kernel.git/arch/arm64/include/asm/pgtable.h, branch linux-4.9.y

arm64: pgtable: Fix pte_accessible()

2020-12-02T07:31:25Z

commit 07509e10dcc77627f8b6a57381e878fe269958d3 upstream. pte_accessible() is used by ptep_clear_flush() to figure out whether TLB invalidation is necessary when unmapping pages for reclaim. Although our implementation is correct according to the architecture, returning true only for valid, young ptes in the absence of racing page-table modifications, this is in fact flawed due to lazy invalidation of old ptes in ptep_clear_flush_young() where we elide the expensive DSB instruction for completing the TLB invalidation. Rather than penalise the aging path, adjust pte_accessible() to return true for any valid pte, even if the access flag is cleared. Cc: Fixes: 76c714be0e5e ("arm64: pgtable: implement pte_accessible()") Reported-by: Yu Zhao Acked-by: Yu Zhao Reviewed-by: Minchan Kim Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20201120143557.6715-2-will@kernel.org Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman

arm64: don't open code page table entry creation

2020-01-23T07:19:33Z

commit 193383043f14a398393dc18bae8380f7fe665ec3 upstream. Instead of open coding the generation of page table entries, use the macros/functions that exist for this - pfn_p*d and p*d_populate. Most code in the kernel already uses these macros, this patch tries to fix up the few places that don't. This is useful for the next patch in this series, which needs to change the page table entry logic, and it's better to have that logic in one place. The KVM extended ID map is special, since we're creating a level above CONFIG_PGTABLE_LEVELS and the required function isn't available. Leave it as is and add a comment to explain it. (The normal kernel ID map code doesn't need this change because its page tables are created in assembly (__create_page_tables)). Tested-by: Suzuki K Poulose Reviewed-by: Suzuki K Poulose Reviewed-by: Marc Zyngier Tested-by: Bob Picco Reviewed-by: Bob Picco Signed-off-by: Kristina Martsenko Signed-off-by: Catalin Marinas [bwh: Backported to 4.9: adjust context] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

arm64: Revert support for execute-only user mappings

2020-01-12T10:24:15Z

commit 24cecc37746393432d994c0dbc251fb9ac7c5d72 upstream. The ARMv8 64-bit architecture supports execute-only user permissions by clearing the PTE_USER and PTE_UXN bits, practically making it a mostly privileged mapping but from which user running at EL0 can still execute. The downside, however, is that the kernel at EL1 inadvertently reading such mapping would not trip over the PAN (privileged access never) protection. Revert the relevant bits from commit cab15ce604e5 ("arm64: Introduce execute-only page access permissions") so that PROT_EXEC implies PROT_READ (and therefore PTE_USER) until the architecture gains proper support for execute-only user mappings. Fixes: cab15ce604e5 ("arm64: Introduce execute-only page access permissions") Cc: # 4.9.x- Acked-by: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

arm64/mm: fix variable 'pud' set but not used

2019-08-25T08:51:47Z

[ Upstream commit 7d4e2dcf311d3b98421d1f119efe5964cafa32fc ] GCC throws a warning, arch/arm64/mm/mmu.c: In function 'pud_free_pmd_page': arch/arm64/mm/mmu.c:1033:8: warning: variable 'pud' set but not used [-Wunused-but-set-variable] pud_t pud; ^~~ because pud_table() is a macro and compiled away. Fix it by making it a static inline function and for pud_sect() as well. Signed-off-by: Qian Cai Signed-off-by: Will Deacon Signed-off-by: Sasha Levin

arm64: Fix compiler warning from pte_unmap() with -Wunused-but-set-variable

2019-05-31T13:48:14Z

[ Upstream commit 74dd022f9e6260c3b5b8d15901d27ebcc5f21eda ] When building with -Wunused-but-set-variable, the compiler shouts about a number of pte_unmap() users, since this expands to an empty macro on arm64: | mm/gup.c: In function 'gup_pte_range': | mm/gup.c:1727:16: warning: variable 'ptem' set but not used | [-Wunused-but-set-variable] | mm/gup.c: At top level: | mm/memory.c: In function 'copy_pte_range': | mm/memory.c:821:24: warning: variable 'orig_dst_pte' set but not used | [-Wunused-but-set-variable] | mm/memory.c:821:9: warning: variable 'orig_src_pte' set but not used | [-Wunused-but-set-variable] | mm/swap_state.c: In function 'swap_ra_info': | mm/swap_state.c:641:15: warning: variable 'orig_pte' set but not used | [-Wunused-but-set-variable] | mm/madvise.c: In function 'madvise_free_pte_range': | mm/madvise.c:318:9: warning: variable 'orig_pte' set but not used | [-Wunused-but-set-variable] Rewrite pte_unmap() as a static inline function, which silences the warnings. Signed-off-by: Qian Cai Signed-off-by: Will Deacon Signed-off-by: Sasha Levin

arm64: mm: Map entry trampoline into trampoline and kernel page tables

2018-04-08T10:12:52Z

commit 51a0048beb44 upstream. The exception entry trampoline needs to be mapped at the same virtual address in both the trampoline page table (which maps nothing else) and also the kernel page table, so that we can swizzle TTBR1_EL1 on exceptions from and return to EL0. This patch maps the trampoline at a fixed virtual address in the fixmap area of the kernel virtual address space, which allows the kernel proper to be randomized with respect to the trampoline when KASLR is enabled. Reviewed-by: Mark Rutland Tested-by: Laura Abbott Tested-by: Shanker Donthineni Signed-off-by: Will Deacon Signed-off-by: Alex Shi Signed-off-by: Mark Rutland [v4.9 backport] Tested-by: Will Deacon Tested-by: Greg Hackmann Signed-off-by: Greg Kroah-Hartman

arm64: Implement arch-specific pte_access_permitted()

2017-11-30T08:39:01Z

commit 6218f96c58dbf44a06aeaf767aab1f54fc397838 upstream. The generic pte_access_permitted() implementation only checks for pte_present() (together with the write permission where applicable). However, for both kernel ptes and PROT_NONE mappings pte_present() also returns true on arm64 even though such mappings are not user accessible. Additionally, arm64 now supports execute-only user permission (PROT_EXEC) which is implemented by clearing the PTE_USER bit. With this patch the arm64 implementation of pte_access_permitted() checks for the PTE_VALID and PTE_USER bits together with writable access if applicable. Reported-by: Al Viro Signed-off-by: Catalin Marinas Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman

arm64: Improve detection of user/non-user mappings in set_pte(_at)

2017-05-14T12:00:15Z

commit ec663d967b2276448a416406ca59ff247c0c80c5 upstream. Commit cab15ce604e5 ("arm64: Introduce execute-only page access permissions") allowed a valid user PTE to have the PTE_USER bit clear. As a consequence, the pte_valid_not_user() macro in set_pte() was replaced with pte_valid_global() under the assumption that only user pages have the nG bit set. EFI mappings, however, also have the nG bit set and set_pte() wrongly ignores issuing the DSB+ISB. This patch reinstates the pte_valid_not_user() macro and adds the PTE_UXN bit check since all kernel mappings have this bit set. For clarity, pte_exec() is renamed to pte_user_exec() as it only checks for the absence of PTE_UXN. Consequently, the user executable check in set_pte_at() drops the pte_ng() test since pte_user_exec() is sufficient. Fixes: cab15ce604e5 ("arm64: Introduce execute-only page access permissions") Signed-off-by: Catalin Marinas Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman

arm64: hibernate: Support DEBUG_PAGEALLOC

2016-08-25T17:00:30Z

DEBUG_PAGEALLOC removes the valid bit of page table entries to prevent any access to unallocated memory. Hibernate uses this as a hint that those pages don't need to be saved/restored. This patch adds the kernel_page_present() function it uses. hibernate.c copies the resume kernel's linear map for use during restore. Add _copy_pte() to fill-in the holes made by DEBUG_PAGEALLOC in the resume kernel, so we can restore data the original kernel had at these addresses. Finally, DEBUG_PAGEALLOC means the linear-map alias of KERNEL_START to KERNEL_END may have holes in it, so we can't lazily clean this whole area to the PoC. Only clean the new mmuoff region, and the kernel/kvm idmaps. This reverts commit da24eb1f3f9e2c7b75c5f8c40d8e48e2c4789596. Reported-by: Will Deacon Signed-off-by: James Morse Cc: Catalin Marinas Reviewed-by: Catalin Marinas Signed-off-by: Will Deacon

arm64: Introduce execute-only page access permissions

2016-08-25T17:00:29Z

The ARMv8 architecture allows execute-only user permissions by clearing the PTE_UXN and PTE_USER bits. However, the kernel running on a CPU implementation without User Access Override (ARMv8.2 onwards) can still access such page, so execute-only page permission does not protect against read(2)/write(2) etc. accesses. Systems requiring such protection must enable features like SECCOMP. This patch changes the arm64 __P100 and __S100 protection_map[] macros to the new __PAGE_EXECONLY attributes. A side effect is that pte_user() no longer triggers for __PAGE_EXECONLY since PTE_USER isn't set. To work around this, the check is done on the PTE_NG bit via the pte_ng() macro. VM_READ is also checked now for page faults. Reviewed-by: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Will Deacon