x86: mmiotrace full patch, preview 1

kmmio.c handles the list of mmio probes with callbacks, list of traced
pages, and attaching into the page fault handler and die notifier. It
arms, traps and disarms the given pages, this is the core of mmiotrace.

mmio-mod.c is a user interface, hooking into ioremap functions and
registering the mmio probes. It also decodes the required information
from trapped mmio accesses via the pre and post callbacks in each probe.
Currently, hooking into ioremap functions works by redefining the symbols
of the target (binary) kernel module, so that it calls the traced
versions of the functions.

The most notable changes done since the last discussion are:
- kmmio.c is a built-in, not part of the module
- direct call from fault.c to kmmio.c, removing all dynamic hooks
- prepare for unregistering probes at any time
- make kmmio re-initializable and accessible to more than one user
- rewrite kmmio locking to remove all spinlocks from page fault path

Can I abuse call_rcu() like I do in kmmio.c:unregister_kmmio_probe()
or is there a better way?

The function called via call_rcu() itself calls call_rcu() again,
will this work or break? There I need a second grace period for RCU
after the first grace period for page faults.

Mmiotrace itself (mmio-mod.c) is still a module, I am going to attack
that next. At some point I will start looking into how to make mmiotrace
a tracer component of ftrace (thanks for the hint, Ingo). Ftrace should
make the user space part of mmiotracing as simple as
'cat /debug/trace/mmio > dump.txt'.

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

1 files changed, 6 insertions, 7 deletions

diff --git a/arch/x86/kernel/mmiotrace/testmmiotrace.c b/arch/x86/kernel/mmiotrace/testmmiotrace.c
index 40e66b0e6480..5ecff578672b 100644
--- a/arch/x86/kernel/mmiotrace/testmmiotrace.c
+++ b/arch/x86/kernel/mmiotrace/testmmiotrace.c
@@ -41,8 +41,7 @@ static void do_test(void)
 {
         void __iomem *p = ioremap_nocache_trace(mmio_address, 0x4000);
         if (!p) {
-                printk(KERN_ERR MODULE_NAME ": could not ioremap IO memory, "
-                                                        "aborting.\n");
+                pr_err(MODULE_NAME ": could not ioremap, aborting.\n");
                 return;
         }
         do_write_test(p);
@@ -53,14 +52,14 @@ static void do_test(void)
 static int __init init(void)
 {
         if (mmio_address == 0) {
-                printk(KERN_ERR MODULE_NAME ": you have to use the module "
-                                                "argument mmio_address.\n");
-                printk(KERN_ERR MODULE_NAME ": DO NOT LOAD THIS MODULE UNLESS"
+                pr_err(MODULE_NAME ": you have to use the module argument "
+                                                        "mmio_address.\n");
+                pr_err(MODULE_NAME ": DO NOT LOAD THIS MODULE UNLESS"
                                 " YOU REALLY KNOW WHAT YOU ARE DOING!\n");
                 return -ENXIO;
         }
 
-        printk(KERN_WARNING MODULE_NAME ": WARNING: mapping 16 kB @ 0x%08lx "
+        pr_warning(MODULE_NAME ": WARNING: mapping 16 kB @ 0x%08lx "
                                         "in PCI address space, and writing "
                                         "rubbish in there.\n", mmio_address);
         do_test();
@@ -69,7 +68,7 @@ static int __init init(void)
 
 static void __exit cleanup(void)
 {
-        printk(KERN_DEBUG MODULE_NAME ": unloaded.\n");
+        pr_debug(MODULE_NAME ": unloaded.\n");
 }
 
 module_init(init);