linux-kernel - Re: [PATCH] x86: Implement _

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Date:   Sat, 25 Feb 2017 20:38:44 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     hpa@...or.com
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        jpoimboe@...hat.com, richard.weinberger@...il.com,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] x86: Implement __WARN using UD0

On Sat, Feb 25, 2017 at 09:55:45AM -0800, hpa@...or.com wrote:
> You mean like the INT instruction?

Right, you mentioned reusing INT $9 upthread.

That doesn't have the additional info in the immed8 - it is the vector
in this case. But that's not really important for our usage.

In any case, the hw does react to it when I do

	"int $9"

so I guess we could look into using that one.

[   93.668930] test: loading out-of-tree module taints kernel.
[   93.674785] Starting test.
[   93.677571] coprocessor segment overrun: 0000 [#1] PREEMPT SMP
[   93.683459] Modules linked in: test(O+) xfs libcrc32c exportfs snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_coded
[   93.683489] CPU: 4 PID: 2136 Comm: insmod Tainted: G           O    4.10.0-rc7+ #7
[   93.683500] Hardware name: MICRO-STAR INTERNATIONAL CO.,LTD MS-7599/870-C45 (MS-7599), BIOS V1.15 03/04/2011
[   93.683503] task: ffff88012f154380 task.stack: ffffc90006cf4000
[   93.683512] RIP: 0010:test_init+0x17/0x20 [test]
[   93.683515] RSP: 0018:ffffc90006cf7cb8 EFLAGS: 00000296
[   93.683518] RAX: 000000000000000e RBX: ffffffffa03ca0c0 RCX: 0000000000000000
[   93.683521] RDX: 000000000000000e RSI: ffffffff802d4e48 RDI: ffffffff802d4e48
[   93.683523] RBP: ffffc90006cf7cb8 R08: 0000000000000000 R09: 0000000000000274
[   93.683525] R10: 0000000000000000 R11: 0000000000000273 R12: ffffffffa03ca000
[   93.683527] R13: 0000000000000000 R14: 0000000000000001 R15: ffffc90006cf7eb0
[   93.683530] FS:  00007f55d1e3e700(0000) GS:ffff880136d00000(0000) knlGS:0000000000000000
[   93.683533] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   93.683535] CR2: 000055be657f51e8 CR3: 0000000131014000 CR4: 00000000000006e0
[   93.683537] Call Trace:
[   93.683548]  do_one_initcall+0x53/0x1a0
[   93.683554]  ? __vunmap+0xaa/0xf0
[   93.683559]  ? kfree+0x151/0x1b0
[   93.683566]  do_init_module+0x5f/0x1d5
[   93.683573]  load_module+0x2026/0x2530
[   93.683578]  ? __symbol_put+0x80/0x80
[   93.683589]  SYSC_finit_module+0xcb/0xd0
[   93.683597]  SyS_finit_module+0xe/0x10
[   93.683602]  entry_SYSCALL_64_fastpath+0x18/0xa8
[   93.683605] RIP: 0033:0x7f55d1970a59
[   93.683607] RSP: 002b:00007ffc3cf781d8 EFLAGS: 00000206 ORIG_RAX: 0000000000000139
[   93.683610] RAX: ffffffffffffffda RBX: 00007f55d1c2ab78 RCX: 00007f55d1970a59
[   93.683612] RDX: 0000000000000000 RSI: 000055be655d73d9 RDI: 0000000000000003
[   93.683614] RBP: 000000000000270f R08: 0000000000000000 R09: 00007f55d1c2cf00
[   93.683616] R10: 0000000000000003 R11: 0000000000000206 R12: 00007f55d1c2ab78
[   93.683618] R13: 0000000000001020 R14: 00007f55d1c2ab78 R15: 00007f55d1c2ab20
[   93.683623] Code: <31> c0 5d c3 0f 1f 44 00 00 0f 1f 44 00 00 55 48 c7 c7 6e a0 3c a0 
[   93.683655] RIP: test_init+0x17/0x20 [test] RSP: ffffc90006cf7cb8
[   93.683699] ---[ end trace e034b65a8bb8cf26 ]---
[   93.683702] Kernel panic - not syncing: Fatal exception
[   93.709252] Kernel Offset: disabled

-- 
Regards/Gruss,
    Boris.

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