whiterose

linux unikernel
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commit a3b5c1065f3fb934a87dd07d23def99916023d6f
parent c6f1b355d451680a45d63ce66cea67057c938a87
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 27 Dec 2018 11:24:43 -0800

Merge tag 'printk-for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

Pull printk updates from Petr Mladek:

 - Keep spinlocks busted until the end of panic()

 - Fix races between calculating number of messages that would fit into
   user space buffers, filling the buffers, and switching printk.time
   parameter

 - Some code clean up

* tag 'printk-for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  printk: Remove print_prefix() calls with NULL buffer.
  printk: fix printk_time race.
  printk: Make printk_emit() local function.
  panic: avoid deadlocks in re-entrant console drivers

Diffstat:
Minclude/linux/printk.h | 5-----
Mkernel/panic.c | 6+++++-
Mkernel/printk/printk.c | 131++++++++++++++++++++++++++++++++++++++-----------------------------------------
3 files changed, 68 insertions(+), 74 deletions(-)

diff --git a/include/linux/printk.h b/include/linux/printk.h @@ -166,11 +166,6 @@ int vprintk_emit(int facility, int level, asmlinkage __printf(1, 0) int vprintk(const char *fmt, va_list args); -asmlinkage __printf(5, 6) __cold -int printk_emit(int facility, int level, - const char *dict, size_t dictlen, - const char *fmt, ...); - asmlinkage __printf(1, 2) __cold int printk(const char *fmt, ...); diff --git a/kernel/panic.c b/kernel/panic.c @@ -14,6 +14,7 @@ #include <linux/kmsg_dump.h> #include <linux/kallsyms.h> #include <linux/notifier.h> +#include <linux/vt_kern.h> #include <linux/module.h> #include <linux/random.h> #include <linux/ftrace.h> @@ -237,7 +238,10 @@ void panic(const char *fmt, ...) if (_crash_kexec_post_notifiers) __crash_kexec(NULL); - bust_spinlocks(0); +#ifdef CONFIG_VT + unblank_screen(); +#endif + console_unblank(); /* * We may have ended up stopping the CPU holding the lock (in diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c @@ -403,6 +403,7 @@ DECLARE_WAIT_QUEUE_HEAD(log_wait); static u64 syslog_seq; static u32 syslog_idx; static size_t syslog_partial; +static bool syslog_time; /* index and sequence number of the first record stored in the buffer */ static u64 log_first_seq; @@ -752,6 +753,19 @@ struct devkmsg_user { char buf[CONSOLE_EXT_LOG_MAX]; }; +static __printf(3, 4) __cold +int devkmsg_emit(int facility, int level, const char *fmt, ...) +{ + va_list args; + int r; + + va_start(args, fmt); + r = vprintk_emit(facility, level, NULL, 0, fmt, args); + va_end(args); + + return r; +} + static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from) { char *buf, *line; @@ -810,7 +824,7 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from) } } - printk_emit(facility, level, NULL, 0, "%s", line); + devkmsg_emit(facility, level, "%s", line); kfree(buf); return ret; } @@ -1213,50 +1227,39 @@ static inline void boot_delay_msec(int level) static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME); module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR); -static size_t print_time(u64 ts, char *buf) +static size_t print_syslog(unsigned int level, char *buf) { - unsigned long rem_nsec; - - if (!printk_time) - return 0; - - rem_nsec = do_div(ts, 1000000000); + return sprintf(buf, "<%u>", level); +} - if (!buf) - return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts); +static size_t print_time(u64 ts, char *buf) +{ + unsigned long rem_nsec = do_div(ts, 1000000000); return sprintf(buf, "[%5lu.%06lu] ", (unsigned long)ts, rem_nsec / 1000); } -static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf) +static size_t print_prefix(const struct printk_log *msg, bool syslog, + bool time, char *buf) { size_t len = 0; - unsigned int prefix = (msg->facility << 3) | msg->level; - - if (syslog) { - if (buf) { - len += sprintf(buf, "<%u>", prefix); - } else { - len += 3; - if (prefix > 999) - len += 3; - else if (prefix > 99) - len += 2; - else if (prefix > 9) - len++; - } - } - len += print_time(msg->ts_nsec, buf ? buf + len : NULL); + if (syslog) + len = print_syslog((msg->facility << 3) | msg->level, buf); + if (time) + len += print_time(msg->ts_nsec, buf + len); return len; } -static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *buf, size_t size) +static size_t msg_print_text(const struct printk_log *msg, bool syslog, + bool time, char *buf, size_t size) { const char *text = log_text(msg); size_t text_size = msg->text_len; size_t len = 0; + char prefix[PREFIX_MAX]; + const size_t prefix_len = print_prefix(msg, syslog, time, prefix); do { const char *next = memchr(text, '\n', text_size); @@ -1271,19 +1274,17 @@ static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *bu } if (buf) { - if (print_prefix(msg, syslog, NULL) + - text_len + 1 >= size - len) + if (prefix_len + text_len + 1 >= size - len) break; - len += print_prefix(msg, syslog, buf + len); + memcpy(buf + len, prefix, prefix_len); + len += prefix_len; memcpy(buf + len, text, text_len); len += text_len; buf[len++] = '\n'; } else { /* SYSLOG_ACTION_* buffer size only calculation */ - len += print_prefix(msg, syslog, NULL); - len += text_len; - len++; + len += prefix_len + text_len + 1; } text = next; @@ -1318,9 +1319,17 @@ static int syslog_print(char __user *buf, int size) break; } + /* + * To keep reading/counting partial line consistent, + * use printk_time value as of the beginning of a line. + */ + if (!syslog_partial) + syslog_time = printk_time; + skip = syslog_partial; msg = log_from_idx(syslog_idx); - n = msg_print_text(msg, true, text, LOG_LINE_MAX + PREFIX_MAX); + n = msg_print_text(msg, true, syslog_time, text, + LOG_LINE_MAX + PREFIX_MAX); if (n - syslog_partial <= size) { /* message fits into buffer, move forward */ syslog_idx = log_next(syslog_idx); @@ -1360,11 +1369,13 @@ static int syslog_print_all(char __user *buf, int size, bool clear) u64 next_seq; u64 seq; u32 idx; + bool time; text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL); if (!text) return -ENOMEM; + time = printk_time; logbuf_lock_irq(); /* * Find first record that fits, including all following records, @@ -1375,7 +1386,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) while (seq < log_next_seq) { struct printk_log *msg = log_from_idx(idx); - len += msg_print_text(msg, true, NULL, 0); + len += msg_print_text(msg, true, time, NULL, 0); idx = log_next(idx); seq++; } @@ -1386,7 +1397,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) while (len > size && seq < log_next_seq) { struct printk_log *msg = log_from_idx(idx); - len -= msg_print_text(msg, true, NULL, 0); + len -= msg_print_text(msg, true, time, NULL, 0); idx = log_next(idx); seq++; } @@ -1397,14 +1408,9 @@ static int syslog_print_all(char __user *buf, int size, bool clear) len = 0; while (len >= 0 && seq < next_seq) { struct printk_log *msg = log_from_idx(idx); - int textlen; + int textlen = msg_print_text(msg, true, time, text, + LOG_LINE_MAX + PREFIX_MAX); - textlen = msg_print_text(msg, true, text, - LOG_LINE_MAX + PREFIX_MAX); - if (textlen < 0) { - len = textlen; - break; - } idx = log_next(idx); seq++; @@ -1528,11 +1534,14 @@ int do_syslog(int type, char __user *buf, int len, int source) } else { u64 seq = syslog_seq; u32 idx = syslog_idx; + bool time = syslog_partial ? syslog_time : printk_time; while (seq < log_next_seq) { struct printk_log *msg = log_from_idx(idx); - error += msg_print_text(msg, true, NULL, 0); + error += msg_print_text(msg, true, time, NULL, + 0); + time = printk_time; idx = log_next(idx); seq++; } @@ -1935,21 +1944,6 @@ asmlinkage int vprintk(const char *fmt, va_list args) } EXPORT_SYMBOL(vprintk); -asmlinkage int printk_emit(int facility, int level, - const char *dict, size_t dictlen, - const char *fmt, ...) -{ - va_list args; - int r; - - va_start(args, fmt); - r = vprintk_emit(facility, level, dict, dictlen, fmt, args); - va_end(args); - - return r; -} -EXPORT_SYMBOL(printk_emit); - int vprintk_default(const char *fmt, va_list args) { int r; @@ -2005,6 +1999,7 @@ EXPORT_SYMBOL(printk); #define LOG_LINE_MAX 0 #define PREFIX_MAX 0 +#define printk_time false static u64 syslog_seq; static u32 syslog_idx; @@ -2028,8 +2023,8 @@ static void console_lock_spinning_enable(void) { } static int console_lock_spinning_disable_and_check(void) { return 0; } static void call_console_drivers(const char *ext_text, size_t ext_len, const char *text, size_t len) {} -static size_t msg_print_text(const struct printk_log *msg, - bool syslog, char *buf, size_t size) { return 0; } +static size_t msg_print_text(const struct printk_log *msg, bool syslog, + bool time, char *buf, size_t size) { return 0; } static bool suppress_message_printing(int level) { return false; } #endif /* CONFIG_PRINTK */ @@ -2387,8 +2382,7 @@ skip: len += msg_print_text(msg, console_msg_format & MSG_FORMAT_SYSLOG, - text + len, - sizeof(text) - len); + printk_time, text + len, sizeof(text) - len); if (nr_ext_console_drivers) { ext_len = msg_print_ext_header(ext_text, sizeof(ext_text), @@ -3112,7 +3106,7 @@ bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog, goto out; msg = log_from_idx(dumper->cur_idx); - l = msg_print_text(msg, syslog, line, size); + l = msg_print_text(msg, syslog, printk_time, line, size); dumper->cur_idx = log_next(dumper->cur_idx); dumper->cur_seq++; @@ -3183,6 +3177,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, u32 next_idx; size_t l = 0; bool ret = false; + bool time = printk_time; if (!dumper->active) goto out; @@ -3206,7 +3201,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, while (seq < dumper->next_seq) { struct printk_log *msg = log_from_idx(idx); - l += msg_print_text(msg, true, NULL, 0); + l += msg_print_text(msg, true, time, NULL, 0); idx = log_next(idx); seq++; } @@ -3217,7 +3212,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, while (l > size && seq < dumper->next_seq) { struct printk_log *msg = log_from_idx(idx); - l -= msg_print_text(msg, true, NULL, 0); + l -= msg_print_text(msg, true, time, NULL, 0); idx = log_next(idx); seq++; } @@ -3230,7 +3225,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, while (seq < dumper->next_seq) { struct printk_log *msg = log_from_idx(idx); - l += msg_print_text(msg, syslog, buf + l, size - l); + l += msg_print_text(msg, syslog, time, buf + l, size - l); idx = log_next(idx); seq++; }