From 0f516ca4767042aec8716369d6d62436fa10593a Mon Sep 17 00:00:00 2001 From: Robert Foley Date: Mon, 18 Nov 2019 16:15:23 -0500 Subject: Fix double free issue in qemu_set_log_filename(). MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit After freeing the logfilename, we set logfilename to NULL, in case of an error which returns without setting logfilename. Signed-off-by: Robert Foley Reviewed-by: Alex Bennée Signed-off-by: Alex Bennée Message-Id: <20191118211528.3221-2-robert.foley@linaro.org> --- util/log.c | 1 + 1 file changed, 1 insertion(+) (limited to 'util/log.c') diff --git a/util/log.c b/util/log.c index 1ca13059ee..4316fe74ee 100644 --- a/util/log.c +++ b/util/log.c @@ -113,6 +113,7 @@ void qemu_set_log_filename(const char *filename, Error **errp) { char *pidstr; g_free(logfilename); + logfilename = NULL; pidstr = strstr(filename, "%"); if (pidstr) { -- cgit 1.4.1 From 045e8861df8ec0922b1c47929d23dd61d8b75f8c Mon Sep 17 00:00:00 2001 From: Robert Foley Date: Mon, 18 Nov 2019 16:15:24 -0500 Subject: Cleaned up flow of code in qemu_set_log(), to simplify and clarify. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Also added some explanation of the reasoning behind the branches. Signed-off-by: Robert Foley Reviewed-by: Alex Bennée Signed-off-by: Alex Bennée Message-Id: <20191118211528.3221-3-robert.foley@linaro.org> --- util/log.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) (limited to 'util/log.c') diff --git a/util/log.c b/util/log.c index 4316fe74ee..417d16ec66 100644 --- a/util/log.c +++ b/util/log.c @@ -54,12 +54,25 @@ static bool log_uses_own_buffers; /* enable or disable low levels log */ void qemu_set_log(int log_flags) { + bool need_to_open_file = false; qemu_loglevel = log_flags; #ifdef CONFIG_TRACE_LOG qemu_loglevel |= LOG_TRACE; #endif - if (!qemu_logfile && - (is_daemonized() ? logfilename != NULL : qemu_loglevel)) { + /* + * In all cases we only log if qemu_loglevel is set. + * Also: + * If not daemonized we will always log either to stderr + * or to a file (if there is a logfilename). + * If we are daemonized, + * we will only log if there is a logfilename. + */ + if (qemu_loglevel && (!is_daemonized() || logfilename)) { + need_to_open_file = true; + } + if (qemu_logfile && !need_to_open_file) { + qemu_log_close(); + } else if (!qemu_logfile && need_to_open_file) { if (logfilename) { qemu_logfile = fopen(logfilename, log_append ? "a" : "w"); if (!qemu_logfile) { @@ -93,10 +106,6 @@ void qemu_set_log(int log_flags) log_append = 1; } } - if (qemu_logfile && - (is_daemonized() ? logfilename == NULL : !qemu_loglevel)) { - qemu_log_close(); - } } void qemu_log_needs_buffers(void) -- cgit 1.4.1 From b8121fe7c005dc3d56e82a0a5ce00563a5fd49d0 Mon Sep 17 00:00:00 2001 From: Robert Foley Date: Mon, 18 Nov 2019 16:15:25 -0500 Subject: Add a mutex to guarantee single writer to qemu_logfile handle. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Also added qemu_logfile_init() for initializing the logfile mutex. Note that inside qemu_set_log() we needed to add a pair of qemu_mutex_unlock() calls in order to avoid a double lock in qemu_log_close(). This unavoidable temporary ugliness will be cleaned up in a later patch in this series. Signed-off-by: Robert Foley Reviewed-by: Alex Bennée Signed-off-by: Alex Bennée Message-Id: <20191118211528.3221-4-robert.foley@linaro.org> --- util/log.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'util/log.c') diff --git a/util/log.c b/util/log.c index 417d16ec66..953a66b5a8 100644 --- a/util/log.c +++ b/util/log.c @@ -24,8 +24,10 @@ #include "qapi/error.h" #include "qemu/cutils.h" #include "trace/control.h" +#include "qemu/thread.h" static char *logfilename; +static QemuMutex qemu_logfile_mutex; FILE *qemu_logfile; int qemu_loglevel; static int log_append = 0; @@ -49,6 +51,11 @@ int qemu_log(const char *fmt, ...) return ret; } +static void __attribute__((__constructor__)) qemu_logfile_init(void) +{ + qemu_mutex_init(&qemu_logfile_mutex); +} + static bool log_uses_own_buffers; /* enable or disable low levels log */ @@ -70,7 +77,9 @@ void qemu_set_log(int log_flags) if (qemu_loglevel && (!is_daemonized() || logfilename)) { need_to_open_file = true; } + qemu_mutex_lock(&qemu_logfile_mutex); if (qemu_logfile && !need_to_open_file) { + qemu_mutex_unlock(&qemu_logfile_mutex); qemu_log_close(); } else if (!qemu_logfile && need_to_open_file) { if (logfilename) { @@ -105,6 +114,7 @@ void qemu_set_log(int log_flags) #endif log_append = 1; } + qemu_mutex_unlock(&qemu_logfile_mutex); } } @@ -240,12 +250,14 @@ void qemu_log_flush(void) /* Close the log file */ void qemu_log_close(void) { + qemu_mutex_lock(&qemu_logfile_mutex); if (qemu_logfile) { if (qemu_logfile != stderr) { fclose(qemu_logfile); } qemu_logfile = NULL; } + qemu_mutex_unlock(&qemu_logfile_mutex); } const QEMULogItem qemu_log_items[] = { -- cgit 1.4.1 From 7606488c0efa8f631d31ab9ff8d33b7cf3e2a4c9 Mon Sep 17 00:00:00 2001 From: Robert Foley Date: Mon, 18 Nov 2019 16:15:27 -0500 Subject: Add use of RCU for qemu_logfile. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This now allows changing the logfile while logging is active, and also solves the issue of a seg fault while changing the logfile. Any read access to the qemu_logfile handle will use the rcu_read_lock()/unlock() around the use of the handle. To fetch the handle we will use atomic_rcu_read(). We also in many cases do a check for validity of the logfile handle before using it to deal with the case where the file is closed and set to NULL. The cases where we write to the qemu_logfile will use atomic_rcu_set(). Writers will also use call_rcu() with a newly added qemu_logfile_free function for freeing/closing when readers have finished. Signed-off-by: Robert Foley Reviewed-by: Alex Bennée Signed-off-by: Alex Bennée Message-Id: <20191118211528.3221-6-robert.foley@linaro.org> --- include/exec/log.h | 33 ++++++++++++++++++++++--- include/qemu/log.h | 41 ++++++++++++++++++++++++++----- tcg/tcg.c | 12 +++++++-- util/log.c | 72 ++++++++++++++++++++++++++++++++++++++---------------- 4 files changed, 125 insertions(+), 33 deletions(-) (limited to 'util/log.c') diff --git a/include/exec/log.h b/include/exec/log.h index e2cfd436e6..9bd1e4aa20 100644 --- a/include/exec/log.h +++ b/include/exec/log.h @@ -15,8 +15,15 @@ */ static inline void log_cpu_state(CPUState *cpu, int flags) { + QemuLogFile *logfile; + if (qemu_log_enabled()) { - cpu_dump_state(cpu, qemu_logfile, flags); + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + cpu_dump_state(cpu, logfile->fd, flags); + } + rcu_read_unlock(); } } @@ -40,19 +47,37 @@ static inline void log_cpu_state_mask(int mask, CPUState *cpu, int flags) static inline void log_target_disas(CPUState *cpu, target_ulong start, target_ulong len) { - target_disas(qemu_logfile, cpu, start, len); + QemuLogFile *logfile; + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + target_disas(logfile->fd, cpu, start, len); + } + rcu_read_unlock(); } static inline void log_disas(void *code, unsigned long size) { - disas(qemu_logfile, code, size); + QemuLogFile *logfile; + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + disas(logfile->fd, code, size); + } + rcu_read_unlock(); } #if defined(CONFIG_USER_ONLY) /* page_dump() output to the log file: */ static inline void log_page_dump(void) { - page_dump(qemu_logfile); + QemuLogFile *logfile; + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + page_dump(logfile->fd); + } + rcu_read_unlock(); } #endif #endif diff --git a/include/qemu/log.h b/include/qemu/log.h index a7c5b01571..e0f4e40628 100644 --- a/include/qemu/log.h +++ b/include/qemu/log.h @@ -3,9 +3,16 @@ /* A small part of this API is split into its own header */ #include "qemu/log-for-trace.h" +#include "qemu/rcu.h" + +typedef struct QemuLogFile { + struct rcu_head rcu; + FILE *fd; +} QemuLogFile; /* Private global variable, don't use */ -extern FILE *qemu_logfile; +extern QemuLogFile *qemu_logfile; + /* * The new API: @@ -25,7 +32,16 @@ static inline bool qemu_log_enabled(void) */ static inline bool qemu_log_separate(void) { - return qemu_logfile != NULL && qemu_logfile != stderr; + QemuLogFile *logfile; + bool res = false; + + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile && logfile->fd != stderr) { + res = true; + } + rcu_read_unlock(); + return res; } #define CPU_LOG_TB_OUT_ASM (1 << 0) @@ -55,8 +71,15 @@ static inline bool qemu_log_separate(void) static inline FILE *qemu_log_lock(void) { - qemu_flockfile(qemu_logfile); - return logfile->fd; + QemuLogFile *logfile; + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + qemu_flockfile(logfile->fd); + return logfile->fd; + } else { + return NULL; + } } static inline void qemu_log_unlock(FILE *fd) @@ -64,6 +87,7 @@ static inline void qemu_log_unlock(FILE *fd) if (fd) { qemu_funlockfile(fd); } + rcu_read_unlock(); } /* Logging functions: */ @@ -73,9 +97,14 @@ static inline void qemu_log_unlock(FILE *fd) static inline void GCC_FMT_ATTR(1, 0) qemu_log_vprintf(const char *fmt, va_list va) { - if (qemu_logfile) { - vfprintf(qemu_logfile, fmt, va); + QemuLogFile *logfile; + + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + vfprintf(logfile->fd, fmt, va); } + rcu_read_unlock(); } /* log only if a bit is set on the current loglevel mask: diff --git a/tcg/tcg.c b/tcg/tcg.c index 0511266d85..4f616ba38b 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -2114,9 +2114,17 @@ static void tcg_dump_ops(TCGContext *s, bool have_prefs) } if (have_prefs || op->life) { - for (; col < 40; ++col) { - putc(' ', qemu_logfile); + + QemuLogFile *logfile; + + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + for (; col < 40; ++col) { + putc(' ', logfile->fd); + } } + rcu_read_unlock(); } if (op->life) { diff --git a/util/log.c b/util/log.c index 953a66b5a8..867264da8d 100644 --- a/util/log.c +++ b/util/log.c @@ -28,7 +28,7 @@ static char *logfilename; static QemuMutex qemu_logfile_mutex; -FILE *qemu_logfile; +QemuLogFile *qemu_logfile; int qemu_loglevel; static int log_append = 0; static GArray *debug_regions; @@ -37,10 +37,14 @@ static GArray *debug_regions; int qemu_log(const char *fmt, ...) { int ret = 0; - if (qemu_logfile) { + QemuLogFile *logfile; + + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { va_list ap; va_start(ap, fmt); - ret = vfprintf(qemu_logfile, fmt, ap); + ret = vfprintf(logfile->fd, fmt, ap); va_end(ap); /* Don't pass back error results. */ @@ -48,6 +52,7 @@ int qemu_log(const char *fmt, ...) ret = 0; } } + rcu_read_unlock(); return ret; } @@ -56,12 +61,24 @@ static void __attribute__((__constructor__)) qemu_logfile_init(void) qemu_mutex_init(&qemu_logfile_mutex); } +static void qemu_logfile_free(QemuLogFile *logfile) +{ + g_assert(logfile); + + if (logfile->fd != stderr) { + fclose(logfile->fd); + } + g_free(logfile); +} + static bool log_uses_own_buffers; /* enable or disable low levels log */ void qemu_set_log(int log_flags) { bool need_to_open_file = false; + QemuLogFile *logfile; + qemu_loglevel = log_flags; #ifdef CONFIG_TRACE_LOG qemu_loglevel |= LOG_TRACE; @@ -79,43 +96,47 @@ void qemu_set_log(int log_flags) } qemu_mutex_lock(&qemu_logfile_mutex); if (qemu_logfile && !need_to_open_file) { - qemu_mutex_unlock(&qemu_logfile_mutex); - qemu_log_close(); + logfile = qemu_logfile; + atomic_rcu_set(&qemu_logfile, NULL); + call_rcu(logfile, qemu_logfile_free, rcu); } else if (!qemu_logfile && need_to_open_file) { + logfile = g_new0(QemuLogFile, 1); if (logfilename) { - qemu_logfile = fopen(logfilename, log_append ? "a" : "w"); - if (!qemu_logfile) { + logfile->fd = fopen(logfilename, log_append ? "a" : "w"); + if (!logfile->fd) { + g_free(logfile); perror(logfilename); _exit(1); } /* In case we are a daemon redirect stderr to logfile */ if (is_daemonized()) { - dup2(fileno(qemu_logfile), STDERR_FILENO); - fclose(qemu_logfile); + dup2(fileno(logfile->fd), STDERR_FILENO); + fclose(logfile->fd); /* This will skip closing logfile in qemu_log_close() */ - qemu_logfile = stderr; + logfile->fd = stderr; } } else { /* Default to stderr if no log file specified */ assert(!is_daemonized()); - qemu_logfile = stderr; + logfile->fd = stderr; } /* must avoid mmap() usage of glibc by setting a buffer "by hand" */ if (log_uses_own_buffers) { static char logfile_buf[4096]; - setvbuf(qemu_logfile, logfile_buf, _IOLBF, sizeof(logfile_buf)); + setvbuf(logfile->fd, logfile_buf, _IOLBF, sizeof(logfile_buf)); } else { #if defined(_WIN32) /* Win32 doesn't support line-buffering, so use unbuffered output. */ - setvbuf(qemu_logfile, NULL, _IONBF, 0); + setvbuf(logfile->fd, NULL, _IONBF, 0); #else - setvbuf(qemu_logfile, NULL, _IOLBF, 0); + setvbuf(logfile->fd, NULL, _IOLBF, 0); #endif log_append = 1; } - qemu_mutex_unlock(&qemu_logfile_mutex); + atomic_rcu_set(&qemu_logfile, logfile); } + qemu_mutex_unlock(&qemu_logfile_mutex); } void qemu_log_needs_buffers(void) @@ -244,18 +265,27 @@ out: /* fflush() the log file */ void qemu_log_flush(void) { - fflush(qemu_logfile); + QemuLogFile *logfile; + + rcu_read_lock(); + logfile = atomic_rcu_read(&qemu_logfile); + if (logfile) { + fflush(logfile->fd); + } + rcu_read_unlock(); } /* Close the log file */ void qemu_log_close(void) { + QemuLogFile *logfile; + qemu_mutex_lock(&qemu_logfile_mutex); - if (qemu_logfile) { - if (qemu_logfile != stderr) { - fclose(qemu_logfile); - } - qemu_logfile = NULL; + logfile = qemu_logfile; + + if (logfile) { + atomic_rcu_set(&qemu_logfile, NULL); + call_rcu(logfile, qemu_logfile_free, rcu); } qemu_mutex_unlock(&qemu_logfile_mutex); } -- cgit 1.4.1