releases/5.0.14/kmemleak-powerpc-skip-scanning-holes-in-the-.bss-sec.patch

   1 From 75a3203c35965f5569f845d690a2e061ab1a4b46 Mon Sep 17 00:00:00 2001
   2 From: Catalin Marinas <catalin.marinas@arm.com>
   3 Date: Fri, 5 Apr 2019 18:38:49 -0700
   4 Subject: kmemleak: powerpc: skip scanning holes in the .bss section
   5
   6 [ Upstream commit 298a32b132087550d3fa80641ca58323c5dfd4d9 ]
   7
   8 Commit 2d4f567103ff ("KVM: PPC: Introduce kvm_tmp framework") adds
   9 kvm_tmp[] into the .bss section and then free the rest of unused spaces
  10 back to the page allocator.
  11
  12 kernel_init
  13   kvm_guest_init
  14     kvm_free_tmp
  15       free_reserved_area
  16         free_unref_page
  17           free_unref_page_prepare
  18
  19 With DEBUG_PAGEALLOC=y, it will unmap those pages from kernel.  As the
  20 result, kmemleak scan will trigger a panic when it scans the .bss
  21 section with unmapped pages.
  22
  23 This patch creates dedicated kmemleak objects for the .data, .bss and
  24 potentially .data..ro_after_init sections to allow partial freeing via
  25 the kmemleak_free_part() in the powerpc kvm_free_tmp() function.
  26
  27 Link: http://lkml.kernel.org/r/20190321171917.62049-1-catalin.marinas@arm.com
  28 Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
  29 Reported-by: Qian Cai <cai@lca.pw>
  30 Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
  31 Tested-by: Qian Cai <cai@lca.pw>
  32 Cc: Paul Mackerras <paulus@samba.org>
  33 Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
  34 Cc: Avi Kivity <avi@redhat.com>
  35 Cc: Paolo Bonzini <pbonzini@redhat.com>
  36 Cc: Radim Krcmar <rkrcmar@redhat.com>
  37 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  38 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  39 Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>
  40 ---
  41  arch/powerpc/kernel/kvm.c |  7 +++++++
  42  mm/kmemleak.c             | 16 +++++++++++-----
  43  2 files changed, 18 insertions(+), 5 deletions(-)
  44
  45 diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
  46 index 683b5b3805bd..cd381e2291df 100644
  47 --- a/arch/powerpc/kernel/kvm.c
  48 +++ b/arch/powerpc/kernel/kvm.c
  49 @@ -22,6 +22,7 @@
  50  #include <linux/kvm_host.h>
  51  #include <linux/init.h>
  52  #include <linux/export.h>
  53 +#include <linux/kmemleak.h>
  54  #include <linux/kvm_para.h>
  55  #include <linux/slab.h>
  56  #include <linux/of.h>
  57 @@ -712,6 +713,12 @@ static void kvm_use_magic_page(void)
  58
  59  static __init void kvm_free_tmp(void)
  60  {
  61 +       /*
  62 +        * Inform kmemleak about the hole in the .bss section since the
  63 +        * corresponding pages will be unmapped with DEBUG_PAGEALLOC=y.
  64 +        */
  65 +       kmemleak_free_part(&kvm_tmp[kvm_tmp_index],
  66 +                          ARRAY_SIZE(kvm_tmp) - kvm_tmp_index);
  67         free_reserved_area(&kvm_tmp[kvm_tmp_index],
  68                            &kvm_tmp[ARRAY_SIZE(kvm_tmp)], -1, NULL);
  69  }
  70 diff --git a/mm/kmemleak.c b/mm/kmemleak.c
  71 index 707fa5579f66..6c318f5ac234 100644
  72 --- a/mm/kmemleak.c
  73 +++ b/mm/kmemleak.c
  74 @@ -1529,11 +1529,6 @@ static void kmemleak_scan(void)
  75         }
  76         rcu_read_unlock();
  77
  78 -       /* data/bss scanning */
  79 -       scan_large_block(_sdata, _edata);
  80 -       scan_large_block(__bss_start, __bss_stop);
  81 -       scan_large_block(__start_ro_after_init, __end_ro_after_init);
  82 -
  83  #ifdef CONFIG_SMP
  84         /* per-cpu sections scanning */
  85         for_each_possible_cpu(i)
  86 @@ -2071,6 +2066,17 @@ void __init kmemleak_init(void)
  87         }
  88         local_irq_restore(flags);
  89
  90 +       /* register the data/bss sections */
  91 +       create_object((unsigned long)_sdata, _edata - _sdata,
  92 +                     KMEMLEAK_GREY, GFP_ATOMIC);
  93 +       create_object((unsigned long)__bss_start, __bss_stop - __bss_start,
  94 +                     KMEMLEAK_GREY, GFP_ATOMIC);
  95 +       /* only register .data..ro_after_init if not within .data */
  96 +       if (__start_ro_after_init < _sdata || __end_ro_after_init > _edata)
  97 +               create_object((unsigned long)__start_ro_after_init,
  98 +                             __end_ro_after_init - __start_ro_after_init,
  99 +                             KMEMLEAK_GREY, GFP_ATOMIC);
 100 +
 101         /*
 102          * This is the point where tracking allocations is safe. Automatic
 103          * scanning is started during the late initcall. Add the early logged
 104 --
 105 2.20.1
 106