Le 11/11/2025 à 22:42, Dave Vasilevsky a écrit :
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 <[email protected]>
Cc: [email protected]
A small comment below
Reviewed-by: Christophe Leroy <[email protected]>
---
Changes in v2:
- Flush entire TLB if full mm is requested.
- Link to v1:
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fr%2F20251027-vasi-mprotect-g3-v1-1-3c5187085f9a%40vasilevsky.ca&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C7b1beec4921c4c67c95108de216b416f%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638984941704616710%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=mJL3gS4YkTUAWmivSWL5AE9BlhAQ0R%2FI3eBwYwN26nA%3D&reserved=0
---
arch/powerpc/include/asm/book3s/32/tlbflush.h | 8 ++++++--
arch/powerpc/mm/book3s32/tlb.c | 9 +++++++++
2 files changed, 15 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();
+ }
You should keep the comment on 603 outside the if/else and remove the
braces, in line with
https://docs.kernel.org/process/coding-style.html#placing-braces-and-spaces
}
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..e54a7b0112322e5818d80facd2e3c7722e6dd520
100644
--- a/arch/powerpc/mm/book3s32/tlb.c
+++ b/arch/powerpc/mm/book3s32/tlb.c
@@ -105,3 +105,12 @@ 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)
+{
+ if (tlb->fullmm || tlb->need_flush_all)
+ hash__flush_tlb_mm(tlb->mm);
+ else
+ hash__flush_range(tlb->mm, tlb->start, tlb->end);
+}
+EXPORT_SYMBOL(hash__flush_gather);
---
base-commit: 24172e0d79900908cf5ebf366600616d29c9b417
change-id: 20251027-vasi-mprotect-g3-f8f5278d4140
Best regards,
