linux-kernel - Re: [PATCH v4 00/10] klp-convert livepatch build tooling

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Message-ID: <alpine.LSU.2.21.1906131451560.22698@pobox.suse.cz>
Date:   Thu, 13 Jun 2019 15:00:19 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Joe Lawrence <joe.lawrence@...hat.com>
cc:     linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
        linux-kbuild@...r.kernel.org
Subject: Re: [PATCH v4 00/10] klp-convert livepatch build tooling

Hi Joe,

first, I'm sorry for the lack of response so far.

Maybe you've already noticed but the selftests fail. Well, at least in 
my VM. When test_klp_convert1.ko is loaded, the process is killed with

[  518.041826] BUG: kernel NULL pointer dereference, address: 0000000000000000
[  518.042816] #PF: supervisor read access in kernel mode
[  518.043393] #PF: error_code(0x0000) - not-present page
[  518.043981] PGD 0 P4D 0 
[  518.044185] Oops: 0000 [#1] SMP PTI
[  518.044518] CPU: 2 PID: 2255 Comm: insmod Tainted: G           O  K   5.1.0-klp_convert_v4-193435-g67748576637e #2
[  518.045784] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-prebuilt.qemu.org 04/01/2014
[  518.046940] RIP: 0010:test_klp_convert_init+0x1c/0x40 [test_klp_convert1]
[  518.047611] Code: 1b a0 48 89 c6 e9 a8 c0 f4 e0 0f 1f 40 00 0f 1f 44 00 00 53 48 c7 c7 00 30 1b a0 e8 5e 33 f6 e0 85 c0 89 c3 74 04 89 d8 5b c3 <48> 8b 35 5d ef e4 5f 48 c7 c7 28 20 1b a0 e8 75 c0 f4 e0 e8 6c ff
[  518.049779] RSP: 0018:ffffc90000f37cc8 EFLAGS: 00010246
[  518.050243] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000027de0
[  518.050922] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffff88807ab54f40
[  518.051619] RBP: ffffffffa01b1080 R08: 0000000096efde7a R09: 0000000000000001
[  518.052332] R10: 0000000000000000 R11: 0000000000000000 R12: 00000000ffffffff
[  518.053012] R13: 0000000000000000 R14: ffff888078b55000 R15: ffffc90000f37ea0
[  518.053714] FS:  00007febece1fb80(0000) GS:ffff88807d400000(0000) knlGS:0000000000000000
[  518.054514] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  518.055078] CR2: 0000000000000000 CR3: 000000007a56a000 CR4: 00000000000006e0
[  518.055818] Call Trace:
[  518.056007]  do_one_initcall+0x6a/0x2da
[  518.056340]  ? do_init_module+0x22/0x230
[  518.056702]  ? rcu_read_lock_sched_held+0x96/0xa0
[  518.057125]  ? kmem_cache_alloc_trace+0x284/0x2e0
[  518.057493]  do_init_module+0x5a/0x230
[  518.057900]  load_module+0x17bc/0x1f50
[  518.058214]  ? __symbol_put+0x40/0x40
[  518.058499]  ? vfs_read+0x12d/0x160
[  518.058766]  __do_sys_finit_module+0x83/0xc0
[  518.059122]  do_syscall_64+0x57/0x190
[  518.059407]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
...

It crashes right in test_klp_convert_init() when print_*() using 
supposed-to-be-converted symbols are called. I'll debug it next week. Can 
you reproduce it too?

Regards,
Miroslav

PS: it is probably not a coincidence that I come across selftests failures 
right before I leave for a holiday...