Messages in this thread Patch in this message | | | Date | Thu, 2 Dec 2021 11:05:47 +0100 | Subject | Re: [PATCH 3/3] x86: mm: add x86_64 support for page table check | From | Jiri Slaby <> |
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On 02. 12. 21, 10:59, Jiri Slaby wrote: > On 01. 12. 21, 14:55, Pasha Tatashin wrote: >> On Wed, Dec 1, 2021 at 3:44 AM Jiri Slaby <jirislaby@kernel.org> wrote: >>> >>> On 01. 12. 21, 9:00, Jiri Slaby wrote: >>>> On 23. 11. 21, 22:48, Pasha Tatashin wrote: >>>>> Add page table check hooks into routines that modify user page tables. >>>> >>>> Hi, >>>> >>>> I bisected to this as this causes crashes during modules load: >>> >>> And it's not enough to unset CONFIG_PAGE_TABLE_CHECK_ENFORCED. I had to >>> unset CONFIG_PAGE_TABLE_CHECK completely to get rid of this. >> >> Hi, >> >> Thanks for reporting this. Seems like module load for some reasons >> does not like the static branches. However, I was not able to repro >> this. Could you please share your config and the module that you were >> loading? > > It's the openSUSE's -next config: > https://raw.githubusercontent.com/openSUSE/kernel-source/linux-next/config/x86_64/vanilla > > > But with CONFIG_IWLMEI=n (as that fails to link). > > One has to load i915, other modules (71 on my system) are apparently fine. > > i915 tries to patch your `page_table_check_disabled' which is defined as > `DEFINE_STATIC_KEY_TRUE_RO': > > jump_label_add_module: key=__tracepoint_mmap_lock_released > (ffffffff93f36d88) mod=0000000000000000 > > jump_label_add_module: key=hugetlb_free_vmemmap_enabled_key > (ffffffff94873560) mod=0000000000000000 > > jump_label_add_module: key=devmap_managed_key (ffffffff94902700) > mod=0000000000000000 > > jump_label_add_module: key=page_table_check_disabled > (ffffffff939da760) mod=0000000000000000 > > BUG: unable to handle page fault for address: ffffffff939da768
Provided you EXPORT page_table_check_disabled and it can be used from modules, it can be barely marked as RO. So the below indeed fixes the problem for me:
--- a/mm/page_table_check.c +++ b/mm/page_table_check.c @@ -18,7 +18,7 @@ struct page_table_check { static bool __page_table_check_enabled __initdata = IS_ENABLED(CONFIG_PAGE_TABLE_CHECK_ENFORCED);
-DEFINE_STATIC_KEY_TRUE_RO(page_table_check_disabled); +DEFINE_STATIC_KEY_TRUE(page_table_check_disabled); EXPORT_SYMBOL(page_table_check_disabled);
static int __init early_page_table_check_param(char *buf) > > regards,
-- js suse labs
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