patches/kernel/0050-x86-tracing-Introduce-a-static-key-for-exception-tra.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Thomas Gleixner <tglx@linutronix.de>
   3 Date: Mon, 28 Aug 2017 08:47:21 +0200
   4 Subject: [PATCH] x86/tracing: Introduce a static key for exception tracing
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 CVE-2017-5754
  10
  11 Switching the IDT just for avoiding tracepoints creates a completely
  12 impenetrable macro/inline/ifdef mess.
  13
  14 There is no point in avoiding tracepoints for most of the traps/exceptions.
  15 For the more expensive tracepoints, like pagefaults, this can be handled with
  16 an explicit static key.
  17
  18 Preparatory patch to remove the tracing IDT.
  19
  20 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  21 Cc: Andy Lutomirski <luto@kernel.org>
  22 Cc: Borislav Petkov <bp@alien8.de>
  23 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  24 Cc: Peter Zijlstra <peterz@infradead.org>
  25 Cc: Steven Rostedt <rostedt@goodmis.org>
  26 Link: http://lkml.kernel.org/r/20170828064956.593094539@linutronix.de
  27 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  28 (cherry picked from commit 2feb1b316d48004d905278c02a55902cab0be8be)
  29 Signed-off-by: Andy Whitcroft <apw@kathleen.maas>
  30 (cherry picked from commit 15e0ff2a63fdd93f8881e2ebba5c048c5b601e57)
  31 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  32 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  33 (cherry picked from commit d58a56e851c339d8d9d311dc9b4fad6abbf8bf19)
  34 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  35 ---
  36  arch/x86/include/asm/trace/common.h      | 15 +++++++++++++++
  37  arch/x86/include/asm/trace/exceptions.h  |  4 +---
  38  arch/x86/include/asm/trace/irq_vectors.h |  4 +---
  39  arch/x86/kernel/tracepoint.c             |  9 ++++++++-
  40  4 files changed, 25 insertions(+), 7 deletions(-)
  41  create mode 100644 arch/x86/include/asm/trace/common.h
  42
  43 diff --git a/arch/x86/include/asm/trace/common.h b/arch/x86/include/asm/trace/common.h
  44 new file mode 100644
  45 index 000000000000..b1eb7b18ee8a
  46 --- /dev/null
  47 +++ b/arch/x86/include/asm/trace/common.h
  48 @@ -0,0 +1,15 @@
  49 +#ifndef _ASM_TRACE_COMMON_H
  50 +#define _ASM_TRACE_COMMON_H
  51 +
  52 +extern int trace_irq_vector_regfunc(void);
  53 +extern void trace_irq_vector_unregfunc(void);
  54 +
  55 +#ifdef CONFIG_TRACING
  56 +DECLARE_STATIC_KEY_FALSE(trace_irqvectors_key);
  57 +#define trace_irqvectors_enabled()                     \
  58 +       static_branch_unlikely(&trace_irqvectors_key)
  59 +#else
  60 +static inline bool trace_irqvectors_enabled(void) { return false; }
  61 +#endif
  62 +
  63 +#endif
  64 diff --git a/arch/x86/include/asm/trace/exceptions.h b/arch/x86/include/asm/trace/exceptions.h
  65 index 2422b14c50a7..960a5b50ac3b 100644
  66 --- a/arch/x86/include/asm/trace/exceptions.h
  67 +++ b/arch/x86/include/asm/trace/exceptions.h
  68 @@ -5,9 +5,7 @@
  69  #define _TRACE_PAGE_FAULT_H
  70
  71  #include <linux/tracepoint.h>
  72 -
  73 -extern int trace_irq_vector_regfunc(void);
  74 -extern void trace_irq_vector_unregfunc(void);
  75 +#include <asm/trace/common.h>
  76
  77  DECLARE_EVENT_CLASS(x86_exceptions,
  78
  79 diff --git a/arch/x86/include/asm/trace/irq_vectors.h b/arch/x86/include/asm/trace/irq_vectors.h
  80 index 32dd6a9e343c..7825b4426e7e 100644
  81 --- a/arch/x86/include/asm/trace/irq_vectors.h
  82 +++ b/arch/x86/include/asm/trace/irq_vectors.h
  83 @@ -5,9 +5,7 @@
  84  #define _TRACE_IRQ_VECTORS_H
  85
  86  #include <linux/tracepoint.h>
  87 -
  88 -extern int trace_irq_vector_regfunc(void);
  89 -extern void trace_irq_vector_unregfunc(void);
  90 +#include <asm/trace/common.h>
  91
  92  DECLARE_EVENT_CLASS(x86_irq_vector,
  93
  94 diff --git a/arch/x86/kernel/tracepoint.c b/arch/x86/kernel/tracepoint.c
  95 index 15515132bf0d..dd4aa04bb95c 100644
  96 --- a/arch/x86/kernel/tracepoint.c
  97 +++ b/arch/x86/kernel/tracepoint.c
  98 @@ -4,9 +4,11 @@
  99   * Copyright (C) 2013 Seiji Aguchi <seiji.aguchi@hds.com>
 100   *
 101   */
 102 +#include <linux/jump_label.h>
 103 +#include <linux/atomic.h>
 104 +
 105  #include <asm/hw_irq.h>
 106  #include <asm/desc.h>
 107 -#include <linux/atomic.h>
 108
 109  atomic_t trace_idt_ctr = ATOMIC_INIT(0);
 110  struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
 111 @@ -15,6 +17,7 @@ struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
 112  /* No need to be aligned, but done to keep all IDTs defined the same way. */
 113  gate_desc trace_idt_table[NR_VECTORS] __page_aligned_bss;
 114
 115 +DEFINE_STATIC_KEY_FALSE(trace_irqvectors_key);
 116  static int trace_irq_vector_refcount;
 117  static DEFINE_MUTEX(irq_vector_mutex);
 118
 119 @@ -36,6 +39,8 @@ static void switch_idt(void *arg)
 120
 121  int trace_irq_vector_regfunc(void)
 122  {
 123 +       static_branch_inc(&trace_irqvectors_key);
 124 +
 125         mutex_lock(&irq_vector_mutex);
 126         if (!trace_irq_vector_refcount) {
 127                 set_trace_idt_ctr(1);
 128 @@ -49,6 +54,8 @@ int trace_irq_vector_regfunc(void)
 129
 130  void trace_irq_vector_unregfunc(void)
 131  {
 132 +       static_branch_dec(&trace_irqvectors_key);
 133 +
 134         mutex_lock(&irq_vector_mutex);
 135         trace_irq_vector_refcount--;
 136         if (!trace_irq_vector_refcount) {
 137 --
 138 2.14.2
 139