Messages in this thread | | | Date | Fri, 21 Dec 2018 15:56:43 +0100 | From | Jiri Bohac <> | Subject | Re: [PATCH 1/1] x86/gart/kcore: Exclude GART aperture from kcore |
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On Fri, Dec 21, 2018 at 09:38:12AM +0800, Kairui Song wrote: > On machines where the GART aperture is mapped over physical RAM, > /proc/kcore contains the GART aperture range and reading it may lead > to kernel panic. > > In 'commit 2a3e83c6f96c ("x86/gart: Exclude GART aperture from vmcore")', > a special workaround is applied for vmcore to let /proc/vmcore return > zeroes when attempting to read the aperture region, as vmcore and kcore > have the same issue, and after 'commit 707d4eefbdb3 ("Revert "[PATCH] > Insert GART region into resource map"")', userspace tools can't detect and > exclude GART region. > > This patch applies the same workaround for kcore. Let /proc/kcore return > zeroes too when trying to read the aperture region to fix the issue that > reading GART region may raise unexpected exceptions. > > This applies to both first and second kernels as GART may get > initialized in the first and second kernels. > > To get the same workaround work for kcore, this patch implement a hook > infrastructure for kcore which is same as the hook infrastructure for > vmcore introduced in 'commit 997c136f518c ("fs/proc/vmcore.c: add hook > to read_from_oldmem() to check for non-ram pages")'', and reuses the > checking function gart_oldmem_pfn_is_ram introduced in > 'commit 2a3e83c6f96c ("x86/gart: Exclude GART aperture from vmcore"),' > as the hook function, but rename to gart_mem_pfn_is_ram as now it's > for a more generic use. > > Suggested-by: Baoquan He <bhe@redhat.com> > Signed-off-by: Kairui Song <kasong@redhat.com>
Reviewed-by: Jiri Bohac <jbohac@suse.cz>
> --- > arch/x86/kernel/aperture_64.c | 6 ++++-- > fs/proc/kcore.c | 34 ++++++++++++++++++++++++++++++++++ > include/linux/kcore.h | 3 +++ > 3 files changed, 41 insertions(+), 2 deletions(-)
-- Jiri Bohac <jbohac@suse.cz> SUSE Labs, Prague, Czechia
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