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kmemleak: powerpc: skip scanning holes in the .bss section

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Commit 2d4f567103 ("KVM: PPC: Introduce kvm_tmp framework") adds
kvm_tmp[] into the .bss section and then free the rest of unused spaces
back to the page allocator.

kernel_init
  kvm_guest_init
    kvm_free_tmp
      free_reserved_area
        free_unref_page
          free_unref_page_prepare

With DEBUG_PAGEALLOC=y, it will unmap those pages from kernel.  As the
result, kmemleak scan will trigger a panic when it scans the .bss
section with unmapped pages.

This patch creates dedicated kmemleak objects for the .data, .bss and
potentially .data..ro_after_init sections to allow partial freeing via
the kmemleak_free_part() in the powerpc kvm_free_tmp() function.

Link: http://lkml.kernel.org/r/20190321171917.62049-1-catalin.marinas@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Qian Cai <cai@lca.pw>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Tested-by: Qian Cai <cai@lca.pw>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Catalin Marinas 2019-04-05 18:38:49 -07:00 committed by Linus Torvalds
parent 5f074f3e19
commit 298a32b132
2 changed files with 18 additions and 5 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

7
arch/powerpc/kernel/kvm.c
View file

@ -22,6 +22,7 @@
#include <linux/kvm_host.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/kmemleak.h>
#include <linux/kvm_para.h>
#include <linux/slab.h>
#include <linux/of.h>
@ -712,6 +713,12 @@ static void kvm_use_magic_page(void)
static __init void kvm_free_tmp(void)
{
/*
* Inform kmemleak about the hole in the .bss section since the
* corresponding pages will be unmapped with DEBUG_PAGEALLOC=y.
*/
kmemleak_free_part(&kvm_tmp[kvm_tmp_index],
ARRAY_SIZE(kvm_tmp) - kvm_tmp_index);
free_reserved_area(&kvm_tmp[kvm_tmp_index],
&kvm_tmp[ARRAY_SIZE(kvm_tmp)], -1, NULL);
}

16
mm/kmemleak.c
View file

@ -1529,11 +1529,6 @@ static void kmemleak_scan(void)
}
rcu_read_unlock();
/* data/bss scanning */
scan_large_block(_sdata, _edata);
scan_large_block(__bss_start, __bss_stop);
scan_large_block(__start_ro_after_init, __end_ro_after_init);
#ifdef CONFIG_SMP
/* per-cpu sections scanning */
for_each_possible_cpu(i)
@ -2071,6 +2066,17 @@ void __init kmemleak_init(void)
}
local_irq_restore(flags);
/* register the data/bss sections */
create_object((unsigned long)_sdata, _edata - _sdata,
KMEMLEAK_GREY, GFP_ATOMIC);
create_object((unsigned long)__bss_start, __bss_stop - __bss_start,
KMEMLEAK_GREY, GFP_ATOMIC);
/* only register .data..ro_after_init if not within .data */
if (__start_ro_after_init < _sdata || __end_ro_after_init > _edata)
create_object((unsigned long)__start_ro_after_init,
__end_ro_after_init - __start_ro_after_init,
KMEMLEAK_GREY, GFP_ATOMIC);
/*
* This is the point where tracking allocations is safe. Automatic
* scanning is started during the late initcall. Add the early logged