patches/kernel/0048-x86-tracing-Introduce-a-static-key-for-exception-tra.patch

   1 From 179faefa769caa263bc88b1f7292be7a60df4298 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 048/241] x86/tracing: Introduce a static key for exception
   5  tracing
   6 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 CVE-2017-5754
  11
  12 Switching the IDT just for avoiding tracepoints creates a completely
  13 impenetrable macro/inline/ifdef mess.
  14
  15 There is no point in avoiding tracepoints for most of the traps/exceptions.
  16 For the more expensive tracepoints, like pagefaults, this can be handled with
  17 an explicit static key.
  18
  19 Preparatory patch to remove the tracing IDT.
  20
  21 Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
  22 Cc: Andy Lutomirski <luto@kernel.org>
  23 Cc: Borislav Petkov <bp@alien8.de>
  24 Cc: Linus Torvalds <torvalds@linux-foundation.org>
  25 Cc: Peter Zijlstra <peterz@infradead.org>
  26 Cc: Steven Rostedt <rostedt@goodmis.org>
  27 Link: http://lkml.kernel.org/r/20170828064956.593094539@linutronix.de
  28 Signed-off-by: Ingo Molnar <mingo@kernel.org>
  29 (cherry picked from commit 2feb1b316d48004d905278c02a55902cab0be8be)
  30 Signed-off-by: Andy Whitcroft <apw@kathleen.maas>
  31 (cherry picked from commit 15e0ff2a63fdd93f8881e2ebba5c048c5b601e57)
  32 Signed-off-by: Andy Whitcroft <apw@canonical.com>
  33 Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
  34 (cherry picked from commit d58a56e851c339d8d9d311dc9b4fad6abbf8bf19)
  35 Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
  36 ---
  37  arch/x86/include/asm/trace/common.h      | 15 +++++++++++++++
  38  arch/x86/include/asm/trace/exceptions.h  |  4 +---
  39  arch/x86/include/asm/trace/irq_vectors.h |  4 +---
  40  arch/x86/kernel/tracepoint.c             |  9 ++++++++-
  41  4 files changed, 25 insertions(+), 7 deletions(-)
  42  create mode 100644 arch/x86/include/asm/trace/common.h
  43
  44 diff --git a/arch/x86/include/asm/trace/common.h b/arch/x86/include/asm/trace/common.h
  45 new file mode 100644
  46 index 000000000000..b1eb7b18ee8a
  47 --- /dev/null
  48 +++ b/arch/x86/include/asm/trace/common.h
  49 @@ -0,0 +1,15 @@
  50 +#ifndef _ASM_TRACE_COMMON_H
  51 +#define _ASM_TRACE_COMMON_H
  52 +
  53 +extern int trace_irq_vector_regfunc(void);
  54 +extern void trace_irq_vector_unregfunc(void);
  55 +
  56 +#ifdef CONFIG_TRACING
  57 +DECLARE_STATIC_KEY_FALSE(trace_irqvectors_key);
  58 +#define trace_irqvectors_enabled()                     \
  59 +       static_branch_unlikely(&trace_irqvectors_key)
  60 +#else
  61 +static inline bool trace_irqvectors_enabled(void) { return false; }
  62 +#endif
  63 +
  64 +#endif
  65 diff --git a/arch/x86/include/asm/trace/exceptions.h b/arch/x86/include/asm/trace/exceptions.h
  66 index 2422b14c50a7..960a5b50ac3b 100644
  67 --- a/arch/x86/include/asm/trace/exceptions.h
  68 +++ b/arch/x86/include/asm/trace/exceptions.h
  69 @@ -5,9 +5,7 @@
  70  #define _TRACE_PAGE_FAULT_H
  71
  72  #include <linux/tracepoint.h>
  73 -
  74 -extern int trace_irq_vector_regfunc(void);
  75 -extern void trace_irq_vector_unregfunc(void);
  76 +#include <asm/trace/common.h>
  77
  78  DECLARE_EVENT_CLASS(x86_exceptions,
  79
  80 diff --git a/arch/x86/include/asm/trace/irq_vectors.h b/arch/x86/include/asm/trace/irq_vectors.h
  81 index 32dd6a9e343c..7825b4426e7e 100644
  82 --- a/arch/x86/include/asm/trace/irq_vectors.h
  83 +++ b/arch/x86/include/asm/trace/irq_vectors.h
  84 @@ -5,9 +5,7 @@
  85  #define _TRACE_IRQ_VECTORS_H
  86
  87  #include <linux/tracepoint.h>
  88 -
  89 -extern int trace_irq_vector_regfunc(void);
  90 -extern void trace_irq_vector_unregfunc(void);
  91 +#include <asm/trace/common.h>
  92
  93  DECLARE_EVENT_CLASS(x86_irq_vector,
  94
  95 diff --git a/arch/x86/kernel/tracepoint.c b/arch/x86/kernel/tracepoint.c
  96 index 15515132bf0d..dd4aa04bb95c 100644
  97 --- a/arch/x86/kernel/tracepoint.c
  98 +++ b/arch/x86/kernel/tracepoint.c
  99 @@ -4,9 +4,11 @@
 100   * Copyright (C) 2013 Seiji Aguchi <seiji.aguchi@hds.com>
 101   *
 102   */
 103 +#include <linux/jump_label.h>
 104 +#include <linux/atomic.h>
 105 +
 106  #include <asm/hw_irq.h>
 107  #include <asm/desc.h>
 108 -#include <linux/atomic.h>
 109
 110  atomic_t trace_idt_ctr = ATOMIC_INIT(0);
 111  struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
 112 @@ -15,6 +17,7 @@ struct desc_ptr trace_idt_descr = { NR_VECTORS * 16 - 1,
 113  /* No need to be aligned, but done to keep all IDTs defined the same way. */
 114  gate_desc trace_idt_table[NR_VECTORS] __page_aligned_bss;
 115
 116 +DEFINE_STATIC_KEY_FALSE(trace_irqvectors_key);
 117  static int trace_irq_vector_refcount;
 118  static DEFINE_MUTEX(irq_vector_mutex);
 119
 120 @@ -36,6 +39,8 @@ static void switch_idt(void *arg)
 121
 122  int trace_irq_vector_regfunc(void)
 123  {
 124 +       static_branch_inc(&trace_irqvectors_key);
 125 +
 126         mutex_lock(&irq_vector_mutex);
 127         if (!trace_irq_vector_refcount) {
 128                 set_trace_idt_ctr(1);
 129 @@ -49,6 +54,8 @@ int trace_irq_vector_regfunc(void)
 130
 131  void trace_irq_vector_unregfunc(void)
 132  {
 133 +       static_branch_dec(&trace_irqvectors_key);
 134 +
 135         mutex_lock(&irq_vector_mutex);
 136         trace_irq_vector_refcount--;
 137         if (!trace_irq_vector_refcount) {
 138 --
 139 2.14.2
 140