arch/ia64: Restore arch-specific pgd_offset_k implementation
Subsystems (2)
Mike Rapoport
reviewerPATCH v4 1/1 arch/ia64: Restore arch-specific pgd_offset_k implementation
From: Jessica Clarke <[email protected]>
IA-64 is special and treats pgd_offset_k() differently to pgd_offset(), using different formulae to calculate the indices into the kernel and user PGDs. The index into the user PGDs takes into account the region number, but the index into the kernel (init_mm) PGD always assumes a predefined kernel region number. Commit 974b9b2c68 ("mm: consolidate pte_index() and pte_offset_*() definitions") made IA-64 use a generic pgd_offset_k() which incorrectly used pgd_index() for kernel page tables. As a result, the index into the kernel PGD was going out of bounds and the kernel hung during early boot.
Allow overrides of pgd_offset_k() and override it on IA-64 with the old implementation that will correctly index the kernel PGD.
---
Changes since v3:
* Correct commit message as Jessica suggested
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(+)
arch/ia64/include/asm/pgtable.h +9 -0
@@ -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. */
include/linux/pgtable.h +2 -0
@@ -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
Signature · 1 line
2.26.2
Quoted 21 lines · Mike Rapoport
From: Jessica Clarke <[email protected]>
IA-64 is special and treats
pgd_offset_k()differently topgd_offset(), using different formulae to calculate the indices into the kernel and user PGDs. The index into the user PGDs takes into account the region number, but the index into the kernel (init_mm) PGD always assumes a predefined kernel region number. Commit974b9b2c68("mm: consolidatepte_index()and pte_offset_*() definitions") made IA-64 use a genericpgd_offset_k()which incorrectly usedpgd_index()for kernel page tables. As a result, the index into the kernel PGD was going out of bounds and the kernel hung during early boot.Allow overrides of
pgd_offset_k()and override it on IA-64 with the old implementation that will correctly index the kernel PGD.Fixes 974b9b2c68 ("mm: consolidate pte_index() and pte_offset_*() definitions")Reported-by John Paul Adrian Glaubitz <[email protected]>Signed-off-by Jessica Clarke <[email protected]>Signed-off-by Mike Rapoport <[email protected]>
Quoted 4 lines
---
Changes since v3:
* Correct commit message as Jessica suggested
I also corrected the comment to:
/*
* 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 must
* never add the region here.
*/
Quoted 50 lines
Changes since v2:
* Rephrase commit message and comment aboutpgd_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(+)arch/ia64/include/asm/pgtable.h +9
-0@@ -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. */ include/linux/pgtable.h +2
-0@@ -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 Signature · 1 line
2.26.2