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alpha: fix user-space corruption during memory compaction

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Alpha systems can suffer sporadic user-space crashes and heap
corruption when memory compaction is enabled.

Symptoms include SIGSEGV, glibc allocator failures (e.g. "unaligned
tcache chunk"), and compiler internal errors. The failures disappear
when compaction is disabled or when using global TLB invalidation.

The root cause is insufficient TLB shootdown during page migration.
Alpha relies on ASN-based MM context rollover for instruction cache
coherency, but this alone is not sufficient to prevent stale data or
instruction translations from surviving migration.

Fix this by introducing a migration-specific helper that combines:
  - MM context invalidation (ASN rollover),
  - immediate per-CPU TLB invalidation (TBI),
  - synchronous cross-CPU shootdown when required.

The helper is used only by migration/compaction paths to avoid changing
global TLB semantics.

Additionally, update flush_tlb_other(), pte_clear(), to use
READ_ONCE()/WRITE_ONCE() for correct SMP memory ordering.

This fixes observed crashes on both UP and SMP Alpha systems.

Reviewed-by: Ivan Kokshaysky <ink@unseen.parts>
Tested-by: Matoro Mahri <matoro_mailinglist_kernel@matoro.tk>
Tested-by: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
Link: https://lore.kernel.org/r/20260102173603.18247-2-linmag7@gmail.com
Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
This commit is contained in:
Magnus Lindholm
2026-01-02 18:30:43 +01:00
parent 8f0b4cce44
commit dd5712f337
4 changed files with 148 additions and 3 deletions
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33
arch/alpha/include/asm/pgtable.h
View File

@@ -17,6 +17,7 @@
#include <asm/processor.h> /* For TASK_SIZE */
#include <asm/machvec.h>
#include <asm/setup.h>
#include <linux/page_table_check.h>
struct mm_struct;
struct vm_area_struct;
@@ -183,6 +184,9 @@ extern inline void pud_set(pud_t * pudp, pmd_t * pmdp)
{ pud_val(*pudp) = _PAGE_TABLE | ((((unsigned long) pmdp) - PAGE_OFFSET) << (32-PAGE_SHIFT)); }
extern void migrate_flush_tlb_page(struct vm_area_struct *vma,
unsigned long addr);
extern inline unsigned long
pmd_page_vaddr(pmd_t pmd)
{
@@ -202,7 +206,7 @@ extern inline int pte_none(pte_t pte) { return !pte_val(pte); }
extern inline int pte_present(pte_t pte) { return pte_val(pte) & _PAGE_VALID; }
extern inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
{
pte_val(*ptep) = 0;
WRITE_ONCE(pte_val(*ptep), 0);
}
extern inline int pmd_none(pmd_t pmd) { return !pmd_val(pmd); }
@@ -264,6 +268,33 @@ extern inline pte_t * pte_offset_kernel(pmd_t * dir, unsigned long address)
extern pgd_t swapper_pg_dir[1024];
#ifdef CONFIG_COMPACTION
#define __HAVE_ARCH_PTEP_GET_AND_CLEAR
static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
unsigned long address,
pte_t *ptep)
{
pte_t pte = READ_ONCE(*ptep);
pte_clear(mm, address, ptep);
return pte;
}
#define __HAVE_ARCH_PTEP_CLEAR_FLUSH
static inline pte_t ptep_clear_flush(struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep)
{
struct mm_struct *mm = vma->vm_mm;
pte_t pte = ptep_get_and_clear(mm, addr, ptep);
page_table_check_pte_clear(mm, pte);
migrate_flush_tlb_page(vma, addr);
return pte;
}
#endif
/*
* The Alpha doesn't have any external MMU info: the kernel page
* tables contain all the necessary information.