ftrace: add mmiotrace plugin

On Sat, 22 Mar 2008 13:07:47 +0100
Ingo Molnar <mingo@elte.hu> wrote:

> > > i'd suggest the following: pull x86.git and sched-devel.git into a
> > > single tree [the two will combine without rejects]. Then try to add a
> > > kernel/tracing/trace_mmiotrace.c ftrace plugin. The trace_sysprof.c
> > > plugin might be a good example.
> >
> > I did this and now I have mmiotrace enabled/disabled via the tracing
> > framework (what do we call this, since ftrace is one of the tracers?).
>
> cool! could you send the patches for that? (even if they are not fully
> functional yet)

Patch attached in the end. Nice to see how much code disappeared. I tried
to mark all the features I had to break with XXX-comments.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 32 insertions, 179 deletions

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index aa0d6462b1fc..7e4b8494078e 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -173,7 +173,8 @@ config MMIOTRACE_HOOKS
 
 config MMIOTRACE
         bool "Memory mapped IO tracing"
-        depends on DEBUG_KERNEL && RELAY && DEBUG_FS
+        depends on DEBUG_KERNEL && RELAY
+        select TRACING
         select MMIOTRACE_HOOKS
         default y
         help
diff --git a/arch/x86/kernel/mmiotrace/mmio-mod.c b/arch/x86/kernel/mmiotrace/mmio-mod.c
index 738644061e4e..c7a67d7e482b 100644
--- a/arch/x86/kernel/mmiotrace/mmio-mod.c
+++ b/arch/x86/kernel/mmiotrace/mmio-mod.c
@@ -22,9 +22,8 @@
 #define DEBUG 1
 
 #include <linux/module.h>
-#include <linux/relay.h>
 #include <linux/debugfs.h>
-#include <linux/proc_fs.h>
+#include <linux/uaccess.h>
 #include <asm/io.h>
 #include <linux/version.h>
 #include <linux/kallsyms.h>
@@ -63,18 +62,18 @@ static const size_t subbuf_size = 256*1024;
 static DEFINE_PER_CPU(struct trap_reason, pf_reason);
 static DEFINE_PER_CPU(struct mm_io_header_rw, cpu_trace);
 
+#if 0 /* XXX: no way gather this info anymore */
 /* Access to this is not per-cpu. */
 static DEFINE_PER_CPU(atomic_t, dropped);
+#endif
 
 static struct dentry *dir;
-static struct dentry *enabled_file;
 static struct dentry *marker_file;
 
 static DEFINE_MUTEX(mmiotrace_mutex);
 static DEFINE_SPINLOCK(trace_lock);
 static atomic_t mmiotrace_enabled;
 static LIST_HEAD(trace_list);           /* struct remap_trace */
-static struct rchan *chan;
 
 /*
  * Locking in this file:
@@ -93,36 +92,24 @@ static unsigned long	filter_offset;
 static int              nommiotrace;
 static int              ISA_trace;
 static int              trace_pc;
-static int              enable_now;
 
 module_param(n_subbufs, uint, 0);
 module_param(filter_offset, ulong, 0);
 module_param(nommiotrace, bool, 0);
 module_param(ISA_trace, bool, 0);
 module_param(trace_pc, bool, 0);
-module_param(enable_now, bool, 0);
 
 MODULE_PARM_DESC(n_subbufs, "Number of 256kB buffers, default 128.");
 MODULE_PARM_DESC(filter_offset, "Start address of traced mappings.");
 MODULE_PARM_DESC(nommiotrace, "Disable actual MMIO tracing.");
 MODULE_PARM_DESC(ISA_trace, "Do not exclude the low ISA range.");
 MODULE_PARM_DESC(trace_pc, "Record address of faulting instructions.");
-MODULE_PARM_DESC(enable_now, "Start mmiotracing immediately on module load.");
 
 static bool is_enabled(void)
 {
         return atomic_read(&mmiotrace_enabled);
 }
 
-static void record_timestamp(struct mm_io_header *header)
-{
-        struct timespec now;
-
-        getnstimeofday(&now);
-        header->sec = now.tv_sec;
-        header->nsec = now.tv_nsec;
-}
-
 /*
  * Write callback for the debugfs entry:
  * Read a marker and write it to the mmio trace log
@@ -141,7 +128,6 @@ static ssize_t write_marker(struct file *file, const char __user *buffer,
         headp = (struct mm_io_header *)event;
         headp->type = MMIO_MAGIC | (MMIO_MARKER << MMIO_OPCODE_SHIFT);
         headp->data_len = len;
-        record_timestamp(headp);
 
         if (copy_from_user(event + sizeof(*headp), buffer, len)) {
                 kfree(event);
@@ -149,9 +135,11 @@ static ssize_t write_marker(struct file *file, const char __user *buffer,
         }
 
         spin_lock_irq(&trace_lock);
+#if 0 /* XXX: convert this to use tracing */
         if (is_enabled())
                 relay_write(chan, event, sizeof(*headp) + len);
         else
+#endif
                 len = -EINVAL;
         spin_unlock_irq(&trace_lock);
         kfree(event);
@@ -242,7 +230,11 @@ static void pre(struct kmmio_probe *p, struct pt_regs *regs,
         else
                 my_trace->rw.pc = 0;
 
-        record_timestamp(&my_trace->header);
+        /*
+         * XXX: the timestamp recorded will be *after* the tracing has been
+         * done, not at the time we hit the instruction. SMP implications
+         * on event ordering?
+         */
 
         switch (type) {
         case REG_READ:
@@ -295,77 +287,19 @@ static void post(struct kmmio_probe *p, unsigned long condition,
         default:
                 break;
         }
-        relay_write(chan, my_trace, sizeof(*my_trace));
+
+        /*
+         * XXX: Several required values are ignored:
+         * - mapping id
+         * - program counter
+         * Also the address should be physical, not virtual.
+         */
+        mmio_trace_record(my_trace->header.type, my_trace->rw.address,
+                                                        my_trace->rw.value);
         put_cpu_var(cpu_trace);
         put_cpu_var(pf_reason);
 }
 
-/*
- * subbuf_start() relay callback.
- *
- * Defined so that we know when events are dropped due to the buffer-full
- * condition.
- */
-static int subbuf_start_handler(struct rchan_buf *buf, void *subbuf,
-                                        void *prev_subbuf, size_t prev_padding)
-{
-        unsigned int cpu = buf->cpu;
-        atomic_t *drop = &per_cpu(dropped, cpu);
-        int count;
-        if (relay_buf_full(buf)) {
-                if (atomic_inc_return(drop) == 1)
-                        pr_err(NAME "cpu %d buffer full!\n", cpu);
-                return 0;
-        }
-        count = atomic_read(drop);
-        if (count) {
-                pr_err(NAME "cpu %d buffer no longer full, missed %d events.\n",
-                                                                cpu, count);
-                atomic_sub(count, drop);
-        }
-
-        return 1;
-}
-
-static struct file_operations mmio_fops = {
-        .owner = THIS_MODULE,
-};
-
-/* file_create() callback.  Creates relay file in debugfs. */
-static struct dentry *create_buf_file_handler(const char *filename,
-                                                struct dentry *parent,
-                                                int mode,
-                                                struct rchan_buf *buf,
-                                                int *is_global)
-{
-        struct dentry *buf_file;
-
-        mmio_fops.read = relay_file_operations.read;
-        mmio_fops.open = relay_file_operations.open;
-        mmio_fops.poll = relay_file_operations.poll;
-        mmio_fops.mmap = relay_file_operations.mmap;
-        mmio_fops.release = relay_file_operations.release;
-        mmio_fops.splice_read = relay_file_operations.splice_read;
-
-        buf_file = debugfs_create_file(filename, mode, parent, buf,
-                                                                &mmio_fops);
-
-        return buf_file;
-}
-
-/* file_remove() default callback.  Removes relay file in debugfs. */
-static int remove_buf_file_handler(struct dentry *dentry)
-{
-        debugfs_remove(dentry);
-        return 0;
-}
-
-static struct rchan_callbacks relay_callbacks = {
-        .subbuf_start = subbuf_start_handler,
-        .create_buf_file = create_buf_file_handler,
-        .remove_buf_file = remove_buf_file_handler,
-};
-
 static void ioremap_trace_core(unsigned long offset, unsigned long size,
                                                         void __iomem *addr)
 {
@@ -387,7 +321,6 @@ static void ioremap_trace_core(unsigned long offset, unsigned long size,
                         .pc   = 0
                 }
         };
-        record_timestamp(&event.header);
 
         if (!trace) {
                 pr_err(NAME "kmalloc failed in ioremap\n");
@@ -410,7 +343,10 @@ static void ioremap_trace_core(unsigned long offset, unsigned long size,
         if (!is_enabled())
                 goto not_enabled;
 
-        relay_write(chan, &event, sizeof(event));
+        /*
+         * XXX: Insufficient data recorded!
+         */
+        mmio_trace_record(event.header.type, event.map.addr, event.map.len);
         list_add_tail(&trace->list, &trace_list);
         if (!nommiotrace)
                 register_kmmio_probe(&trace->probe);
@@ -454,7 +390,6 @@ static void iounmap_trace_core(volatile void __iomem *addr)
         struct remap_trace *found_trace = NULL;
 
         pr_debug(NAME "Unmapping %p.\n", addr);
-        record_timestamp(&event.header);
 
         spin_lock_irq(&trace_lock);
         if (!is_enabled())
@@ -469,7 +404,8 @@ static void iounmap_trace_core(volatile void __iomem *addr)
                         break;
                 }
         }
-        relay_write(chan, &event, sizeof(event));
+        mmio_trace_record(event.header.type, event.map.addr,
+                                        found_trace ? found_trace->id : -1);
 
 not_enabled:
         spin_unlock_irq(&trace_lock);
@@ -512,77 +448,23 @@ static void clear_trace_list(void)
         }
 }
 
-static ssize_t read_enabled_file_bool(struct file *file,
-                char __user *user_buf, size_t count, loff_t *ppos)
-{
-        char buf[3];
-
-        if (is_enabled())
-                buf[0] = '1';
-        else
-                buf[0] = '0';
-        buf[1] = '\n';
-        buf[2] = '\0';
-        return simple_read_from_buffer(user_buf, count, ppos, buf, 2);
-}
-
-static void enable_mmiotrace(void);
-static void disable_mmiotrace(void);
-
-static ssize_t write_enabled_file_bool(struct file *file,
-                const char __user *user_buf, size_t count, loff_t *ppos)
-{
-        char buf[32];
-        int buf_size = min(count, (sizeof(buf)-1));
-
-        if (copy_from_user(buf, user_buf, buf_size))
-                return -EFAULT;
-
-        switch (buf[0]) {
-        case 'y':
-        case 'Y':
-        case '1':
-                enable_mmiotrace();
-                break;
-        case 'n':
-        case 'N':
-        case '0':
-                disable_mmiotrace();
-                break;
-        }
-
-        return count;
-}
-
-/* this ripped from kernel/kprobes.c */
-static struct file_operations fops_enabled = {
-        .owner =        THIS_MODULE,
-        .read =         read_enabled_file_bool,
-        .write =        write_enabled_file_bool
-};
-
 static struct file_operations fops_marker = {
         .owner =        THIS_MODULE,
         .write =        write_marker
 };
 
-static void enable_mmiotrace(void)
+void enable_mmiotrace(void)
 {
         mutex_lock(&mmiotrace_mutex);
         if (is_enabled())
                 goto out;
 
-        chan = relay_open("cpu", dir, subbuf_size, n_subbufs,
-                                                &relay_callbacks, NULL);
-        if (!chan) {
-                pr_err(NAME "relay app channel creation failed.\n");
-                goto out;
-        }
-
         reference_kmmio();
 
+#if 0 /* XXX: tracing does not support text entries */
         marker_file = debugfs_create_file("marker", 0660, dir, NULL,
                                                                 &fops_marker);
+#endif
         if (!marker_file)
                 pr_err(NAME "marker file creation failed.\n");
 
@@ -598,7 +480,7 @@ out:
         mutex_unlock(&mmiotrace_mutex);
 }
 
-static void disable_mmiotrace(void)
+void disable_mmiotrace(void)
 {
         mutex_lock(&mmiotrace_mutex);
         if (!is_enabled())
@@ -615,17 +497,13 @@ static void disable_mmiotrace(void)
                 debugfs_remove(marker_file);
                 marker_file = NULL;
         }
-        if (chan) {
-                relay_close(chan);
-                chan = NULL;
-        }
 
         pr_info(NAME "disabled.\n");
 out:
         mutex_unlock(&mmiotrace_mutex);
 }
 
-static int __init init(void)
+int __init init_mmiotrace(void)
 {
         pr_debug(NAME "load...\n");
         if (n_subbufs < 2)
@@ -636,31 +514,5 @@ static int __init init(void)
                 pr_err(NAME "Couldn't create relay app directory.\n");
                 return -ENOMEM;
         }
-
-        enabled_file = debugfs_create_file("enabled", 0600, dir, NULL,
-                                                                &fops_enabled);
-        if (!enabled_file) {
-                pr_err(NAME "Couldn't create enabled file.\n");
-                debugfs_remove(dir);
-                return -ENOMEM;
-        }
-
-        if (enable_now)
-                enable_mmiotrace();
-
         return 0;
 }
-
-static void __exit cleanup(void)
-{
-        pr_debug(NAME "unload...\n");
-        if (enabled_file)
-                debugfs_remove(enabled_file);
-        disable_mmiotrace();
-        if (dir)
-                debugfs_remove(dir);
-}
-
-module_init(init);
-module_exit(cleanup);
-MODULE_LICENSE("GPL");