From fdd2c1f4e2c2e2fee1d95d18b4b06bc0d15c368a Mon Sep 17 00:00:00 2001 From: John Ogness Date: Wed, 3 Mar 2021 11:15:14 +0100 Subject: um: synchronize kmsg_dumper The kmsg_dumper can be called from any context and CPU, possibly from multiple CPUs simultaneously. Since a static buffer is used to retrieve the kernel logs, this buffer must be protected against simultaneous dumping. Skip dumping if another context is already dumping. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20210303101528.29901-2-john.ogness@linutronix.de --- arch/um/kernel/kmsg_dump.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch/um') diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c index 6516ef1f8274..a765d235e50e 100644 --- a/arch/um/kernel/kmsg_dump.c +++ b/arch/um/kernel/kmsg_dump.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include +#include #include #include #include @@ -9,8 +10,10 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason) { + static DEFINE_SPINLOCK(lock); static char line[1024]; struct console *con; + unsigned long flags; size_t len = 0; /* only dump kmsg when no console is available */ @@ -29,11 +32,16 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, if (con) return; + if (!spin_trylock_irqsave(&lock, flags)) + return; + printf("kmsg_dump:\n"); while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) { line[len] = '\0'; printf("%s", line); } + + spin_unlock_irqrestore(&lock, flags); } static struct kmsg_dumper kmsg_dumper = { -- cgit v1.2.3 From f9f3f02db98bbe678a8e57fe9432b196174744a3 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Wed, 3 Mar 2021 11:15:25 +0100 Subject: printk: introduce a kmsg_dump iterator Rather than storing the iterator information in the registered kmsg_dumper structure, create a separate iterator structure. The kmsg_dump_iter structure can reside on the stack of the caller, thus allowing lockless use of the kmsg_dump functions. Update code that accesses the kernel logs using the kmsg_dumper structure to use the new kmsg_dump_iter structure. For kmsg_dumpers, this also means adding a call to kmsg_dump_rewind() to initialize the iterator. All this is in preparation for removal of @logbuf_lock. Signed-off-by: John Ogness Reviewed-by: Kees Cook # pstore Reviewed-by: Petr Mladek Signed-off-by: Petr Mladek Link: https://lore.kernel.org/r/20210303101528.29901-13-john.ogness@linutronix.de --- arch/powerpc/kernel/nvram_64.c | 8 ++++-- arch/powerpc/xmon/xmon.c | 6 ++-- arch/um/kernel/kmsg_dump.c | 5 +++- drivers/hv/vmbus_drv.c | 4 ++- drivers/mtd/mtdoops.c | 5 +++- fs/pstore/platform.c | 5 +++- include/linux/kmsg_dump.h | 36 +++++++++++++----------- kernel/debug/kdb/kdb_main.c | 10 +++---- kernel/printk/printk.c | 63 +++++++++++++++++++++--------------------- 9 files changed, 80 insertions(+), 62 deletions(-) (limited to 'arch/um') diff --git a/arch/powerpc/kernel/nvram_64.c b/arch/powerpc/kernel/nvram_64.c index 532f22637783..3c8d9bbb51cf 100644 --- a/arch/powerpc/kernel/nvram_64.c +++ b/arch/powerpc/kernel/nvram_64.c @@ -647,6 +647,7 @@ static void oops_to_nvram(struct kmsg_dumper *dumper, { struct oops_log_info *oops_hdr = (struct oops_log_info *)oops_buf; static unsigned int oops_count = 0; + static struct kmsg_dump_iter iter; static bool panicking = false; static DEFINE_SPINLOCK(lock); unsigned long flags; @@ -681,13 +682,14 @@ static void oops_to_nvram(struct kmsg_dumper *dumper, return; if (big_oops_buf) { - kmsg_dump_get_buffer(dumper, false, + kmsg_dump_rewind(&iter); + kmsg_dump_get_buffer(&iter, false, big_oops_buf, big_oops_buf_sz, &text_len); rc = zip_oops(text_len); } if (rc != 0) { - kmsg_dump_rewind(dumper); - kmsg_dump_get_buffer(dumper, false, + kmsg_dump_rewind(&iter); + kmsg_dump_get_buffer(&iter, false, oops_data, oops_data_sz, &text_len); err_type = ERR_TYPE_KERNEL_PANIC; oops_hdr->version = cpu_to_be16(OOPS_HDR_VERSION); diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index a777573a0c38..dbcf403b1d8d 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -3005,7 +3005,7 @@ print_address(unsigned long addr) static void dump_log_buf(void) { - struct kmsg_dumper dumper; + struct kmsg_dump_iter iter; unsigned char buf[128]; size_t len; @@ -3017,9 +3017,9 @@ dump_log_buf(void) catch_memory_errors = 1; sync(); - kmsg_dump_rewind_nolock(&dumper); + kmsg_dump_rewind_nolock(&iter); xmon_start_pagination(); - while (kmsg_dump_get_line_nolock(&dumper, false, buf, sizeof(buf), &len)) { + while (kmsg_dump_get_line_nolock(&iter, false, buf, sizeof(buf), &len)) { buf[len] = '\0'; printf("%s", buf); } diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c index a765d235e50e..0224fcb36e22 100644 --- a/arch/um/kernel/kmsg_dump.c +++ b/arch/um/kernel/kmsg_dump.c @@ -10,6 +10,7 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason) { + static struct kmsg_dump_iter iter; static DEFINE_SPINLOCK(lock); static char line[1024]; struct console *con; @@ -35,8 +36,10 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, if (!spin_trylock_irqsave(&lock, flags)) return; + kmsg_dump_rewind(&iter); + printf("kmsg_dump:\n"); - while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) { + while (kmsg_dump_get_line(&iter, true, line, sizeof(line), &len)) { line[len] = '\0'; printf("%s", line); } diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 10dce9f91216..b341b144bde8 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1391,6 +1391,7 @@ static void vmbus_isr(void) static void hv_kmsg_dump(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason) { + struct kmsg_dump_iter iter; size_t bytes_written; phys_addr_t panic_pa; @@ -1404,7 +1405,8 @@ static void hv_kmsg_dump(struct kmsg_dumper *dumper, * Write dump contents to the page. No need to synchronize; panic should * be single-threaded. */ - kmsg_dump_get_buffer(dumper, false, hv_panic_page, HV_HYP_PAGE_SIZE, + kmsg_dump_rewind(&iter); + kmsg_dump_get_buffer(&iter, false, hv_panic_page, HV_HYP_PAGE_SIZE, &bytes_written); if (bytes_written) hyperv_report_panic_msg(panic_pa, bytes_written); diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c index 8bbfba40a554..862c4a889234 100644 --- a/drivers/mtd/mtdoops.c +++ b/drivers/mtd/mtdoops.c @@ -277,14 +277,17 @@ static void mtdoops_do_dump(struct kmsg_dumper *dumper, { struct mtdoops_context *cxt = container_of(dumper, struct mtdoops_context, dump); + struct kmsg_dump_iter iter; /* Only dump oopses if dump_oops is set */ if (reason == KMSG_DUMP_OOPS && !dump_oops) return; + kmsg_dump_rewind(&iter); + if (test_and_set_bit(0, &cxt->oops_buf_busy)) return; - kmsg_dump_get_buffer(dumper, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE, + kmsg_dump_get_buffer(&iter, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE, record_size - MTDOOPS_HEADER_SIZE, NULL); clear_bit(0, &cxt->oops_buf_busy); diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c index d963ae7902f9..b9614db48b1d 100644 --- a/fs/pstore/platform.c +++ b/fs/pstore/platform.c @@ -385,6 +385,7 @@ void pstore_record_init(struct pstore_record *record, static void pstore_dump(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason) { + struct kmsg_dump_iter iter; unsigned long total = 0; const char *why; unsigned int part = 1; @@ -405,6 +406,8 @@ static void pstore_dump(struct kmsg_dumper *dumper, } } + kmsg_dump_rewind(&iter); + oopscount++; while (total < kmsg_bytes) { char *dst; @@ -435,7 +438,7 @@ static void pstore_dump(struct kmsg_dumper *dumper, dst_size -= header_size; /* Write dump contents. */ - if (!kmsg_dump_get_buffer(dumper, true, dst + header_size, + if (!kmsg_dump_get_buffer(&iter, true, dst + header_size, dst_size, &dump_size)) break; diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h index 84eaa2090efa..36c8c57e1051 100644 --- a/include/linux/kmsg_dump.h +++ b/include/linux/kmsg_dump.h @@ -29,6 +29,16 @@ enum kmsg_dump_reason { KMSG_DUMP_MAX }; +/** + * struct kmsg_dump_iter - iterator for retrieving kernel messages + * @cur_seq: Points to the oldest message to dump + * @next_seq: Points after the newest message to dump + */ +struct kmsg_dump_iter { + u64 cur_seq; + u64 next_seq; +}; + /** * struct kmsg_dumper - kernel crash message dumper structure * @list: Entry in the dumper list (private) @@ -36,35 +46,29 @@ enum kmsg_dump_reason { * through the record iterator * @max_reason: filter for highest reason number that should be dumped * @registered: Flag that specifies if this is already registered - * @cur_seq: Points to the oldest message to dump - * @next_seq: Points after the newest message to dump */ struct kmsg_dumper { struct list_head list; void (*dump)(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason); enum kmsg_dump_reason max_reason; bool registered; - - /* private state of the kmsg iterator */ - u64 cur_seq; - u64 next_seq; }; #ifdef CONFIG_PRINTK void kmsg_dump(enum kmsg_dump_reason reason); -bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog, +bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter, bool syslog, char *line, size_t size, size_t *len); -bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog, +bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog, char *line, size_t size, size_t *len); -bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, +bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog, char *buf, size_t size, size_t *len_out); -void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper); +void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter); -void kmsg_dump_rewind(struct kmsg_dumper *dumper); +void kmsg_dump_rewind(struct kmsg_dump_iter *iter); int kmsg_dump_register(struct kmsg_dumper *dumper); @@ -76,30 +80,30 @@ static inline void kmsg_dump(enum kmsg_dump_reason reason) { } -static inline bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, +static inline bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter, bool syslog, const char *line, size_t size, size_t *len) { return false; } -static inline bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog, +static inline bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog, const char *line, size_t size, size_t *len) { return false; } -static inline bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, +static inline bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog, char *buf, size_t size, size_t *len) { return false; } -static inline void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper) +static inline void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter) { } -static inline void kmsg_dump_rewind(struct kmsg_dumper *dumper) +static inline void kmsg_dump_rewind(struct kmsg_dump_iter *iter) { } diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 315169d5e119..8544d7a55a57 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2101,7 +2101,7 @@ static int kdb_dmesg(int argc, const char **argv) int adjust = 0; int n = 0; int skip = 0; - struct kmsg_dumper dumper; + struct kmsg_dump_iter iter; size_t len; char buf[201]; @@ -2126,8 +2126,8 @@ static int kdb_dmesg(int argc, const char **argv) kdb_set(2, setargs); } - kmsg_dump_rewind_nolock(&dumper); - while (kmsg_dump_get_line_nolock(&dumper, 1, NULL, 0, NULL)) + kmsg_dump_rewind_nolock(&iter); + while (kmsg_dump_get_line_nolock(&iter, 1, NULL, 0, NULL)) n++; if (lines < 0) { @@ -2159,8 +2159,8 @@ static int kdb_dmesg(int argc, const char **argv) if (skip >= n || skip < 0) return 0; - kmsg_dump_rewind_nolock(&dumper); - while (kmsg_dump_get_line_nolock(&dumper, 1, buf, sizeof(buf), &len)) { + kmsg_dump_rewind_nolock(&iter); + while (kmsg_dump_get_line_nolock(&iter, 1, buf, sizeof(buf), &len)) { if (skip) { skip--; continue; diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index ce4cc64ba7c9..b49dee256947 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3390,7 +3390,6 @@ EXPORT_SYMBOL_GPL(kmsg_dump_reason_str); void kmsg_dump(enum kmsg_dump_reason reason) { struct kmsg_dumper *dumper; - unsigned long flags; rcu_read_lock(); list_for_each_entry_rcu(dumper, &dump_list, list) { @@ -3407,12 +3406,6 @@ void kmsg_dump(enum kmsg_dump_reason reason) if (reason > max_reason) continue; - /* initialize iterator with data about the stored records */ - logbuf_lock_irqsave(flags); - dumper->cur_seq = latched_seq_read_nolock(&clear_seq); - dumper->next_seq = prb_next_seq(prb); - logbuf_unlock_irqrestore(flags); - /* invoke dumper which will iterate over records */ dumper->dump(dumper, reason); } @@ -3421,7 +3414,7 @@ void kmsg_dump(enum kmsg_dump_reason reason) /** * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version) - * @dumper: registered kmsg dumper + * @iter: kmsg dump iterator * @syslog: include the "<4>" prefixes * @line: buffer to copy the line to * @size: maximum size of the buffer @@ -3438,24 +3431,28 @@ void kmsg_dump(enum kmsg_dump_reason reason) * * The function is similar to kmsg_dump_get_line(), but grabs no locks. */ -bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog, +bool kmsg_dump_get_line_nolock(struct kmsg_dump_iter *iter, bool syslog, char *line, size_t size, size_t *len) { + u64 min_seq = latched_seq_read_nolock(&clear_seq); struct printk_info info; unsigned int line_count; struct printk_record r; size_t l = 0; bool ret = false; + if (iter->cur_seq < min_seq) + iter->cur_seq = min_seq; + prb_rec_init_rd(&r, &info, line, size); /* Read text or count text lines? */ if (line) { - if (!prb_read_valid(prb, dumper->cur_seq, &r)) + if (!prb_read_valid(prb, iter->cur_seq, &r)) goto out; l = record_print_text(&r, syslog, printk_time); } else { - if (!prb_read_valid_info(prb, dumper->cur_seq, + if (!prb_read_valid_info(prb, iter->cur_seq, &info, &line_count)) { goto out; } @@ -3464,7 +3461,7 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog, } - dumper->cur_seq = r.info->seq + 1; + iter->cur_seq = r.info->seq + 1; ret = true; out: if (len) @@ -3474,7 +3471,7 @@ out: /** * kmsg_dump_get_line - retrieve one kmsg log line - * @dumper: registered kmsg dumper + * @iter: kmsg dump iterator * @syslog: include the "<4>" prefixes * @line: buffer to copy the line to * @size: maximum size of the buffer @@ -3489,14 +3486,14 @@ out: * A return value of FALSE indicates that there are no more records to * read. */ -bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog, +bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog, char *line, size_t size, size_t *len) { unsigned long flags; bool ret; logbuf_lock_irqsave(flags); - ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len); + ret = kmsg_dump_get_line_nolock(iter, syslog, line, size, len); logbuf_unlock_irqrestore(flags); return ret; @@ -3505,7 +3502,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line); /** * kmsg_dump_get_buffer - copy kmsg log lines - * @dumper: registered kmsg dumper + * @iter: kmsg dump iterator * @syslog: include the "<4>" prefixes * @buf: buffer to copy the line to * @size: maximum size of the buffer @@ -3522,9 +3519,10 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line); * A return value of FALSE indicates that there are no more records to * read. */ -bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, +bool kmsg_dump_get_buffer(struct kmsg_dump_iter *iter, bool syslog, char *buf, size_t size, size_t *len_out) { + u64 min_seq = latched_seq_read_nolock(&clear_seq); struct printk_info info; struct printk_record r; unsigned long flags; @@ -3537,16 +3535,19 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, if (!buf || !size) goto out; + if (iter->cur_seq < min_seq) + iter->cur_seq = min_seq; + logbuf_lock_irqsave(flags); - if (prb_read_valid_info(prb, dumper->cur_seq, &info, NULL)) { - if (info.seq != dumper->cur_seq) { + if (prb_read_valid_info(prb, iter->cur_seq, &info, NULL)) { + if (info.seq != iter->cur_seq) { /* messages are gone, move to first available one */ - dumper->cur_seq = info.seq; + iter->cur_seq = info.seq; } } /* last entry */ - if (dumper->cur_seq >= dumper->next_seq) { + if (iter->cur_seq >= iter->next_seq) { logbuf_unlock_irqrestore(flags); goto out; } @@ -3557,7 +3558,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, * because this function (by way of record_print_text()) will * not write more than size-1 bytes of text into @buf. */ - seq = find_first_fitting_seq(dumper->cur_seq, dumper->next_seq, + seq = find_first_fitting_seq(iter->cur_seq, iter->next_seq, size - 1, syslog, time); /* @@ -3570,7 +3571,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, len = 0; prb_for_each_record(seq, prb, seq, &r) { - if (r.info->seq >= dumper->next_seq) + if (r.info->seq >= iter->next_seq) break; len += record_print_text(&r, syslog, time); @@ -3579,7 +3580,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, prb_rec_init_rd(&r, &info, buf + len, size - len); } - dumper->next_seq = next_seq; + iter->next_seq = next_seq; ret = true; logbuf_unlock_irqrestore(flags); out: @@ -3591,7 +3592,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer); /** * kmsg_dump_rewind_nolock - reset the iterator (unlocked version) - * @dumper: registered kmsg dumper + * @iter: kmsg dump iterator * * Reset the dumper's iterator so that kmsg_dump_get_line() and * kmsg_dump_get_buffer() can be called again and used multiple @@ -3599,26 +3600,26 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer); * * The function is similar to kmsg_dump_rewind(), but grabs no locks. */ -void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper) +void kmsg_dump_rewind_nolock(struct kmsg_dump_iter *iter) { - dumper->cur_seq = latched_seq_read_nolock(&clear_seq); - dumper->next_seq = prb_next_seq(prb); + iter->cur_seq = latched_seq_read_nolock(&clear_seq); + iter->next_seq = prb_next_seq(prb); } /** * kmsg_dump_rewind - reset the iterator - * @dumper: registered kmsg dumper + * @iter: kmsg dump iterator * * Reset the dumper's iterator so that kmsg_dump_get_line() and * kmsg_dump_get_buffer() can be called again and used multiple * times within the same dumper.dump() callback. */ -void kmsg_dump_rewind(struct kmsg_dumper *dumper) +void kmsg_dump_rewind(struct kmsg_dump_iter *iter) { unsigned long flags; logbuf_lock_irqsave(flags); - kmsg_dump_rewind_nolock(dumper); + kmsg_dump_rewind_nolock(iter); logbuf_unlock_irqrestore(flags); } EXPORT_SYMBOL_GPL(kmsg_dump_rewind); -- cgit v1.2.3