Messages in this thread | | | Date | Thu, 17 Jun 2021 12:10:43 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH v7 0/5] printk: Userspace format indexing support |
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On Tue 2021-06-15 17:52:20, Chris Down wrote: > We have a number of systems industry-wide that have a subset of their > functionality that works as follows: > > 1. Receive a message from local kmsg, serial console, or netconsole; > 2. Apply a set of rules to classify the message; > 3. Do something based on this classification (like scheduling a > remediation for the machine), rinse, and repeat. > > This provides a solution to the issue of silently changed or deleted > printks: we record pointers to all printk format strings known at > compile time into a new .printk_index section, both in vmlinux and > modules. At runtime, this can then be iterated by looking at > <debugfs>/printk/index/<module>, which emits the following format, both > readable by humans and able to be parsed by machines: > > $ head -1 vmlinux; shuf -n 5 vmlinux > # <level[,flags]> filename:line function "format" > <5> block/blk-settings.c:661 disk_stack_limits "%s: Warning: Device %s is misaligned\n" > <4> kernel/trace/trace.c:8296 trace_create_file "Could not create tracefs '%s' entry\n" > <6> arch/x86/kernel/hpet.c:144 _hpet_print_config "hpet: %s(%d):\n" > <6> init/do_mounts.c:605 prepare_namespace "Waiting for root device %s...\n" > <6> drivers/acpi/osl.c:1410 acpi_no_auto_serialize_setup "ACPI: auto-serialization disabled\n" > > This mitigates the majority of cases where we have a highly-specific > printk which we want to match on, as we can now enumerate and check > whether the format changed or the printk callsite disappeared entirely > in userspace. This allows us to catch changes to printks we monitor > earlier and decide what to do about it before it becomes problematic. > > There is no additional runtime cost for printk callers or printk itself, > and the assembly generated is exactly the same. > > Chris Down (5): > string_helpers: Escape double quotes in escape_special > printk: Straighten out log_flags into printk_info_flags > printk: Rework parse_prefix into printk_parse_prefix > printk: Userspace format indexing support > printk: index: Add indexing support to dev_printk
The patchset looks ready for linux-next from my POV. I could fixup the messages as suggested by Andy when pushing.
Well, I would still like to get acks from:
+ Andy for the 1st patch + Jessica for the changes in the module loader code in 4th patch.
Best Regards, Petr
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