From 88f9ee2b3040991ff40628fa9e3516ebe36dd6fa Mon Sep 17 00:00:00 2001 From: Jim Cromie Date: Thu, 16 Nov 2023 15:43:17 -0700 Subject: [PATCH] kmemleak: drop (age ) from leak record Patch series "tweak kmemleak report format". These 2 patches make minor changes to the report: 1st strips "age " from output. This makes the output idempotent; unchanging until a new leak is reported. 2nd adds the backtrace.checksum to the "backtrace:" line. This lets a user see repeats without actually reading the whole backtrace. So now the backtrace line looks like this: backtrace (crc 603070071): I surveyed for un-wanted effects upon users: Syzkaller parses kmemleak in executor/common_linux.h: static void check_leaks(char** frames, int nframes) It just counts occurrences of "unreferenced object", specifically it does not look for "age", nor would it choke on "crc" being added. github has 3 repos with "kmemleak" mentioned, all are moribund. gitlab has 0 hits on "kmemleak". This patch (of 2): Displaying age is pretty, but counter-productive; it changes with current-time, so it surrenders idempotency of the output, which breaks simple hash-based cataloging of the records by the user. The trouble: sequential reads, wo new leaks, get new results: :#> sum /sys/kernel/debug/kmemleak 53439 74 /sys/kernel/debug/kmemleak :#> sum /sys/kernel/debug/kmemleak 59066 74 /sys/kernel/debug/kmemleak and age is why (nothing else changes): :#> grep -v age /sys/kernel/debug/kmemleak | sum 58894 67 :#> grep -v age /sys/kernel/debug/kmemleak | sum 58894 67 Since jiffies is already printed in the "comm" line, age adds nothing. Notably, syzkaller reads kmemleak only for "unreferenced object", and won't care about this reform of age-ism. A few moribund github repos mention it, but don't compile. Link: https://lkml.kernel.org/r/20231116224318.124209-1-jim.cromie@gmail.com Link: https://lkml.kernel.org/r/20231116224318.124209-2-jim.cromie@gmail.com Signed-off-by: Jim Cromie Reviewed-by: Catalin Marinas Signed-off-by: Andrew Morton --- mm/kmemleak.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 5501363d6b31..a87b3dd8f3b7 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -355,14 +355,12 @@ static void print_unreferenced(struct seq_file *seq, int i; unsigned long *entries; unsigned int nr_entries; - unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies); nr_entries = stack_depot_fetch(object->trace_handle, &entries); warn_or_seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n", object->pointer, object->size); - warn_or_seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n", - object->comm, object->pid, object->jiffies, - msecs_age / 1000, msecs_age % 1000); + warn_or_seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu\n", + object->comm, object->pid, object->jiffies); hex_dump_object(seq, object); warn_or_seq_printf(seq, " backtrace:\n");