Commit Graph

3 Commits

Author SHA1 Message Date
Steven Rostedt (VMware) 59566b0b62 x86/ftrace: Have ftrace trampolines turn read-only at the end of system boot up
Booting one of my machines, it triggered the following crash:

 Kernel/User page tables isolation: enabled
 ftrace: allocating 36577 entries in 143 pages
 Starting tracer 'function'
 BUG: unable to handle page fault for address: ffffffffa000005c
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0003) - permissions violation
 PGD 2014067 P4D 2014067 PUD 2015063 PMD 7b253067 PTE 7b252061
 Oops: 0003 [#1] PREEMPT SMP PTI
 CPU: 0 PID: 0 Comm: swapper Not tainted 5.4.0-test+ #24
 Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS SDBLI944.86P 05/08/2007
 RIP: 0010:text_poke_early+0x4a/0x58
 Code: 34 24 48 89 54 24 08 e8 bf 72 0b 00 48 8b 34 24 48 8b 4c 24 08 84 c0 74 0b 48 89 df f3 a4 48 83 c4 10 5b c3 9c 58 fa 48 89 df <f3> a4 50 9d 48 83 c4 10 5b e9 d6 f9 ff ff
0 41 57 49
 RSP: 0000:ffffffff82003d38 EFLAGS: 00010046
 RAX: 0000000000000046 RBX: ffffffffa000005c RCX: 0000000000000005
 RDX: 0000000000000005 RSI: ffffffff825b9a90 RDI: ffffffffa000005c
 RBP: ffffffffa000005c R08: 0000000000000000 R09: ffffffff8206e6e0
 R10: ffff88807b01f4c0 R11: ffffffff8176c106 R12: ffffffff8206e6e0
 R13: ffffffff824f2440 R14: 0000000000000000 R15: ffffffff8206eac0
 FS:  0000000000000000(0000) GS:ffff88807d400000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: ffffffffa000005c CR3: 0000000002012000 CR4: 00000000000006b0
 Call Trace:
  text_poke_bp+0x27/0x64
  ? mutex_lock+0x36/0x5d
  arch_ftrace_update_trampoline+0x287/0x2d5
  ? ftrace_replace_code+0x14b/0x160
  ? ftrace_update_ftrace_func+0x65/0x6c
  __register_ftrace_function+0x6d/0x81
  ftrace_startup+0x23/0xc1
  register_ftrace_function+0x20/0x37
  func_set_flag+0x59/0x77
  __set_tracer_option.isra.19+0x20/0x3e
  trace_set_options+0xd6/0x13e
  apply_trace_boot_options+0x44/0x6d
  register_tracer+0x19e/0x1ac
  early_trace_init+0x21b/0x2c9
  start_kernel+0x241/0x518
  ? load_ucode_intel_bsp+0x21/0x52
  secondary_startup_64+0xa4/0xb0

I was able to trigger it on other machines, when I added to the kernel
command line of both "ftrace=function" and "trace_options=func_stack_trace".

The cause is the "ftrace=function" would register the function tracer
and create a trampoline, and it will set it as executable and
read-only. Then the "trace_options=func_stack_trace" would then update
the same trampoline to include the stack tracer version of the function
tracer. But since the trampoline already exists, it updates it with
text_poke_bp(). The problem is that text_poke_bp() called while
system_state == SYSTEM_BOOTING, it will simply do a memcpy() and not
the page mapping, as it would think that the text is still read-write.
But in this case it is not, and we take a fault and crash.

Instead, lets keep the ftrace trampolines read-write during boot up,
and then when the kernel executable text is set to read-only, the
ftrace trampolines get set to read-only as well.

Link: https://lkml.kernel.org/r/20200430202147.4dc6e2de@oasis.local.home

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: stable@vger.kernel.org
Fixes: 768ae4406a ("x86/ftrace: Use text_poke()")
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2020-05-12 18:24:34 -04:00
Joel Fernandes (Google) 0a5b99f578 treewide: Rename rcu_dereference_raw_notrace() to _check()
The rcu_dereference_raw_notrace() API name is confusing.  It is equivalent
to rcu_dereference_raw() except that it also does sparse pointer checking.

There are only a few users of rcu_dereference_raw_notrace(). This patches
renames all of them to be rcu_dereference_raw_check() with the "_check()"
indicating sparse checking.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
[ paulmck: Fix checkpatch warnings about parentheses. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-08-01 14:16:21 -07:00
Steven Rostedt (VMware) 3306fc4aff ftrace: Create new ftrace_internal.h header
In order to move function graph infrastructure into its own file (fgraph.h)
it needs to access various functions and variables in ftrace.c that are
currently static. Create a new file called ftrace-internal.h that holds the
function prototypes and the extern declarations of the variables needed by
fgraph.c as well, and make them global in ftrace.c such that they can be
used outside that file.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2018-12-08 20:54:06 -05:00