Linux Kernel Markers

The marker activation functions sits in kernel/marker.c.  A hash table is used
to keep track of the registered probes and armed markers, so the markers
within a newly loaded module that should be active can be activated at module
load time.

marker_query has been removed. marker_get_first, marker_get_next and
marker_release should be used as iterators on the markers.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Acked-by: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Mike Mason <mmlnx@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 148 insertions, 1 deletions

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 5615440027ec..9f584cc5c5fb 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -12,7 +12,11 @@
 /* .data section */
 #define DATA_DATA                                                       \
         *(.data)                                                        \
-        *(.data.init.refok)
+        *(.data.init.refok)                                             \
+        . = ALIGN(8);                                                   \
+        VMLINUX_SYMBOL(__start___markers) = .;                          \
+        *(__markers)                                                    \
+        VMLINUX_SYMBOL(__stop___markers) = .;
 
 #define RO_DATA(align)                                                  \
         . = ALIGN((align));                                             \
@@ -20,6 +24,7 @@
                 VMLINUX_SYMBOL(__start_rodata) = .;                     \
                 *(.rodata) *(.rodata.*)                                 \
                 *(__vermagic)           /* Kernel version magic */      \
+                *(__markers_strings)    /* Markers: strings */          \
         }                                                               \
                                                                         \
         .rodata1          : AT(ADDR(.rodata1) - LOAD_OFFSET) {          \
diff --git a/include/linux/marker.h b/include/linux/marker.h
new file mode 100644
index 000000000000..8038d89b835d
--- /dev/null
+++ b/include/linux/marker.h
@@ -0,0 +1,130 @@
+#ifndef _LINUX_MARKER_H
+#define _LINUX_MARKER_H
+
+/*
+ * Code markup for dynamic and static tracing.
+ *
+ * See Documentation/marker.txt.
+ *
+ * (C) Copyright 2006 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ *
+ * This file is released under the GPLv2.
+ * See the file COPYING for more details.
+ */
+
+#include <linux/types.h>
+
+struct module;
+struct marker;
+
+/**
+ * marker_probe_func - Type of a marker probe function
+ * @mdata: pointer of type struct marker
+ * @private_data: caller site private data
+ * @fmt: format string
+ * @...: variable argument list
+ *
+ * Type of marker probe functions. They receive the mdata and need to parse the
+ * format string to recover the variable argument list.
+ */
+typedef void marker_probe_func(const struct marker *mdata,
+        void *private_data, const char *fmt, ...);
+
+struct marker {
+        const char *name;       /* Marker name */
+        const char *format;     /* Marker format string, describing the
+                                 * variable argument list.
+                                 */
+        char state;             /* Marker state. */
+        marker_probe_func *call;/* Probe handler function pointer */
+        void *private;          /* Private probe data */
+} __attribute__((aligned(8)));
+
+#ifdef CONFIG_MARKERS
+
+/*
+ * Note : the empty asm volatile with read constraint is used here instead of a
+ * "used" attribute to fix a gcc 4.1.x bug.
+ * Make sure the alignment of the structure in the __markers section will
+ * not add unwanted padding between the beginning of the section and the
+ * structure. Force alignment to the same alignment as the section start.
+ */
+#define __trace_mark(name, call_data, format, args...)                  \
+        do {                                                            \
+                static const char __mstrtab_name_##name[]               \
+                __attribute__((section("__markers_strings")))           \
+                = #name;                                                \
+                static const char __mstrtab_format_##name[]             \
+                __attribute__((section("__markers_strings")))           \
+                = format;                                               \
+                static struct marker __mark_##name                      \
+                __attribute__((section("__markers"), aligned(8))) =     \
+                { __mstrtab_name_##name, __mstrtab_format_##name,       \
+                0, __mark_empty_function, NULL };                       \
+                asm volatile("" : : "i" (&__mark_##name));              \
+                __mark_check_format(format, ## args);                   \
+                if (unlikely(__mark_##name.state)) {                    \
+                        preempt_disable();                              \
+                        (*__mark_##name.call)                           \
+                                (&__mark_##name, call_data,             \
+                                format, ## args);                       \
+                        preempt_enable();                               \
+                }                                                       \
+        } while (0)
+
+extern void marker_update_probe_range(struct marker *begin,
+        struct marker *end, struct module *probe_module, int *refcount);
+#else /* !CONFIG_MARKERS */
+#define __trace_mark(name, call_data, format, args...) \
+                __mark_check_format(format, ## args)
+static inline void marker_update_probe_range(struct marker *begin,
+        struct marker *end, struct module *probe_module, int *refcount)
+{ }
+#endif /* CONFIG_MARKERS */
+
+/**
+ * trace_mark - Marker
+ * @name: marker name, not quoted.
+ * @format: format string
+ * @args...: variable argument list
+ *
+ * Places a marker.
+ */
+#define trace_mark(name, format, args...) \
+        __trace_mark(name, NULL, format, ## args)
+
+#define MARK_MAX_FORMAT_LEN     1024
+
+/**
+ * MARK_NOARGS - Format string for a marker with no argument.
+ */
+#define MARK_NOARGS " "
+
+/* To be used for string format validity checking with gcc */
+static inline void __printf(1, 2) __mark_check_format(const char *fmt, ...)
+{
+}
+
+extern marker_probe_func __mark_empty_function;
+
+/*
+ * Connect a probe to a marker.
+ * private data pointer must be a valid allocated memory address, or NULL.
+ */
+extern int marker_probe_register(const char *name, const char *format,
+                                marker_probe_func *probe, void *private);
+
+/*
+ * Returns the private data given to marker_probe_register.
+ */
+extern void *marker_probe_unregister(const char *name);
+/*
+ * Unregister a marker by providing the registered private data.
+ */
+extern void *marker_probe_unregister_private_data(void *private);
+
+extern int marker_arm(const char *name);
+extern int marker_disarm(const char *name);
+extern void *marker_get_private_data(const char *name);
+
+#endif
diff --git a/include/linux/module.h b/include/linux/module.h
index 642f325e4917..2cbc0b87e329 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -15,6 +15,7 @@
 #include <linux/stringify.h>
 #include <linux/kobject.h>
 #include <linux/moduleparam.h>
+#include <linux/marker.h>
 #include <asm/local.h>
 
 #include <asm/module.h>
@@ -354,6 +355,10 @@ struct module
         /* The command line arguments (may be mangled).  People like
            keeping pointers to this stuff */
         char *args;
+#ifdef CONFIG_MARKERS
+        struct marker *markers;
+        unsigned int num_markers;
+#endif
 };
 #ifndef MODULE_ARCH_INIT
 #define MODULE_ARCH_INIT {}
@@ -457,6 +462,8 @@ int unregister_module_notifier(struct notifier_block * nb);
 
 extern void print_modules(void);
 
+extern void module_update_markers(struct module *probe_module, int *refcount);
+
 #else /* !CONFIG_MODULES... */
 #define EXPORT_SYMBOL(sym)
 #define EXPORT_SYMBOL_GPL(sym)
@@ -556,6 +563,11 @@ static inline void print_modules(void)
 {
 }
 
+static inline void module_update_markers(struct module *probe_module,
+                int *refcount)
+{
+}
+
 #endif /* CONFIG_MODULES */
 
 struct device_driver;