From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Rapoport Date: Thu, 13 Aug 2020 19:05:46 +0000 Subject: [PATCH v3] arch/ia64: Restore arch-specific pgd_offset_k implementation Message-Id: <20200813190546.4788-1-rppt@kernel.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jessica Clarke Cc: John Paul Adrian Glaubitz , Tony Luck , linux-ia64@vger.kernel.org, Anatoly Pugachev , Sergei Trofimovich , linux-mm@kvack.org, Frank Scheiner , Mike Rapoport , Mike Rapoport From: Jessica Clarke IA-64 is special and treats pgd_offset_k() differently from pgd_offset() by using different formulas to calculate index into kernel and user PGD tables. The index into user PGDs takes into account the region number and the index into the kernel (init_mm) PGD always presumes predefined kernel region number. Commit 974b9b2c68 ("mm: consolidate pte_index() and pte_offset_*() definitions") made IA-64 to use generic pgd_offset_k() which wrongly used pgd_index() for user page tables. As the result, the index into kernel PGD was going out of bounds and the kernel hang during early boot. Allow overrides of pgd_offset_k() and use an override on IA-64 with the old implementation that will correctly index kernel PGD. Fixes: 974b9b2c68 ("mm: consolidate pte_index() and pte_offset_*() definitions") Reported-by: John Paul Adrian Glaubitz Signed-off-by: Jessica Clarke Tested-by: John Paul Adrian Glaubitz Signed-off-by: Mike Rapoport --- Changes since v2: * Rephrase commit message and comment about pgd_offset_k() Changes since v1: * Fixed typo in commit message * Slightly reworded commit message to sound less weird * Included Adrian's Tested-by arch/ia64/include/asm/pgtable.h | 9 +++++++++ include/linux/pgtable.h | 2 ++ 2 files changed, 11 insertions(+) diff --git a/arch/ia64/include/asm/pgtable.h b/arch/ia64/include/asm/pgtable.h index 10850897a91c..6ef501cd0166 100644 --- a/arch/ia64/include/asm/pgtable.h +++ b/arch/ia64/include/asm/pgtable.h @@ -366,6 +366,15 @@ pgd_index (unsigned long address) } #define pgd_index pgd_index +/* + * In the kernel's mapped region we know everything is in region number 5, so + * as an optimisation its PGD already points to the area for that region. + * However, this also means that we cannot use pgd_index() and we never + * should add the region here. + */ +#define pgd_offset_k(addr) \ + (init_mm.pgd + (((addr) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))) + /* Look up a pgd entry in the gate area. On IA-64, the gate-area resides in the kernel-mapped segment, hence we use pgd_offset_k() here. */ diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index a124c21e3204..e8cbc2e795d5 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -117,7 +117,9 @@ static inline pgd_t *pgd_offset_pgd(pgd_t *pgd, unsigned long address) * a shortcut which implies the use of the kernel's pgd, instead * of a process's */ +#ifndef pgd_offset_k #define pgd_offset_k(address) pgd_offset(&init_mm, (address)) +#endif /* * In many cases it is known that a virtual address is mapped at PMD or PTE -- 2.26.2