When the coredump server raises COREDUMP_RECORDS send the coredump in records. A record consists of a struct coredump_record_header and data. A header and the bytes it describes go out in one iovec.
A hole is flushed through __dump_emit() like before. So zeroes still are sent on the socket as actual data records. Making holes cheap is COREDUMP_SPARSE's job. Signed-off-by: Christian Brauner (Amutable) <[email protected]> --- fs/coredump.c | 150 +++++++++++++++++---- include/linux/coredump.h | 5 + .../selftests/coredump/coredump_test_helpers.c | 2 +- 3 files changed, 127 insertions(+), 30 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index 6af3ff0e19a6..b1679930094c 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -51,7 +51,6 @@ #include <net/sock.h> #include <uapi/linux/pidfd.h> #include <uapi/linux/un.h> -#include <uapi/linux/coredump.h> #include <linux/uaccess.h> #include <asm/mmu_context.h> @@ -68,6 +67,7 @@ static bool dump_vma_snapshot(struct coredump_params *cprm); static void free_vma_snapshot(struct coredump_params *cprm); +static void dump_end_record(struct coredump_params *cprm); #define CORE_FILE_NOTE_SIZE_DEFAULT (4*1024*1024) /* Define a reasonable max cap */ @@ -661,6 +661,8 @@ static int umh_coredump_setup(struct subprocess_info *info, struct cred *new) return 0; } +static_assert(sizeof(struct coredump_record_header) == COREDUMP_RECORD_HEADER_SIZE_VER0); + #ifdef CONFIG_UNIX /* af_unix halves the send buffer to size a single skb. */ #define COREDUMP_SOCK_SNDBUF_MIN (3 * PAGE_SIZE) @@ -803,7 +805,8 @@ static bool coredump_sock_request(struct core_name *cn, struct coredump_params * struct coredump_req req = { .size = sizeof(struct coredump_req), .mask = COREDUMP_KERNEL | COREDUMP_USERSPACE | - COREDUMP_REJECT | COREDUMP_WAIT, + COREDUMP_REJECT | COREDUMP_WAIT | + COREDUMP_RECORDS, .size_ack = sizeof(struct coredump_ack), }; struct coredump_ack ack = {}; @@ -857,6 +860,19 @@ static bool coredump_sock_request(struct core_name *cn, struct coredump_params * return false; } + /* Records only describe a coredump the kernel writes. */ + if ((ack.mask & COREDUMP_RECORDS) && !(ack.mask & COREDUMP_KERNEL)) { + coredump_sock_mark(cprm->file, COREDUMP_MARK_CONFLICTING); + return false; + } + + /* Record header scratch; a bvec can't point at the stack. */ + if (ack.mask & COREDUMP_RECORDS) { + cprm->record_hdr = kmalloc_obj(*cprm->record_hdr); + if (!cprm->record_hdr) + return false; + } + cprm->mask = ack.mask; return coredump_sock_mark(cprm->file, COREDUMP_MARK_REQACK); } @@ -1046,7 +1062,6 @@ static bool coredump_pipe(struct core_name *cn, struct coredump_params *cprm, static bool coredump_write(struct coredump_params *cprm, const struct linux_binfmt *binfmt) { - if (dump_interrupted()) { cprm->state |= COREDUMP_STATE_TRUNCATED; return true; @@ -1062,15 +1077,17 @@ static bool coredump_write(struct coredump_params *cprm, cprm->state |= COREDUMP_STATE_TRUNCATED; /* * Ensures that file size is big enough to contain the current - * file postion. This prevents gdb from complaining about + * file position. This prevents gdb from complaining about * a truncated file if the last "write" to the file was - * dump_skip. + * dump_skip. A record stream relies on it too: the flush + * emits the records that cover a trailing hole. */ if (cprm->to_skip) { cprm->to_skip--; if (!dump_emit(cprm, "", 1)) cprm->state |= COREDUMP_STATE_TRUNCATED; } + dump_end_record(cprm); file_end_write(cprm->file); free_vma_snapshot(cprm); return true; @@ -1085,6 +1102,7 @@ static void coredump_cleanup(struct core_name *cn, struct coredump_params *cprm) atomic_dec(&core_pipe_count); } kfree(cn->corename); + kfree(cprm->record_hdr); coredump_finish(cprm->state); } @@ -1218,26 +1236,74 @@ void vfs_coredump(const kernel_siginfo_t *siginfo) * do on a core-file: use only these functions to write out all the * necessary info. */ -/* One write, never more than a page. See __dump_emit(). */ -static bool dump_emit_chunk(struct coredump_params *cprm, const void *addr, - int nr) +static bool dump_records(const struct coredump_params *cprm) +{ + return cprm->mask & COREDUMP_RECORDS; +} + +/* Describe the next @len bytes of the coredump. Returns the header size. */ +static size_t dump_record_init(struct coredump_params *cprm, + enum coredump_record_type type, u64 flags, + u64 len) +{ + if (!dump_records(cprm)) + return 0; + + *cprm->record_hdr = (struct coredump_record_header) { + .size = sizeof(*cprm->record_hdr), + .type = type, + .flags = flags, + .offset = cprm->pos, + .len = len, + }; + + return sizeof(*cprm->record_hdr); +} + +/* Write @iter whole or fail. @len is what it advances the coredump by. */ +static bool dump_write_iter(struct coredump_params *cprm, struct iov_iter *iter, + size_t len) { struct file *file = cprm->file; + size_t count = iov_iter_count(iter); loff_t pos = file->f_pos; ssize_t n; - if (dump_interrupted()) + n = __kernel_write_iter(file, iter, &pos); + if (n != (ssize_t)count) return false; + file->f_pos = pos; + cprm->written += count; + cprm->pos += len; + + return true; +} + +/* One record, never more than a page. See __dump_emit(). */ +static bool dump_emit_chunk(struct coredump_params *cprm, const void *addr, + int nr) +{ + struct kvec kvec[2]; + struct iov_iter iter; + unsigned int nseg = 0; + size_t hdrlen; - n = __kernel_write(file, addr, nr, &pos); - if (n != nr) + if (dump_interrupted()) return false; - file->f_pos = pos; - cprm->written += n; - cprm->pos += n; + hdrlen = dump_record_init(cprm, COREDUMP_RECORD_DATA, 0, nr); + if (hdrlen) { + kvec[nseg].iov_base = cprm->record_hdr; + kvec[nseg].iov_len = hdrlen; + nseg++; + } + kvec[nseg].iov_base = (void *)addr; + kvec[nseg].iov_len = nr; + nseg++; - return true; + iov_iter_kvec(&iter, ITER_SOURCE, kvec, nseg, hdrlen + nr); + + return dump_write_iter(cprm, &iter, nr); } static bool __dump_emit(struct coredump_params *cprm, const void *addr, int nr) @@ -1258,6 +1324,34 @@ static bool __dump_emit(struct coredump_params *cprm, const void *addr, int nr) return true; } +/* Send a record that stands on its own: a header and nothing else. */ +static bool dump_emit_record(struct coredump_params *cprm, + enum coredump_record_type type, u64 flags, u64 len) +{ + struct kvec kvec; + struct iov_iter iter; + size_t hdrlen; + + hdrlen = dump_record_init(cprm, type, flags, len); + if (!hdrlen) + return false; + + kvec.iov_base = cprm->record_hdr; + kvec.iov_len = hdrlen; + iov_iter_kvec(&iter, ITER_SOURCE, &kvec, 1, hdrlen); + + return dump_write_iter(cprm, &iter, len); +} + +/* Close the record stream. Only a whole coredump gets an end record. */ +static void dump_end_record(struct coredump_params *cprm) +{ + if (cprm->state & COREDUMP_STATE_TRUNCATED) + return; + + dump_emit_record(cprm, COREDUMP_RECORD_END, 0, 0); +} + static bool __dump_skip(struct coredump_params *cprm, size_t nr) { static char zeroes[PAGE_SIZE]; @@ -1318,11 +1412,10 @@ EXPORT_SYMBOL(dump_skip); #ifdef CONFIG_ELF_CORE static bool dump_emit_page(struct coredump_params *cprm, struct page *page) { - struct bio_vec bvec; + struct bio_vec bvec[2]; struct iov_iter iter; - struct file *file = cprm->file; - loff_t pos; - ssize_t n; + unsigned int nseg = 0; + size_t hdrlen; if (!page) return false; @@ -1333,17 +1426,16 @@ static bool dump_emit_page(struct coredump_params *cprm, struct page *page) return false; if (dump_interrupted()) return false; - pos = file->f_pos; - bvec_set_page(&bvec, page, PAGE_SIZE, 0); - iov_iter_bvec(&iter, ITER_SOURCE, &bvec, 1, PAGE_SIZE); - n = __kernel_write_iter(cprm->file, &iter, &pos); - if (n != PAGE_SIZE) - return false; - file->f_pos = pos; - cprm->written += PAGE_SIZE; - cprm->pos += PAGE_SIZE; - return true; + /* Hand the record header to the same write as the page it describes. */ + hdrlen = dump_record_init(cprm, COREDUMP_RECORD_DATA, 0, PAGE_SIZE); + if (hdrlen) + bvec_set_virt(&bvec[nseg++], cprm->record_hdr, hdrlen); + bvec_set_page(&bvec[nseg++], page, PAGE_SIZE, 0); + + iov_iter_bvec(&iter, ITER_SOURCE, bvec, nseg, hdrlen + PAGE_SIZE); + + return dump_write_iter(cprm, &iter, PAGE_SIZE); } /* diff --git a/include/linux/coredump.h b/include/linux/coredump.h index 709388dd5659..b252bb2843b3 100644 --- a/include/linux/coredump.h +++ b/include/linux/coredump.h @@ -6,6 +6,7 @@ #include <linux/mm.h> #include <linux/fs.h> #include <linux/sched/coredump.h> +#include <uapi/linux/coredump.h> #include <asm/siginfo.h> #ifdef CONFIG_COREDUMP @@ -40,7 +41,11 @@ struct coredump_params { u64 mask; /* COREDUMP_STATE_* raised while the coredump is written. */ enum coredump_state state; + /* Record header scratch, NULL unless the coredump is a record stream. */ + struct coredump_record_header *record_hdr; + /* Bytes handed to the file, record headers included. */ loff_t written; + /* Offset in the coredump, record headers excluded. */ loff_t pos; loff_t to_skip; int vma_count; diff --git a/tools/testing/selftests/coredump/coredump_test_helpers.c b/tools/testing/selftests/coredump/coredump_test_helpers.c index 570fc2e005c2..1c8658f35735 100644 --- a/tools/testing/selftests/coredump/coredump_test_helpers.c +++ b/tools/testing/selftests/coredump/coredump_test_helpers.c @@ -275,7 +275,7 @@ bool send_coredump_ack(int fd, const struct coredump_req *req, /* Every option the kernel is expected to advertise in coredump_req->mask. */ #define TEST_REQ_MASK_ALL \ (COREDUMP_KERNEL | COREDUMP_USERSPACE | \ - COREDUMP_REJECT | COREDUMP_WAIT) + COREDUMP_REJECT | COREDUMP_WAIT | COREDUMP_RECORDS) bool check_coredump_req(const struct coredump_req *req) { -- 2.53.0
