From: Dave Vasilevsky dave@vasilevsky.ca

On 32-bit book3s with hash-MMUs, tlb_flush() was a no-op. This was unnoticed because all uses until recently were for unmaps, and thus handled by __tlb_remove_tlb_entry().

After commit 4a18419f71cd ("mm/mprotect: use mmu_gather") in kernel 5.19, tlb_gather_mmu() started being used for mprotect as well. This caused mprotect to simply not work on these machines:

int *ptr = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); *ptr = 1; // force HPTE to be created mprotect(ptr, 4096, PROT_READ); *ptr = 2; // should segfault, but succeeds

Fixed by making tlb_flush() actually flush TLB pages. This finally agrees with the behaviour of boot3s64's tlb_flush().

Fixes: 4a18419f71cd ("mm/mprotect: use mmu_gather") Signed-off-by: Dave Vasilevsky dave@vasilevsky.ca --- arch/powerpc/include/asm/book3s/32/tlbflush.h | 8 ++++++-- arch/powerpc/mm/book3s32/tlb.c | 6 ++++++ 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/32/tlbflush.h b/arch/powerpc/include/asm/book3s/32/tlbflush.h index e43534da5207aa3b0cb3c07b78e29b833c141f3f..b8c587ad2ea954f179246a57d6e86e45e91dcfdc 100644 --- a/arch/powerpc/include/asm/book3s/32/tlbflush.h +++ b/arch/powerpc/include/asm/book3s/32/tlbflush.h @@ -11,6 +11,7 @@ void hash__flush_tlb_mm(struct mm_struct *mm); void hash__flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr); void hash__flush_range(struct mm_struct *mm, unsigned long start, unsigned long end); +void hash__flush_gather(struct mmu_gather *tlb);

#ifdef CONFIG_SMP void _tlbie(unsigned long address); @@ -28,9 +29,12 @@ void _tlbia(void); */ static inline void tlb_flush(struct mmu_gather *tlb) { - /* 603 needs to flush the whole TLB here since it doesn't use a hash table. */ - if (!mmu_has_feature(MMU_FTR_HPTE_TABLE)) + if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) { + hash__flush_gather(tlb); + } else { + /* 603 needs to flush the whole TLB here since it doesn't use a hash table. */ _tlbia(); + } }

static inline void flush_range(struct mm_struct *mm, unsigned long start, unsigned long end) diff --git a/arch/powerpc/mm/book3s32/tlb.c b/arch/powerpc/mm/book3s32/tlb.c index 9ad6b56bfec96e989b96f027d075ad5812500854..3da95ecfbbb296303082e378425e92a5fbdbfac8 100644 --- a/arch/powerpc/mm/book3s32/tlb.c +++ b/arch/powerpc/mm/book3s32/tlb.c @@ -105,3 +105,9 @@ void hash__flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr) flush_hash_pages(mm->context.id, vmaddr, pmd_val(*pmd), 1); } EXPORT_SYMBOL(hash__flush_tlb_page); + +void hash__flush_gather(struct mmu_gather *tlb) +{ + hash__flush_range(tlb->mm, tlb->start, tlb->end); +} +EXPORT_SYMBOL(hash__flush_gather);

--- base-commit: dcb6fa37fd7bc9c3d2b066329b0d27dedf8becaa change-id: 20251027-vasi-mprotect-g3-f8f5278d4140

Best regards,