Support page table check PowerPC #724

…e_check_pud_set" This reverts commit 6d14443. Reinstate previously unused parameters for the purpose of supporting powerpc platforms, as many do not encode user/kernel ownership of the page in the pte, but instead in the address of the access. riscv: Respect change to delete mm, addr parameters from __set_pte_at() This commit also changed calls to __set_pte_at() to use fewer parameters on riscv. Keep that change rather than reverting it, as the signature of __set_pte_at() is changed in a different commit. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

…e_check_pmd_set" This reverts commit a3b8371. Reinstate previously unused parameters for the purpose of supporting powerpc platforms, as many do not encode user/kernel ownership of the page in the pte, but instead in the address of the access. riscv: Respect change to delete mm, addr parameters from __set_pte_at() This commit also changed calls to __set_pte_at() to use fewer parameters on riscv. Keep that change rather than reverting it, as the signature of __set_pte_at() is changed in a different commit. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

To provide support for powerpc platforms, provide an address parameter to the page_table_check_pte_set() routine. This parameter is needed on some powerpc platforms which do not encode whether a mapping is for user or kernel in the pte. On such platforms, this can be inferred from the addr parameter. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

…e_check_pud_clear" This reverts commit 931c38e. Reinstate previously unused parameters for the purpose of supporting powerpc platforms, as many do not encode user/kernel ownership of the page in the pte, but instead in the address of the access. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

…e_check_pmd_clear" This reverts commit 1831414. Reinstate previously unused parameters for the purpose of supporting powerpc platforms, as many do not encode user/kernel ownership of the page in the pte, but instead in the address of the access. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

…e_check_pte_clear" This reverts commit aa23220. Reinstate previously unused parameters for the purpose of supporting powerpc platforms, as many do not encode user/kernel ownership of the page in the pte, but instead in the address of the access. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

On several powerpc platforms, a page table entry may not imply whether the relevant mapping is for userspace or kernelspace. Instead, such platforms infer this by the address which is being accessed. Add an additional address argument to each of these routines in order to provide support for page table check on powerpc. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

Replace occurrences of p{u,m,4}d_is_leaf with p{u,m,4}_leaf, as the latter is the name given to checking that a higher-level entry in multi-level paging contains a page translation entry (pte) throughout all other archs. Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

Prior to this commit, pud_pfn was implemented with BUILD_BUG as the inline function for 64-bit Book3S systems but is never included, as its invocations in generic code are guarded by calls to pud_devmap which return zero on such systems. A future patch will provide support for page table checks, the generic code for which depends on a pud_pfn stub being implemented, even while the patch will not interact with puds directly. Remove the 64-bit Book3S stub and define pud_pfn to warn on all platforms. pud_pfn may be defined properly on a per-platform basis should it grow real usages in future. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

Page table checking depends on architectures providing an implementation of p{te,md,ud}_user_accessible_page. With refactorisations made on powerpc/mm, the pte_access_permitted() and similar methods verify whether a userland page is accessible with the required permissions. Since page table checking is the only user of p{te,md,ud}_user_accessible_page(), implement these for all platforms, using some of the same preliminay checks taken by pte_access_permitted() on that platform. Since Commit 8e9bd41 ("powerpc/nohash: Replace pte_user() by pte_read()") pte_user() is no longer required to be present on all platforms as it may be equivalent to or implied by pte_read(). Hence implementations are specialised. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

In the new set_ptes() API, set_pte_at() (a special case of set_ptes()) is intended to be instrumented by the page table check facility. There are however several other routines that constitute the API for setting page table entries, including set_pmd_at() among others. Such routines are themselves implemented in terms of set_ptes_at(). A future patch providing support for page table checking on powerpc must take care to avoid duplicate calls to page_table_check_p{te,md,ud}_set(). Allow for assignment of pte entries without instrumentation through the set_pte_at_unchecked() routine introduced in this patch. Cause API-facing routines that call set_pte_at() to instead call set_pte_at_unchecked(), which will remain uninstrumented by page table check. set_ptes() is itself implemented by calls to __set_pte_at(), so this eliminates redundant code. Also prefer set_pte_at_unchecked() in early-boot usages which should not be instrumented. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

On creation and clearing of a page table mapping, instrument such calls by invoking page_table_check_pte_set and page_table_check_pte_clear respectively. These calls serve as a sanity check against illegal mappings. Enable ARCH_SUPPORTS_PAGE_TABLE_CHECK for all platforms. See also: riscv support in commit 3fee229 ("riscv/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK") arm64 in commit 42b2547 ("arm64/mm: enable ARCH_SUPPORTS_PAGE_TABLE_CHECK") x86_64 in commit d283d42 ("x86: mm: add x86_64 support for page table check") Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>

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Support page table check PowerPC #724

Support page table check PowerPC #724

Commits on Mar 15, 2024