linux-toradex.git/kernel/trace/ftrace.c, branch v3.19.4

ftrace: Fix ftrace enable ordering of sysctl ftrace_enabled

2015-03-26T12:59:41+00:00

commit 524a38682573b2e15ab6317ccfe50280441514be upstream.

Some archs (specifically PowerPC), are sensitive with the ordering of
the enabling of the calls to function tracing and setting of the
function to use to be traced.

That is, update_ftrace_function() sets what function the ftrace_caller
trampoline should call. Some archs require this to be set before
calling ftrace_run_update_code().

Another bug was discovered, that ftrace_startup_sysctl() called
ftrace_run_update_code() directly. If the function the ftrace_caller
trampoline changes, then it will not be updated. Instead a call
to ftrace_startup_enable() should be called because it tests to see
if the callback changed since the code was disabled, and will
tell the arch to update appropriately. Most archs do not need this
notification, but PowerPC does.

The problem could be seen by the following commands:

 # echo 0 > /proc/sys/kernel/ftrace_enabled
 # echo function > /sys/kernel/debug/tracing/current_tracer
 # echo 1 > /proc/sys/kernel/ftrace_enabled
 # cat /sys/kernel/debug/tracing/trace

The trace will show that function tracing was not active.

Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

ftrace: Fix en(dis)able graph caller when en(dis)abling record via sysctl

2015-03-26T12:59:41+00:00

commit 1619dc3f8f555ee1cdd3c75db3885d5715442b12 upstream.

When ftrace is enabled globally through the proc interface, we must check if
ftrace_graph_active is set. If it is set, then we should also pass the
FTRACE_START_FUNC_RET command to ftrace_run_update_code(). Similarly, when
ftrace is disabled globally through the proc interface, we must check if
ftrace_graph_active is set. If it is set, then we should also pass the
FTRACE_STOP_FUNC_RET command to ftrace_run_update_code().

Consider the following situation.

# echo 0 > /proc/sys/kernel/ftrace_enabled

After this ftrace_enabled = 0.

# echo function_graph > /sys/kernel/debug/tracing/current_tracer

Since ftrace_enabled = 0, ftrace_enable_ftrace_graph_caller() is never
called.

# echo 1 > /proc/sys/kernel/ftrace_enabled

Now ftrace_enabled will be set to true, but still
ftrace_enable_ftrace_graph_caller() will not be called, which is not
desired.

Further if we execute the following after this:
# echo nop > /sys/kernel/debug/tracing/current_tracer

Now since ftrace_enabled is set it will call
ftrace_disable_ftrace_graph_caller(), which causes a kernel warning on
the ARM platform.

On the ARM platform, when ftrace_enable_ftrace_graph_caller() is called,
it checks whether the old instruction is a nop or not. If it's not a nop,
then it returns an error. If it is a nop then it replaces instruction at
that address with a branch to ftrace_graph_caller.
ftrace_disable_ftrace_graph_caller() behaves just the opposite. Therefore,
if generic ftrace code ever calls either ftrace_enable_ftrace_graph_caller()
or ftrace_disable_ftrace_graph_caller() consecutively two times in a row,
then it will return an error, which will cause the generic ftrace code to
raise a warning.

Note, x86 does not have an issue with this because the architecture
specific code for ftrace_enable_ftrace_graph_caller() and
ftrace_disable_ftrace_graph_caller() does not check the previous state,
and calling either of these functions twice in a row has no ill effect.

Link: http://lkml.kernel.org/r/e4fbe64cdac0dd0e86a3bf914b0f83c0b419f146.1425666454.git.panand@redhat.com

Signed-off-by: Pratyush Anand
[
removed extra if (ftrace_start_up) and defined ftrace_graph_active as 0
if CONFIG_FUNCTION_GRAPH_TRACER is not set.
]
Signed-off-by: Steven Rostedt
Signed-off-by: Greg Kroah-Hartman

ftrace: Clear REGS_EN and TRAMP_EN flags on disabling record via sysctl

2015-03-26T12:59:40+00:00

commit b24d443b8f17d9776f5fc1f6c780a0a21eb02913 upstream.

When /proc/sys/kernel/ftrace_enabled is set to zero, all function
tracing is disabled. But the records that represent the functions
still hold information about the ftrace_ops that are hooked to them.

ftrace_ops may request "REGS" (have a full set of pt_regs passed to
the callback), or "TRAMP" (the ops has its own trampoline to use).
When the record is updated to represent the state of the ops hooked
to it, it sets "REGS_EN" and/or "TRAMP_EN" to state that the callback
points to the correct trampoline (REGS has its own trampoline).

When ftrace_enabled is set to zero, all ftrace locations are a nop,
so they do not point to any trampoline. But the _EN flags are still
set. This can cause the accounting to go wrong when ftrace_enabled
is cleared and an ops that has a trampoline is registered or unregistered.

For example, the following will cause ftrace to crash:

 # echo function_graph > /sys/kernel/debug/tracing/current_tracer
 # echo 0 > /proc/sys/kernel/ftrace_enabled
 # echo nop > /sys/kernel/debug/tracing/current_tracer
 # echo 1 > /proc/sys/kernel/ftrace_enabled
 # echo function_graph > /sys/kernel/debug/tracing/current_tracer

As function_graph uses a trampoline, when ftrace_enabled is set to zero
the updates to the record are not done. When enabling function_graph
again, the record will still have the TRAMP_EN flag set, and it will
look for an op that has a trampoline other than the function_graph
ops, and fail to find one.

Reported-by: Pratyush Anand 
Signed-off-by: Steven Rostedt 
Signed-off-by: Greg Kroah-Hartman

ftrace: Check both notrace and filter for old hash

2015-01-15T14:37:33+00:00

Using just the filter for checking for trampolines or regs is not enough
when updating the code against the records that represent all functions.
Both the filter hash and the notrace hash need to be checked.

To trigger this bug (using trace-cmd and perf):

 # perf probe -a do_fork
 # trace-cmd start -B foo -e probe
 # trace-cmd record -p function_graph -n do_fork sleep 1

The trace-cmd record at the end clears the filter before it disables
function_graph tracing and then that causes the accounting of the
ftrace function records to become incorrect and causes ftrace to bug.

Link: http://lkml.kernel.org/r/20150114154329.358378039@goodmis.org

Cc: stable@vger.kernel.org
[ still need to switch old_hash_ops to old_ops_hash ]
Reviewed-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt

ftrace: Fix updating of filters for shared global_ops filters

2015-01-15T14:37:07+00:00

As the set_ftrace_filter affects both the function tracer as well as the
function graph tracer, the ops that represent each have a shared
ftrace_ops_hash structure. This allows both to be updated when the filter
files are updated.

But if function graph is enabled and the global_ops (function tracing) ops
is not, then it is possible that the filter could be changed without the
update happening for the function graph ops. This will cause the changes
to not take place and may even cause a ftrace_bug to occur as it could mess
with the trampoline accounting.

The solution is to check if the ops uses the shared global_ops filter and
if the ops itself is not enabled, to check if there's another ops that is
enabled and also shares the global_ops filter. In that case, the
modification still needs to be executed.

Link: http://lkml.kernel.org/r/20150114154329.055980438@goodmis.org

Cc: stable@vger.kernel.org # 3.17+
Reviewed-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt

ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict

2014-11-21T19:42:10+00:00

Introduce FTRACE_OPS_FL_IPMODIFY to avoid conflict among
ftrace users who may modify regs->ip to change the execution
path. If two or more users modify the regs->ip on the same
function entry, one of them will be broken. So they must add
IPMODIFY flag and make sure that ftrace_set_filter_ip() succeeds.

Note that ftrace doesn't allow ftrace_ops which has IPMODIFY
flag to have notrace hash, and the ftrace_ops must have a
filter hash (so that the ftrace_ops can hook only specific
entries), because it strongly depends on the address and
must be allowed for only few selected functions.

Link: http://lkml.kernel.org/r/20141121102516.11844.27829.stgit@localhost.localdomain

Cc: Jiri Kosina 
Cc: Seth Jennings 
Cc: Petr Mladek 
Cc: Vojtech Pavlik 
Cc: Miroslav Benes 
Cc: Ingo Molnar 
Cc: Ananth N Mavinakayanahalli 
Cc: Josh Poimboeuf 
Cc: Namhyung Kim 
Signed-off-by: Masami Hiramatsu 
[ fixed up some of the comments ]
Signed-off-by: Steven Rostedt

tracing/trivial: Fix typos and make an int into a bool

2014-11-20T15:05:36+00:00

Fix up a few typos in comments and convert an int into a bool in
update_traceon_count().

Link: http://lkml.kernel.org/r/546DD445.5080108@hitachi.com

Suggested-by: Masami Hiramatsu 
Signed-off-by: Steven Rostedt

ftrace/x86/extable: Add is_ftrace_trampoline() function

2014-11-19T20:25:26+00:00

Stack traces that happen from function tracing check if the address
on the stack is a __kernel_text_address(). That is, is the address
kernel code. This calls core_kernel_text() which returns true
if the address is part of the builtin kernel code. It also calls
is_module_text_address() which returns true if the address belongs
to module code.

But what is missing is ftrace dynamically allocated trampolines.
These trampolines are allocated for individual ftrace_ops that
call the ftrace_ops callback functions directly. But if they do a
stack trace, the code checking the stack wont detect them as they
are neither core kernel code nor module address space.

Adding another field to ftrace_ops that also stores the size of
the trampoline assigned to it we can create a new function called
is_ftrace_trampoline() that returns true if the address is a
dynamically allocate ftrace trampoline. Note, it ignores trampolines
that are not dynamically allocated as they will return true with
the core_kernel_text() function.

Link: http://lkml.kernel.org/r/20141119034829.497125839@goodmis.org

Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Acked-by: Thomas Gleixner 
Signed-off-by: Steven Rostedt

tracing: Replace seq_printf by simpler equivalents

2014-11-14T02:32:19+00:00

Using seq_printf to print a simple string or a single character is a
lot more expensive than it needs to be, since seq_puts and seq_putc
exist.

These patches do

  seq_printf(m, s) -> seq_puts(m, s)
  seq_printf(m, "%s", s) -> seq_puts(m, s)
  seq_printf(m, "%c", c) -> seq_putc(m, c)

Subsequent patches will simplify further.

Link: http://lkml.kernel.org/r/1415479332-25944-2-git-send-email-linux@rasmusvillemoes.dk

Signed-off-by: Rasmus Villemoes 
Signed-off-by: Steven Rostedt

ftrace: Have the control_ops get a trampoline

2014-11-14T00:40:56+00:00

With the new logic, if only a single user of ftrace function hooks is
used, it will get its own trampoline assigned to it.

The problem is that the control_ops is an indirect ops that perf ops
uses. What that means is that when perf registers its ops with
register_ftrace_function(), it has the CONTROL flag set and gets added
to the control list instead of the global ftrace list. The control_ops
gets added to that instead and the mcount trampoline calls the control_ops
function. The control_ops function will iterate the control list and
call the ops functions that are attached to it.

But currently the trampoline is added to the perf ops and not the
control ops, and when ftrace tries to find a trampoline hook for it,
it fails to find one and gives the following splat:

 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 10133 at kernel/trace/ftrace.c:2033 ftrace_get_addr_new+0x6f/0xc0()
 Modules linked in: [...]
 CPU: 0 PID: 10133 Comm: perf Tainted: P               3.18.0-rc1-test+ #388
 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
  00000000000007f1 ffff8800c2643bc8 ffffffff814fca6e ffff88011ea0ed01
  0000000000000000 ffff8800c2643c08 ffffffff81041ffd 0000000000000000
  ffffffff810c388c ffffffff81a5a350 ffff880119b00000 ffffffff810001c8
 Call Trace:
  [] dump_stack+0x46/0x58
  [] warn_slowpath_common+0x81/0x9b
  [] ? ftrace_get_addr_new+0x6f/0xc0
  [] ? 0xffffffff810001c8
  [] warn_slowpath_null+0x1a/0x1c
  [] ftrace_get_addr_new+0x6f/0xc0
  [] ftrace_replace_code+0xd6/0x334
  [] ftrace_modify_all_code+0x41/0xc5
  [] arch_ftrace_update_code+0x10/0x19
  [] ftrace_run_update_code+0x21/0x42
  [] ftrace_startup_enable+0x32/0x34
  [] ftrace_startup+0x14e/0x15a
  [] register_ftrace_function+0x27/0x40
  [] perf_ftrace_event_register+0x3e/0xee
  [] perf_trace_init+0x29d/0x2a9
  [] perf_tp_event_init+0x27/0x3a
  [] perf_init_event+0x9e/0xed
  [] perf_event_alloc+0x299/0x330
  [] SYSC_perf_event_open+0x3ee/0x816
  [] ? mntput+0x2d/0x2f
  [] ? __fput+0xa7/0x1b2
  [] ? do_gettimeofday+0x22/0x3a
  [] SyS_perf_event_open+0x9/0xb
  [] system_call_fastpath+0x12/0x17
 ---[ end trace 81a53565150e4982 ]---
 Bad trampoline accounting at: ffffffff810001c8 (run_init_process+0x0/0x2d) (10000001)

Update the control_ops trampoline instead of the perf ops one.

Reported-by: lkp@01.org
Signed-off-by: Steven Rostedt