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Subject[patch 2/6] Linux Kernel Markers, architecture independent code.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
---
include/asm-generic/vmlinux.lds.h | 6
include/linux/marker.h | 99 +++++++++++
include/linux/module.h | 3
kernel/module.c | 330 ++++++++++++++++++++++++++++++++++++++
4 files changed, 437 insertions(+), 1 deletion(-)
Index: linux-2.6-lttng/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux-2.6-lttng.orig/include/asm-generic/vmlinux.lds.h 2007-05-17 02:12:41.000000000 -0400
+++ linux-2.6-lttng/include/asm-generic/vmlinux.lds.h 2007-05-17 02:12:41.000000000 -0400
@@ -143,7 +143,11 @@
\
. = ALIGN(4096);

-#define EXTRA_RWDATA
+#define EXTRA_RWDATA \
+ . = ALIGN(8); \
+ VMLINUX_SYMBOL(__start___markers) = .; \
+ *(__markers) \
+ VMLINUX_SYMBOL(__stop___markers) = .; \

#define SECURITY_INIT \
.security_initcall.init : AT(ADDR(.security_initcall.init) - LOAD_OFFSET) { \
Index: linux-2.6-lttng/include/linux/marker.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6-lttng/include/linux/marker.h 2007-05-17 02:13:29.000000000 -0400
@@ -0,0 +1,99 @@
+#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.
+ */
+
+#ifdef __KERNEL__
+
+#include <linux/condcall.h>
+
+struct __mark_marker;
+
+typedef void marker_probe_func(const struct __mark_marker *mdata,
+ const char *fmt, ...);
+
+struct __mark_marker {
+ const char *name;
+ const char *format;
+ const char *args;
+ int flags;
+ marker_probe_func *call;
+ void *pdata;
+} __attribute__((packed));
+
+#ifdef CONFIG_MARKERS
+
+/* Macro calling the callback. Placed inside the cond_call() parameters. */
+#define trace_mark_call(func, name, format, args...) \
+ ({ \
+ preempt_disable(); \
+ (func)(name, format, ## args); \
+ preempt_enable(); \
+ })
+
+/* Generic marker flavor always available.
+ * Note : the empty asm volatile with read constraint is used here instead of a
+ * "used" attribute to fix a gcc 4.1.x bug. */
+#define _trace_mark(flags, name, format, args...) \
+ do { \
+ static const char __mstrtab_name_##name[] \
+ __attribute__((section("__cond_call_strings"))) \
+ = #name; \
+ static const char __mstrtab_format_##name[] \
+ __attribute__((section("__cond_call_strings"))) \
+ = format; \
+ static const char __mstrtab_args_##name[] \
+ __attribute__((section("__cond_call_strings"))) \
+ = #args; \
+ static struct __mark_marker __mark_##name \
+ __attribute__((section("__markers"))) = \
+ { __mstrtab_name_##name, __mstrtab_format_##name, \
+ __mstrtab_args_##name, (flags), __mark_empty_function, NULL }; \
+ asm volatile ( "" : : "i" (&__mark_##name)); \
+ __mark_check_format(format, ## args); \
+ _cond_call((flags), name, \
+ trace_mark_call(*__mark_##name.call, \
+ &__mark_##name, format, ## args)); \
+ } while (0)
+
+/* Marker with default behavior */
+#define trace_mark(name, format, args...) \
+ _trace_mark(CF_DEFAULT, name, format, ## args)
+
+#else /* !CONFIG_MARKERS */
+#define trace_mark(flags, name, format, args...) \
+ __mark_check_format(format, ## args)
+#endif /* CONFIG_MARKERS */
+
+#define MARK_MAX_FORMAT_LEN 1024
+/* Pass this as a format string for a marker with no argument */
+#define MARK_NOARGS " "
+
+/* To be used for string format validity checking with sparse */
+static inline
+void __mark_check_format(const char *fmt, ...)
+{ }
+
+extern marker_probe_func __mark_empty_function;
+
+extern int _marker_arm_probe(int flags, const char *name, const char *format,
+ marker_probe_func *probe, void *pdata);
+
+#define marker_arm_probe(name, format, probe, pdata) \
+ _marker_arm_probe(CF_DEFAULT, name, format, probe, pdata)
+
+extern int marker_disarm_probe(const char *name);
+extern int marker_list_probe(marker_probe_func *probe);
+const struct __mark_marker *marker_query(const char *name, int instance);
+
+#endif /* __KERNEL__ */
+#endif
Index: linux-2.6-lttng/include/linux/module.h
===================================================================
--- linux-2.6-lttng.orig/include/linux/module.h 2007-05-17 02:12:41.000000000 -0400
+++ linux-2.6-lttng/include/linux/module.h 2007-05-17 02:13:15.000000000 -0400
@@ -17,6 +17,7 @@
#include <linux/kobject.h>
#include <linux/moduleparam.h>
#include <linux/condcall.h>
+#include <linux/marker.h>
#include <asm/local.h>

#include <asm/module.h>
@@ -360,6 +361,8 @@

const struct __cond_call_struct *cond_calls;
unsigned int num_cond_calls;
+ struct __mark_marker *markers;
+ unsigned int num_markers;
};
#ifndef MODULE_ARCH_INIT
#define MODULE_ARCH_INIT {}
Index: linux-2.6-lttng/kernel/module.c
===================================================================
--- linux-2.6-lttng.orig/kernel/module.c 2007-05-17 02:12:41.000000000 -0400
+++ linux-2.6-lttng/kernel/module.c 2007-05-17 02:13:29.000000000 -0400
@@ -33,6 +33,7 @@
#include <linux/moduleparam.h>
#include <linux/errno.h>
#include <linux/condcall.h>
+#include <linux/marker.h>
#include <linux/jhash.h>
#include <linux/list.h>
#include <linux/err.h>
@@ -160,6 +161,8 @@
extern const unsigned long __start___kcrctab_unused_gpl[];
extern const struct __cond_call_struct __start___cond_call[];
extern const struct __cond_call_struct __stop___cond_call[];
+extern const struct __mark_marker __start___markers[];
+extern const struct __mark_marker __stop___markers[];

#ifndef CONFIG_MODVERSIONS
#define symversion(base, idx) NULL
@@ -577,6 +580,313 @@
}
#endif

+#ifdef CONFIG_MARKERS
+
+/* Empty callback provided as a probe to the markers. By providing this to a
+ * disabled marker, we makes sure the execution flow is always valid even
+ * though the function pointer change and the marker enabling are two distinct
+ * operations that modifies the execution flow of preemptible code. */
+void __mark_empty_function(const struct __mark_marker_data *mdata,
+ const char *fmt, ...)
+{
+}
+EXPORT_SYMBOL_GPL(__mark_empty_function);
+
+/* Sets the probe callback corresponding to a range of markers.
+ */
+static int _marker_set_probe_range(int flags, const char *name,
+ const char *format,
+ marker_probe_func *probe,
+ void *pdata,
+ const struct __mark_marker *begin,
+ const struct __mark_marker *end)
+{
+ const struct __mark_marker *iter;
+ int found = 0;
+
+ for (iter = begin; iter < end; iter++) {
+ if (strcmp(name, iter->mdata->name) != 0)
+ continue;
+
+ if (format) {
+ if (strcmp(format, iter->mdata->format) != 0) {
+ printk(KERN_NOTICE
+ "Format mismatch for probe %s "
+ "(%s), marker (%s)\n",
+ name,
+ format,
+ iter->mdata->format);
+ continue;
+ }
+ } else
+ format = iter->mdata->format;
+
+ if (flags & CF_LOCKDEP
+ && !(iter->mdata->flags & CF_LOCKDEP)) {
+ printk(KERN_NOTICE
+ "Incompatible lockdep flags for "
+ "probe %s\n",
+ name);
+ continue;
+ }
+ if (flags & CF_PRINTK
+ && !(iter->mdata->flags & CF_PRINTK)) {
+ printk(KERN_NOTICE
+ "Incompatible printk flags for "
+ "probe %s\n",
+ name);
+ continue;
+ }
+ if (probe == __mark_empty_function) {
+ if (iter->mdata->call != __mark_empty_function)
+ iter->mdata->call = __mark_empty_function;
+ } else {
+ if (iter->mdata->call != __mark_empty_function) {
+ if (iter->mdata->call != probe) {
+ printk(KERN_NOTICE
+ "Marker %s busy, "
+ "probe %p already "
+ "installed\n",
+ name,
+ iter->mdata->call);
+ continue;
+ }
+ } else
+ iter->mdata->call = probe;
+ iter->mdata->pdata = pdata;
+ }
+ found++;
+ }
+ return found;
+}
+
+/* Sets a range of markers to a disabled state : unset the enable bit and
+ * provide the empty callback.
+ * Keep a count of other markers connected to the same module as the one
+ * provided as parameter. */
+static int marker_remove_probe_range(const char *name,
+ struct module *probe_module,
+ int *ref_count,
+ const struct __mark_marker *begin,
+ const struct __mark_marker *end)
+{
+ const struct __mark_marker *iter;
+ int found = 0;
+
+ for (iter = begin; iter < end; iter++) {
+ if (strcmp(name, iter->mdata->name) != 0) {
+ if (probe_module)
+ if (__module_text_address(
+ (unsigned long)iter->mdata->call)
+ == probe_module)
+ (*ref_count)++;
+ continue;
+ }
+ iter->mdata->call = __mark_empty_function;
+ found++;
+ }
+ return found;
+}
+
+/* Provides a listing of the markers present in the kernel along with their
+ * callback and format string. */
+static int marker_list_probe_range(marker_probe_func *probe,
+ const struct __mark_marker *begin,
+ const struct __mark_marker *end)
+{
+ const struct __mark_marker *iter;
+ int found = 0;
+
+ for (iter = begin; iter < end; iter++) {
+ if (probe)
+ if (probe != iter->mdata->call) continue;
+ printk("name %s func 0x%p format \"%s\"\n",
+ iter->mdata->name,
+ iter->mdata->call, iter->mdata->format);
+ found++;
+ }
+ return found;
+}
+
+/* Get the module to which the probe handler's text belongs.
+ * Called with module_mutex taken.
+ * Returns NULL if the probe handler is not in a module. */
+static struct module *__marker_get_probe_module(const char *name)
+{
+ struct module *mod;
+ const struct __mark_marker *iter;
+
+ list_for_each_entry(mod, &modules, list) {
+ if (mod->taints)
+ continue;
+ for (iter = mod->markers;
+ iter < mod->markers+mod->num_markers; iter++) {
+ if (strcmp(name, iter->mdata->name) != 0)
+ continue;
+ if (iter->mdata->call)
+ return __module_text_address(
+ (unsigned long)iter->mdata->call);
+ }
+ }
+ return NULL;
+}
+
+/* Looks up a marker by its name and instance number within the specificed
+ * range and returns the associated data structure. */
+const struct __mark_marker_data *marker_query_range(const char *name,
+ int instance,
+ const struct __mark_marker *begin,
+ const struct __mark_marker *end)
+{
+ const struct __mark_marker *iter;
+ int found = 0;
+
+ for (iter = begin; iter < end; iter++) {
+ if (strcmp(name, iter->mdata->name) != 0)
+ continue;
+
+ if (found++ == instance)
+ return iter->mdata;
+ }
+ return NULL;
+}
+
+/* Calls _marker_set_probe_range for the core markers and modules markers.
+ * Marker arm uses the modlist_lock to synchronise. */
+static int marker_set_probe(int flags, const char *name, const char *format,
+ marker_probe_func *probe,
+ void *pdata)
+{
+ struct module *mod;
+ int found = 0;
+
+ mutex_lock(&module_mutex);
+ /* Core kernel markers */
+ found += _marker_set_probe_range(flags, name, format, probe,
+ pdata,
+ __start___markers, __stop___markers);
+ /* Markers in modules. */
+ list_for_each_entry(mod, &modules, list) {
+ if (!mod->taints)
+ found += _marker_set_probe_range(flags, name, format,
+ probe, pdata,
+ mod->markers, mod->markers+mod->num_markers);
+ }
+ mutex_unlock(&module_mutex);
+ return found;
+}
+
+/* Calls _marker_remove_probe_range for the core markers and modules markers.
+ * Marker enabling/disabling use the modlist_lock to synchronise.
+ * ref_count is the number of markers still connected to the same module
+ * as the one in which sits the probe handler currently removed, excluding the
+ * one currently removed. If the count is 0, we issue a synchronize_sched() to
+ * make sure the module can safely unload. */
+static int marker_remove_probe(const char *name)
+{
+ struct module *mod, *probe_module;
+ int found = 0;
+ int ref_count = 0;
+
+ mutex_lock(&module_mutex);
+ /* In what module is the probe handler ? */
+ probe_module = __marker_get_probe_module(name);
+ /* Core kernel markers */
+ found += marker_remove_probe_range(name, probe_module, &ref_count,
+ __start___markers, __stop___markers);
+ /* Markers in modules. */
+ list_for_each_entry(mod, &modules, list) {
+ if (!mod->taints)
+ found += marker_remove_probe_range(name, probe_module,
+ &ref_count,
+ mod->markers, mod->markers+mod->num_markers);
+ }
+ mutex_unlock(&module_mutex);
+ if (!ref_count)
+ synchronize_sched();
+ return found;
+}
+
+/* Arming a probe (set handler, enable cond_call). */
+int _marker_arm_probe(int flags, const char *name, const char *format,
+ marker_probe_func *probe, void *pdata)
+{
+ int ret;
+
+ ret = marker_set_probe(flags, name, format, probe, pdata);
+ if (ret)
+ ret = cond_call_arm(name);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(_marker_arm_probe);
+
+/* Disarm a probe (disable cond_call, remove handler). */
+int marker_disarm_probe(const char *name)
+{
+ int ret;
+
+ ret = cond_call_disarm(name);
+ if (ret)
+ ret = marker_remove_probe(name);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(marker_disarm_probe);
+
+/* Calls _marker_list_probe_range for the core markers and modules markers.
+ * Marker listing uses the modlist_lock to synchronise.
+ * TODO : should output this listing to a procfs file. */
+int marker_list_probe(marker_probe_func *probe)
+{
+ struct module *mod;
+ int found = 0;
+
+ mutex_lock(&module_mutex);
+ /* Core kernel markers */
+ printk("Listing kernel markers\n");
+ found += marker_list_probe_range(probe,
+ __start___markers, __stop___markers);
+ /* Markers in modules. */
+ printk("Listing module markers\n");
+ list_for_each_entry(mod, &modules, list) {
+ if (!mod->taints) {
+ printk("Listing markers for module %s\n", mod->name);
+ found += marker_list_probe_range(probe,
+ mod->markers, mod->markers+mod->num_markers);
+ }
+ }
+ mutex_unlock(&module_mutex);
+ return found;
+}
+EXPORT_SYMBOL_GPL(marker_list_probe);
+
+/* Looks up a marker by its name and instance number and returns the
+ * associated data structure. */
+const struct __mark_marker_data *marker_query(const char *name, int instance)
+{
+ struct module *mod;
+ const struct __mark_marker_data *mdata;
+
+ mutex_lock(&module_mutex);
+ /* Core kernel markers */
+ mdata = marker_query_range(name, instance,
+ __start___markers, __stop___markers);
+ if (!mdata) {
+ /* Markers in modules. */
+ list_for_each_entry(mod, &modules, list)
+ if (!mod->taints) {
+ mdata = marker_query_range(name, instance,
+ mod->markers,
+ mod->markers+mod->num_markers);
+ if (mdata)
+ break;
+ }
+ }
+ mutex_unlock(&module_mutex);
+ return mdata;
+}
+EXPORT_SYMBOL_GPL(marker_query);
+#endif
+
#ifdef CONFIG_SMP
/* Number of blocks used and allocated. */
static unsigned int pcpu_num_used, pcpu_num_allocated;
@@ -1936,6 +2246,8 @@
unsigned int unusedgplcrcindex;
unsigned int condcallindex;
unsigned int condcallstringsindex;
+ unsigned int markersindex;
+ unsigned int markersdataindex;
struct module *mod;
long err = 0;
void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
@@ -2034,6 +2346,8 @@
#endif
condcallindex = find_sec(hdr, sechdrs, secstrings, "__cond_call");
condcallstringsindex = find_sec(hdr, sechdrs, secstrings, "__cond_call_strings");
+ markersindex = find_sec(hdr, sechdrs, secstrings, "__markers");
+ markersdataindex = find_sec(hdr, sechdrs, secstrings, "__markers_data");

/* Don't keep modinfo section */
sechdrs[infoindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
@@ -2056,6 +2370,17 @@
sechdrs[condcallstringsindex].sh_flags
&= ~(unsigned long)SHF_ALLOC;
#endif
+#ifdef CONFIG_MARKERS
+ if (markersindex)
+ sechdrs[markersindex].sh_flags |= SHF_ALLOC;
+ if (markersdataindex)
+ sechdrs[markersdataindex].sh_flags |= SHF_ALLOC;
+#else
+ if (markersindex)
+ sechdrs[markersindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
+ if (markersdataindex)
+ sechdrs[markersdataindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
+#endif

/* Check module struct version now, before we try to use module. */
if (!check_modstruct_version(sechdrs, versindex, mod)) {
@@ -2201,6 +2526,11 @@
mod->num_cond_calls =
sechdrs[condcallindex].sh_size / sizeof(*mod->cond_calls);
}
+ if (markersindex) {
+ mod->markers = (void *)sechdrs[markersindex].sh_addr;
+ mod->num_markers =
+ sechdrs[markersindex].sh_size / sizeof(*mod->markers);
+ }

mod->unused_syms = (void *)sechdrs[unusedindex].sh_addr;
if (unusedcrcindex)
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
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