ulong_type()) + gdb.parse_and_eval("page_owner_ops")["offset"].cast(utils.get_ulong_type())
+ return addr.cast(page_owner_t.get_type().pointer())
+
+ def read_page_owner_by_addr(self, struct_page_addr):
+ page = gdb.Value(struct_page_addr).cast(utils.get_page_type().pointer())
+ pfn = self.p_ops.page_to_pfn(page)
+
+ if pfn < self.min_pfn or pfn > self.max_pfn or (not self.p_ops.pfn_valid(pfn)):
+ gdb.write("pfn is invalid\n")
+ return
+
+ page = self.p_ops.pfn_to_page(pfn)
+ page_ext = self.page_ext_get(page)
+
+ if page_ext == gdb.Value(0):
+ gdb.write("page_ext is null\n")
+ return
+
+ if not (page_ext['flags'] & (1 << PAGE_EXT_OWNER)):
+ gdb.write("page_owner flag is invalid\n")
+ raise gdb.GdbError('page_owner info is not present (never set?)\n')
+
+ if mm.test_bit(PAGE_EXT_OWNER_ALLOCATED, page_ext['flags'].address):
+ gdb.write('page_owner tracks the page as allocated\n')
+ else:
+ gdb.write('page_owner tracks the page as freed\n')
+
+ if not (page_ext['flags'] & (1 << PAGE_EXT_OWNER_ALLOCATED)):
+ gdb.write("page_owner is not allocated\n")
+
+ try:
+ page_owner = self.get_page_owner(page_ext)
+ gdb.write("Page last allocated via order %d, gfp_mask: 0x%x, pid: %d, tgid: %d (%s), ts %u ns, free_ts %u ns\n" %\
+ (page_owner["order"], page_owner["gfp_mask"],\
+ page_owner["pid"], page_owner["tgid"], page_owner["comm"],\
+ page_owner["ts_nsec"], page_owner["free_ts_nsec"]))
+ gdb.write("PFN: %d, Flags: 0x%x\n" % (pfn, page['flags']))
+ if page_owner["handle"] == 0:
+ gdb.write('page_owner allocation stack trace missing\n')
+ else:
+ stackdepot.stack_depot_print(page_owner["handle"])
+
+ if page_owner["free_handle"] == 0:
+ gdb.write('page_owner free stack trace missing\n')
+ else:
+ gdb.write('page last free stack trace:\n')
+ stackdepot.stack_depot_print(page_owner["free_handle"])
+ if page_owner['last_migrate_reason'] != -1:
+ gdb.write('page has been migrated, last migrate reason: %s\n' % self.migrate_reason_names[page_owner['last_migrate_reason']])
+ except:
+ gdb.write("\n")
+
+ def read_page_owner(self):
+ pfn = self.min_pfn
+
+ # Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area
+ while ((not self.p_ops.pfn_valid(pfn)) and (pfn & (self.p_ops.MAX_ORDER_NR_PAGES - 1))) != 0:
+ pfn += 1
+
+ while pfn < self.max_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 & (self.p_ops.MAX_ORDER_NR_PAGES - 1)) == 0) and (not self.p_ops.pfn_valid(pfn)):
+ pfn += (self.p_ops.MAX_ORDER_NR_PAGES - 1)
+ continue;
+
+ page = self.p_ops.pfn_to_page(pfn)
+ page_ext = self.page_ext_get(page)
+ if page_ext == gdb.Value(0):
+ pfn += 1
+ continue
+
+ if not (page_ext['flags'] & (1 << PAGE_EXT_OWNER)):
+ pfn += 1
+ continue
+ if not (page_ext['flags'] & (1 << PAGE_EXT_OWNER_ALLOCATED)):
+ pfn += 1
+ continue
+
+ try:
+ page_owner = self.get_page_owner(page_ext)
+ gdb.write("Page allocated via order %d, gfp_mask: 0x%x, pid: %d, tgid: %d (%s), ts %u ns, free_ts %u ns\n" %\
+ (page_owner["order"], page_owner["gfp_mask"],\
+ page_owner["pid"], page_owner["tgid"], page_owner["comm"],\
+ page_owner["ts_nsec"], page_owner["free_ts_nsec"]))
+ gdb.write("PFN: %d, Flags: 0x%x\n" % (pfn, page['flags']))
+ stackdepot.stack_depot_print(page_owner["handle"])
+ pfn += (1 << page_owner["order"])
+ continue
+ except:
+ gdb.write("\n")
+ pfn += 1
+
+DumpPageOwner()
diff --git a/scripts/gdb/vmlinux-gdb.py b/scripts/gdb/vmlinux-gdb.py
index 24f149694b81..89465f0de548 100644
--- a/scripts/gdb/vmlinux-gdb.py
+++ b/scripts/gdb/vmlinux-gdb.py
@@ -46,3 +46,4 @@ else:
import linux.interrupts
import linux.mm
import linux.stackdepot
+ import linux.page_owner
--
2.18.0

Next message: Delphine CC Chiu: "[PATCH v7 0/2] ARM: dts: Facebook Yosemite 4 platform"
Previous message: Thippeswamy Havalige: "[PATCH v2 0/2] Increase ecam size value to discover 256 buses during"
In reply to: Kuan-Ying Lee: "[PATCH v2 8/8] scripts/gdb/vmalloc: add vmallocinfo support"
Next in thread: Kuan-Ying Lee: "[PATCH v2 1/8] scripts/gdb/symbols: add specific ko module load command"
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