Re: [PATCH 05/23] m68k: allow pte_offset_map[_lock]() to fail
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: 2023-05-10 07:14:38
Also in:
linux-m68k, linux-mips, linux-mm, linux-riscv, linux-s390, linux-sh, lkml, sparclinux
Hi Hugh, Thanks for your patch! On Wed, May 10, 2023 at 6:48 AM Hugh Dickins [off-list ref] wrote:
In rare transient cases, not yet made possible, pte_offset_map() and pte_offset_map_lock() may not find a page table: handle appropriately. Restructure cf_tlb_miss() with a pte_unmap() (previously omitted) at label out, followed by one local_irq_restore() for all.
That's a bug fix, which should be a separate patch?
Signed-off-by: Hugh Dickins <hughd@google.com>
quoted hunk ↗ jump to hunk
--- a/arch/m68k/include/asm/mmu_context.h +++ b/arch/m68k/include/asm/mmu_context.h@@ -99,7 +99,7 @@ static inline void load_ksp_mmu(struct task_struct *task) p4d_t *p4d; pud_t *pud; pmd_t *pmd; - pte_t *pte; + pte_t *pte = NULL; unsigned long mmuar; local_irq_save(flags);@@ -139,7 +139,7 @@ static inline void load_ksp_mmu(struct task_struct *task) pte = (mmuar >= PAGE_OFFSET) ? pte_offset_kernel(pmd, mmuar) : pte_offset_map(pmd, mmuar); - if (pte_none(*pte) || !pte_present(*pte)) + if (!pte || pte_none(*pte) || !pte_present(*pte)) goto bug;
If the absence of a pte is to become a non-abnormal case, it should probably jump to "end" instead, to avoid spamming the kernel log.
quoted hunk ↗ jump to hunk
set_pte(pte, pte_mkyoung(*pte));@@ -161,6 +161,8 @@ static inline void load_ksp_mmu(struct task_struct *task) bug: pr_info("ksp load failed: mm=0x%p ksp=0x08%lx\n", mm, mmuar); end: + if (pte && mmuar < PAGE_OFFSET) + pte_unmap(pte);
Is this also a bugfix, not mentioned in the patch description?
local_irq_restore(flags); }
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds