linux-kernel - Re: [PATCH v4 0/7] mm/vmalloc.c: allow vread() to read out vm_map

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Date:   Sat, 4 Feb 2023 12:12:08 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Stephen Brennan <stephen.s.brennan@...cle.com>,
        akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, urezki@...il.com, lstoakes@...il.com,
        willy@...radead.org, hch@...radead.org, error27@...il.com
Subject: Re: [PATCH v4 0/7] mm/vmalloc.c: allow vread() to read out
 vm_map_ram areas

On 02/02/23 at 09:47am, Stephen Brennan wrote:
......snip...
> > Testing
> > ***
> > Only did the basic testing on kvm guest, and run below commands to
> > access kcore file to do statistics:
> >
> > 	makedumpfile --mem-usage /proc/kcore
> 
> Hi Baoquan,
> 
> Sorry I haven't commented with testing info or review on each revision:
> I'm not really familiar with the details necessary for review. However,
> it looks like this is getting close to ready, so I did another test:

That's OK, and your testing is very helpful because I don't know how to
create vm_map_ram() area to test the patches, just did basic testing.

> 
> [opc@...pbren-ol8-1 drgn_vmalloc_test]$ sudo insmod drgn_vmalloc_test.ko
> [opc@...pbren-ol8-1 drgn_vmalloc_test]$ sudo dmesg | tail -n 5
> [   20.763310] missing module BTF, cannot register kfuncs
> [   20.840200] missing module BTF, cannot register kfuncs
> [   91.475814] drgn_vmalloc_test: loading out-of-tree module taints kernel.
> [   91.479913] drgn_vmalloc_test: module verification failed: signature and/or required key missing - tainting kernel
> [   91.484926] drgn_vmalloc_test: 0xffffa51ac2d00000
> [opc@...pbren-ol8-1 drgn_vmalloc_test]$ sudo drgn
> drgn 0.0.22 (using Python 3.6.8, elfutils 0.186, with libkdumpfile)
> For help, type help(drgn).
> >>> import drgn
> >>> from drgn import NULL, Object, cast, container_of, execscript, offsetof, reinterpret, sizeof
> >>> from drgn.helpers.common import *
> >>> from drgn.helpers.linux import *
> warning: could not get debugging information for:
> drgn_vmalloc_test (could not find module in depmod)
> >>> prog.read(0xffffa51ac2d00000, 64)
> b'\x00\x00\x00\x00\x01\x00\x00\x00\x02\x00\x00\x00\x03\x00\x00\x00\x04\x00\x00\x00\x05\x00\x00\x00\x06\x00\x00\x00\x07\x00\x00\x00\x08\x00\x00\x00\t\x00\x00\x00\n\x00\x00\x00\x0b\x00\x00\x00\x0c\x00\x00\x00\r\x00\x00\x00\x0e\x00\x00\x00\x0f\x00\x00\x00'
> >>>
> 
> So this definitely still resolves the originally reported issue. Feel
> free to add, if you want:
> 
> Tested-by: Stephen Brennan <stephen.s.brennan@...cle.com>

I noticed Andrew had picked this v4 into his mm tree, maybe Andrew can
help add this Tested-by tag.