From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Kefeng Wang <wangkefeng.wang@huawei.com>
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 11:44:50 +0100 [thread overview]
Message-ID: <20210602104450.GH30436@shell.armlinux.org.uk> (raw)
In-Reply-To: <20210602070246.83990-5-wangkefeng.wang@huawei.com>
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.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
next prev parent reply other threads:[~2021-06-02 10:45 UTC|newest]
Thread overview: 21+ 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 ` [PATCH v2 1/7] ARM: mm: Rafactor the __do_page_fault() Kefeng Wang
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 10:31 ` Russell King (Oracle)
2021-06-02 7:02 ` [PATCH v2 3/7] ARM: mm: Cleanup access_error() Kefeng Wang
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 10:44 ` Russell King (Oracle) [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 10:47 ` Russell King (Oracle)
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 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 10:52 ` Russell King (Oracle)
2021-06-02 15:13 ` Kefeng Wang
2021-06-02 15:58 ` Russell King (Oracle)
2021-06-03 9:38 ` Kefeng Wang
2021-06-07 8:32 ` Kefeng Wang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210602104450.GH30436@shell.armlinux.org.uk \
--to=linux@armlinux.org.uk \
--cc=akpm@linux-foundation.org \
--cc=catalin.marinas@arm.com \
--cc=js07.lee@gmail.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=wangkefeng.wang@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).