Merge branch 'tracing/mmiotrace' into auto-ftrace-next

Documentation/tracers/mmiotrace.txt

@@ -0,0 +1,164 @@
+		In-kernel memory-mapped I/O tracing
+
+
+Home page and links to optional user space tools:
+
+	http://nouveau.freedesktop.org/wiki/MmioTrace
+
+MMIO tracing was originally developed by Intel around 2003 for their Fault
+Injection Test Harness. In Dec 2006 - Jan 2007, using the code from Intel,
+Jeff Muizelaar created a tool for tracing MMIO accesses with the Nouveau
+project in mind. Since then many people have contributed.
+
+Mmiotrace was built for reverse engineering any memory-mapped IO device with
+the Nouveau project as the first real user. Only x86 and x86_64 architectures
+are supported.
+
+Out-of-tree mmiotrace was originally modified for mainline inclusion and
+ftrace framework by Pekka Paalanen <pq@iki.fi>.
+
+
+Preparation
+-----------
+
+Mmiotrace feature is compiled in by the CONFIG_MMIOTRACE option. Tracing is
+disabled by default, so it is safe to have this set to yes. SMP systems are
+supported, but tracing is unreliable and may miss events if more than one CPU
+is on-line, therefore mmiotrace takes all but one CPU off-line during run-time
+activation. You can re-enable CPUs by hand, but you have been warned, there
+is no way to automatically detect if you are losing events due to CPUs racing.
+
+
+Usage Quick Reference
+---------------------
+
+$ mount -t debugfs debugfs /debug
+$ echo mmiotrace > /debug/tracing/current_tracer
+$ cat /debug/tracing/trace_pipe > mydump.txt &
+Start X or whatever.
+$ echo "X is up" > /debug/tracing/marker
+$ echo none > /debug/tracing/current_tracer
+Check for lost events.
+
+
+Usage
+-----
+
+Make sure debugfs is mounted to /debug. If not, (requires root privileges)
+$ mount -t debugfs debugfs /debug
+
+Check that the driver you are about to trace is not loaded.
+
+Activate mmiotrace (requires root privileges):
+$ echo mmiotrace > /debug/tracing/current_tracer
+
+Start storing the trace:
+$ cat /debug/tracing/trace_pipe > mydump.txt &
+The 'cat' process should stay running (sleeping) in the background.
+
+Load the driver you want to trace and use it. Mmiotrace will only catch MMIO
+accesses to areas that are ioremapped while mmiotrace is active.
+
+[Unimplemented feature:]
+During tracing you can place comments (markers) into the trace by
+$ echo "X is up" > /debug/tracing/marker
+This makes it easier to see which part of the (huge) trace corresponds to
+which action. It is recommended to place descriptive markers about what you
+do.
+
+Shut down mmiotrace (requires root privileges):
+$ echo none > /debug/tracing/current_tracer
+The 'cat' process exits. If it does not, kill it by issuing 'fg' command and
+pressing ctrl+c.
+
+Check that mmiotrace did not lose events due to a buffer filling up. Either
+$ grep -i lost mydump.txt
+which tells you exactly how many events were lost, or use
+$ dmesg
+to view your kernel log and look for "mmiotrace has lost events" warning. If
+events were lost, the trace is incomplete. You should enlarge the buffers and
+try again. Buffers are enlarged by first seeing how large the current buffers
+are:
+$ cat /debug/tracing/trace_entries
+gives you a number. Approximately double this number and write it back, for
+instance:
+$ echo 128000 > /debug/tracing/trace_entries
+Then start again from the top.
+
+If you are doing a trace for a driver project, e.g. Nouveau, you should also
+do the following before sending your results:
+$ lspci -vvv > lspci.txt
+$ dmesg > dmesg.txt
+$ tar zcf pciid-nick-mmiotrace.tar.gz mydump.txt lspci.txt dmesg.txt
+and then send the .tar.gz file. The trace compresses considerably. Replace
+"pciid" and "nick" with the PCI ID or model name of your piece of hardware
+under investigation and your nick name.
+
+
+How Mmiotrace Works
+-------------------
+
+Access to hardware IO-memory is gained by mapping addresses from PCI bus by
+calling one of the ioremap_*() functions. Mmiotrace is hooked into the
+__ioremap() function and gets called whenever a mapping is created. Mapping is
+an event that is recorded into the trace log. Note, that ISA range mappings
+are not caught, since the mapping always exists and is returned directly.
+
+MMIO accesses are recorded via page faults. Just before __ioremap() returns,
+the mapped pages are marked as not present. Any access to the pages causes a
+fault. The page fault handler calls mmiotrace to handle the fault. Mmiotrace
+marks the page present, sets TF flag to achieve single stepping and exits the
+fault handler. The instruction that faulted is executed and debug trap is
+entered. Here mmiotrace again marks the page as not present. The instruction
+is decoded to get the type of operation (read/write), data width and the value
+read or written. These are stored to the trace log.
+
+Setting the page present in the page fault handler has a race condition on SMP
+machines. During the single stepping other CPUs may run freely on that page
+and events can be missed without a notice. Re-enabling other CPUs during
+tracing is discouraged.
+
+
+Trace Log Format
+----------------
+
+The raw log is text and easily filtered with e.g. grep and awk. One record is
+one line in the log. A record starts with a keyword, followed by keyword
+dependant arguments. Arguments are separated by a space, or continue until the
+end of line. The format for version 20070824 is as follows:
+
+Explanation	Keyword	Space separated arguments
+---------------------------------------------------------------------------
+
+read event	R	width, timestamp, map id, physical, value, PC, PID
+write event	W	width, timestamp, map id, physical, value, PC, PID
+ioremap event	MAP	timestamp, map id, physical, virtual, length, PC, PID
+iounmap event	UNMAP	timestamp, map id, PC, PID
+marker		MARK	timestamp, text
+version		VERSION	the string "20070824"
+info for reader	LSPCI	one line from lspci -v
+PCI address map	PCIDEV	space separated /proc/bus/pci/devices data
+unk. opcode	UNKNOWN	timestamp, map id, physical, data, PC, PID
+
+Timestamp is in seconds with decimals. Physical is a PCI bus address, virtual
+is a kernel virtual address. Width is the data width in bytes and value is the
+data value. Map id is an arbitrary id number identifying the mapping that was
+used in an operation. PC is the program counter and PID is process id. PC is
+zero if it is not recorded. PID is always zero as tracing MMIO accesses
+originating in user space memory is not yet supported.
+
+For instance, the following awk filter will pass all 32-bit writes that target
+physical addresses in the range [0xfb73ce40, 0xfb800000[
+
+$ awk '/W 4 / { adr=strtonum($5); if (adr >= 0xfb73ce40 &&
+adr < 0xfb800000) print; }'
+
+
+Tools for Developers
+--------------------
+
+The user space tools include utilities for:
+- replacing numeric addresses and values with hardware register names
+- replaying MMIO logs, i.e., re-executing the recorded writes
+
+

arch/x86/Kconfig.debug

@@ -172,13 +172,33 @@ config IOMMU_LEAK
 	  Add a simple leak tracer to the IOMMU code. This is useful when you
 	  are debugging a buggy device driver that leaks IOMMU mappings.
 
-config PAGE_FAULT_HANDLERS
-	bool "Custom page fault handlers"
-	depends on DEBUG_KERNEL
+config MMIOTRACE_HOOKS
+	bool
+
+config MMIOTRACE
+	bool "Memory mapped IO tracing"
+	depends on DEBUG_KERNEL && PCI
+	select TRACING
+	select MMIOTRACE_HOOKS
+	default y
+	help
+	  Mmiotrace traces Memory Mapped I/O access and is meant for
+	  debugging and reverse engineering. It is called from the ioremap
+	  implementation and works via page faults. Tracing is disabled by
+	  default and can be enabled at run-time.
+
+	  See Documentation/tracers/mmiotrace.txt.
+	  If you are not helping to develop drivers, say N.
+
+config MMIOTRACE_TEST
+	tristate "Test module for mmiotrace"
+	depends on MMIOTRACE && m
 	help
-	  Allow the use of custom page fault handlers. A kernel module may
-	  register a function that is called on every page fault. Custom
-	  handlers are used by some debugging and reverse engineering tools.
+	  This is a dumb module for testing mmiotrace. It is very dangerous
+	  as it will write garbage to IO memory starting at a given address.
+	  However, it should be safe to use on e.g. unused portion of VRAM.
+
+	  Say N, unless you absolutely know what you are doing.
 
 #
 # IO delay types:

arch/x86/mm/Makefile

@@ -8,6 +8,11 @@ obj-$(CONFIG_X86_PTDUMP)	+= dump_pagetables.o
 
 obj-$(CONFIG_HIGHMEM)		+= highmem_32.o
 
+obj-$(CONFIG_MMIOTRACE_HOOKS)	+= kmmio.o
+obj-$(CONFIG_MMIOTRACE)		+= mmiotrace.o
+mmiotrace-y			:= pf_in.o mmio-mod.o
+obj-$(CONFIG_MMIOTRACE_TEST)	+= testmmiotrace.o
+
 ifeq ($(CONFIG_X86_32),y)
 obj-$(CONFIG_NUMA)		+= discontig_32.o
 else

arch/x86/mm/fault.c

@@ -10,6 +10,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/ptrace.h>
+#include <linux/mmiotrace.h>
 #include <linux/mman.h>
 #include <linux/mm.h>
 #include <linux/smp.h>
@@ -49,58 +50,14 @@
 #define PF_RSVD		(1<<3)
 #define PF_INSTR	(1<<4)
 
-#ifdef CONFIG_PAGE_FAULT_HANDLERS
-static HLIST_HEAD(pf_handlers); /* protected by RCU */
-static DEFINE_SPINLOCK(pf_handlers_writer);
-
-void register_page_fault_handler(struct pf_handler *new_pfh)
-{
-	unsigned long flags;
-	spin_lock_irqsave(&pf_handlers_writer, flags);
-	hlist_add_head_rcu(&new_pfh->hlist, &pf_handlers);
-	spin_unlock_irqrestore(&pf_handlers_writer, flags);
-}
-EXPORT_SYMBOL_GPL(register_page_fault_handler);
-
-/**
- * unregister_page_fault_handler:
- * The caller must ensure @old_pfh is not in use anymore before freeing it.
- * This function does not guarantee it. The list of handlers is protected by
- * RCU, so you can do this by e.g. calling synchronize_rcu().
- */
-void unregister_page_fault_handler(struct pf_handler *old_pfh)
+static inline int kmmio_fault(struct pt_regs *regs, unsigned long addr)
 {
-	unsigned long flags;
-	spin_lock_irqsave(&pf_handlers_writer, flags);
-	hlist_del_rcu(&old_pfh->hlist);
-	spin_unlock_irqrestore(&pf_handlers_writer, flags);
-}
-EXPORT_SYMBOL_GPL(unregister_page_fault_handler);
+#ifdef CONFIG_MMIOTRACE_HOOKS
+	if (unlikely(is_kmmio_active()))
+		if (kmmio_handler(regs, addr) == 1)
+			return -1;
 #endif
-
-/* returns non-zero if do_page_fault() should return */
-static int handle_custom_pf(struct pt_regs *regs, unsigned long error_code,
-							unsigned long address)
-{
-#ifdef CONFIG_PAGE_FAULT_HANDLERS
-	int ret = 0;
-	struct pf_handler *cur;
-	struct hlist_node *ncur;
-
-	if (hlist_empty(&pf_handlers))
-		return 0;
-
-	rcu_read_lock();
-	hlist_for_each_entry_rcu(cur, ncur, &pf_handlers, hlist) {
-		ret = cur->handler(regs, error_code, address);
-		if (ret)
-			break;
-	}
-	rcu_read_unlock();
-	return ret;
-#else
 	return 0;
-#endif
 }
 
 static inline int notify_page_fault(struct pt_regs *regs)
@@ -660,7 +617,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 
 	if (notify_page_fault(regs))
 		return;
-	if (handle_custom_pf(regs, error_code, address))
+	if (unlikely(kmmio_fault(regs, address)))
 		return;
 
 	/*

arch/x86/mm/ioremap.c

@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
+#include <linux/mmiotrace.h>
 
 #include <asm/cacheflush.h>
 #include <asm/e820.h>
@@ -122,10 +123,13 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
 {
 	unsigned long pfn, offset, vaddr;
 	resource_size_t last_addr;
+	const resource_size_t unaligned_phys_addr = phys_addr;
+	const unsigned long unaligned_size = size;
 	struct vm_struct *area;
 	unsigned long new_prot_val;
 	pgprot_t prot;
 	int retval;
+	void __iomem *ret_addr;
 
 	/* Don't allow wraparound or zero size */
 	last_addr = phys_addr + size - 1;
@@ -233,7 +237,10 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
 		return NULL;
 	}
 
-	return (void __iomem *) (vaddr + offset);
+	ret_addr = (void __iomem *) (vaddr + offset);
+	mmiotrace_ioremap(unaligned_phys_addr, unaligned_size, ret_addr);
+
+	return ret_addr;
 }
 
 /**
@@ -325,6 +332,8 @@ void iounmap(volatile void __iomem *addr)
 	addr = (volatile void __iomem *)
 		(PAGE_MASK & (unsigned long __force)addr);
 
+	mmiotrace_iounmap(addr);
+
 	/* Use the vm area unlocked, assuming the caller
 	   ensures there isn't another iounmap for the same address
 	   in parallel. Reuse of the virtual address is prevented by