[PATCH v4 05/16] Add LogMessageVerbSigSafe() for logging messages while in signal context

Chase Douglas chase.douglas at canonical.com
Mon May 14 14:14:26 PDT 2012


Signed-off-by: Chase Douglas <chase.douglas at canonical.com>
---
Changes since v3:
* Rebased onto master
  - Log writing now occurs in LogSWrite, which is now signal-safe
* Removed timestamp logging, it's not safe to get the current timestamp
* Updated pnprintf to use 21 character string for number formats

 include/os.h |   54 ++++++++++++++++++++++++++
 os/log.c     |  120 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 170 insertions(+), 4 deletions(-)

diff --git a/include/os.h b/include/os.h
index 276eb52..8e7aedb 100644
--- a/include/os.h
+++ b/include/os.h
@@ -49,6 +49,7 @@ SOFTWARE.
 
 #include "misc.h"
 #include <stdarg.h>
+#include <stdint.h>
 #include <string.h>
 
 #define SCREEN_SAVER_ON   0
@@ -583,6 +584,8 @@ typedef enum {
     X_UNKNOWN = -1              /* unknown -- this must always be last */
 } MessageType;
 
+typedef const uint64_t log_param_t;
+
 extern _X_EXPORT const char *
 LogInit(const char *fname, const char *backup);
 extern _X_EXPORT void
@@ -604,6 +607,9 @@ _X_ATTRIBUTE_PRINTF(3, 4);
 extern _X_EXPORT void
 LogMessage(MessageType type, const char *format, ...)
 _X_ATTRIBUTE_PRINTF(2, 3);
+extern _X_EXPORT void
+_LogMessageVerbSigSafe(MessageType type, int verb, const char *format,
+                       const log_param_t *args, int num_args);
 
 extern _X_EXPORT void
 LogVHdrMessageVerb(MessageType type, int verb,
@@ -654,4 +660,52 @@ LogPrintMarkers(void);
 extern _X_EXPORT void
 xorg_backtrace(void);
 
+#define NARG(...) (NARG_(__VA_ARGS__, RSEQ_N) - (sizeof(#__VA_ARGS__) == 1))
+#define NARG_(...) NARG__(__VA_ARGS__)
+#define NARG__( _1, _2, _3, _4, _5, _6, _7, _8, _9, _10, N, ...) (N)
+#define RSEQ_N 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0
+
+#define ARG_N_9_(_1, _2, _3, _4, _5, _6, _7, _8, _9, N, ...) (log_param_t)(N)
+#define ARG_N_9(...) ARG_N_9_(__VA_ARGS__)
+#define ARG_N_8_(_1, _2, _3, _4, _5, _6, _7, _8, N, ...) (log_param_t)(N)
+#define ARG_N_8(...) ARG_N_8_(__VA_ARGS__)
+#define ARG_N_7_(_1, _2, _3, _4, _5, _6, _7, N, ...) (log_param_t)(N)
+#define ARG_N_7(...) ARG_N_7_(__VA_ARGS__)
+#define ARG_N_6_(_1, _2, _3, _4, _5, _6, N, ...) (log_param_t)(N)
+#define ARG_N_6(...) ARG_N_6_(__VA_ARGS__)
+#define ARG_N_5_(_1, _2, _3, _4, _5, N, ...) (log_param_t)(N)
+#define ARG_N_5(...) ARG_N_5_(__VA_ARGS__)
+#define ARG_N_4_(_1, _2, _3, _4, N, ...) (log_param_t)(N)
+#define ARG_N_4(...) ARG_N_4_(__VA_ARGS__)
+#define ARG_N_3_(_1, _2, _3, N, ...) (log_param_t)(N)
+#define ARG_N_3(...) ARG_N_3_(__VA_ARGS__)
+#define ARG_N_2_(_1, _2, N, ...) (log_param_t)(N)
+#define ARG_N_2(...) ARG_N_2_(__VA_ARGS__)
+#define ARG_N_1_(_1, N, ...) (log_param_t)(N)
+#define ARG_N_1(...) ARG_N_1_(__VA_ARGS__)
+#define ARG_N_0(N, ...) (log_param_t)(sizeof(#N) != 1 ? N : 0)
+
+/* Only 10 arguments are supported. If more are needed, update the NARG__,
+ * RSEQ_N, and ARG_N_* macros. */
+#define LogMessageVerbSigSafe(type, verb, fmt, ...) do { \
+    int _num_args = NARG(__VA_ARGS__); \
+    uint64_t _args[_num_args]; \
+_Pragma("GCC diagnostic push") \
+_Pragma("GCC diagnostic ignored \"-Wbad-function-cast\"") \
+    switch (_num_args) { \
+        case 10: _args[9] = ARG_N_9(__VA_ARGS__, RSEQ_N); \
+        case 9: _args[8] = ARG_N_8(__VA_ARGS__, RSEQ_N); \
+        case 8: _args[7] = ARG_N_7(__VA_ARGS__, RSEQ_N); \
+        case 7: _args[6] = ARG_N_6(__VA_ARGS__, RSEQ_N); \
+        case 6: _args[5] = ARG_N_5(__VA_ARGS__, RSEQ_N); \
+        case 5: _args[4] = ARG_N_4(__VA_ARGS__, RSEQ_N); \
+        case 4: _args[3] = ARG_N_3(__VA_ARGS__, RSEQ_N); \
+        case 3: _args[2] = ARG_N_2(__VA_ARGS__, RSEQ_N); \
+        case 2: _args[1] = ARG_N_1(__VA_ARGS__, RSEQ_N); \
+        case 1: _args[0] = ARG_N_0(__VA_ARGS__, RSEQ_N); \
+    } \
+_Pragma("GCC diagnostic pop") \
+    _LogMessageVerbSigSafe(type, verb, fmt, _args, _num_args); \
+} while(0)
+
 #endif                          /* OS_H */
diff --git a/os/log.c b/os/log.c
index 5394847..8adf6cc 100644
--- a/os/log.c
+++ b/os/log.c
@@ -172,6 +172,14 @@ asm(".desc ___crashreporter_info__, 0x10");
 #define X_NONE_STRING			""
 #endif
 
+static size_t
+strlen_sigsafe(const char *s)
+{
+    size_t len;
+    for (len = 0; s[len]; len++);
+    return len;
+}
+
 /*
  * LogInit is called to start logging to a file.  It is also called (with
  * NULL arguments) when logging to a file is not wanted.  It must always be
@@ -271,16 +279,90 @@ LogSetParameter(LogParameter param, int value)
     }
 }
 
-/* This function does the actual log message writes. */
+static int
+pnprintf(char *string, size_t size, const char *f, log_param_t *args,
+         int num_args)
+{
+    int f_idx = 0;
+    int s_idx = 0;
+    int p_idx = 0;
+    int f_len = strlen_sigsafe(f);
+    char *string_arg;
+    char number[21];
+    int p_len;
+    int i;
+
+    for (; f_idx < f_len && s_idx < size - 1; f_idx++) {
+        if (f[f_idx] != '%' || p_idx >= num_args) {
+            string[s_idx++] = f[f_idx];
+            continue;
+        }
+
+        switch (f[++f_idx]) {
+        case 's':
+            string_arg = (char *)args[p_idx++];
+            p_len = strlen_sigsafe(string_arg);
+
+            for (i = 0; i < p_len && s_idx < size - 1; i++)
+                string[s_idx++] = string_arg[i];
+            break;
+
+        case 'u':
+            FormatUInt64((uint64_t)args[p_idx++], number);
+            p_len = strlen_sigsafe(number);
+
+            for (i = 0; i < p_len && s_idx < size - 1; i++)
+                string[s_idx++] = number[i];
+            break;
+
+        case 'p':
+            string[s_idx++] = '0';
+            if (s_idx < size - 1)
+                string[s_idx++] = 'x';
+            /* Intentional fall-through */
+
+        case 'x':
+            FormatUInt64Hex((uint64_t)args[p_idx++], number);
+            p_len = strlen_sigsafe(number);
+
+            for (i = 0; i < p_len && s_idx < size - 1; i++)
+                string[s_idx++] = number[i];
+            break;
+
+        default:
+            p_idx++;
+            string[s_idx++] = '%';
+            if (s_idx < size - 1)
+                string[s_idx++] = f[f_idx];
+            break;
+        }
+    }
+
+    string[s_idx] = '\0';
+
+    return s_idx;
+}
+
+/* This function does the actual log message writes. It must be signal safe.
+ * When attempting to call non-signal-safe functions, guard them with a check
+ * of the inSignalContext global variable. */
 static void
 LogSWrite(int verb, const char *buf, size_t len, Bool end_line)
 {
     static Bool newline = TRUE;
 
     if (verb < 0 || logVerbosity >= verb)
-        fwrite(buf, len, 1, stderr);
+        write(2, buf, len);
+
     if (verb < 0 || logFileVerbosity >= verb) {
-        if (logFile) {
+        if (inSignalContext && logFileFd >= 0) {
+            write(logFileFd, buf, len);
+#ifdef WIN32
+            if (logFlush && logSync)
+                fsync(logFileFd);
+#endif
+        }
+        else if (!inSignalContext && logFile) {
             if (newline)
                 fprintf(logFile, "[%10.3f] ", GetTimeInMillis() / 1000.0);
             newline = end_line;
@@ -293,7 +375,7 @@ LogSWrite(int verb, const char *buf, size_t len, Bool end_line)
 #endif
             }
         }
-        else if (needBuffer) {
+        else if (!inSignalContext && needBuffer) {
             if (len > bufferUnused) {
                 bufferSize += 1024;
                 bufferUnused += 1024;
@@ -415,6 +497,36 @@ LogMessage(MessageType type, const char *format, ...)
     va_end(ap);
 }
 
+/* Log a message using only signal safe functions. */
+void
+_LogMessageVerbSigSafe(MessageType type, int verb, const char *format,
+                       const log_param_t *args, int num_args)
+{
+    const char *type_str;
+    char buf[1024];
+    int len;
+    Bool newline;
+
+    type_str = LogMessageTypeVerbString(type, verb);
+    if (!type_str)
+        return;
+
+    /* if type_str is not "", prepend it and ' ', to message */
+    if (type_str[0] != '\0') {
+        LogSWrite(verb, type_str, strlen_sigsafe(type_str), FALSE);
+        LogSWrite(verb, " ", 1, FALSE);
+    }
+
+    len = pnprintf(buf, sizeof(buf), format, args, num_args);
+
+    /* Force '\n' at end of truncated line */
+    if (sizeof(buf) - len == 1)
+        buf[len - 1] = '\n';
+
+    newline = (buf[len - 1] == '\n');
+    LogSWrite(verb, buf, len, newline);
+}
+
 void
 LogVHdrMessageVerb(MessageType type, int verb, const char *msg_format,
                    va_list msg_args, const char *hdr_format, va_list hdr_args)
-- 
1.7.9.5



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