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Please consider pulling these changes from the signed vfs-7.4-rc1.coredump tag. Thanks! Christian -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQRAhzRXHqcMeLMyaSiRxhvAZXjcogUCatHrlgAKCRCRxhvAZXjc ouhIAP9q03aGe3fMs3tnLWC+JzSc1D48MMmo71rPxGnV6G6V+AEAzZV6Xkq8eFTU Zbwq6FhYvhptWeNGyNa9phUDFcBQIw4= =Pt3z -----END PGP SIGNATURE----- Merge tag 'vfs-7.4-rc1.coredump' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs Pull coredump updates from Christian Brauner: "This adds sparse coredumps and per-request memory type selection to the coredump socket protocol. A coredump sent over the socket transfers every zero of every hole in every mapping. For a process with 128 threads that's 1 GB of mostly thread stacks, 8 MB reservations with a few pages touched, and the holes sit in the middle of the dump rather than at the end. The coredump_filter bit that was proposed for this stops each PT_LOAD at the last populated page. But that mask says which kinds of memory to include and propagates across fork and exec, whereas what is selected here is an encoding. The usermodehelper isn't salvagable for this either. The coredump socket already has a handshake for exactly this. A server that raises COREDUMP_RECORDS in coredump_ack->mask gets the coredump as a sequence of records, each a struct coredump_record_header followed by what it describes. The stream ends explicitly with an end record that reports the size, so a missing one means truncation. With COREDUMP_SPARSE holes cross the socket as a bare header that says how many zero bytes were skipped. Reassembling the records gives back the same coredump, so a debugger and everything else still see an ordinary core file. Numbers from the selftests: the 128 thread process sends 1424153 bytes for a coredump of 1075150848 bytes, a 256 MB mapping with the first and the last page touched sends 188793 bytes for 268890112 bytes, and with COREDUMP_RECORDS alone the record overhead is under one percent. The selftests also simulate a server uploading to a blob store that can't seek and rewrites the program headers so the object is an ordinary ELF core file without the holes. COREDUMP_MEMORY_TYPES lets the server choose what memory to dump per request instead of relying on the static /proc/<pid>/coredump_filter of the crashing task. The request carries the default types and a mask of every type the kernel knows about, the ack carries the selection. Zero is valid and dumps the program headers and notes and nothing but the mappings that are always dumped. Preparatory cleanups refuse negative skips in dump_skip_to(), chunk every write at a page so a pipe or a socket never takes a short write in the middle of a record, make the dump helpers return bool and replace the core_dumped integer with COREDUMP_STATE_STARTED and COREDUMP_STATE_TRUNCATED flags. Also included is a fix for coredump_parse() reading core_pattern while it is being modified. The sysctl handler now validates a copy and publishes it under a spinlock and the parser works on a snapshot, so a rejected pattern is never visible and the rollback logic goes away. And to_kthread()'s lockless flags read is annotated with READ_ONCE()" * tag 'vfs-7.4-rc1.coredump' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (29 commits) kthread: Annotate lockless to_kthread() flags access coredump: parse a snapshot of core_pattern selftests/coredump: test failed handshakes selftests/coredump: improve coredump size negotiation tests selftests/coredump: test COREDUMP_MEMORY_TYPES selftests/coredump: simplify the refusal tests tools: sync coredump.h header coredump: select memory types to include selftests/coredump: show how to inspect the task to decide how the coredump should be sent selftests/coredump: simulate a blob store selftests/coredump: put a hole in the middle of a sparse mapping selftests/coredump: hand the record stream to a sink selftests/coredump: test COREDUMP_RECORDS and COREDUMP_SPARSE coredump: describe the holes when COREDUMP_SPARSE is negotiated coredump: send the coredump in records if requested tools: sync coredump.h header coredump: add COREDUMP_SPARSE to the coredump socket protocol coredump: add COREDUMP_RECORDS to the coredump socket protocol coredump: clean up coredump state handling coredump: always chunk writes ... |
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