From: Kefeng Wang <wangkefeng.wang@huawei.com> To: "Russell King (Oracle)" <linux@armlinux.org.uk> Cc: <linux-arm-kernel@lists.infradead.org>, Catalin Marinas <catalin.marinas@arm.com>, <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Jungseung Lee <js07.lee@gmail.com> Subject: Re: [PATCH v2 4/7] ARM: mm: print out correct page table entries Date: Wed, 2 Jun 2021 19:24:47 +0800 [thread overview] Message-ID: <79a2aae4-834e-7ce1-e755-633d4073c088@huawei.com> (raw) In-Reply-To: <20210602104450.GH30436@shell.armlinux.org.uk> On 2021/6/2 18:44, Russell King (Oracle) wrote: > On Wed, Jun 02, 2021 at 03:02:43PM +0800, Kefeng Wang wrote: >> Like commit 67ce16ec15ce ("arm64: mm: print out correct page table entries") >> does, drop the struct mm_struct argument of show_pte(), print the tables >> based on the faulting address. >> >> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> > This can be misleading on 32-bit ARM. > > The effective page tables for each thread are the threads *own* page > tables. There is no hardware magic for addresses above PAGE_OFFSET being > directed to the init_mm page tables. > > So, when we hit a fault in kernel space, we need to be printing the > currently in-use page tables associated with the running thread. > > Hence: > >> /* >> - * This is useful to dump out the page tables associated with >> - * 'addr' in mm 'mm'. >> + * Dump out the page tables associated with 'addr' in the currently active mm >> */ >> -void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr) >> +void show_pte(const char *lvl, unsigned long addr) >> { >> pgd_t *pgd; >> - >> - if (!mm) >> + struct mm_struct *mm; >> + >> + if (addr < TASK_SIZE) { >> + mm = current->active_mm; >> + if (mm == &init_mm) { >> + printk("%s[%08lx] user address but active_mm is swapper\n", >> + lvl, addr); >> + return; >> + } >> + } else { >> mm = &init_mm; >> + } > is incorrect here. > > It's completely fine for architectures where kernel accesses always go > to the init_mm page tables, but for 32-bit ARM that is not the case. OK, I will drop this one, thanks >
WARNING: multiple messages have this Message-ID (diff)
From: Kefeng Wang <wangkefeng.wang@huawei.com> To: "Russell King (Oracle)" <linux@armlinux.org.uk> Cc: <linux-arm-kernel@lists.infradead.org>, Catalin Marinas <catalin.marinas@arm.com>, <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Jungseung Lee <js07.lee@gmail.com> Subject: Re: [PATCH v2 4/7] ARM: mm: print out correct page table entries Date: Wed, 2 Jun 2021 19:24:47 +0800 [thread overview] Message-ID: <79a2aae4-834e-7ce1-e755-633d4073c088@huawei.com> (raw) In-Reply-To: <20210602104450.GH30436@shell.armlinux.org.uk> On 2021/6/2 18:44, Russell King (Oracle) wrote: > On Wed, Jun 02, 2021 at 03:02:43PM +0800, Kefeng Wang wrote: >> Like commit 67ce16ec15ce ("arm64: mm: print out correct page table entries") >> does, drop the struct mm_struct argument of show_pte(), print the tables >> based on the faulting address. >> >> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> > This can be misleading on 32-bit ARM. > > The effective page tables for each thread are the threads *own* page > tables. There is no hardware magic for addresses above PAGE_OFFSET being > directed to the init_mm page tables. > > So, when we hit a fault in kernel space, we need to be printing the > currently in-use page tables associated with the running thread. > > Hence: > >> /* >> - * This is useful to dump out the page tables associated with >> - * 'addr' in mm 'mm'. >> + * Dump out the page tables associated with 'addr' in the currently active mm >> */ >> -void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr) >> +void show_pte(const char *lvl, unsigned long addr) >> { >> pgd_t *pgd; >> - >> - if (!mm) >> + struct mm_struct *mm; >> + >> + if (addr < TASK_SIZE) { >> + mm = current->active_mm; >> + if (mm == &init_mm) { >> + printk("%s[%08lx] user address but active_mm is swapper\n", >> + lvl, addr); >> + return; >> + } >> + } else { >> mm = &init_mm; >> + } > is incorrect here. > > It's completely fine for architectures where kernel accesses always go > to the init_mm page tables, but for 32-bit ARM that is not the case. OK, I will drop this one, thanks > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-06-02 11:25 UTC|newest] Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-02 7:02 [PATCH v2 0/7] ARM: mm: cleanup page fault and fix pxn process issue Kefeng Wang 2021-06-02 7:02 ` Kefeng Wang 2021-06-02 7:02 ` [PATCH v2 1/7] ARM: mm: Rafactor the __do_page_fault() Kefeng Wang 2021-06-02 7:02 ` Kefeng Wang 2021-06-02 10:29 ` Russell King (Oracle) 2021-06-02 10:29 ` Russell King (Oracle) 2021-06-02 7:02 ` [PATCH v2 2/7] ARM: mm: Kill task_struct argument for __do_page_fault() Kefeng Wang 2021-06-02 7:02 ` Kefeng Wang 2021-06-02 10:31 ` Russell King (Oracle) 2021-06-02 10:31 ` Russell King (Oracle) 2021-06-02 7:02 ` [PATCH v2 3/7] ARM: mm: Cleanup access_error() Kefeng Wang 2021-06-02 7:02 ` Kefeng Wang 2021-06-02 10:39 ` Russell King (Oracle) 2021-06-02 10:39 ` Russell King (Oracle) 2021-06-02 7:02 ` [PATCH v2 4/7] ARM: mm: print out correct page table entries Kefeng Wang 2021-06-02 7:02 ` Kefeng Wang 2021-06-02 10:44 ` Russell King (Oracle) 2021-06-02 10:44 ` Russell King (Oracle) 2021-06-02 11:24 ` Kefeng Wang [this message] 2021-06-02 11:24 ` Kefeng Wang 2021-06-02 7:02 ` [PATCH v2 5/7] ARM: mm: Print physical address of page table base in show_pte() Kefeng Wang 2021-06-02 7:02 ` Kefeng Wang 2021-06-02 10:47 ` Russell King (Oracle) 2021-06-02 10:47 ` Russell King (Oracle) 2021-06-02 11:25 ` Kefeng Wang 2021-06-02 11:25 ` Kefeng Wang 2021-06-02 7:02 ` [PATCH v2 6/7] ARM: mm: Provide die_kernel_fault() helper Kefeng Wang 2021-06-02 7:02 ` Kefeng Wang 2021-06-02 10:49 ` Russell King (Oracle) 2021-06-02 10:49 ` Russell King (Oracle) 2021-06-02 7:02 ` [PATCH v2 7/7] ARM: mm: Fix PXN process with LPAE feature Kefeng Wang 2021-06-02 7:02 ` Kefeng Wang 2021-06-02 10:52 ` Russell King (Oracle) 2021-06-02 10:52 ` Russell King (Oracle) 2021-06-02 15:13 ` Kefeng Wang 2021-06-02 15:13 ` Kefeng Wang 2021-06-02 15:58 ` Russell King (Oracle) 2021-06-02 15:58 ` Russell King (Oracle) 2021-06-03 9:38 ` Kefeng Wang 2021-06-03 9:38 ` Kefeng Wang 2021-06-07 8:32 ` Kefeng Wang 2021-06-07 8:32 ` Kefeng Wang
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