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systemd/src/basic/log.h
Daan De Meyer 7c7a9138a2 basic: Add log context 
This commit adds support for attaching extra metadata to log
messages written to the journal via log.h. We keep track of a
thread local log context in log.c onto which we can push extra
metadata fields that should be logged. Once a field is no longer
relevant, it can be popped again from the log context.

On top of this, we then add macros to allow pushing extra fields
onto the log context.

LOG_CONTEXT_PUSH() will push the provided field onto the log context
and pop the last field from the log context when the current block
ends. LOG_CONTEXT_PUSH_STRV() will do the same but for all fields in
the given strv.

Using the macros is as simple as putting them anywhere inside a block
to add a field to all following log messages logged from inside that
block.

void myfunction(...) {
	...

	LOG_CONTEXT_PUSH("MYMETADATA=abc");

	// Every journal message logged will now have the MYMETADATA=abc
        // field included.
}

For convenience, there's also LOG_CONTEXT_PUSHF() to allow constructing
the field to be logged using printf() syntax.

log_context_new()/log_context_free() can be used to attach a log context
to an async operation by storing it in the associated userdata struct.
2023-01-08 16:31:16 +01:00

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#pragma once
#include <stdarg.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include "list.h"
#include "macro.h"
#include "ratelimit.h"
#include "stdio-util.h"
/* Some structures we reference but don't want to pull in headers for */
struct iovec;
struct signalfd_siginfo;
typedef enum LogTarget{
LOG_TARGET_CONSOLE,
LOG_TARGET_CONSOLE_PREFIXED,
LOG_TARGET_KMSG,
LOG_TARGET_JOURNAL,
LOG_TARGET_JOURNAL_OR_KMSG,
LOG_TARGET_SYSLOG,
LOG_TARGET_SYSLOG_OR_KMSG,
LOG_TARGET_AUTO, /* console if stderr is not journal, JOURNAL_OR_KMSG otherwise */
LOG_TARGET_NULL,
_LOG_TARGET_MAX,
_LOG_TARGET_INVALID = -EINVAL,
} LogTarget;
/* This log level disables logging completely. It can only be passed to log_set_max_level() and cannot be
* used a regular log level. */
#define LOG_NULL (LOG_EMERG - 1)
/* Note to readers: << and >> have lower precedence (are evaluated earlier) than & and | */
#define SYNTHETIC_ERRNO(num) (1 << 30 | (num))
#define IS_SYNTHETIC_ERRNO(val) ((val) >> 30 & 1)
#define ERRNO_VALUE(val) (abs(val) & ~(1 << 30))
/* The callback function to be invoked when syntax warnings are seen
* in the unit files. */
typedef void (*log_syntax_callback_t)(const char *unit, int level, void *userdata);
void set_log_syntax_callback(log_syntax_callback_t cb, void *userdata);
static inline void clear_log_syntax_callback(dummy_t *dummy) {
set_log_syntax_callback(/* cb= */ NULL, /* userdata= */ NULL);
}
const char *log_target_to_string(LogTarget target) _const_;
LogTarget log_target_from_string(const char *s) _pure_;
void log_set_target(LogTarget target);
int log_set_target_from_string(const char *e);
LogTarget log_get_target(void) _pure_;
void log_set_max_level(int level);
int log_set_max_level_from_string(const char *e);
int log_get_max_level(void) _pure_;
void log_set_facility(int facility);
void log_show_color(bool b);
bool log_get_show_color(void) _pure_;
void log_show_location(bool b);
bool log_get_show_location(void) _pure_;
void log_show_time(bool b);
bool log_get_show_time(void) _pure_;
void log_show_tid(bool b);
bool log_get_show_tid(void) _pure_;
int log_show_color_from_string(const char *e);
int log_show_location_from_string(const char *e);
int log_show_time_from_string(const char *e);
int log_show_tid_from_string(const char *e);
/* Functions below that open and close logs or configure logging based on the
* environment should not be called from library code — this is always a job
* for the application itself. */
assert_cc(STRLEN(__FILE__) > STRLEN(RELATIVE_SOURCE_PATH) + 1);
#define PROJECT_FILE (&__FILE__[STRLEN(RELATIVE_SOURCE_PATH) + 1])
int log_open(void);
void log_close(void);
void log_forget_fds(void);
void log_parse_environment_variables(void);
void log_parse_environment(void);
int log_dispatch_internal(
int level,
int error,
const char *file,
int line,
const char *func,
const char *object_field,
const char *object,
const char *extra,
const char *extra_field,
char *buffer);
int log_internal(
int level,
int error,
const char *file,
int line,
const char *func,
const char *format, ...) _printf_(6,7);
int log_internalv(
int level,
int error,
const char *file,
int line,
const char *func,
const char *format,
va_list ap) _printf_(6,0);
int log_object_internalv(
int level,
int error,
const char *file,
int line,
const char *func,
const char *object_field,
const char *object,
const char *extra_field,
const char *extra,
const char *format,
va_list ap) _printf_(10,0);
int log_object_internal(
int level,
int error,
const char *file,
int line,
const char *func,
const char *object_field,
const char *object,
const char *extra_field,
const char *extra,
const char *format, ...) _printf_(10,11);
int log_struct_internal(
int level,
int error,
const char *file,
int line,
const char *func,
const char *format, ...) _printf_(6,0) _sentinel_;
int log_oom_internal(
int level,
const char *file,
int line,
const char *func);
int log_format_iovec(
struct iovec *iovec,
size_t iovec_len,
size_t *n,
bool newline_separator,
int error,
const char *format,
va_list ap) _printf_(6, 0);
int log_struct_iovec_internal(
int level,
int error,
const char *file,
int line,
const char *func,
const struct iovec *input_iovec,
size_t n_input_iovec);
/* This modifies the buffer passed! */
int log_dump_internal(
int level,
int error,
const char *file,
int line,
const char *func,
char *buffer);
/* Logging for various assertions */
_noreturn_ void log_assert_failed(
const char *text,
const char *file,
int line,
const char *func);
_noreturn_ void log_assert_failed_unreachable(
const char *file,
int line,
const char *func);
void log_assert_failed_return(
const char *text,
const char *file,
int line,
const char *func);
#define log_dispatch(level, error, buffer) \
log_dispatch_internal(level, error, PROJECT_FILE, __LINE__, __func__, NULL, NULL, NULL, NULL, buffer)
/* Logging with level */
#define log_full_errno_zerook(level, error, ...) \
({ \
int _level = (level), _e = (error); \
_e = (log_get_max_level() >= LOG_PRI(_level)) \
? log_internal(_level, _e, PROJECT_FILE, __LINE__, __func__, __VA_ARGS__) \
: -ERRNO_VALUE(_e); \
_e < 0 ? _e : -ESTRPIPE; \
})
#if BUILD_MODE_DEVELOPER && !defined(TEST_CODE)
# define ASSERT_NON_ZERO(x) assert((x) != 0)
#else
# define ASSERT_NON_ZERO(x)
#endif
#define log_full_errno(level, error, ...) \
({ \
int _error = (error); \
ASSERT_NON_ZERO(_error); \
log_full_errno_zerook(level, _error, __VA_ARGS__); \
})
#define log_full(level, fmt, ...) \
({ \
if (BUILD_MODE_DEVELOPER) \
assert(!strstr(fmt, "%m")); \
(void) log_full_errno_zerook(level, 0, fmt, ##__VA_ARGS__); \
})
int log_emergency_level(void);
/* Normal logging */
#define log_debug(...) log_full(LOG_DEBUG, __VA_ARGS__)
#define log_info(...) log_full(LOG_INFO, __VA_ARGS__)
#define log_notice(...) log_full(LOG_NOTICE, __VA_ARGS__)
#define log_warning(...) log_full(LOG_WARNING, __VA_ARGS__)
#define log_error(...) log_full(LOG_ERR, __VA_ARGS__)
#define log_emergency(...) log_full(log_emergency_level(), __VA_ARGS__)
/* Logging triggered by an errno-like error */
#define log_debug_errno(error, ...) log_full_errno(LOG_DEBUG, error, __VA_ARGS__)
#define log_info_errno(error, ...) log_full_errno(LOG_INFO, error, __VA_ARGS__)
#define log_notice_errno(error, ...) log_full_errno(LOG_NOTICE, error, __VA_ARGS__)
#define log_warning_errno(error, ...) log_full_errno(LOG_WARNING, error, __VA_ARGS__)
#define log_error_errno(error, ...) log_full_errno(LOG_ERR, error, __VA_ARGS__)
#define log_emergency_errno(error, ...) log_full_errno(log_emergency_level(), error, __VA_ARGS__)
/* This logs at the specified level the first time it is called, and then
* logs at debug. If the specified level is debug, this logs only the first
* time it is called. */
#define log_once(level, ...) \
({ \
if (ONCE) \
log_full(level, __VA_ARGS__); \
else if (LOG_PRI(level) != LOG_DEBUG) \
log_debug(__VA_ARGS__); \
})
#define log_once_errno(level, error, ...) \
({ \
int _err = (error); \
if (ONCE) \
_err = log_full_errno(level, _err, __VA_ARGS__); \
else if (LOG_PRI(level) != LOG_DEBUG) \
_err = log_debug_errno(_err, __VA_ARGS__); \
else \
_err = -ERRNO_VALUE(_err); \
_err; \
})
#if LOG_TRACE
# define log_trace(...) log_debug(__VA_ARGS__)
# define log_trace_errno(...) log_debug_errno(__VA_ARGS__)
#else
# define log_trace(...) do {} while (0)
# define log_trace_errno(e, ...) (-ERRNO_VALUE(e))
#endif
/* Structured logging */
#define log_struct_errno(level, error, ...) \
log_struct_internal(level, error, PROJECT_FILE, __LINE__, __func__, __VA_ARGS__, NULL)
#define log_struct(level, ...) log_struct_errno(level, 0, __VA_ARGS__)
#define log_struct_iovec_errno(level, error, iovec, n_iovec) \
log_struct_iovec_internal(level, error, PROJECT_FILE, __LINE__, __func__, iovec, n_iovec)
#define log_struct_iovec(level, iovec, n_iovec) log_struct_iovec_errno(level, 0, iovec, n_iovec)
/* This modifies the buffer passed! */
#define log_dump(level, buffer) \
log_dump_internal(level, 0, PROJECT_FILE, __LINE__, __func__, buffer)
#define log_oom() log_oom_internal(LOG_ERR, PROJECT_FILE, __LINE__, __func__)
#define log_oom_debug() log_oom_internal(LOG_DEBUG, PROJECT_FILE, __LINE__, __func__)
bool log_on_console(void) _pure_;
/* Helper to wrap the main message in structured logging. The macro doesn't do much,
* except to provide visual grouping of the format string and its arguments. */
#if LOG_MESSAGE_VERIFICATION || defined(__COVERITY__)
/* Do a fake formatting of the message string to let the scanner verify the arguments against the format
* message. The variable will never be set to true, but we don't tell the compiler that :) */
extern bool _log_message_dummy;
# define LOG_MESSAGE(fmt, ...) "MESSAGE=%.0d" fmt, (_log_message_dummy && printf(fmt, ##__VA_ARGS__)), ##__VA_ARGS__
#else
# define LOG_MESSAGE(fmt, ...) "MESSAGE=" fmt, ##__VA_ARGS__
#endif
void log_received_signal(int level, const struct signalfd_siginfo *si);
/* If turned on, any requests for a log target involving "syslog" will be implicitly upgraded to the equivalent journal target */
void log_set_upgrade_syslog_to_journal(bool b);
/* If turned on, and log_open() is called, we'll not use STDERR_FILENO for logging ever, but rather open /dev/console */
void log_set_always_reopen_console(bool b);
/* If turned on, we'll open the log stream implicitly if needed on each individual log call. This is normally not
* desired as we want to reuse our logging streams. It is useful however */
void log_set_open_when_needed(bool b);
/* If turned on, then we'll never use IPC-based logging, i.e. never log to syslog or the journal. We'll only log to
* stderr, the console or kmsg */
void log_set_prohibit_ipc(bool b);
int log_dup_console(void);
int log_syntax_internal(
const char *unit,
int level,
const char *config_file,
unsigned config_line,
int error,
const char *file,
int line,
const char *func,
const char *format, ...) _printf_(9, 10);
int log_syntax_invalid_utf8_internal(
const char *unit,
int level,
const char *config_file,
unsigned config_line,
const char *file,
int line,
const char *func,
const char *rvalue);
#define log_syntax(unit, level, config_file, config_line, error, ...) \
({ \
int _level = (level), _e = (error); \
(log_get_max_level() >= LOG_PRI(_level)) \
? log_syntax_internal(unit, _level, config_file, config_line, _e, PROJECT_FILE, __LINE__, __func__, __VA_ARGS__) \
: -ERRNO_VALUE(_e); \
})
#define log_syntax_invalid_utf8(unit, level, config_file, config_line, rvalue) \
({ \
int _level = (level); \
(log_get_max_level() >= LOG_PRI(_level)) \
? log_syntax_invalid_utf8_internal(unit, _level, config_file, config_line, PROJECT_FILE, __LINE__, __func__, rvalue) \
: -EINVAL; \
})
#define DEBUG_LOGGING _unlikely_(log_get_max_level() >= LOG_DEBUG)
void log_setup(void);
typedef struct LogRateLimit {
int error;
int level;
RateLimit ratelimit;
} LogRateLimit;
#define log_ratelimit_internal(_level, _error, _ratelimit, _format, _file, _line, _func, ...) \
({ \
int _log_ratelimit_error = (_error); \
int _log_ratelimit_level = (_level); \
static LogRateLimit _log_ratelimit = { \
.ratelimit = (_ratelimit), \
}; \
unsigned _num_dropped_errors = ratelimit_num_dropped(&_log_ratelimit.ratelimit); \
if (_log_ratelimit_error != _log_ratelimit.error || _log_ratelimit_level != _log_ratelimit.level) { \
ratelimit_reset(&_log_ratelimit.ratelimit); \
_log_ratelimit.error = _log_ratelimit_error; \
_log_ratelimit.level = _log_ratelimit_level; \
} \
if (log_get_max_level() == LOG_DEBUG || ratelimit_below(&_log_ratelimit.ratelimit)) \
_log_ratelimit_error = _num_dropped_errors > 0 \
? log_internal(_log_ratelimit_level, _log_ratelimit_error, _file, _line, _func, _format " (Dropped %u similar message(s))", ##__VA_ARGS__, _num_dropped_errors) \
: log_internal(_log_ratelimit_level, _log_ratelimit_error, _file, _line, _func, _format, ##__VA_ARGS__); \
_log_ratelimit_error; \
})
#define log_ratelimit_full_errno(level, error, _ratelimit, format, ...) \
({ \
int _level = (level), _e = (error); \
_e = (log_get_max_level() >= LOG_PRI(_level)) \
? log_ratelimit_internal(_level, _e, _ratelimit, format, PROJECT_FILE, __LINE__, __func__, ##__VA_ARGS__) \
: -ERRNO_VALUE(_e); \
_e < 0 ? _e : -ESTRPIPE; \
})
#define log_ratelimit_full(level, _ratelimit, format, ...) \
log_ratelimit_full_errno(level, 0, _ratelimit, format, ##__VA_ARGS__)
/* Normal logging */
#define log_ratelimit_info(...) log_ratelimit_full(LOG_INFO, __VA_ARGS__)
#define log_ratelimit_notice(...) log_ratelimit_full(LOG_NOTICE, __VA_ARGS__)
#define log_ratelimit_warning(...) log_ratelimit_full(LOG_WARNING, __VA_ARGS__)
#define log_ratelimit_error(...) log_ratelimit_full(LOG_ERR, __VA_ARGS__)
#define log_ratelimit_emergency(...) log_ratelimit_full(log_emergency_level(), __VA_ARGS__)
/* Logging triggered by an errno-like error */
#define log_ratelimit_info_errno(error, ...) log_ratelimit_full_errno(LOG_INFO, error, __VA_ARGS__)
#define log_ratelimit_notice_errno(error, ...) log_ratelimit_full_errno(LOG_NOTICE, error, __VA_ARGS__)
#define log_ratelimit_warning_errno(error, ...) log_ratelimit_full_errno(LOG_WARNING, error, __VA_ARGS__)
#define log_ratelimit_error_errno(error, ...) log_ratelimit_full_errno(LOG_ERR, error, __VA_ARGS__)
#define log_ratelimit_emergency_errno(error, ...) log_ratelimit_full_errno(log_emergency_level(), error, __VA_ARGS__)
/*
* The log context allows attaching extra metadata to log messages written to the journal via log.h. We keep
* track of a thread local log context onto which we can push extra metadata fields that should be logged.
*
* LOG_CONTEXT_PUSH() will add the provided field to the log context and will remove it again when the
* current block ends. LOG_CONTEXT_PUSH_STRV() will do the same but for all fields in the given strv.
* LOG_CONTEXT_PUSHF() is like LOG_CONTEXT_PUSH() but takes a format string and arguments.
*
* Using the macros is as simple as putting them anywhere inside a block to add a field to all following log
* messages logged from inside that block.
*
* void myfunction(...) {
* ...
*
* LOG_CONTEXT_PUSHF("MYMETADATA=%s", "abc");
*
* // Every journal message logged will now have the MYMETADATA=abc
* // field included.
* }
*
* One special case to note is async code, where we use callbacks that are invoked to continue processing
* when some event occurs. For async code, there's usually an associated "userdata" struct containing all the
* information associated with the async operation. In this "userdata" struct, we can store a log context
* allocated with log_context_new() and freed with log_context_free(). We can then add and remove fields to
* the `fields` member of the log context object and all those fields will be logged along with each log
* message.
*/
typedef struct LogContext LogContext;
bool log_context_enabled(void);
LogContext* log_context_attach(LogContext *c);
LogContext* log_context_detach(LogContext *c);
LogContext* log_context_new(char **fields, bool owned);
LogContext* log_context_free(LogContext *c);
/* Same as log_context_new(), but frees the given fields strv on failure. */
LogContext* log_context_new_consume(char **fields);
/* Returns the number of attached log context objects. */
size_t log_context_num_contexts(void);
/* Returns the number of fields in all attached log contexts. */
size_t log_context_num_fields(void);
DEFINE_TRIVIAL_CLEANUP_FUNC(LogContext*, log_context_detach);
DEFINE_TRIVIAL_CLEANUP_FUNC(LogContext*, log_context_free);
#define LOG_CONTEXT_PUSH(...) \
LOG_CONTEXT_PUSH_STRV(STRV_MAKE(__VA_ARGS__))
#define LOG_CONTEXT_PUSHF(...) \
LOG_CONTEXT_PUSH(snprintf_ok((char[LINE_MAX]) {}, LINE_MAX, __VA_ARGS__))
#define _LOG_CONTEXT_PUSH_STRV(strv, c) \
_unused_ _cleanup_(log_context_freep) LogContext *c = log_context_new(strv, /*owned=*/ false);
#define LOG_CONTEXT_PUSH_STRV(strv) \
_LOG_CONTEXT_PUSH_STRV(strv, UNIQ_T(c, UNIQ))
/* LOG_CONTEXT_CONSUME_STR()/LOG_CONTEXT_CONSUME_STRV() are identical to
* LOG_CONTEXT_PUSH_STR()/LOG_CONTEXT_PUSH_STRV() except they take ownership of the given str/strv argument.
*/
#define _LOG_CONTEXT_CONSUME_STR(s, c, strv) \
_unused_ _cleanup_strv_free_ strv = strv_new(s); \
if (!strv) \
free(s); \
_unused_ _cleanup_(log_context_freep) LogContext *c = log_context_new_consume(TAKE_PTR(strv))
#define LOG_CONTEXT_CONSUME_STR(s) \
_LOG_CONTEXT_CONSUME_STR(s, UNIQ_T(c, UNIQ), UNIQ_T(sv, UNIQ))
#define _LOG_CONTEXT_CONSUME_STRV(strv, c) \
_unused_ _cleanup_(log_context_freep) LogContext *c = log_context_new_consume(strv);
#define LOG_CONTEXT_CONSUME_STRV(strv) \
_LOG_CONTEXT_CONSUME_STRV(strv, UNIQ_T(c, UNIQ))
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