Messages in this thread | | | Subject | Re: [PATCH v1 1/4] kasan: introduce set_pmd_early_shadow() | From | Jürgen Groß <> | Date | Thu, 16 Jan 2020 08:54:59 +0100 |
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On 15.01.20 17:32, Sergey Dyasli wrote: > On 15/01/2020 11:09, Jürgen Groß wrote: >> On 15.01.20 11:54, Sergey Dyasli wrote: >>> Hi Juergen, >>> >>> On 08/01/2020 15:20, Sergey Dyasli wrote: >>>> It is incorrect to call pmd_populate_kernel() multiple times for the >>>> same page table. Xen notices it during kasan_populate_early_shadow(): >>>> >>>> (XEN) mm.c:3222:d155v0 mfn 3704b already pinned >>>> >>>> This happens for kasan_early_shadow_pte when USE_SPLIT_PTE_PTLOCKS is >>>> enabled. Fix this by introducing set_pmd_early_shadow() which calls >>>> pmd_populate_kernel() only once and uses set_pmd() afterwards. >>>> >>>> Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com> >>> >>> Looks like the plan to use set_pmd() directly has failed: it's an >>> arch-specific function and can't be used in arch-independent code >>> (as kbuild test robot has proven). >>> >>> Do you see any way out of this other than disabling SPLIT_PTE_PTLOCKS >>> for PV KASAN? >> >> Change set_pmd_early_shadow() like the following: >> >> #ifdef CONFIG_XEN_PV >> static inline void set_pmd_early_shadow(pmd_t *pmd, pte_t *early_shadow) >> { >> static bool pmd_populated = false; >> >> if (likely(pmd_populated)) { >> set_pmd(pmd, __pmd(__pa(early_shadow) | _PAGE_TABLE)); >> } else { >> pmd_populate_kernel(&init_mm, pmd, early_shadow); >> pmd_populated = true; >> } >> } >> #else >> static inline void set_pmd_early_shadow(pmd_t *pmd, pte_t *early_shadow) >> { >> pmd_populate_kernel(&init_mm, pmd, early_shadow); >> } >> #endif >> >> ... and move it to include/xen/xen-ops.h and call it with >> lm_alias(kasan_early_shadow_pte) as the second parameter. > > Your suggestion to use ifdef is really good, especially now when I > figured out that CONFIG_XEN_PV implies X86. But I don't like the idea > of kasan code calling a non-empty function from xen-ops.h when > CONFIG_XEN_PV is not defined. I'd prefer to keep set_pmd_early_shadow() > in mm/kasan/init.c with the suggested ifdef.
Fine with me.
Juergen
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