Page Detective is a new kernel debugging tool that provides detailed information about the usage and mapping of physical memory pages. It is often known that a particular page is corrupted, but it is hard to extract more information about such a page from live system. Examples are: - Checksum failure during live migration - Filesystem journal failure - dump_page warnings on the console log - Unexcpected segfaults Page Detective helps to extract more information from the kernel, so it can be used by developers to root cause the associated problem. It operates through the Linux debugfs interface, with two files: "virt" and "phys". The "virt" file takes a virtual address and PID and outputs information about the corresponding page. The "phys" file takes a physical address and outputs information about that page. The output is presented via kernel log messages (can be accessed with dmesg), and includes information such as the page's reference count, mapping, flags, and memory cgroup. It also shows whether the page is mapped in the kernel page table, and if so, how many times. Pasha Tatashin (6): mm: Make get_vma_name() function public pagewalk: Add a page table walker for init_mm page table mm: Add a dump_page variant that accept log level argument misc/page_detective: Introduce Page Detective misc/page_detective: enable loadable module selftests/page_detective: Introduce self tests for Page Detective Documentation/misc-devices/index.rst | 1 + Documentation/misc-devices/page_detective.rst | 78 ++ MAINTAINERS | 8 + drivers/misc/Kconfig | 11 + drivers/misc/Makefile | 1 + drivers/misc/page_detective.c | 808 ++++++++++++++++++ fs/inode.c | 18 +- fs/kernfs/dir.c | 1 + fs/proc/task_mmu.c | 61 -- include/linux/fs.h | 5 +- include/linux/mmdebug.h | 1 + include/linux/pagewalk.h | 2 + kernel/pid.c | 1 + mm/debug.c | 53 +- mm/memcontrol.c | 1 + mm/oom_kill.c | 1 + mm/pagewalk.c | 32 + mm/vma.c | 60 ++ tools/testing/selftests/Makefile | 1 + .../selftests/page_detective/.gitignore | 1 + .../testing/selftests/page_detective/Makefile | 7 + tools/testing/selftests/page_detective/config | 4 + .../page_detective/page_detective_test.c | 727 ++++++++++++++++ 23 files changed, 1787 insertions(+), 96 deletions(-) create mode 100644 Documentation/misc-devices/page_detective.rst create mode 100644 drivers/misc/page_detective.c create mode 100644 tools/testing/selftests/page_detective/.gitignore create mode 100644 tools/testing/selftests/page_detective/Makefile create mode 100644 tools/testing/selftests/page_detective/config create mode 100644 tools/testing/selftests/page_detective/page_detective_test.c -- 2.47.0.338.g60cca15819-goog
